Technical bulletin no. 38

              I ,
.,.
AIR SERVICE INFORMATION CIRCULAR
VOLUME V
(AVIATION AND AEROSTATION)
BY DIREC.T ION OF CHIEF OF AIR SERVICE '
JANUARY, FEBRUARY, MARCH. 1924
TECI-INICAL BUl~LETIN
No. 38
NUMBER 431
DEVELOPMENT QF MILITARY AIRCRAFT MATERIAL FOR UNITED STATES
AIR SERVICE UNDER SUPERVISION OF ENGINEERING DIVISION.
Prepared and Published
f! ~, Direction of the Chief of Air ~rvice
.:,nd under the supervision of
MAJOR L. W. McINTOSH,
Chief of Engineering Divi•ion.
McCook Field-3-14-24-IM
(~ -
CONFIDENTIAL
,. ~fhe information contained herein is confidentia1t~d the-refore
must not be republished, either in whole or in part, without
express permission of the Chief of Air Service, U. S. Army.
r
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AIRCRAFT DEVELOPMENT
PART I-CURRENT PROGRESS.
AIRPLANES.
Curtiss Pursuit, Model PW:8 (description, views and performance_) ...................... ~·· ····
Boeing Pursuit, Model PW-9 ( description, views ·and performance) ..... , ........... .............. .
Fokker Pursuit, Model PW-7 (description, views and performance) .. ............ ............ , .. .
New Long Distance Bombeir (Larger Than Barling) ..................................... .............. : .. '. .. .
Experimentation with Inverted Liberty and Radial Engines in DH-4B ....... ...... ...... .... .
Progress on DH-4M's and DH-4M-l's ........ , ....................................................... ... ......... ..... .
Preliminary Fli e-ht Tests of Production Fokker C0-4 Airplane ......... , ......... .... .............. .
Testof New TW-5 Training 'plane ................. ............... ...... : ... ....... ........................... ... ........ .
Performance of Vought with Detachable-blade Micarta Propeller ................. .. ............ .. .
Preliminary Performance of New T-3 Transport .. .. .......... .,.. ..... ......................... .... ......... .
Study of Variable Camber Airfoil ........................... .......... ...................................... .............. .
Detachable-blade Micarta Propellers for VE,7 and JN-4H ............................................. .
Supercharger Propellers ··························.······················ ···················· ······,-····························
AIRSHIPS AND BALLOONS.
Progress on RS-1, TA and TC Airships ··························· ·····························~················· ·····
Propellers for Zodiac Airship with Packard Engines ........... ......... .................... .. ..... ..... .. . ~~eir:~:{: Z:8ci~:S~\fo~~r~;;~ri~~~~ :::::::::::;::::::::::::::::::::::::;:1
~::::::::::::::: : :: : :: : ::: :: :: ::: ::: :::
Luminous Manometers ................................. ........ .................................................... .............. .
ARMAMENT.
New External Bomb Racks, Types B-3, C-3 and H-4 .... ..................................................... .
New Internal Bomb Racks, Types D-1 and G-5 .. ...•.............................................. ... .L ..... .
-.:.. Wearin~ Tests on B-4 Bomb Shackle ---------------····-··········-······· ····-·-···-·------------------- ------·· ·· ---- -
Bomb Hoists and Chests ......... ................................................................................................ .
Remote Trigger Control for Browning Gun ······· ·········· ···· ····· ·· t······ ·····················--·· ············--
EQUIPMENT.
New Aircraft Storage Batteries, Williard and Exide ................. ............................... ..... ,
Electric Starters with New Hand-cranking Feature ................ .. · ... .................................... .
New Instruments and Padded Instrument Board ..................................... ............... ........... .
Navigation Calculators · ........... ................. ..... .. .. ..... ...................... .................................. ......... .
Recording Manometer ........ '. ...... ........... ......................... ...... ........... ... ....... ................ ............... .
Recording Tachometer and Test Stand for Standard Tachometers .... ........................... .
~it:t~i1~~~0Ei:~~~:~e~~~~.~ .. ::::::::::::::::::::::::::::::::::::~:::::::::::::::::::::::::::::::~:::~::::::::::::::::
T-1 Aircraft Camera and Transforming Printer (description and views) ... ........... .... ... .
POWER PLANTS.
Tests on Curti¥3 "D-12" Engines .................................................................. ........ ................. .
Geared Liberty, Magnesium Bear:ings and Other Modificatfons ..................................... .
Purchase of Packard "1Aa1500" Engines ········· ··························· ·· ·····························r ···· ···
PART II-REVIEW OF TECHNICAL ACTIVITIES OF 1923.
I '
Part Two of this chapter contains a general review of tne· Engineering
Division's major developments in aircraft material during the year, 1923. For
convenience, the subject is treated under the following headings: Airplanes,
Armament, Lighter-than-Air, Material Research, and Powe,r Plants. In con­clusion
a few projects of general interest are discussed.
7
12
17
20
21
22
23
23
23!
24
24·
24
24
25
25
25
2fi
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26
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28
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29
36
,36
38
Airplanes-principal types, aerodynamics and propeller development....................... ..... 38
Armament-new bomb-carrying equipment and machine gun accessories...... ... .... .. ..... 45
Equipment-instruments, electrical equipment, aerial photography, parachutes,
radio, and field servicing units ........... ................... .................... ............ ......................... 46
Lighter-than-Air Craft, mooring and handling equipment and transportation units.. 54
Material Research ... .............................................................................. ... ...... ....... ,.................. 59
l:'owe.r Plants-new engines, superchargus, and engine accessory equipment.......... .... 59
-:..
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C O N T E N T S - (Cont'd)
RESEARCH AND EXPERIMENT
RESUME' OF ENGINEERING DIVISION SERIAL REPORTS.
Static Test of Fokker C0-4 Ah,plane ____ ---- ----- --------------- ------ ------ -------
Gottingen Airfoil No. 387 ---- ----------- -- ---- -- ------ ------------- ,·--- ___ __________ _
RAF and Curtiss Airfoils as--Racing Wings --"- _ --- --- -- --,------- -----
Serial on "Material in Airplane Construction" for New Handbook "Structural
Analysis and Design of Airplanes" _____________ __ ___ --- ----------------
Wind Tunnel Test of Model of C0-2 A;rplane --- ----- ------------- ­Static
Test of TA-6 Airplane and R-3 Race,r Wing (Verville-Sperry)
Proof Tests of Barling. Bomber Control Surfaces __ ___'. ____ _____________ _
Relative Merits of Wood and Metal Chassis for SE-5A Airnlanes _____ _
Effectiveness of Ailerons with Skewed Hinge __ __ ______________ __ ___ :~ ------------------ -
TA-4 Design with Different Airfoils ----- --- ------- ---- ------- -------------- ------------ -----·
65
65
65
------ 65
65
Adjustable-pitch Propeller for Supercharged DH Airplane --- ----·--------- ------ ------- - ___________ _
66
6G
66
66
67
67
67
67
68
68
68
68
69 ·
69
69
69
Air Blowers for Ballonets of RS-1 and USMB Airships _____________ _______ __ ___________ --------- --- -
Wind Tunnel Test of TW-2 Airplane __ · __ __ --- ---- -------- ------- -- -- ------- ----- -- --------- -------·- -·--·----- --------
Resistances of Antennae Weights -- ---------------------- ---------- -- ---- -- --- -- -------- --- --=---------- ------ -----------­Test
of Tail Surfaces and Controls of TA-6 Airplane_________ _________ ______ -- ·--- -·----------- __
Spade Grips, Types F-1 and X-2, for Browning Gun ----- ----- ·-
Thompson Sub-machine Gun Installat· ons and Tests -- -- --- ---·----- --- ------·-------- ____ ___ ·------
Development of Spade .Grip, Type F-1 -- ----------------
Electric Generators for Aircraft ---- --- ---- . ·-- --------- -- - ---- --------- -·-------
Drag Characteristics of C0-4 and C0-5 Airplanes ______ _________ _
Control Stick Forces with Respect to Elevator Positions ___________ ___ _
Performance Test Reports on Boeing PW-9, Eng. Div. C0-5, and Fokker C0-4's
with side and nose radiators --- ---------------------------------------·------------------ -- --- --- ------------- _____ _ 70
70
70
Metallography of Sand Cast Aluminum Alloys -- -----·---- ·--- . ----- ·--· _______ _
Carborundum Sand Molds for, Cast-ng Duralumin ---------··-------- ------
Comparison of Aluminum Alloys for Crankcases __________ _____ _
Appiic,ition of Varnish to Balloon Fabrics __ _____ ------------------
Heat Treatment and Metallography of Cast Alum:num-Mag nesium Alloys __
Alcohol-Gasoline Mixtures ______ __ -- -- --- -- --- -- -- ---------------- -- ------- -------- ---------
Duralumin Disk Airplane Wheel ____ ---- ---------- ---- ------ ------·------
"Bellows" Fuel Pump ---- ---- ----- ----- -- ---- --- -- -------- -- -------------·- ---- ---- --
Pre:-'ai'ation Tests for Engine Storage _·_ ---·----------------·
Smooth Orifices for Measurement of Air Flow ---- ------------- ----------------
INVESTIGATION OF MATERIALS.
Largest Airplane, Tire ( 64x14) --------- --------------- ---- ------------ --------------- --- --- ---­Lead-
Coated Fabric for Chemical Warfare ------ --- --- -- -·
Glue Tests and Specifica.tions ----- ---- -- -- ------ ------- -- - --- --------------------------------­Rubber
Substitute for Bakelite Micarta -------- -- ---- ------------------ -·-----·-·-- -- ------·
Comparison of Aluminum and Magnesium Pistons ------ ·------- --- --·---­'£
ellurium in Aluminum and Its Alloys ---- -- --- --- ----- --- ---------- ------ --- ­Duralumin
and Steel Fittings -- ------- ---- - --- ----------· -- -------------------- ----­Chadwick
Process for Babbitting ----- ------ --- ---· -- ---------------- ---------
Electric Welding of Nickel Stee,l Tubing -------------- -----
'.Che "Rich" Steel Valve --- ------------------- ----- ---- -- --- -------------.----·-- ·----
NEW BOOKS AND DOCUMENTS
Documents added to Technical Files during First Quarter of 1924 ___ ___ _
---- 70
71
71
71
71
72
72
72
-- ----------- 72
72
72
73
73
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74
74
74
75
:.
LIST OF ILLUSTRATIONS
Page
Curtiss Pursuit, Model PW-8 (Second Article) ----------- ---·- ··------·--· ---- -- ------- --- --- --------- -- ------ 6
Section of Curtiss Skin Radiator _ ________ __ __ _____ __ _____ ___ --- ---- --- -------------- --------- --- - 9
General ,Arrangement of Curtiss PW -8 ( dwg.) ____ _________ __ _
Boeing Pursu:t, Model PW -9 ____ ___ ___________ ----- ------ ---- ----------------
General Arrangement of Boeing PW-9 (dwg.) ________ _____ ____________ __ __ _
Fokker Pursuit, Model PW-7, with Plywood Wings __ __ ---- --·- ------ ·--
Inverted Liberty Installation in DH-4B ----------- --------- ---------- ----------
Airways Padded Instrument Board, Model 1924 __ ___ ______ ---------- ----- --
T-1 Aircraft Camera (Bagley Tri-lens) with Gimbal Mount _____ _
Arrangement of Lenses in T-1 Camera -- ---- ------ ----- -- --- --- --- -- ---------- --------- ------------ ------------ ·----- -
Magazine with Wirrdow Cap and Ce,nter Pressure-Plate Removed ________ -- --- ---------------- ----
Release Mechan:sm foi, T-1 Camera ---- ---------- ----- --- ---- ------- -------------- ----------- --- -- ·-------- ----- ------ --
T-1 Camera as Installed in DH-4B-P-1 (Photographic) Airplane ____ -------- ----- ----- -------- ---- -
Printer for Transforming Tri-lens Negatives ---- ------ ---- --- -- ---- -- ---- -- -- --------- -- ----· -- ----- -----------
Shipping Case for T-1 Camera and Accessories -- ------ --- --- -- -- - __ ____ ------------------------- --- -·------- --
T-1 Composite (transformed) Photograph ---------------------------- ---- -------- -- ----------- --- ---- --- --- ------ -
11
13
15
19
21
28
30
31
31
32
33
34
35
37
Bird's-ey-e View of Dayton (Ohio) and Vicinity Made, with T-1 CaJil_era -- ------- -------------- 37
Engineering Division TP-1 with Side Supercharged Liberty, ------ -- --- -- ------- ---- ---- ---------------- 39
Gallaudet All-metal Observation, Model C0-1 -- ---------- ------------------ --·-- -- --- --- -- ---- -- ----- - 41
Gallaudet Day Bomber, Model DB-lB (Redesigned Article) __ _
Generator Unit for Distant-reading, Earth Inductor Compass
43
47
Distant-reading, Earth Inductor Compass as installed in Airplane___ ___ _____________________ __ ______ 48
' -
Field Photographic Truck in Operation ---- ------------ ----- ------------------------ -- -- ---------- ----- -------- -- ------ 50
Field Service Unit for Hot Oil and Water ------------ ------- ---- ------- ------- ----------- -- --· --- ---------- ------- ­Field
Service Unit for Fuel, Oil and Water ---- ---------- ---------- -- -- ------·
Anti-Aircraft Artillery Tow Target and Reel on DH-4B -- --------
Engine Crankeo: (Lazy Tongs Type)-Starting Vought Airplane ___ -------- -- ------------- --- ------
7 M Continuous Hydrogen Generator Plant (Silicol Process) ---------- ----- -- ---- - ---- ------ -- ------­Light
Weight Truck Compressor for Field Hydrogen Generating Plants _ -- -- --- --------- ·--
Engineering Division Model W-lA 18-Cylinder, 700-h. p. Engine ______ _________ : _ __ __ ___ ___ _______ _
Almen "Barrel" 18-Cylnder, 375-h. p. Eng:ne, Model A-2 ---------- ---- ---------- ----- -- ------ -- -- --------
52
53
54
515
57
58
61
63
Wing-Tip Plan Forms with "Ske,wed" Ailerons--- ------ ----- _ -- --- --- --------- -------------- ----- -- 66
Ballo_net Air Blower, for USMB Airship ------- --------------- ..~ . ---- ---- -------- ------------------- -- ----- ----- -------- 67
6 T E C H N I C A L B U L L E T I N N o. 3 8
CURTISS PURSUIT. MODEL PW-8 (Second Article }
(Curtiss "D-12" 375-h. p. Engine. )
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AIRCRAFT DEVELOPMENT
PART I - CURRENT PROGRESS
AIRPLANES
PURSUIT
Curtiss Pursuit, Model PW-8.
