Technical bulletin no. 41. Development of military aircraft material for United States Air Service under supervision of Engineering Division

              VOLUME V
(AVIATION AND AEROSTATION)
BY DIRECTION OF CHIEF OF AIR SERVICE
OCTOBER. NOVEMBER AND DECEMBER, 1924
TECHNICAL BULLETIN
No. 41
NUMBER 482
DEVELOPMENT OF MILITARY AIRCRAFT MATERIAL FOR UNITED STATES
AIR SERVICE UNDER SUPERVISION OF ENGINEERING DIVISION.
Prepared and Published
By Direction of the Chief of Air Service
and under the supervision of
MAJOR JOHN F. CURRY,
Chief of Engineering Division.
McCook Field-I 2-12-!4-JOOO.
CONFIDENTIAL
The information contained ·herein is confidential and therefore
must not be republished, either in whole or in part, without
express permission of the Chief of Air Service, U. S. Army.
CONTENTS
AIRCRAFT DEVELOPMENT
AIRPLANES
Observation Airplane Competition (Libe11ty Engine) ····················--- -···· -·-·-· ········ ·············· 7
New Records by Barling and Curtiss Bombers ··· ···-···· ·················· ········-········· ·· ··· ················ 9
Douglas 0-2 to Supersede DH-4B (with description of X0-2)........................................ 10
Curtiss XNBS-4 on Acceptance Test ··-···- ·········· -·-·············· ·· ·········· -·····--·-·· ················· ········-·- 12
XLB-1 Test Fuselage Received ······-----------·--·--· -- -- -----·····- ······- ········· -····· ·····--···················-······ ·· 12
New Pursuit Design Based on Boeing PW-9 ·········-- ·-··-·-···-·······- ·-·· -·· ······-· ··········-··-------····--· 12
Changes 'in Curtiss Pursuit..................... .......... .. .................. ............ ... ................... ................. 12
Standardization of Detachable Propeller Blades .... -----········-········· ···· ··· ··-··-·········-········..... 12
Elias XNBS-3 Below P erformance Requirement .... ----·················-···-·· -···-············-· ···· -······ 14
Skis for Winter Flying ......... ........................... ... ..... ..... ........................... -·--·-····-·-·······- ·- -····-·· 16
AIRSHIPS AND BALLOONS
Improvements to Terry Mooring Masts ........ ... ...... .... ..... ................. ...... .................. ....... ...... 17
RS-1 Airship Completed ······· ·-··-· -·-····················-·············· ······ ········· ····· -··-·········-·········-·- ··-···- ·· 18
Construction on TE-1 Airship Started .............................................. -··-·····- ················ -- ........ 18
ARMAMENT
New Beams for NBS-1 Bomb Racks ...................... .... ................ -·-·······-··-·········· ····-··········· ··· 18
The Oscillog r aph ·-·-·····-··········· ··-·····- ····· ············-·····: ... .... ---· ············· ··························-····· -··-· --·· 19
Gun Improvements on MB-3A Airplanes ........ ..... ........ ... ............. ..... ·········· ·-········ -·············· 20
EQUIPMENT
Night Illumination for A. S. Flying Fields. .... .................... ........ .......... ................ ............ ... 20
New Night-Flying Equipment for Airplanes.. ..................... ..... ............................................ 21
Ground Temperature ·Compensated Altimeter... ...................... ........ ................... ..... ........... .. 21
Mayall Airplane Engine Heater.......................................... ... .......... ....................................... 22
Handbook on New Direct-driven Generators .... .. ······· -··-······-·· -···-··························· -·-·········· 22
New Parachute Designs- Maintenance Transferred. to F. A. I. D......... .. .. ........ .............. 23
Supercharger Gage ····-·················-······ ······ ·-········ --··-···-·········· ·············· ······· ··-·-········· -················ 23
Photographic Trucks (Description) ··············-· -·-·····-···-················-····························· -··-·· ····· 24
New Camera for High Altitude Photography........................... .... ................. ..... ................ ... 27
Unjversal Camera Mount .......................... ... ...... ......................... .............. ······ ··········-··········-· 29
POWER PLANTS
Division Builds an Air-Cooled Liberty....... ............... ................... ....... .......... ........................ 29
Allison Four-engine Transmission (Description) ...................... ........................................ 29
First Cm•ti ss R-1454 Radial Accepted... .............. ................ .. ................................................. 30
RESEARCH AND EXPERIMENT