The remarkable success of the Curtiss D-12 engine and wing radiator as demonstrated by the
famous Curtiss racers, those beautifully coorclin1ted mechanisms which now hold the World's
speed records, marked a new epoch in the development of high speed pursuit aircraft whose sub­sequent
performance is no less wonderful from a military standpoint than that of the racers from
a speed standpoint. The two new types of airplanes which have acquired this enviable position as
the fastest pursuits in the Air Service are known as the Curtiss PW-8 and the Boeing P\i\T-9.
The first of the new pursuits to be submitted to the Air Service was the Curtiss PW-8, de­signed
and built about the "D-12" engine by the Curtiss Aeroplane and Motor Company as the
exemplification of their conception of a fast pursuit 'plane. Flight tests quickly demonstrated
that this airplane, altho not built strictly in accordance with military specificatiou.i__possessed two
valuable characteristics, high speed and great man ~uve:-ability, to a degree that presaged an im­mediate
innovation in the design of pursuit aircraft.
In order that subsequent articles of this des ·gn would fulfill military requirements, the second
experimental airplane was built by the Curtiss C )mpany to incorporate certain changes and re.com­mendations
made by the Engineering Division. It is with this airplane that the present article has
to deal.
The second experimental model PW-8 is a two-bay, externally-braced biplane with thin sym­metric:
il wings of plywood construction, tubular steel fuselage mounting a Curtiss D-12 engine,
split-axle landing gear and Curtiss patent wing ra :liators. All surfaces are covered with cotton
fabric with the exception of the fuselage nose co Nling and that portion of the continuous upper
wing between the ailerons where the unique sk :n radiators form the surface covering. The
general design is similar to the first PW-8 whi :h was derived from the Army Curtiss R-6 racflr
except that the second model-has a different airfoil section, a lower wing of narrower chord, four
ailerons instead of two, and other changes in conformity with Air Service specifications. The wing
section and covering are the same as those used on the Curtiss Navy racer.
Both wings are of multi-spar construction of equal span but of different chord, the chord of
the lower wing being 18 inches narrower than that of the upper. There is no dihedral or sweep­b1ck.
The stagger is large, however, amounting to over 50 per cent. The upper wing is in one
piece, supported at the fuselage by short N-shaped cabane struts. The lower wing is in two sec­tions,
right and left panels, attached to the fuselage by means of hinge fittings and pins and
b~aced to upper wing hy two metal interplane N struts on each side. The wing structure consists
of wood spars and ribs, the whole covered with two-ply spruce planking laid at 22-1/ 2° angle with
the spars. Portions of the leading and trailing edges of the upper wing a1e cut away to accommo­date
the installation of the skin radiators.
Two unbalanced ailerons of duralumin and fabric construction are inserted in tl1e outer trail­iPg
edges of each wing, the lower set having a 5-inch narrower chord. The ailerons are intercon­nected
and actuated by a rod and lever placed inside lower wing in front of re1r spar.
Owing to the large positive stagger, the double streamline wires which furnish the external
bracing in the outer bay run from the rear spar of the upper wing to the front spar of the lower
8 T E C H N I C A L B U L L E T I N N o. 3 8
wing. In the inner bay, single flying wires run from the upper front and rear spars to the front
landing gear strut fuselage fitting and double landing wires from the lower wing front spa1- to the
rear cabane strut fu selage fitting. In the plane of the rear spars of the inner bay, single wires
cross to the top and bottom fu selage longerons. All brace wire fittings are inclosed in the wing.
The tail planes are thin externally-braced surfaces whose horizontal members. stabilizer and
elevator, have double camber sections and aspect ratio of 2-1 / 2 to 1. The stabili zer which absorbs
about 60 per cent of the horizontal area is adjustable in flight, the adjustment being effected by
means of a simple mechani sm in side the fu selage. to which the leading edge of the stabili zer is at­tached
by two eye bolts in such a manner that the entire sur face is pivoted about the fittings on the
elevator spar. The elevator with its span of 9-1 / 2 feet is unbalanced. The vertical fin which
carries a large balanced rudder is adjustable on the ground. Six brace wires lead from the outer
elevator hinges to top of fin and fuselage tail post.
The fuselage is a fabri c-covered structure of welded steel tubing, tin -coated to inhibit cor­rosion.
Its maximum cross section is ot rectangular shape, 29 inches wide and 34 inches deep.
surmounted by a curved superstructure 10 inches high. The engine is supported on a metal
mounting with the bearers resting on Raybestos, a shock-absorbing material. . This section is com­pletely
housed by a rear firewall of terne plate and by a carefully streamlined aluminum cowling­supported
on duralurnin channels secured to the fuselage and nose plate. Short drilled studs and
lock wires facilitate removal of cowling. ·
The cockpit is very accessible and comfortable and well protected from the wind, in fact ·a
climb to high altitudes where the temperature was 40 degrees below zero was made with prac­tically
no discomfort altho the pilot wore no goggles or face mask. The in struments are arranged
along the sides of the cockpit, an arrangement which would probably be improved by a central
location. Both stick and rudder (pedal type) are conveniently located.
The 'plane is equipped with a simple compact 'Chassis consisting of two V-shaped metal struts
and divided axles mounting two 28x4-inch straight-side wheels and tires and terminating at their .
upper extremities in side fuselage in a simple shock absorbing device containing 20 one-half inch
rubber washers held in compression. An elongated s lot is cut in the ax le fairing to allow for the
scissor-like movement of the intersecting axles in taxying. The treacl is 5 feet 11-J / 4 inches. A
tail skid of- the non-steerable type completes the equipment.
Power is furni shed by a standard Curtiss D--12 engine equipped with a Curti ss two-blade high
speed walnut propeller, 7 feet 10 inches in diameter. The engine is equipped with two new model
NA Y-5 Stromberg carburetors having a common verti cal air scoop, two Type SS-1 2 Splitclorf
magnetos with jump-spark distributor, and low compression pi stons ( ratio 5.3 to ] ) · which give it
a rated horsepower of 375 at 2000 r. p. rn. Short individual exhaust stacks are also provi'ded.
Provision is made for in stallation of a Curtiss hand starter. · 1 ·
Lubricating oil is supplied by a gear pump from an irregularly-shaped tank of 9-3/ 4, gallons
capacity mounted underneath the engine. The oi l is heated from the cooling system by hot• water
which is by-passed to the heater thru a valve operated by a fourth ]eyer on the engine control unit
in the cockpit.
There is no gravity tank. All f.uel is carried in a single leakproof tank of 77 gallons capacity
mounted in a cradle in the fuselage at rear of engine and is feel to carburetors by means of, an '.en­gine-
driven Type C-5 gear pump fitted with a T _vpe B-1 pressure relief valve. A manual ly-operated
wabble pump is provided for emergency.
The installation of Curti ss wing surface radiators on the PW-8 marks their fir st application
other than to racing aircraft. Their design is of particular i:,terest altho it is not especially suit­able
for military purposes. As mounted upon the wing of this airplane, the radiator consists of
fi ve separate sections-a center section containing two expansion tanks, two main or intermediate
sections and two outboard sections mounted beyond the inner I struts-each section having separ­able
upper and lower ha lves joined to each other around the wing by means of hinge pin s. T his
construction allows removal of individual sections without removing the wing. , The center and_
outboard sections are made of 9-inch corrugated strips, containing three and two panels, respec- .'
tively, whereas the main or intermediate sections are built in 8-inch strips of six panels each. The ·
upper and lower halves of these panels are conne cted separately in parallel by means of hose con­nections
in order that there will be no direct flow of water between them. T he total wing
AIRC R A FT DEV E LOPMENT 9
a··ea covered by the radi ators is 73.2 square feet which represents a cooling surface of approxi­mately
220 square f eet. Cooling depends upon skin friction; the water from the engine enters
the leading edge of the radiator, passes thru the corrugations in the surface to the trai ling edge .
and then returns to the engine thru a by-pass val ve between the racliatbr and the water pump.
'\ /\ C\A /\ /\/\/\ A ,,: -~--=-= L= RRo,-,~ co«
/ ~ .
~ _/ -~~;__ vc7.:c,2 covct 1, -:rG
---
IVVVVVQV\
SECTION OF CURTISS SKIN RADIATOR.
Thermal control is attain ed by means of a sing-le by-pass valve thru which varying amounts
nf water tray he returned to the engine without passi1ig thru the radiator, the amount of water so
pa ssed being regulated at the wi ll of the pilot. The valve is so constructed as to permit a small
!'ow of water thru the radiator at all times in order to prevent freezing in fligh~.
In its present stage of development, the adaptability of this type of r~diator to military air­cr:
i.ft has not been sati sfactorily established owing to the difficulty of maintenance, ineffecti veness
of cooling under certain conditions and.its vulner abi lity to gun fire.
Bes ides the well-lighted and well-arranged in strument board on right side of cockpit cantain­ing
the usual complement of in struments for this type of pursuit. the equipment includes an A. 5.
type B-3 compass mounted on Aoor of cockpit, a new A. S. shoulder type safety belt and three Ii fe
preser ver seat cushion s. and the Dreyer oxygen apparatus with fla sks located back of seat. Pro­vision
is made for carrying a K-3 camera and one type A-2 external bomb rack and release
handle in addition to the regular armament in sta llati on which consists of two synchroni zed air­c
a ft machine guns of .30 and .SO caliber, togeth er w1th the necessary sight s, ammunition boxes.
and other accessories. Pyrntechtii cal equipment consists of two Holt flares in stalled under each
lower wing near outer strut.
C[ f J\ RACTERISTICS 1\ ND PERFORfl[ANCE.
( Curtiss PW -8-2nd Ex. 1\1 ode])
DIMEKS TONS.
0 \,erall S_l)a 11 .. . .... .. ..... 1
; . · : .· • • • ••••• •• •• • •••••••• • •• • •• • • • • •
Overall length ......... .. ...... ... ......... .. .. . . .. . . . .. . . .. . .
Overall height . .......... . . ... . .. ... .. . .. .. .. . ..... ... . .. . .. . .. .
i\irfoil ..... . .. . . · ....... · ...... ..... . . .... .. . ... ... .. . . . .... . . . .
Dihedra:I .. . ' .................. .. .. ....... .. . . .. . . .. .. .... . : . .. : .
Gap ... . . .. .. . . .. . . ............... . . . . .. . . ...... .. ... .... . . . . .
Stagger . . . .. . ............. .... . . ....... . . ...... ... ... ... . . .. . .
Sweep back ... ... . , . . ..... ......... ... . . . . .. ......... . ... ... .... .
\ \l ing span ( upper ar;cl lower same) ... . ... . . . . . . ..... . . .. . . ... . ... .
Wing chord ( upper ) . ... .... . . ... . . .. .. · ..... . . .. . . ... . . . .... . .. .
VVing chord ( lower ) . .... .. ....... .. .. ' ..................... . . . . .
I nciclence ( upper and lower same) .. .. .... . .. ... . . .... .. .. . .. .. ... .
32' 0;'
?.2' 6"
8' 10"
Curti ss C-62 oo
4' 7-1 / 2"
3' l"
None
32' 0"
5' 6"
4' 0" oo
10 T E C H N I C A L B U L L E T I N N o. 3 8
AREAS IN SQUARE FEET.
Total supporting surface . .. ..... . .. .. .. . . . . ..... .. ..... .. ..... . ... 287
Upper wing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161.18
Lower wing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106.4
Ailerons . .. . . ... . . .. .. . .. . .... .... .. .. . ..... . .. ... .. ..... .. .... 19.42
Elevator , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5
Fin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.34
Rudder ( incl. bal. 0.975) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4
Stabilizer .......... . ... . . .. .... .... ........ . ·. . . . . . . . . . . . . . . . . . . 12.2
WEIGHTS I N POUNDS.
Empty ( including water) .... .. ..... . .... .. ........... . ..... . . .. .
Useful load ......... . ... . .... . .. . .. .. ... . ... .. .. ... .. . ......... .
Crew .... .. .... . . .. ......... ... . .. .............. . 180
Armament ........ . .... . . . . ... .. . .. ... . . .. . .. .. . . 215
Equipment . . ....... .. ..... . . . . . .... . ........ ... , . 55
Fuel ( 76 gal. 5.91 lb.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 450
Oil (8 gal. 7.5 lb.) . ... . . .. . ... .. .... .... . . . .. ... .. 60
2191
960
Gross weight ..... . . .... . .. ...... . . . . . . ... . .. . ... . .. . . ..... .. . . . .
Weight per sq. ft. of supporting surface .... . .. .. ... . ... . .. . . ...... . .
Weight per horsepower ( 438 h. p. @ 2225 r. p. m.) .... .. .. ........ . .
3151
10.98
7.2
*PERFORMANCE.
Standard CLIMB
\
SPEED
Altitude · Ti1ne Rate I· Engine Level Flight I Engine
in Feet in min. ft. / mi11. r. p.m. m . p. h. I r.p.m.
0 I 0 1830 I 1990 168
. I
2225
6,500 I 4.2 1275 1975 163.2 2165
10,000 ··1 7.4 980 i 1960 159.2 2125
15,000 I 14.2 455 i 1925 149.8
I
2035
20,000 I 30.6 ' 130
I
1865 127.0 1905
20,350 S. C. I 32.8 100 1860 124.2 1890
21,500 A. C. I 0 I 1840 103 i 1840
--- -
Endurance at 10,000 feet altitude .......... . ... 2 hr. 45 min. (approx.)
Minimum speed at sea level . . . . ........... . .. 63 m. p. h. (approx.)
* This performance was obtained with Curti ss high speed propeller ( X-29048).
The following consensus of flying qualities on the second experimental PW-8 pursuit is sub­mitted
as based upon pilots' observations in preliminary fl ights:
Taxying: Taxies well considering that the 'plane is not equipped with steerable skid.
Take-off: It takes off quite slowly due to low propeller efficiency at low airspeed. Directional con­trol
is good and there is no tendency to turn or ground loop.
Landing: Lands normally and easily with average roll. Handles well in side or forward slips in
landing. Landing gear with disk shock absor bers functions satisfactorily.
Maneuverability: Controls are effective at all speeds. Spins well with or without power and comes
out easily. Loops must be executed at speeds over 160 m. p. h. The 'plane does a true Im­melman
turn exceptionally well. Rolls and half-rolls may be executed to right or left. Engine
usually stops at top of loop, probably caused by position of carburetors.
Stability: Slight tail heaviness is noted under full power with stabilizer set in full position for nose
heaviness.
Visibility: Visibility from all angles except directly forward is good. The low setting of the upper
wing so_mewhat hinders visibility forward.
GENERAL DESCRIPTION.
Airplane ............... .... C:.i:tiss PW-8
Type ·· --······-·· ····· ____ ... Pur uit Biplane
Status __ : __ .Experimental
Manufacturer ... ___ . __ Curti , s Aero &
4 Engine .............. .' ... ... Curt.i1s "D-12"
Air foil° ···-· ·-----·· __ __ ____ Curt iss C-6J
Supporting area ...... '! 87 £qua re f£et
Gross weight -- .. 315-l ;'poun do
Usefu l l'\:i.<l .. :'. ~6 0" f ounds
t---------'---U ·- 6 ..
GENERAL ARRANGEMENT OF CURTISS PW -8 AIRPLANE.
M?to: Co.
-
>-
>--<
:::0
n
:::0
>-
'-=1
>-l
tJ
trJ
<
trJ
r'
0
'"d
~
trJ z
>-l
............
12 T E C H N I C A L B U L L E T I N N o. 3 8
Accessibility: Cockpit is very accessible and comfortable. Controls bbth directional and longi­tudinal
are well located and operate easily and effectively. Entrance to cockpit with para­chute
on could be improved by placing a handhold on the upper wing.
The third airplane on the experimental contract is to be of special construction with a view of
increasing the high speed and ceiling. This is to be accQmplished by installing a high compression
D- I 2 engine and by lightening or otherwise improving the structure.
Twenty-five production model PW-S·s are in pc.ogress of construction. One of these will be
used by Lt. 1faughan this coming June in a second attempt to make a transcontinental daylight
flight from New York to San Francisco followin~ practically the same route as used last year.
Boeing Pursuit, Model PW-9.
The Boeing pursuit, Air Service designation PW-9, is a single bay, semi-cantilever, tapered­wing
biplane of wood and steel construction, designed and built about the Curtiss D-12 engine by
the Boeing Airplane Company, Seattle, Washington. This airplane and its contemporary, the
Curtiss PW -8, are the fastest pursuit 'planes in the Air Service today and perhaps in the entire
world also. Their performances are' almost identical. Structurally, however, the Boeing is super­ior
in that its radiation system is less vulnerable and its maintenance more facile.
,vood construction is employed for the stabilizer as well as the wing cellule except for the in­terplane
and cabane struts which are of steel. The balance of the structure, including fuselage,
landi1ig gear, elevator, rudder and fin are of welded steel tube construction. All surfaces .are
covered with cotton fabric.
The upper and lower wings taper both in chord and in thickness. There is no center section
as the upper wing is built in one continuous piece. The lower wing is made in two panels, right
and left, each of which is attached to the fuselage by means of two 1/ 2-inch bolts and to the upper
wing by a single N-strut. The spars are of the box type with spruce flanges, top and bottom, con­nected
on both sides by 3-ply webs of birch and popular. The lower compression ribs between
the spars are made of solid spruce .
. External bracing is employed in the front truss only. This consists of a pair of streamline
flying wires, 3/ 8-inch in diameter, and a single landing wire, 5/16-inch in diameter, intersecting in
the plane of the front spars. Torsional stresses are carried by the N -struts.
The two ailerons am inserted in the trailing edge of the upper wing only, each supported by
four hinges and controlled by means of flexible wire cables placed inside wing along rear spar from
which they extend to pulley on lower longeron a. nd thence to control stick. The aileron structure
consists of a box spar of similar construction to the wing spar, supporting plywood ribs made of
3-ply webs of poplar and mahogany capped with spruce and terminating in a flexible wire cable
which forms the trailing edge. The ailerons are not balanced.
Tail surfaces are externally braced and unbalanced. All surfaces are of metal construction
with the exception of the stabilizer which is built with spruce spars and ribs. The front sta­bilizer
spar is an "I" section formed of six thin sprue~ strips giued together and shaped to con­form
to curvature of the leading edge. which is covered• with 1/ 1(}-inch, 3-ply veneer consisting of
mahogany sides with poplar core. The rear spar is of solid _spruce routed to provide clearance
for the tubular elevator spar. Adjustment is made at the front spar, the whole structure pivoting
upon the elevator hinges.
The elevator is a. steel structure with electrically-welded joints and fabric covering. The spar
is a continuous steel tube held in position by means of a bearing on the tail post and attached to .
the rear stabilizer spar by six band type hinges, three on a side, thru which the stabilizer is in­directly
connected to the fuselage. From the center hinge on each side, external brace wires ex­tend
downward to lower fuselage longeron and upward to the fin mast.
The horizontal surfaces are symmetrical and of double <:_amber section.
The vertical surfaces are of the same metal construction as the elevator. The rudder is at­tached
to fuselage and fin by three hinges, one on the fuselage tail post and two on the fin mast
which is telescoped into the tail post for about one inch and held there by compression from the
two external brace wires which connect the fin mast with the elevator-stabilizer hinges.
AIRCRAF T DEVE LOPMENT
BOEING PURSUIT, MODEL PW-9.
(Curt is s "D-12" 375-h. p. Engine.)
13
T E C H N I C A L B U L L E T I N N o. 3 8
All movable surfaces are actuated bv mea ns of flexible steel cables connecting the control
stick with the control masts. '
The fuselage is a fabric-covered met:il structure having a maximum cross section , 28-l/ ~ inches
wide by 51-1 / 2 inches deep, and enclosing a well located and accessible c'..lckpjt. The wire-braced
structure is built of iji.ild steel tubing, elect-r:i.~ally , ~ elded· at joints, ·the size of the tubes v:ir y­ing
from one and one-fourth inches for .1'h;e ma in longerons to one-half inch for the cross braces.
The lower portion of the forward fuselage structure is recessed to receive the lower wing panels.
The engine mounting, which is of steel also, is characte~ized by its accessibility and simplicity of
construction. An alumip'u,m cowling in sections to facilitate removal completely houses the power
plant and the underslung radiator.
T he landi~g g~ar i · of:~ll-steel construction wjJh the exception of the axle fairing which acts
as a cross tie between the struts. This fairing ca'i;isists of a woor!,en frame covered with plywood
which forms a thick section airfoil having an 18-inch chord and a li £ting· s"urface of 6.3 sq. ft . The
V struts are formed of sheet steel, acetylene w~.Jdecl at the trailing edge. The chassis is equipped
with an· elastic cord shock abs~rber and a floati rrg,\ axle carrying. 28x4-inch straight-side wheels and
tir.es. The entire unit including:, wheels weighs only 107 pourfds.
The tail skid is steerable, foot control being provided by flexible cables connecting the rudder
bar with the skid mast. Each cable is fitted with a spring cf fix ed travel so that the movements
of the skid in taxying will not be t,ansmitted to 1.the rudder bar:·
The power plant consists of a Curtiss D-12, 375-h. p. engine equipped with two Splitdorf mag­netos,
jump-spark distributor, and two Stromberg NAY -5 carburetors using one vertical scoop
air intake. T!1e exhaust manifo lds are of streamline shape and diviclecl, two on e:ich side, one
manifold accommodating three cylinders.
Oil is carried in two irregula; ly -shaped, inte .. connected tanks. one on each side of engine, hay­ing
a total capacity of 7 gallons.
F ue) i~ s~J1lied to carbureto?s .,by a force-£ eed pr~ssure system operated by a Cu~tiss plung~r
type engme'-dr1yen pump. The system has a total capacity of 69 gallons, 54, gallons 111 the mam
tank located in' ·the fuselage and 15 gallons in the gravity tank in the upper center section. Both
tanks are crash-proof. "·
T he radiator is of the tunnel type and is mounted underneath engine. It has a h01ieycomb
core of Air· Service standard 9-inch tubes an.cl a . cooling surface of 218 sq. ft. Louvres and shut­ters
are provided to control the flow of air.
'· T~he airplane is/ equipped with a two-bladed Curtiss .climbing propeller havi11g a diameter of
8' 2" and pitch of 5' 10-25/ 32". It is made of walnut.
The following characteristics and performances apply to the first airplane of this type to be
completed by the Boeing Company. Inasmuch as this airplane is in an experiment:il stage and
was not built in full accordance with Engineering ' Division specifications, further improvement.
both in design and in performance. ·is anticipated in the two remaining articles on this contract.
CHARACTERISTICS AND PERFORMANCE.
(Boeing PW-9-First Article)
DJMENSIOKS.
Overall spa,n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32' 1"
Overall length . ... ....... , ..... . ...... . .... .. ................... 22' 10-1 / 4"
Overall heigh~ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8' 9"
Air fo il .............. . . .. ....... . ........... . .. . ........ .... . . . Gottingep 436
Dihedral ( lower surface of upper wing) .. . .. . .... . ................. 1 °
Dihedral ( lower surface 9f lower· wing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 ° 23'
Gap . .. . ....... . .. .. .... . . ..... .. ....... . ... ...... .. ... . ....... 4' 4"
Stagger .... • . . ............ . ; . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14° or 11"
Sweepbac.k . . ... ... . . .... .. . .... .. . ..... .... . . . . . ......... .... . . .. Taper
Wing span (upper) ~- .............. .. . . ... ... . ... . .. . . . . .... . . ... 32' 1"
Wing span (lower) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22' 6"
·w ing chord (upper) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.5" to 30"
\Ving chord ( lower ) . . ... . . ... . .... . ... . .. . . .. . .. .. ..... . .. . .. .. 50" to 0"
Incidence ( upper) .. .. . ...... . .. . ........ . . ..... Root 0°, right 30', left 10'
Incidence ( lower ) . . .. ........ .. .............. . . .. . . . . Root 0° tip 20'
-~
,-_
.~ .
GENERAL DESCRIPTION.
Airp lane ..... ..... ........ .. Hoeing PW-9
Type ... L ..... .... ~.-Purs uit Biplane
Status .... .. ...... ... ....... Experimental
Manufacturer ...... .... Boeing Airplane Co.
Engine .... .. ...... .. ...... .. Curtiss "D-1 2"
Airfoil .. .... .. ..... ...... ... Gottingen 436
Supporting area ....... . 252 square fe~t
G.ros s weight .. ... ... .... 2971 pounds
U seful load ..... .... ... .. .. 960 p ounds
:i-'1 /1 ·.
__________. .:_ ____J z!- ;r-· -------------- fo-------------22-10-J------~---..i
GENERAL ARRANGEMENT OF BOEING PW-9 AIRPLANE.
(Pr~liminary Layout.) )
;., ..
>-
>-<
?:1
n
:::,:i
;.i>
'Tj
>-l
u
M·
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M
l'
0
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>-:l
......
'.JI
16 TE CH N I CAL B U LL ET I N N o. 3 8
AREAS IN SQUARE FEET.
Total supporting surface ..... . .... . . .. .......... . .. .... ..... . ... .
Upper wing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150.44
Lower wing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.5
Ailerons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . 14.76
Axle fairing . .. ... . . . . . . '. . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3
Elevator . ....... . . ..... . . . . . . . . . . . . . ... . .... . .. ...... . . . ... . .. .
F in . . . .. . . .... . .. . ........ . .... . . . . _ . . ..... . ... . . ... .. . . .. . . . . .
Rudder . .. ... ..... . . .... ... . . .. . .... ... . . . . ... . ....... . ... . .. . . .
Stabilizer .. . ...... . . .... . , .. .. ... . . .. . ... .. . . , . ..... .. . . . . . . . . .
WEIGHT IN POUNDS.
253
11
3.88
5.73
20
Empty ( including water) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2011
1J seful load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _ . . . . . . . . 960
Cre\\' .......... . ........ . .. . .. . _ . .. _ . . . . .. . . . _ . _ . . 180
A.rmament . . . . .... . ... . . .. , . .... _ . . . . . . . . . . . . . . . . . . 215
Equipn1ent . ...... .. · . .... .. . . ... _. . . . . . . . . . . . . . . . . . . 55
Fuel ....... . . ... .. . . . .. .. .. _. . . . .... ..... . ... . .. .. 450
Oil . . ... . . .. . . . ..... .... . . . . . .. ... . . .. . .... .. . ..... 60
Gross weight . .. .. ..... . . .. . . . .. . .. . .... . ... . .. .. ...... . .. .... .. 2971
Weight per sq. ft. supporting surface... . . . . . . . . . . . . . . . . . . . . . . . .. . . . 11.74
Weight per horsepower ( 440 h. p. @ 2380 r . p.m.) . . . . . . . . . . . . . . . . . . 6.76
* PERFORMANCE.
~ - --
Sta11dard CLIMB SPEED
Altitude Time Rate
I.
Engine Level Fliglit Engine
in Feet 1.1i n-nn. ft. / min. r. p. m. m. p. h. r.p.m.
Ground 2055 2130 160.9 2380
6,500 3.8 1365 2090 154.3 2330
10,000 6.7 1025 2075 150.2 2295
15,000 12.8 625 2055 142.9 2235
20000 24.7 270 2040 132.2 2135
22000 S. C. 34.9 100 2035 124.0 2070
22850 A. C. 0 2030 11 5.5 28-30
'
Endurance at 10,000 feet . ... .. . .. ... .. .... .. . 2 hr. 50 min. (Approx.)
Minimum speed at sea level . . ...... . .......... 67 m. p. h. at 1355 r. p. m.
*This performance was obtained with Curtiss climbing propeller. It is probable that by using a
Curtiss high speed propeller, the performance of the Boeing PV\T -9 will equal if not exceed that
of the Curtiss PW-8.
The flying qualities of the PW-9 as summarized from the pilots' observations are very com­mendable
and_ are given as follows:
Taxying: This 'plane taxies excellently even in strong wind, which is probably due to a very ef­fective
steerable tail skid.
Take-off: It takes off easily after moderate run with no tendency to ground loop.
Lauding: It lands slowly ;me!. very easi ly, .showing no tendency to pancake or ground loop. Con-trols
are effective . .
Stability: Laterally and directionally, stability is good but the 'plane is slightly unstable longitudin-
-· ally at high speeds. This condition is not serious, however. ·
Maneuverability: This airplane is exceptiomlly maneuverable. It loops easi ly, spins and rolls.very
rapidly, performing all of the usual maneuvers in a very satisfactory manner. The controls,
tho unbalanced, are very effective and easy to operate. There is a tendency to "squash" upon
being pulled up too quickly into a vertical tu rn, and altho this is undesirable. it is not con­sidered
sufficiently disqualifying in view of the wing loading and speed.
AIRCRAFT DEVELOPMENT 17
The visibility of this airplane is excellent for pursuit and combat purposes. The blind area is
relatively small, giving good visibility in landing. Due to the sim2licity of construction and ac­cessibility
of parts, maintenance should be easy. In conclusion it may be confidently stated that
the PW-9 is much superior to the present standa rel pursuit 'plane, the MB-3A.
Fokker Pursuit, Model PW-7.
In August, 1922, the Air Service placed a contract with Anthony H. G. Fokker of Holland
for the design and construction of three experimental single-seater pursuit airplanes mounting
Curtiss D-12 aircraft engines, these articles to be patterned after the Fokker design D-XI and
designated the Air Service Model PW-7. Special inducements were inserted in the contract to
promote performances .in excess of the specifications.
The first two 'planes completed on this contract were received at McCook Field in January
of the present year for inspection and test. Prior to delivery, one of these was extensively tested
at the Netherlands Aircraft factory, the Fokker establishment in Holland, in an effort to perfect
design and to obtain maximum performance. Completion of the third article is held in abeyance
pending incorporation of changes recommended by the Engineering Division as a result of tests on
fir st articles.
In general design, the PW-7 is a typical Fokker thick wing biplane incorporating continuous­spar
wings, steel fuselage structure, double cambered tail surfaces, and divided type landing gear.
Both wings are tapered, the upper being more than twice the area of the lower._ There is no di­hedral
but a large positive stagger which with the narrow chord lower wing affords excellent
vi sibility, The upper wing, a single unit carrying ailerons and fuel tanks, is suspended above the
fu selage by two short N -struts from top longeron s and by two long struts from lower longerons
at the points of attachment of the landing gear. The lower wing is clamped to horizontal members
of the fuselage, the spars continuing thru the structure.
The tail planes follow the usual Fokker shape. small yet adequate. A double camber sec­tion
is used for the horizontal surfaces. Both stabilizer and vertical fin are adjustable on the
ground, the setting of the stabilizer being effected by means of a special clamp fitting at its lead­ing
edge, whereby the whole surface is pivoted upon the rear spar which is hinged to the tail
post. The elevator and rudder have balanced surfaces.
The welded-tube fuselage which appears wider than necessary in this type of 'plane encloses
a very accessible and commodious cockpit that affords much comfort and good visibility for the
pilot. The structure, itself, is rectangular in sh ape with its maximum cross-section 3' 1" wic;le
by 2' 10" deep, not including a 10-inch curved top, the whole consisting of welded steel tubing
braced with wire and covered with fabric except for the aluminum engine cowling. This cowling
is quickly detachable by simply removing the steel pins which lock the long brass rod hinges, and
when thus removed it exposes a simple engine mount which affords excellent accessibility to the
power plant.
The PW-7 is equipped with a two-wheeled, floating axle, divided type all-metal landing gear
carrying 28x4 straight-side wheels and tires and a rubber cord shock absorber. The tread is
5' 2-1 / 2". The braking device consists of a combination wood and metal tail skid of the non­steerable
type.
Propulsion is furnished by a low compression 375-h. p. Curtiss D-12 engine driving a Hugo
Heine 8-foot propeller fitted with spinner. The engine accessories are unusually accessible. The
oil is carried in a IO-gallon tank underneath engine, so placed that its corrugated bottom is cooled
by the slipstream.. Fuel is supplied to carburetors, two Strom.berg NA Y-5, by a combination
pressure and gravity system from three crash-proof 22.4-gallon tanks in the upper wing and a 36.2-
gallon tank in the fuselage. The fuselage tank and gear fuel pump were removed before flight
tes~ Ignition is furnished by two Splitdorf Type SS-12 magnetos. ' .
Cooling is effected-by means of two retractable honeycomib-type side radiators which when ·
fully extended project about 10 inches on each side of fuselage at rear of firewall. These radiators
operate _on rollers in . V tracks at top and bottom and are retracted by means of bevel gears
ope~ating right and left-hand worm shafts. The system is of the closed type and has a total cool­ing
sm face of 260 sq. ft.
18 T E C H N I C A L B U L L E T I N N o. 3 8
The principal characteri stics of the PvV-7 and summary of performances of the model with
plywood wings are given in the following tables :
CHARACTERISTICS AND PERFORMANCE.
(Fokker PW-7- Plywood Wings)
DIMENSIONS.
Overall span ( incl. balance) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39' 10"
Overall length ........... ... . .... ......... . ........ .. ..... . .. . .. 23' 11"
Overall height ............. . ... . . . ; . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9' 4"
Airfoil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fokker
Dihedral .. .............. · .......... . . .. . . . .... ... .... ... ... .... None
Gap . .. . . .... . ... .. .. .. ..... . ... .. ...... : . . . . . . . . . . . . . . . . . . . . . 4' 0"
Stagger ........ , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3' 0"
Sweepback.,. ............................ . ......... .... . ......... Tapered
Wing span (upper) .. ... . . ...... ... . ... . . .. . . . . . . . .. .. . ........ . 38' 4"
Wing span '(lower ( .· .. . ......... .. . ... ...... ; . . . . . . . . . . . . . . . . . . . 19' 9"
Wing chord- (upper) root to toip .. .. ........... .. ............... 71" to 40"
Wing chord-(lower ) root to tip . . .... ... . . ... ... .. .......... . .... 40" to 260"
AREAS I N SQUARE FEET.
Tbtal supporting surface ( incl. ailerons) ... . . . .... . ...... . .. . .. .
Upper wing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186.6
Lower wing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Ai lerons (two) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.8
E!evator (incl. bal. area 1.10 sq. ft .) .... . ....................... . . .
Fin ..... . .............. . ...... . . ....... .... ... .. . ........ .... .
Rudder ( incl. bal. area 1.52 sq. ft.) .. .... .. ... . . ... .. . . .. .... .. . .. .
Stabili zer ..... .. ............. . . ....... . . ...... ... ..... . .. . .... .
WEIGHT I N POUNDS.
250.4
13.6
1.14
10
12.2
Empty ( incl. water) . ... ...... · . . . . .. . ... . .......... .. ..... . . .... 2271
Useful load ............ . ..... .. .... . ... . . ... . . . .... . .......... 905
Ci;ew . . ........... ..... . . . ... . .. .. .. . . . . . .. ... .... ... 180
Armament . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
.Fuel ( 66 gal. ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 390
Oil ( 10 gal. ) ... . .. . .. . ........ . . , . . . . . . . . . . . . . . . . . . . . 75
Gross we:ght .. .. ....... .. .. . ......... . ... . ............. .. ... ... 3176
vVeight per sg. ft. !=!f supporting surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.7
Weight per horsepower ( Est. 440@2380r. p. rn. ) . . . . . . . . . . . . . . . . . . . . 7.22
*PERFORM ANGE .
... '
CLIMB SPEED Standard
A ltitude
in F eet
Time
in n-iin.
Rate
.ft./ nii'II.
Engine
r. p. m.
L evel Flight E 11gi11e
0
6,500
10,000
15,000
20,000
20,700 S. C.
22.000 A. C.
4.5
7.8
14.7
30.5
35
1690
1190
925
540
155
100
0
2120
2055
2010
1945
1855
1840
1810
'In. p. h.
151.1
148.2
144.8
136.3
118.8
11 4.5
95.7
Endurance at 10,000 feet. ... . ... ... . ......... 2 hr. 25 min.
Minimum speed at sea level. ... . ..... . .... .... 70 rn. p. h.
*This performance was obtained with Curtiss climbing ·propeller.
I r . p. m . . ·1--~11~--
11 ~i~~ 1995
I 1965
i 1810
•
A IR C R A FT D E V E L OP. 1 E ;(T
FOKKER PURSUIT, MODEL PW-7 (Plywood Wings)
(Curtiss "D-12" 3 75 - h. p . Eng ine.)
.19 •
,,,
20 T E C H N I C A L i3 U L L E T I N N o. 3 8
The. following summary gives a consensus of the, flying qualities of this airplane as deduced ' ...,
from the pilots' observations, namely:
Taxying: The PW-7 does not taxi easily, chiefly on accou,nt of a non-steerable tail skid and a
rather heavy tail structure.
Take-off: Take-off is steady and easy but requires a long run as 'plane is slow in gathering speed.
Lauding: The 'plane has tendency to hover for considerable distance in landing unless brought in ·
very slowly. Tail is difficult to force down for a three-point landing unless fully loaded, a
condition probably due to insufficient elevator surface.
Stability: It is sufficiently stable laterally, directionally and longitudinally altho stabilizer is not ad-justable
in flight. ·
J,fa,11 euvera.bility: Ailerons and rudder surfaces are satisfactory. The elevator, however, appears
to be ineffective in take-off or in landing. The 'plane is very light on all controls, and it,
manueverability in the air is excellent. Despite this favorable showing, severe wing fluttu
developed at extremely high speeds after only fourteen hours' of flying.
Visibility: This feature is excellent for all purposes.
Maintenance: On the whole, maintenance is poor, due to weak construction of tail skid, landing gear,
and struts and also to the absence of varnish or other protection to wood on inside of wings.
, Adaptability: Altho there are several commendable features about this pursl}it 'plane such as visi­bility
and maneuverability in the air, it is thought that these are greatly outweighed by the
less desirable ones.
This aitplane is designed to permit the installation of radio and photographic apparatus in
addition to the regular equipment carried on pursuit airplanes. Provision is also made for attach-ing
bomb racks to carry either light bombs or a detachable fuel tank. . ' · ·
The two PW-7's at McCook Field are identical in construction except for the wings, one
'plane being equipped with plywood-covered wings braced by V-shaped metal interplane struts and
the other with fabric-covered wings using N -shaped metal interplane struts.
BOMBARDMENT
New Long Distance Bomber.
The Engineering Division has initiated preliminary designs for a large night bombardment
airplane utilizing a centralized power plant. The general design embodies a single-bay, external­ly-
braced biplane with an exceptionally long fuselage and a semi-biplane tail. The proposed
bomber will have a wing span of 133 feet, an overall length of 85 feet, and a wing area of 4,000
square feet, all of which make it larger dimensionally than the Barling Bomber. The centralized
power plant will consist of four Liberty "12" engines driving a single 22-foot two-bladed pro­peller
by means of a power transmission which permits the cutting-out of one or more engines
as desired. '
The structural arrangement of the wing cellule and landing gear will be similar to that used on
the Douglas World Cruiser which employs a large upper center section, lower wing stubs, and
a wide-tread split-type landing gear. The chassis will consist of two units or trucks similar to
those used on the Barling except that each truck will be equipped with two wheels instead of
four, the rear wheel being rigidly attached to the "V" struts and provided with a brake and
the front wheel suspended forward by radius ro.i;ls and connected with lower front wing spar by
means of oil dash-pots to absorb shock~ The size of the wheels and tires will be 64x14 inches,
the largest yet developed (see page 72). Side bracing will be furni shed by diagonal struts to
lower longerons.
A crew of seven will be carried as follows: two pilots located aft of e11gine room; three
gunners, two in upper wing turrets and one in tail, an engineer and a navigator.
Al tho the aggregate horsepower will be 800 less than that of the Barling Bomber,· the new
bomber will have much less parasite area and be capable of carrying the same bomb load with the
same endurance.
AIRCRAFT DEVELOPMENT
OBSERVATION
21
Experimentation with DH-4B.
As cited in previous issues of Technical Bulletin, the DH-4B airplane is being used as a
vehicle for extensive experimentation on various types of engines, power plant accessories and
other equipment in determining their feasibility for aircraft use.
The installation of an inverted Liberty engine in a modified DH-4B has been very SUCCe!>sful
both with respect to the operation of the engine and to the performance of the airplane. Perhaps,
the greatest advantage attributable to this installation is the marked increase in visibility forward
which not only simplifies the landing problem but greatly faci litates maneuvering in combat. An­other
great advantage lies in t11e simplification of the fuel system ·which can be operated by grav­ity.
Accessibility of the engine is also much improved by the inverted position.
From a design standpoint, it appears that the Liberty engine is peculiarly adaptable for in­verted
operation due to the fact that its cylinders project for quite a distance into the crankcase.
When the engine is inverted· the
upper half of the crankcase be­comes
an oil sump and the lower
merely a b~aring support and
cover. The changes made in the
engine were all of a minor nature,
involving principally the oiling
system. The flow of oil was
faci litated in several ways, name­ly;
by drilling y,i-inch holes in
the upper crankcase webs, by
employing a gear-type fuel pump
to drain the camshaft housings,
by rearranging the passages in
suction-side of oil pump so that
the oil thrown off from the con­necting
rods and main bearings
and collected in the crankcase
could be conducted to the
scavengi.ng pumps, and by fitting
oil-tight adapters in the dis­tributor
heads. No changes were
made in the pistons or difficulty
experienced with_ spark plugs
INVERTED LIBERTY INSTALLATION IN DH-48 fouling, due to position of the
cylinders.
Standard US-52 Zenith carburetors were used in conjunction with inverted manifolds. Prac­tically
the only change made in the cooling system was the reversal in the direction of the flow
of water which apparently improved the cooling.
The success of this experiment has resulted in the design and construction of two experi­mental
observation airplanes mounting inverted Liberty engines.
Another recent experiment involving the Liberty engine is the installation of the two-speed
gean;d Liberty in a standard DH-4B equipped with side supercharger, a four-bladed 12-foot pro­peller
designed to turn at 700 r. p. m. at ground, and an extra high landing gear. Several suc­cessful
flights have been made.
Cooling performances on DH-4B equipped with wing surface radiators similar to those used
on the Curtiss pursuit have so far proved very unsatisfactory. From present indications, it is
doubtful whether this type of radiator will be satisfactory on these airplanes. Speed tests are to
be run on a DH-4B using standard wings and underslung radiator.
An airplane of this type was provided with a special tubular steel engine mounting, metal
cowling and propeller spinner as shown in Techrμcal Bulletin Na. 37 in order to obtain flight char-
' r
22 T E C H N I ,C A L B U L L E T I N .N o. 3 8
acteristics and comparative perfort11ances on two air-cooled radial engines, <the 14-cylinder, 325-h.
p. Siddeley '''Jaguar" (British} and the 9-cylinder 350-h. p. Wright R-1. The relative flight per­formances
of these engines as mounted in the DH-4B apparently favor the Wr'ight engine which
gave a high speed of 11\56 m. p. h. at 1683 r. p. m. over the speed course as against 111.9 m.
p. h. at 1520 r.p.m. for the Siddeley "Jaguar." .
From the following table, it may be seen that the performance of the Wright R-1 engine in
flight compares favorably with that of the Liberty in a standard DH-4, due allowance being made
for differences in weight1 and propellers.
COMPARATIVE RATES OF CLIMB.
Altitude
0
6,500
10,000
15,000
Service ceiling
Absolute ceiling
WRIGHT ENGINE IN DH-4.
Altitude Engine
ft. r. p. ni.
0 1683
, 6,600 1635
11,700 1595
14,500 1575
17,000 S. C. 1535
Wright "R-1"
ft .jmin.
1410
730
490
207
17,000 feet
19,000 feet-
SPEED IN LEVEL FLIGHT.
Airs_peed
m: p. h.
115.6
113.5
90.7
87.6
79.8
LIBERTY
Altitude
ft.
0
6,500
10,000
15,000
17,600 A. C.
Liberty "12"
ft. / min.
1000
630
430
145
15,800 feet
17,600 feet
E NGINE IN DH-4.
Engine
r.p.m.
1700
1647
1607
1530
1475
Airspeed
1n. p. h.
123.7
120.3
116.5
106.0
86.0
The fig~res given in the above tables are approximately correct, and inasmuch as the Wright
engine is still in an experimental stage, its performa~ce can μndoubtedly be improved,
Progress on DH-4M and DH-4M-1.
Considerable experimentation is being done by the Engi11eering Division in c~'nnection with
the new DH-4M and DH-4M-1 airplanes under construction by the Boeing Airplane Company,
Seattle, ·washington. This work involves engineering supervision over four contracts as dis­cussed
in Technical Bulletin Na. 36. These contracts are listed below in chronological order:
Contract No. 625-11hree experimental DH-4M's.
A. S. Orde~ 1173-23-Fifty production DH-4M's.
A. S. Order 1403-24-0ne hundred production DH-41VI-l's.
A. S. Order 1441-24- Experimental wings and chassis for DH-4M-1.
All three DH-4M airplaT\eS on first contract have been completed, the first being static tested
at the factory and the other two flight-tested by Engineering Division pilots at the Sand Point
Airdrome near Seattle. One of.t.lie Jatter 'planes has been received at McCook Field for further
tests.
. .. !: ,.· '., !'. .
Work on the secom! cpptri'i\Ct (A. S. Order 1173-23) for fifty production DH-4M's 1s near­ing
completion. These airplanes are modernized DH-4's utilizing standard DH-4 and DR-4B
wings with tubular steel fuselages and increased fuel capacity.
The third contract (A. S., Order 1403-24) which is nicely under way necessitates considerable
experimentation and numerous tests on the part of the ~ngineering Division due to the fact that
this contract involves the construction of practically new airplanes altho parts of old DH-4's a.nd
DH-4B's are utilized insofar as their use is applicable. Inasmuch as the fourth contract (A. S.
Order 1441-24) is complimental to the third in that it involves the c;onstruction of three sets of
wings and landing gears .embody.ing the design proposed by the Boeing Company for use on the
DH-4M-1, both contracts · will be discussed together.
AIRCRAFT DEVELOPMENT 23
The experimental wings submitted by Boeing on A. S. Order 144"1-24 embody a two-bay ex­ternall
y-braced biplane cellule consisting of uppe·r and lower panels of Gottingen No. 436 thick
section and a center section containing two 55-gallon fuel tanks. 011e set of wings was mounted
upon a new DH-4M-l fuselage constructed under A. S. Order 1403-24 for static tests at Mc­Cook
Field. The wings proved satisfactory for all loadings i~ low and high incidence and in re­\'
erse position. Another set of experimental wings was installed on the second DH-4M-1 air­plane
produced by Boeing and flight-tested by an E ngineerihg Division pilot at Seattle, and later
at McCook F ield. The third set of wings was retained by contractor for use as a production model.
The ex]?erimental landing gears which accompanied· the wings on A. S. Order 1441-24 were
subj ected to impact tests. This chassis, a tubular steel strut structure with a split or di vided axle
having a tread of 120 inches, was under-strength, having failed under a 30-inch drop with one­half
load (2450 pounds). The requirement in this in stance specifies a drop of 42 inches without
failure.
In view of the above tests and other considerations, the Chief bf Air Service decided that the
thick wings with fuel tanks in upper cerit~r section, as designed by the Boeing Company, will not-­be
used on the DH -4M-l's on A. S. Ordh 1403-24. Three other major changes are covered by
this order, namely; first, return to standard DH-4B landing gear; second, installation of crashproof
main fuel tanks of a capacity of approximately 82 gallons capacity with plain gravity tank; and
third, the use of standard DH-4B wings. \ i\Tith the exception of thes~ 'changes, the airplanes will
be constructed as originally specified, that is, with new pilot's seat, 14-gallon oil tank, K-3 camera
installation, single .30 caliber machine gun and new compact in strument board with bumper pad to
protect pilot's head. ·
Production Foi\ker C0-4.
One of the five production Fokker C0-4 ohservation airplanes recently delivered to Langley
Field from the Netherlands Aircraft Company of Holland has been received at McCook Field for
~xperi~1ef!taJ puq?oses. Included _in the shipment are sever~] experimental part_s used by Fo!f~er
111 test11Jg these aJrplanes, _who claims that the new lower wmg mcluded therem ·together , with
chaIJg~s in setting of present upper wing will effect a considerable increase in speed. The alter­nate
parts include a new lower wing with decreased chord, a set of N struts, one set each of
large and small size Fokker type ailerons, two Fokker type rudders ( one of 25 per cent larger
area than the other), and a new cowling complete with supports, utili zing a spinner which some­what
changes the appearance of the nose. ·
This airplane which is equipped with side radiators similar to those usecf ~-; -the experimental
model as shown in T echnical Bulletin No. 37, was assembled and erected for flight. · The average
timed speed, using· duralumin propeller with blade angle set at 18.50° at 48-inch radius, was
.135.7 rn. p. h. at 1725 r. p. m. (observed) with side radiators one-fourth exposed, and 129.2 m.
p. h. at 1710 r. p. m. ( observed) with side radiators full out. Tests will be continued to obtain
performances with the new short-chord _wing, cowling and propeller.
TRAINING
Huff-Daland TW-5.
During preliminary flight tests at McCook Fie!?, the first TW-5 airplane built for the_ A'ir
Service by H uff, Daland and Company, Inc., of Ogdensburg, N. Y., developed struc,tural weak­nesses
in the engine and radiator mountings, due to excessive vibration of the engine, a vVright
Model E of 180 horsepower.
1 The Division proceeded to overcome this defect by welding in additional members at rear of
engine bearers and by providing greater rigidity in the radiator bracing, which changes were ap­plied
to the fir st, article only. Meanwhile the contractor designed and constructed <l V ~brace which
could be bolted in place without further modification for incorporation in the four remaining
TW-S's on this contract, all of which have been completed and deli vered to Brooks Field for
service test.
Vought with Detachable-blade Propeller.
Two Vought VE-9 advanced training 'planes recently delivered to the Division have been in­spected
in accordance with instructions receive_.9 from Chief of Air Service.
24 T E C H N I C A L B U L L E T I N N o. 3 8
Several types of detachable-blade micarta propellers fitted to a Vought 'plane for comparative
flight tests gave highly satisfactory results. · The use of this type of propeller materially improved
the performance, a high speed of 128.5 m. p. h. at 2080 r. p. m. being attained with a blade pitch
setting of 13.9. The rate of climb with the micarta propeller was 1053 feet per minute at approxi­mately
5,000 feet altitude as against a rate of climb of 950 feet per minute for the standard wooden
propeller.
MISCELLANEOUS PROJECTS
L. W. F. Transport T-3.
Transport, model T-3, a large, single Liberty-engined biplane designed and built for the Air
Service by the L-W-F Engineering Company, Inc., of New York, was flown to this station in
January for test. This 'plan~, the first of ten to _be. completed, weighed ?,316 pounds or 546
pounds over the designed weight, thereby necess1tatmg several changes to lighten structure before
flight.
In a preliminary flight, this airplane loaded to a gross weight of approximately 6,180 lb. and
fitted with a duralumin propeller attained a high speed of 99.78 m. p. h. at 1675 r. p. m. over
speed course. In a subsequent flight for climb with a special propeller designed by the Division,
the following performances were obtained :
Rate of climb at zero altitude..... . ........................... 315 ft. / min.
Service ceiling . . ............ . ........ . ... . ,. . . . . . . . . . . . . . . . . . 6,150 ft.
Absolute ceiling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9,000 ft.
Actual altitude reached during flight. . . . . . . . . . . . . . . . . . . . . . . . . . . 8,600 ft.
Since this airplane does not conform to the specifications in several respects, the Division is
contemplating certain corrective measures for incorporation in the remaining articles on this con­tract.
Meanwhile the contractor's plant has been closed for an indefinite period.
Variable Camber Airf~il.
The study of a variable camber airfoil with a single rear flap has been instituted. From a
preliminary examination it appears that this device, though somewhat difficult to produce mechanic­ally,
would decrease the landing speed and therefore, be most useful on heavily loaded airplanes
equipped with supercharger.
Propeller Development.
Micarta.-Ten detachable-blade mjcarta propellers similar to that used on the Vought airplane
mentioned above, have been built and assembled at McCook Field for distribution to the Service
for use on VE-7 and JN-4H airplanes equipped with 180-h. p. Wright engines.
The performance of the JN-4H showed marked improvement with the use of this type of pro­peller
which weighs about 78 pounds. The high speed and ceiling which are normally about 89 m.
p. h. and 13,500 feet with standard wooden propeller were increased to 92.1 m. p. h. and 15,200
feet, respectively, with the micarta propeller. With the Curtiss-Reed duralumin propeller, the speed
and ceiling of this same airplane were increased to 92.8 m. p: h. and 14,000 feet, respectively.
The blade angles of the micarta propeller may be adjusted on the ground to allow the engine
to turn at any desired r. p. m. The blades are so constructed that they 11¥lY be .easily replaced in
case of breakage, the time consumed in replacing a pair of blades being less than than that re­quired
to "hub," "track," and balance a standard wooden propeller. The micarta blades are also
balanced against the standard wooden propeller blades and may also be used interchangeably, a prac­tice
that has proved very success.ful in the manufacture of micarta propellers.
Supercharger Propeller Research.-Three geometrically similar propellers for use on DH-4B
airplane with the Liberty engine and the 20,000-fout side supercharger have been designed by the
Division for the purpose of studying their characteristics as to speed and climb at altitudes of ten.
fifteen and twenty thousand feet, respectively.
AIRCRAFT DEVELOPMENT 25
Comparative tests are made by supercharging to ground conditions up to the respective alti­tude
for which each propeller is designed in order to determine what propeller gives the most
efficient performance under the conditions specified. These tests will be extended to include a
series of climbing propellers to discover whether there will be any advantage in designing them
especially for climbing purposes.
AIRSHIPS AND BALLOONS
Progress on RS-1 Airship.
Design and construction on the Army's new semi-rigid airship RS-1 which is scheduled for
delivery in June, 1924, is proceeding satisfactorily at the plant of the Goodyear Tire and Rubber
Company, Akron, Ohio. Designs for control surfaces and power units have been approved for
production. Fabrication of all keel members has been finished with the exception of six trans­'
versals. Twenty-four of the twenty-seven sections of the keel walk-way have been completed
also. Four designs for the nose cone structure have been submitted. Layouts and working draw­ings
for the control car and its equipment have been completed as well as the layout for the in­terstructure
and connections of the power cars. Work has been started on the six 270-gallon fuel
tanks and their suspending structure. The design for the fixed surfaces and the method of support
to the envelope are undergoing investigation Tests are being made to determine the feasibility of
using wires insteads of beams
Structural details of this airship have been forwarded to the National Advisory Committee for
Aeronautics at Washington for consideration. The Committee contemplates a series of flight tests
as a check upon the design as soon as the RS-1 is placed in commission.
In connection with the recent escape of the Navy rigid airship "Shenandoah" from its moor­ing
mast at Lakehurst, New Jersey, and its miraculous ten-hour flight before being returned to its
hangar, it seems pertinent to remark that the Army semi-rigid airship RS-1, now under con­struction
at Akron, Ohio, is designed to meet just such an exigency as the "Shenandoah" ex­perienced.
The mooring arrangement of the RS-1 is designed to resist a 70-m. p. h; wind with
a factor of safety of two, and is so arranged that the stresses are distributed thruout the keel and
envelope.
Progress on "TA" and "TC" Airships.
Engineering data and weight schedule on the "TA" airships recently manufactured and de­livered
by the Goodyear Tire and Rubber Company have been received by the Division for use
in compiling procurement data for the proposed purchase of three additional airships by the Chief
of Air Service.
Construction on the airship TC-4, 5, and 6, is proceeding satisfactorily at the factory, of Air­ships
Incorporated, Hammondsport, N. Y., under supervision of the Division, the TC-4 being
about ready for delivery. The Division is designing a propeller for use on the Lawrance J-1 air­cooled
engines of the TC-6 airship. These engines will be equipped with Bijur electric starters
and Type 1-L electric generators furnished by the Government. Special adapters are being de­signed
for attaching the generators.
Propellers for Zodiac Airship RN -1.
Action has been taken to design. and build two new ·propellers for use with Packard "lA-
1237" engines recently installed in Zodiac airship RN-1. These propellers will be designed to give
a maximum speed to the airship at full throttle of about 56.5 m. p. h. at 220 h. p., when turn­ing
at 1300 r. p. m. and are intended to replace those originally built for the Liberty "12" in~talla­tion
and subseqeuntly used in preliminary tests on the Packard engine after being equipped with
Packard hubs.
Barrage Balloon.
The experimental barrage balloon of 20,000 cubic feet capacity, designed and built by the En­gineering
D~vision for operation at 15,000 feet altitude, has been flown to an altitude of 3,500 feet
attached to a 5/ 16-inch .cable to determine the trim with present arrangement of patches and
suspension. In this test the balloon showed good stability but was "out of trim." It is now pro­posed
to determine definitely by means of water model tests the proper arrangement of patches and
suspensions, with lobes inflated, that _will produce correct trim. New lobes of larger capacity will
also be constructed to improve performance.
26 T E C H N I C A L B U L L E T I N N o. 3 8
This balloon is an adaptation of the Italian A-P ( Avorio-Prassone) observation balloon, the
lobes acting as receptacles fo~ gas that is automatically val ved from the balloon envelope as the
· pressure increases with temperature and altitude. This arrangement of placing the valves between
the envelope and the expansible lobes permits the gas to pass to and from the en velope thus main­taining
practically constant pressure in the balloon and precluding loss of gas and consequently loss
of lift. ·
A small portable winch adapted from the French design is under construction for handling the
b:trrage oalloon. The wi nch is to be driven by an ordinary four-cylinder Ford automobile engine
mounted upon .a two-wheeled t railer. In operation, the winch is securely staked to the ground.
The cable from the winch to the balloon is run along the ground for approximately a hundred
feet to an anchored swivel pdley over which it is passed.
Gypsy Moth Experiment.
The Department of Agriculture, Bure:tu of E:1tomology, has requested ~urther cooperation of /•
the Engineering Division in their efforts to check the spread of the Gypsy Moth in the New E ng->'
land States. A tentative design has been made of apparatus for attachment to TC airships, con­sisting
of a blower, an agitator, and a hopper, for scattering the insecticide. This equipment in ­volves
new hopper and blower units of greater ca pacity than those used on the U. S. l\L B. air­ship
in the experiments conducted last year. A tentative design was sent to the Department of
Agriculture for comment, and if satisfactory it will be developed full y. Meanwhile an estimate of
cost is being ma·de. It is proposed to utili ze the new two-cylinder gasoline engine designed for
the airship blower unit to operate the in secticide di stributor.
Liquid Manometers (Pioneer Ty~e.)
Two 10-inch liquid manometers, P ioneer T ype, were procured and fitted with a strip of lumin­ous
material 1/ 16-inch wide on the back of the tube for illuminating the liquid without the use
of individual clash lights. U pon drying, this material was covered with white enamel and then
with black shell ac, the enamel serving as a refl ec ting surface and the black shellac as an opaque
and kerosene-proof coating. The light from the luminous strip is visible above the liquid, but is
invisible below, clue to the opacity of the colored kerosene. The two altered in struments have been
sent ro Scott Field for service test s.
ARMAMENT
External Bomb Racks, Types B-3, C-3, and H-4.
The B-3 external bomb rack was designed and built by the Division to r eplace the old Ordnance
Mark XVI bomb rack. The new bomb rack is constructed entirely of metal and is capable of
carrying two 100-lb. or two 300-lb. demolition bombs. It incorporates a new arming mechani sm
and improved safety features not found in the earlier design. Experimental tests have been sati s­factory.
1'he C-3 external bomb rack which is designed for carrying one 600-lb. or one 1100-lb. demo­lition
bomb is a redesign of the old Ordnance Mark XIX bomb rack; incorporating metallic beams
to eliminate the rapid deterioration of the wood parts formerly used. The new rack is provided
with an improved arming mechanism identical to the one used on the T ype B-3 rack and other new
safety features. Functioning tests of the mecha ni sm have demonstrated that the rack is sati sfac­torv
for service use.
An external bomb rack, T ype H -4, designed and constructed by the Engineering Division for
carrying either the 2,000 or the 4,000-lb. bomb, is now ready for test. This rack which weighs
only 112 pounds complete for in stallation is built in accordance with standard factors of safety as
based on the large1· bomb load. as follows: a fac tor of seven for loading in normal position, a fac­tor
of three for for e-and-aft stress and a factor of two for side stress. The rack is also provided
with bearings to receive bomb hoist units. thus making it a combination bomb rack and bomb hoist.
Internal Bomb Racks, Types D-1 and G-5.
The D-1 internal bomb rack is the fir st bomb rack to be constructed with duralumin main
support member s. It weighs only 42 pounds rea dy for in stallation , yet it is capable of carrying
four 300-lb. bombs or two 600-lb. bombs or a combination of 100, 300. and 600-lb. · bombs. lt ,s
designed for standard factors of safety of 7, 3, and 2, respectively, with maximum load , -~he
strength of the rack having been proved by exten sive laboratory test s. A rack of this type has been
in stalled in redesigned Gallauclet DB-1 day bomber for carrying either six 100-lb. , two 300-lb., or
one 600-lb. bomb.
AIRCRAFT DEV EL OPMENT 27
Th~ Air Service recently received· fifty Type G-5 internal bomb racks that were constructed
by the Rock Island Arsenal for use in the new NBS-1 bombers now in service and in the three new
types of short distance night bombers now under construction and also for use in future bombing
'planes having an internal compartment for bombs. Both of the above racks are provided with
adapters for carrying external racks.
Bomb Shackle, Type B-4.
- · )
A Type B-4 bomb shackle was tested to determine its wearing qualities, and the force required
to release a 1100-lb. bomb. In these tests, the shackle was tripped fifty times before any appreci­.
able wear was noticable. A force varying from 7-1 / 2 to 8-1/2 pounds was required to release the
load. The tests were continued until the load had been tripped over one hundred times, the force re­quired
to release load gradually increasing to 20 pounds as the wear on sear increased.
This shackle is designed for use on B-3, C-3, D-1, G-4 and G-5 bomb racks. It is built entirely
of Air Service materials according to Air Service specifications, the arming mechani sm being incor­porated
as part of the shackle itself.
Bomb Hoists and Chests.
Two types of internal bomb hoists designated as the "C-1" and "C-2" for accommodating·
bombs weighing from 100 to 2000 pounds have been load tested. The hoist cables used in the test
have a strength factor equivalent to six, using the 1100-lb. bomb. Both slings have a factor of
safety in excess of seven for the same loading. The Type C-1 hoist, exclusive of cable, withstood
a loading of 14,600 pounds which corresponds to a factor of 13.5. Lack of available weight pre­vented
the test being carried to destruction. The Type C-2 hoist failed at a load of 14,680 pounds.
These two bomb hoists are practically identical in construction. The only difference is that the
C-2 hoist is provided with slots for connecting with the C-1 hoist so that bombs can be hoi sted into
both sides of the compartment simultaneously. These hoists were used successfully in the bomb­ing
maneuvers off Cape Hatteras last summer and are designed so as to be adaptable for both
·present and future usage.
A test made on the Type C-2 bomb hoist installed in a Martin bomber to determine the_ time
required to hoist a ?000-lb. bomb in place compared very favorably with the time requir,ed with
other types of bomb hoists. Six men, operating the hoist were able to hoist a 2000-lb. bomb in
position in five minutes, including the time required for adjusting the shackle and fu sing the bomb.
1'wo types of chests have been developed for holding and transporting these hoists and also
the external bomb hoist, Type E -1. These chests are now undergoing destructive tests and will be
placed in production. ·
Remote Trigger Cm;1trol for Browning (Type D-2.)
An improved tyP,e of Bowden contro1 for u se with the .30 cal. Browning gun when mounted
remotely, has been tested and found to be satisfactory. This device· is an improvement over previ­ous
model s, in that it can be operated in a line co-axial with the bore of the gun or at right angles
to it. This flexibility is necessary, due to the variation in differ; n} types of floor mounts.
EQUIPMENT
New Aircraft Storage Batteries.
The \!Villard Storage Battery Company have developed a new type of aircraft storage bat­tery
than can be shipped in a dry or unfilled condition. Upon adding the acid the battery is ready
fot μse, the initial current strength being about 60 per cent of the full charge. If the battery is
Jeff standing for five hours, the full charge can be obtained.
Laboratory tests on the Exide Type' TC-11 storage batteries have disclosed repeated low ca­pacities.
The cause of the trouble is attributt+d to the lead-active_ material on the negative plate
comipg loose from the grid.
28 TECHN I CAL BULLET I N No. 38
Engine Starters.
Three new Bijur starters with hand-cranking devices have been tested with satisfactory results.
After the engine tests are completed, one of these devices will be installed in a:n airplane for ser­vice
test. Tests are also in progress on hand-crank starters manufactured by the Curtiss and Aero­ma
rine Companies.
Efficiency tests have been made on ne'w Westinghouse and Aeromarine electric starters.
New Instruments.
Twenty new airspeed meters, Model 1923, have been receiYed. Ten of these will be reserved
for use on the new Airways in strument boards which are under construction. T he new meters are
of the vertical strai ght-scale type.
Five hydrostatic gasoline gages manufactured by the Cox-Klemin Aircraft Corporation have
been received for test. Two of these are designed for in stallation in fuel tanks-having a 20-inch -J
depth and three for tanks having a 40-inch depth.
Two Stover-Lang electric chronometric tachometers have been installed in airplanes, one for
Airways test and the other for navigation purposes.
A sample pyrometer, range 400 degrees, received from the Bristol Company, E ngland, is tm­dergoing
laboratory test. T his instrument is used on air-cooled ~ngines to measure the tempera­ture
of the cylinder wall.
Navigation Calculators.
Ten navigation calculators were received from the P ioneer . Instrument Company. This in­strument
aids in solving the "wind star" after two courses have been flown and the -drifts along
each determined. After the velocity and direction of the wind have been found by plotting the
wind vectors, the ground speed and heading for any course become known. The in strument is
only semi-automatic and presents some difficul ties in operation, especially during cold weather
when the navigator must wear gloves. This calculator is, however, more satisfactory than the
circular type of "wind star" computer heretofore used.
New Airways Padded Instrument Board.
The first model of padded compact in strument boards for in stallation in Airway airplanes has
been received. T his board, ten of which have been ordered, is equipped with the new-Iy developed
vertical straight-scale in struments and the new se lf -locking clock-mount.
It is proposed to in stall this type of instrument board on Airways 'planes and on the new
DH-41\1 and DH-4M-l's under construction by Boeing.
AIRWAYS PADDED INSTRUMENT BOARD, MODEL 1924.
AIRCRAFT DEVELOPMENT 29
rding Manometers (Low Pressure Type)
Two low pressure recording manometers have been received from the Pioneer Instrument
mpany also. This manometer has a range from O to 3 inches ·of water pressure and is designed
or use on lighter-than-air craft to record the gas pressure. The pressure element is a slack
her diaphragm actuating the recording mechanism by a simple linkage. Upon test this instru­t
has exceeded its performance specification.
A recording tachometer, designed and built for use in flight research, was tested in a DH-4B
lane with satisfactory results. It is planned to use this device for recording engine r. p. m. in
formance testing .
. The first model of a hand-operatel tachometer test-stand has been completed and tested. This
t-stand is intended for use in stockrooms where there is only an occasional demand for check­ing
up tachometers. It is a modifi c::ation of a standard hand-grinding machine adapted for compar­ing
a tachometer with the standard chronometric tachometer. Arrangements will be made to place
these stands in the Service. ·
gand Meterograph (German).
A \i\Tigand meteorograph, an instrument that automatically records pressure, temperature an<l
idity of the air, and absolute speed of the airplane, has been received from Germany. All
rds are made on a single sheet of smoked paper which is carried on a slowly revolving drum.
h stylus moves in a straight line. The press ·1re element has a range equivalent to 11,000 feet.
e temperature element is operated by a bimetalLc spiral, the humidity element by a band of hairs
and the speed element by a fan. The whole mech:rnism is enclosed in an aluminum streamline
case.
ight Flying Equipment.
Photometric tests in the laboratory on the new Model 1924 airplane landing lights have given
:very gratifying results. These lights were built at McCook Field and have been painted and in­stalled
on a night flying airplane for test. New lamps and reflectors that are 100 per cent more
efficient than the ones formerly used are under development for use in the new landing lights. · The
Jamps, which are to be known as Type G-25 and designed to operate on a 12-volt current of 20, 25,
Jnd 30 amperes, are being made by the Edison and ·westinghouse Lamp Companies. They will
have the same light center dimensions as the present lamps and in addition U-shaped filaments
dUOunted for hori zontal burning.
Four 36-inch high intensity arc searchlights of the General Electric type, have been com­pletely
remodeled for use as combination revolving beacons and field flood lights. This includes
the installation of a new lamp mot1nting, diverging doors and revolving mechanism. Complete
photographs of the remodeled lights have been taken for future reference and use in compiling
operating· in structions.
Night observation flights were made by the Division to obtain data on the spread beam of·
1he Army 36-inch searchlight for comparison with the new spread-lens searchlight beam developed
by the Benard, Barbier and Turenne Company. The McCook Field illuminated wind cone was
lllso observed during these flights with the result that several alterations will be made to improve
its usefulness.
:'lbe T 1 Aircraft Camera and Transforming Printer.
The Air Service T-1 aircraft camera was designed and developed by the Engineering Division
for the purpose of obtaining a series of overlapping photographs for use in military reconnaissance
m in making aerial maps. It is fitted with three lenses for taking pictures simultaneously; hence .
F-is frequently called the Bagley "Tri-lens" camera after its designer. The pictures are made
upon a roll of film having a capacity of 190 exposures which are sufficient to photograph a strip of
30 1' E C H N I C A L B U L L E T I N N o. 3 8
terrain 9 miles wide and 190 miles long at an elevation of 15 .000 feet with overlaps of 60 per cent.
This amount of overlap is very necessary in aerial photography for mapping purposes for three
reasons: first, to provide stereoscopic areas in the photographs; second, to establi sh positions for
secondary co11trol points, and third , to offset loss in definition of details due to unfavorable light
reflections at certain angles of view. In photographic flights it therefore follows that the ,,·idth
of terrain photographed at any chosen elevation is practically equal to three times that elevation
and the length one-third that elevation multiplied by 190. the exposure capacity of the film.
~,,
1
T-1 CAMERA (Bagley Tri-lens) WITH GIMBAL MOUNT.
The camera proper consists of two main parts, a base and a film magazine. The base is
divided into three compartments or focal chambers. A. B, and C. each of which is fitted with a
lens and a_ foca l-plane plate of thin glass. The compartment letter and tl~e number of the camera
are etched on each plate, thus formi ng a stencil that automatically lab~ls each negative. In the
focal plane of the center compartment two bubble levels are placed at right angles with each other
so that their images are registered on the center or "B" negative. The lenses, three in all. are
mounted with "between-lens" automatic shutters which are released simultaneous! y by a three­pronged
plunger. The focal length of the center lens is about 6-1 / 2 inches and that of each siclt
lens 7-1 / 2 inches, the focal lengths of the latter being carefully matched. Each lens is also
equipped with a disk-shaped color screen -placed between its front element :::nd the shutter. The
optical axis of the center lens is practically vertical whereas the optical axes of the side lens are in­clined
35° toward that of the center lens, this arrangement giving an angular scope of 120° for
the camera. The base is also fitted with a marker, actuated by the release plunger, to automatically
mark the film at the mid-point between sets of negatives taken at each exposure.
AIRCRAFT DEV ELOPMENT 31
ARRANGEJ\:1ENT OF LENSES IN T-_l CAMERA.
MAGAZINE WITH WINDOW CAP AND CENTER PRESSURE-PLATE REMOVED.
32 T E C H.N I C A L B U L L E T I N N o. 3 8
The magazine accommodates a single roll of film 6 inches wide and 380 feet long which is
drawn thru the camera by means of a hand crank, the path of the film being indicated by a heavy
white arrowed line on the outside of the case. The film is carried on two spools revolving in seats,
being wound from one to the other by a crank. The amount .of film required for each exposure is
indicated by a dial attached to the winding spool and actuated by a sharp-toothed wheel which
bears against the film . One revolution of the dial releases the length of film necessary for one ex­posure.
The film is held against the focal planes by three cloth-faced pressure plates. Rollers
are placed at all points where the film turns in its course thru the camera.
RELEASE MECHANISM FOR T-1 CAMERA,
For convenience in
manipulating
the camera, the top of
the magazine is pro­vided
with a leather
handle and two bub- ~
ble-levels placed in
the form of a letter
T. The bubbles on
top of camera are ad­justed
to accord with
those in the center
focal plane.
The release mech­anism
that operates
the shutters is a sep­arate
unit consisting
of a lever, a counter,
a plunger, and a stop
watch, mounted on a
metal plate for at­tachment
to the right­hand
side of the ob­server's
cockpit. A
flexible encased cable
connects the release
mechanism with the
camera.
The camera is supported in the airplane by an adjustable mount consisting of a gimbal frame
trunnioned to circular metallic guide arms which terminate in soft rubber cushions which, in turn,
rest on the clamping posts. The mount permits the camera to be adjusted for level position and
rotated about its vertical axis to compensate for "crab" of the airplane.
Ordinarily the camera is mounted in the airplane in a vertical position for mapping and r~­connaissance
purposes. However, it may be used as a hand-held camera in taking bird's-eye views
of large areas provided it is mounted so as to obtain an unobstructed view of the landscape.
Present photographic airplanes however are not designed for the latter purpose.
The Air Service standard view finder, which is used with both the T-1 and the K-1 camera.
is fitted with plates of ground glass labeled according to the type of camera with which they are to
be used. Plates for the T-1 camera are ruled with transverse Jines 2-3/ 4 inches apart. These
lines are so spaced as to indicate the correct exposure interval between consecutive negatives in
order to give the necessary 60 per cent overlap which must be allowed in all aerial photographs in­tended
for mapping purposes. Longitudinal lines are also ruled on the ground glass one-half inch
apart and a cross indicates the center of the field of vision.
Extreme care is necessary in handling the hypersensitive film that is used in the T-1 camera.
It is so sensitive that opening of the film container and loading of the c:imera must be clone in to­tal
darkness, all light-red or green included-being unsafe. Loading or unloading the camera
in daylight may result in fogging.
'
AIRCRAF T DEVELOPMENT 33
T-1 CAMERA AS INSTALLED IN DH-4B-P-1 AIRPLANE.
Preparatory to making aerial photographs, to be used in mapping it is first necessary to make
a trial flight OYer the course to determine the exposure interval and the "crab" of the airplane.
The exposure intern! is found by noting the ti me required for an image of some obj ect on the
ground to travel the di stance between the two tran sverse lines on the ground glass of the view
finder. The amount of compensation allowed for "crabbing '' is determined by rotating the view t
finder about its optical axis until images of ground objects travel parallel to the longitudinal lines
on the ground glass, that is, in the direction of flight. If no "crab" is to be given to the camera,
its position when squared with respect to view find er is the proper position in which photographs
are to be taken. After this is accomplished, the actual photographic flight is made.
With film in place, the taking of photographs consists in simply leveling the camera and
th rowing the release mechanism to make an exposure. After each exposure, the cycle of opera­tions
recurs as follows: F irst, exposed section of film is wound off as indicated by one revolution
of dial; second. the camera is kept level as indicated by bubble levels on top of case; third, ex­posure
is made by throwing shutter release lever when stop watch indicates the proper instant as
pre-determined in trial flight. The pilot who is r esponsible fo r following the course, signals the
operator about one minqte before reaching the starting point and again signals to cease photo­graphing
as soon as the border of area is passed. The observer may sometimes determine when
to stop photographing by obser ving the number of exposures that have been nnde.
In order to make use of photographs taken with the T-1 camera it is necessary to project the
obl ique negatiYes thru the required ::tnglc to bring them into the same plane with the negative
made by the center lens. To accompli sh this a t ransforming printer is required. The oblique pho­tographs.
labeled A and C, which have been transformed in the printer and the center lens photo­graph,
labeled B, can then be mounted and joined to form a single composite picture.
T he tran sfo rming printer and its accessories comprise several units including a metal ··box
fitted with lens, negative and paper holders, interior lamp, a shutter, brackets to support rolls of
34 TE CH N I CA L B U LL ET I N N o. 3 8
negatives, heat guards, a separately mounted electric-driven vacuum pump, an arc-light, diffu sing
glass and frame, a negative punch. three trimming templates, an inclination scale and a ruler­the
whole equipment being supplied in a wooden case 40-1 / 2 by 27-1 / 2 by 17 inches, weighing
264 pounds. The arc lamps with their stand, reflec tor, rheostat, wire and switch are supplied in a
separate box. Each transforming printer is adjusted for use with a particular and correspond­ing
camera, both printer and camera bearing the same serial number.
The printer box is rigidly made of duralumin so that it will withstand shocks incident to ship­ment
and use without becoming deranged in adjustment. The negative holder has a thin glass
focal-plane plate and a heavy glass door, the negative being held between them. T here is pro­vided
on the holder a small post over which the properly-punched negatives are slipped in order to
hold them in alignment during transformation. A vacuum-back is fitted to the photographic
paper holder in order to keep the sensitized paper fl at again st the plate in correct position for
printing. The vacuum is supplied by a small electric motor and an air pump mounted together
upon a thick board. The printer is fitted with a Protar lens having an aperhtre of f/ 18 and a ,
focal length of 7-1 / 2 inches. This lens is equipped with an iris diaphragm which gives a range
of stops from f / 18 to f/ 45. A shutter or Ulind is used to protect the sensitized paper in the
holder from light passing thru the lens. It acts automatically when the interior incandescent lamp
which is used to illuminate the negatives during adjustment, is switched on and off. Two spools
for holding rolls of negatives are rotated in their brackets by means of cranks and fr iction brakes
as tJ1e negatives are drawn before the lens.
The exposures are made by means of a double arc-lamp using either direct or alternafr1g cur­rent.
Light-diffusing glass is used to secure a proper gradation of illumination necessary tc ob­tain
uni form density on the photograpl--1s.
After transformation, the -photographic prints, A, B and C, must be carefully trimmed and
matched together to form the composite photograph. Before trimming, the vertical point is de­termined
and plottecl on the B photograph by mea ns of the inclination scale. After this is done, the
PRINTER FOR TRANSFORMING TRI-LENS NEGATIVES.
AIRCRAFT DEVELOPM EN T 35
trimming of the A, B and C prints is accomplished by means of special templates which are sup­plied
with each printer in order that the trimmed prints may be neatly and accurately matched
for mounting. The composite picture is then made by mounting the prints according to a pre-de­termined
alignment which must be followed.
In order to use the photographs in mapping, it is necessary to choose a series of points (images
of objects) which are to be accurately located to serve as points of secondary control. Nine points
are chosen on each composite picture and each of these points must be in three photographs. The
points are then labeled in a systematic order, after which the photographs are ready for the
draftsman to work upon. The specimen of the marked and labeled photograph reproduced on
page 37 illustrates the type of composite photograph obtained with the T-1 camera. The lower
view on the same page iJlustrates a panorama or bird's-eye view photograph made with this cam'era.
SHIPPING CASE FOR T-1 CAMERA AND ACCESSORIES.
For com·enience in handling, the T-1 camera and its accessories including a release mechanism
~nd its operating cable, an adjustable mount and other extras, are supplied in a special case 33-1 / 2
by 25 by 13 inches weighing 129 pounds complete. The Air Service standard view finder which
is used with both the T-1 and K-1 cameras is suppl ied. A similar case is also supplied for the
transforming printer and its accessories as previously noted.
Within the past two years, several thousand square miles of territory in this country embrac­ing
Reelfoot Lake, Mississippi River and Nashville cli sticts of Tennessee, parts of California,
Ohio and the Pana,rn« Canal Zone have been photographed with the T-1 camera within a compara-
36 T E C H N I C A L B U L L E T I N N o. 3 8
tively few hours of flying. These photographs have supplied information for maps, which would
ordinarily require several years to complete by the usual methods of mapping. One flight in
particular required only one hour and fifteen minutes to completely photograph 2,200 square miles
of territory from an altitude of 16,000 feet. Such photographic feats especially in inaccessible
regions are of incalculable value in exploratory, geological, soil, forest surveys, and in river and
harbor improvement works and in mapping airways.
Photographs obtained with the T-1 camera possess certain advantages over those made with
the single-lens camera for mapping use. Embracing much greater areas of terrain, they may be
employed to make quite accurate locations by a method of triangulation from the photographs
themselves. They reduce the time required for air work to one-third that required with single­lens
photographs as well as the amount of ground work necessary to establish the primary points
for controlling the photographs.
On the other hand, T-1 photographs are not so suitable for making miosaics as plain vertical
aerial photographs and altho they can be used for this purpose, the results are neither so pleasing
nor so satisfactory.
Recently, a further de\'elopment of the multiple-lens type of aircraft camera has resulted in
the construction of an experimental model of a four-lens camera. This was accomplished by add­ing
a fourth chamber to a T-1 camera. The camera thus made has been quite extensively tested.
Photographs taken with it greatly faci litate the orientation of one photograph upon another, for
the fourth chamber embraces the terrain over which the airplane has just passed. The same
ground objects are thus embraced by six successive photographs. A second four- lens camera is
under construction.
POWER PLANTS
Test of Curtiss D-12 Engines.
Two Curtiss D-lf engines have been undergoing extensive dynamometer tests at McCook
Field for the purpose of determining structural weaknesses and improving performances. One en­gine
which had been fitted with high compression pistons suffered fa ilure of the vertical drive shaft
and the water jacket during the SO-hour endurance test to which it was subjected. The cracked
water jacket was removed from the cylinder block and the broken parts sent to the laboratory
for material examination. This engine will be reassembled and recalibrated on the dynamometer.
The second engine was run on the clynamometer at high speed until the speed curve began to fall.
Afterwards it was removed and prepared for a SO-hour high speed test at the speed indicated by
the peak of the curve. In the disassembling and inpection for this test, it was found that the ver­tical
drive shaft had seized in the bronze bushings causing cracks in the gear housing. The shaft
showed discoloration at all of these bushings indicating excessive heat. This fault has been noticed
on all Curtiss engines run in the laboratory, and it is believed that it will become necessary to
substitute some other material for the bronze bushings now in use. A new gear housing will be
fitted before continuing the test.
A transmission for two Curtiss D-12 engines driving a single propeller has been received
from the Allison Engineering Company. T he complete unit weighs only 238 pounds and has passed
a IO-hours acceptance test in excellent condition.
Geared Liberty Engine, Magnesium Bearings and Other Modifications.
About one year ago the Engineering Division contracted with the Allison Engineering Com­pany
of Indianapolis, Indiana, for the rebuilding of a standard Liberty "12-A" engine with a
variable speed reduction gear to permit operation at either of the following gear ratios: 73 to 36
or 66 to 43. The weight of the variable speed geared engine was not to exceed that of the stan­dard
engine by more than 200 pounds.
This engine has been received and flight-tested in a DH-4B airplane which had been equipped
with a special landing gear to accommodate the four-bladed 12-foot propeller. Several successful
gear changes were made during flight. At "take-off," the r. p. m. of the propeller was approxi­mately
700.
T-1 COMPOSITE (Transformed) PHOTOGRAPH MARKED WITH CONTROL POINTS FOR MAP MAKING.
BIRD'S-EYE VIEW OF DAYTON, OHIO, AND VICINITY MADE WITH T · l CAMERA FROM MARTIN BOMBER
These Photographs were taken on a dull, c]oudy day a t an .... hi .. u de of 3,300 fee t with ca1nera faced in a westerly direction and titled
z90 below horizontal. Approximate a 1·ea photographed ( one exposure) 6 miles in width by 10 miles in d epth.
w
'-l
38 TE C H N I CA L B U LL ET I N N o. 3 8
E xperimentation with magnesium bearings has been underway for some time. Examination
of these bearings after several hours' running in a single cylinder Liberty testing engine di sclosed
some very interesting points. The pi ston pin hushing completed 108 hours at full throttle with
less than .001 of an inch of average wear and appeared to be in excellent condition. The connect­ing
rod bearings did not wear so favorably, the average bearing wear being about .004-inch and the
appearance of the bearing very poor. The surface was badly marred by circumfe rential scratches.
Different compositions of ri1agnesium bearing al!oy will be tried out in an effort to obtain a sati s­factory
bearing material.
In regard to superchargers, it was found that one of the chief disadvantages of the nose type
supercharger equipment on the Liberty engine is its excessive fuel consumption. This fault, how­ever,
is not applicable to the Liberty engine with the side type supercharger as it has been demon­strated
in recent tests that the fuel consumption with this type of supercha rger is no greater than
with the standard engine. Side type superchargers are being built for both the Liberty and Curtiss
D~l2 engines.
Drawings for a Liberty 12-cylinder air-cooled engine have been prepared and bids for parts
have been requested from various airplane engine manufacturers.
Purchase of Packard lA-1500 Engines.
Recently the E ngineering Division placed an order for two Packard Model lA-1 500 aeronau­tical
engines from the P ackard Motor Company, of Detroit. These engines will have a guaranteed
output of S 10 h. p. at 2100 r. p. m. Inasmuch a s the Navy Department is also purchasing a few
engines of the same type, it has been mutually agreed that the Navy Department will conduct a SO­hour
endurance test on one of the engines at the contractor's plant and that the Engineering Di-vision
will a ssume the expenses of the test. ·
AIRCRAFT DEVELOPMENT (Continued)
PART II-TECHNICAL ACTIVITIES OF 1923.
Discussion of the technical activit ies of the Engineering Division fo r 1923 must be confined
to a review of only the most outstanding achievements, fir st because the multiplicity of pro jects
under experimentation and research cannot be adequately treated in such a limited space ; and sec­ond,
because military secrecy precludes to some extent their detailed exploitation. For conveni­ence
these activities are treated under six main headings as fo llows: Airplanes ; Armament; Equip­ment;
Lighter-than-air projects ; Material r esearch; and Power P lants.
Airplanes.
T.he E ngineering Division, since its inception , has carried on all experimental development
and research engineering necessary to supply the Air Service with effi cient aircraft which may be
classified under the following general types : pursuit, attack. observation, bombardment and train­ing.
To these must be added the mi scellaneous and special types such as transports, racers, am­bulance
'planes, messengers, glider s, etc.
Pursuit T ypes : Pursuit development during the past year has been largely confin ed to the de­velopment
of three different models of airplanes about the Curtiss D-12 engine. Shortly after
the P ulitzer contests in 1922, contract was let to the Fokker Company for three 'planes, model
P\i\T-7, to be of biplane construction and capable of attaining a high speed around 160 rn. p. h.
Two of these airplanes have been completed and tested by the Division at McCook F ield-see
_page 17.
Meanwhile the Curtiss Company submitted a pursuit airplane, -powered by a Curtiss D-12
engine and equipped with skin radiators similar to those used so success fully on the Curti ss racers.
This airplane, known as the PvV-8, was thoroughly tested by the Division and as a result two ad-
A IR CRAFT DEVE LOPMENT
ENGINEERING DIVISION TWO-SEATER PURSUIT, MODEL TP-1 (Rebuilt)
(Liberty "12" Engine with Side Superch;,rger.)
39
40 T E C H N I C A L B U L L E T I N N o. 3 8
ditional 'planes were ordered incorporating such changes as were necessary to fulfill military re­quirements.
The second experimental model has been delivered and tested as di scussed on page
7, and twenty-five production articles ordered for the service.
Shortly after the Curtiss airplane was received , the Boeing Airplane Company submitted a
high speed pursuit, Model PvV-9, also powered with the Curtiss D-12 engine. After giving this
airplane a thorough test, the Engineering Division contracted for two additional articles embrac­ing
several improvements. Shortage of funds prevented the purchase of production models.
Both of these airplanes, the P\V-8 and P\V-9, were comparatively tested for speed, climb, and
combat maneuverability. The speed attained by both airplanes was close to 170 miles per hour,
other characteristics being practically the same, thus making them in all probability the fastest
and latest types of pursuit 'planes in existence.
During the early part of the calendar year, the second and third Dayton vVright PS-1 air­planes
were received for flight test. These were small pursuit monoplanes of the alert type
powered by a Lawrence air-cooled engine. The r esults obtained were not sufficient to warrant fur­ther
production. Future development of the air-cooled pursuit airplane is directly dependent upon
the development of the air-cooled engine, to which end the Engineering Division is conducting
elaborate experiments.
The TP-1 , a two-seater pursuit of biplane construction, powered with a 400-h. p. supercharged
Liberty engine, designed and constructed by the Engineering Division, has been completely rebuilt
to embrace several new characteristics, such as wing radiators, and side type supercharger. This
airplane is a two-seater, carrying practically the same armament as·an observation airplane. At an
altitude of 20,300 feet, it showed a high speed of 149.8 miles per hour as well as remarkable ma­neuverability,
being far superior to even a single-seater pursuit airplane at that altitude.
Further development of the monoplane pursuit has been abandoned for the reason that this
type of construction has not proved readily adaptable to high speed.
The data so far obtained from experimentation with specially designed night pursuit air­planes
have not proved conclusively the feasibility of designing pursuit 'planes especially for this
purpose. For this reason the Division has equipped the standard clay pursuit 'plane with the
necessary flare s, landing and running lights to fulfill requirements for night-flying.
Attack T ypes: Experimentation with ground attack airplanes has been confined to modifica­tion
and improvement of the armored GA-1 triplane, ten of which were built and delivered to the
service some time ago.
Flight tests and experimentation are still under way on the Boeing GA-2, an armored biplane
designed and built by the Boeing Company about the E ngineering Division's 18-cylinder, 700-h. p.
Model vV engine.
Observation Types: The close of the \Vorlcl \Var found the Air Service with a large number
of DH-4 airplanes on hand. After considerable experimentation and numerou;; changes, two
hundred and fifty of these airplanes were converted into the DH-4B type which has since been
used extensively by the Service for cross-country flights and in flight-testing various kinds of
equipment such as aerial cameras, radio in stallations, etc.
Recent development of the DH-4B has brought about a rehabilitation of these airplanes into
an improved type known as the DH-4M using a steel fu selage and standard DH-4 wings. Fifty of
these are under construction. A further improvement of this type is embodied in the DH-4M-l.
a design similar to the DH-4M but with several new features added such as a new fuel system.
baggage compartment and landing gear. One hundred DH-4M-l 's are under construction also, the
work on both types being done by the Boeing Airplane Company.
,About two years ago, the Division designed and built an all-metal 'plane of duralumin for
use in regions where atmospheric conditions cause rapid deterioration of wood parts. Later one
production model, the C0-1 , shown opposite was built by the Gallaudet Company. All experi­.
mentation has been completed with the l:'.xception of the service test.
About the same time, the Fokker Company of Holland submitted a corps observation air­plane,
Model C0~4, to the Division for tests which led to the construction of two additional eK-
AIRCRAF T DEVELOPMENT
GALLAUDET ALL-METAL OBSERVATION, MODEL C0-1.
(Liberty "12" Engine. )
41
42 TE C H N I C A L B U L L E T I N N o. 3 8
perimental model s. After testing these articles five production models were ordered and received
for service test. During the construction of the production models, the Division reworked two
experimental models for the air races at St. Louis in which one model equipped with an E ngineer­ing
Division cluralumin propeller attained first place in the race for this type of airplane.
The Division has recently designed and built a new obser vation airplane, designated Model
C0-5, which resembles the Engineering Division TP-1 in general construction. Experimentation
is still in pxogress on this model. At present, the Division is designing another type of observa­tion
'plane to be powered by an inverted Liberty engine. This model will be designated the
X-C0-6. A contract has also been awarded for the construction of an amphibian observation
'plane, Model COA-1, using an inverted Liberty also. This design employs a seaplane construction
with retractable land wheel gear. It is being built by the Loening Company.
All types of observation airplanes used by the Air Service are powered by Liberty engines.
Bo11ibi11g Types: Thruout the past year, the Division has been actively engaged in the de­velopment
of several types of bombardment airplanes including both clay and night bombers in ,
various stages of experimentation and production.
One new day bomber, a redesign of an earlier model known as the DB-1, was received for
test. This airplane is a large single-engined monoplane of metal and fabr ic construction, designed
and built around the new 18-cylincler, 700-h. p. Model 'vV engine by the Gallaudet Aircraft Cor­poration.
Prior to construction, the Engineering Division super vised the design of the wing, in
order to insure adequate rigidity in a thick section of this type. Flight tests are still in progress.
Meanwhile, three aircraft manufacturers, the Curtiss, L-W-F and Aeromarine Companies,
completed on production contracts 110 short distance night bombers, Model NBS-1, 85 of which
were built under direct supervision of the E ngin eering Division. The N BS-1 is a biplane of con­ventional
construction mounting two Liberty engines, and is similar to the Martin Bomber after
which it is patterned. 1"':he· new NBS-l's, several of which have been equipped with supercharged
engines, can be accredited with the success of the recent bombing maneuvers off the Virginia Coast.
On the experim,ental program, the Division's efforts were concentrated on three new short
distance night bombers, Models N BS-2, 3 and 4, under construction by the L-'vV-F, E lias and
Curtiss Companies, respectively. These two-engined biplanes entailed a great amount of experi­mentation
and research in the nature of design analysis, material research and tests prior to and co­incidental
with their construction, which has result ed in the production of a finished article ready
for flight without the necessity of static test. By applying this method of construction to all large
airplanes, the Division is able to effect great savings in materials, time and money. ·
Only one long distance night bomber, model NBL-1, has been built. This model , popularly
known as the Barling Bomber, was designed at the Engineering Division in collaboration with
'vValter H. Barling, an Engli sh aeronautical engineer, and subsequently constructed by the \Vitte­man
Aircraft Corporation on experimental contract. The NBL-1 is the largest airplane ever built
in Ameri ca. It is a triplane of conve tional con struction having a span of 120 feet, length 65
feet and height 27 feet, with its six Liberty engi nes, four tractors and two pushers, mounted in
nacelles above the lower wing. Fully loaded it weights over 21 tons, about 8 of which constitute
the useful load which includes a crew of four, six tons of fuel, and other equipment. Bombs to­talling
2-1 / 2 tons may be carried with reduced fuel load.
Altha the NBL-1 ,vas completed and delivered to \iVilbur 'vVright Field by the close of 1922,
its assembly, erection and proof test were not completed until six months later after which it was
flown on several cross-country exhibition flights. Later in the year, the NBL-1 establi shed several
load-carrying records for altitude and duration .
T he Engineering Division has begun the design of another new long distance night bombing
'plane which will be powered by a centralized power plant consisting of four Liberty engines clriv­i-
1.1g one propeller. Dimensionally, this airplane will be larger than the Barling Bomber.
Training Types: Insofar as the development of the water-cooled training type is concerned,
the Division has been occupied mainly with the supervision of twenty production T\V-3's purchased
by the Air Service Procurement Section at \iVash ington. 1fodel TvV-3 is a Dayton-'vVright de­sign
similar to their air-cooled "Chummy" Model TA-3, ten of which have been produced and
distributed to the Service.
AIRCRAFT DEVE LOPMENT
GALLAUDET DAY BOMBER, MODEL DB-IB (Redesigned Ar t icle )
(Eng . Div. Model "W-IA" 700-h . p . Eng ine.)
43
44 T E C H N I C A L B U L L E T I N N o. 3 8
During 1923, two experimental training 'planes, Models T A-5 and 6. desig ned about the
Lawrance air-cooled radial engine. were submitted to the Division. The T A~5 is a Dayton­\
i\Tright product resembling the T W-3 except for the engine, whereas the TA-6 is a new tandem­seater
design submitted by the Huff-Daland Company. Due to shortage of engines neither of these
types were produced. H owever , the Huff-Daland model showed such excellent characteri stics that
the design was reproduced as the T\i\T-5 using a water-cooled engine. ·
Special T ,ypes : Since the delivery of the two Fokker transports and the subsequent modifica­tion
of one model into the famous Air Service T-2 in which Lts. Kelly and l\facready crossed
the continent in their memorable non-stop flight, the E ngineering Division has directed its atten­tion
to the development of a new transport, Model T-3, a large single-engined passenger-carrying
biplane propelled by a Liberty engine. · So far only one model has been built. From present indica­tions
the completion of the order of ten appears doubtful owing to financial difficulties.
No new racing airplanes have been construct ed by the Air Service for the P ulitzer contests
since 1922 and no new types are being built fo r the coming contest in 1924, owing to lack of
funds, al tho several designs have been contemplated. However, the Verville-Sperry racer, model
R-3, was rebuilt with a Curtiss D-12 engine and skin radiator for the 1923 contest. This airplane
is the fa stest monoplane yet built and still holds the \iVorld's record for 500 kilometer s.
Thirty messenger airplanes from a design originated by the Division around the 3-cylinder 60-
h. p. Lawrance engine. have been completed and placed in service. One of these is equipped with a
special hooking device mounted above upper wing for attachment to and release from an ai rship
ship in flight. Experimentation with this device is continuing.
A design for an ambulance airplane to carry a pilot, medical officer and two patients was com­pleted,
the proposed 'plane to be of biplane construction mounting one Liberty engin e.
Several models of a target glider for use in ;Jerial g11nnery practice have been built and sent to
the Senice. This glider is so constructed that it can be mounted upon an airplane and released
during flight. Upon release it performs a series of maneu vers simulating those of an airplane in
combat. A man-carrying glider has also been designed. constructed and flown for the purpose of
obtaining data relative to gliding flight.
Aerodynaniical Research a11d Test: Studies r elative to airplane structures have been made on
distribution of load in ,multi-spar wings, new methods for computing laterally-loaded columns,
stresses in tripod structures, eccentric strut loads and wire pulls, and ratios of strength and weight
in wing ribs. \ i\Tork is continuing on a proj ect of utmost importance- the study of stresses clue
to combined bending and compression.
All new designs are submitted to the Division for stress analysis and check before construc­tion.
This effects a great saving in that many defects which would not otherwise be apparent until
static test. are thus brought to light and remedied. Experimental contract designs thus analyzed
and checked during the year included the new NBS-2, 3 and 4 bombers. the PW-8 and 9 pursuits,
the T\i\T-5 training. the T-3 transport. the COA-1 amphibian and the RS-1 semi-rigid airship.
The new five-foot wind tunnel, designed and built by the Divi~ion at McCook F ield, has
proved of in estimable value in predetermining t he aerodynamical characteri stics of new air foils and
new airship and airplane models as well as in measuring parasite resistance. in calibrating instru­ments
and in other indispensable work In this wind tunnel, air velocities from 10 to 250
miles per hour are obtainable. the air stream being remarkably steady at all speeds. For smaller
work, the Division has a high-speed 14-inch wind tunnel where velocities up to 500 miles per hour
are possible.
Propellers : T he DiYision's policy not to accept propellers, regardless of source. unless they
have satisfactorily passed the destructive whirling test. has proved very success ful in that there
has never been a failure in ser vice of any propeller which has passed this test. This fact, together
with the thoroughness of the test, has led the Navy Department to have its propellers tested
at this station.
\i\Tood, metal and micarta are used in propeller construction, of which metal and micarta are
best adapted for adjustable and reversible propeller s. A few outstanding developments are cited
in the fo llowing to show the trend of design.
AIRCRAFT DEVELOPMENT 45
For the RS-1 airship in process of construction, a balsa wood propeller, 17-1/2 feet in diameter,
s been built. This large propeller has a balsa core, covered with a skin of 1/64-inch mahoganv
eneer with the grain alternating along the blade and at 45 ° to the angle of attack. Six plies of
veneer are used at the tip and forty-five at the hub. The propeller weighs only 110 pounds as
mpared with 300 pounds for a standard wooden propeller of like size.
A drop-forged aluminum alloy propeller has ,been developed for the Liberty engine. A set
of forging dies has heen made so that the propeller can can be finished in the dies, making rapid
d inexpensive production possible. The efficiency of using this propeller was demonstrated in
the Air Races at St. Louis last fall, in which two observation airplanes equipped with these pro­pellers
finished first and second in the race for that class of airplane. the gain in speed clue the pro­peller
alone as found by actual test being about 9 miles per hour. The adaptability of this pro­peller
is manifest in that it is not affected by climate, and that its light construction permits blade
adjustments, within certain limits, to various pitches.
Several prope