RESUME' OF ENGINEERING DIVISION SERIAL REPORTS
Resume' of Development of Gallaudet DB-1............... ...... ................................................... 31
General Procedure in Airplane Design... ....... .. .......... ..................... ......... ..... ....... ...... ............ 31
C 0 N T E N T S - (Cont'd)
Resistance of Streamline Fuselages of Racing Airplanes... .............. ............... ..... ... .. .. .... 31
Aerodynamical Characteristics of TP-1 and C0-2 Fuselages............ ..... .... .. ................... 31
Collection of Unrelated Model Airfoil Tests......... ..... ... ........... ............. ...... ................ ......... .. 32
High Speed Test of Wing Section With Bullet Holes in Fabric.. ....... ... ....... ........ ............ 32
Application of "Method of Least Work" to Redundant Structures .. .. .......... ................ 32
Determination of Engine Power at Altitude from Propeller Characteristics. ... 33
Resistance of Center Section Type Radiator.. ......... ... ..... ... .... ................ .. ..... ... .... ... 3-1
Wing Analysis of Lepere (USA-C-11) Airplane...... ......... .. ........... ......................... 34
The Power Plant Problem in Heavy Bombardment Airplanes ... ... .. .... ...... ......... .. 3·1
Static Tests Conducted at the Division.......... ............. ............... .. .............. ....... ... ................. 34
\Vind Tunnel Tests ... .................. ................ ...... ... ......... ............. ...... ......... ............ ......... ... ........ 35
Babbitting Direct to Steel .................... ................. 35
Mechanical Properties of Magnesium-Zinc-Aluminum Alloy Castings 35
Column Strength of Duralumin Tubing with Fixed Ends.................. ... 35
Application of Load in Testing Fabric................... .. ... ..... ................ ........... .. .... ...... ....... ....... 35
Laboratory Tests Made Sole Basis for Accepting Spar Varnish.... ................ ...... 36
Salt-cooled Valves and Hardened Guides for Aircraft Engines.......... ............... .... ....... 36
Power Plant Laboratory Standard Test Methods and Computations....... ... ... ....... .. 36
M'orehouse Blower Engine (First Design)....... ........ .. ..... ... .................. ..... ...... ....... 37
Crank Pin Bearing Pressures on Liberty 1-inch Connecting Rod Bearing... 37
Test of Rockwell Slotted Head Liberty Valves.. ...... ........ ..... ..... .. ... ............ 38
The Mercury-Vapor Turbine as an Aircraft Power Plant... ..... ... ............... 38
Behavior of Standard Spark Plugs in High Compression Liberty......... ........................ 39
. Performances and Sectional Views of Aircraft Engines.. ..... ............ .... ......... ..... .... .... .... ·39
Reliability Test s of Two Rock Island Arsenal Liberty Engines...... ..................... 39
Endurance Tests of Curtiss D-12 Engines.. ..... .. .... ........ ..... ...... .......... ..... .. 39
Competing Airplanes in Air Races (1924) ........... ....... ....... .. ......... ... ............. .......... .... 39
INVESTIGATION OF MATERIALS
Paste Colors for Insig·nia............. ...... .. .. ... ................. ............. ...... .. ......... ........ ... ............ ....... .. 40
"Krachow" and "TaSua" Wood from Siam........ ....... ................... ... ........... ..... ...... ............. 40
Cadm'ium and Chromium Plating......... ...................................... ........ ..................... ........ ... 40
Effect of Gage Width on Elongation- Standard Test-Piece .. .. ... ........ ............... ............. 40
World's Largest Airplane Wheel and Tire, Size 64x14... ..... ..... .............. ... ........ .. ..... 40
NEW BOOKS AND DOCUMENTS
Documents added to Technical Files during Fourth Quarter of 1924....... ......... ............ 42
LIST OF ILLUSTRATIONS
Airplane in Observation Competition- Liberty Engine ..
Douglas Observat'on X0-2 __ _____ ___ ____ ______ ... ..... ....... . ... ........... .... .
General Arrangement of Douglas X0-2 with Liberty Engine .... ..... ..... .... ....... .
Elias Night Bomber XNBS-3
Rear View of Elias Night Bomber _________ _
General Arrangement of Elias XNBS-3 .
DH-4B Fitted with Metal Skis -- ------- -------·--
TC-5 Airship Moored to Terry Mast
The Oscillograph ...
Page
6
11
13
14
14
15
'16
] '7
19
36-inch Beacon Equipped with Incandescent Lamp and Donnelly Door... .............. 20
Altimeter Compensated for Ground Temperature 21
Mayall Electric Heater 22
Supercharger Gage (Sketch) _________ ________ ____ 23
Photographic Trucks Ready for Field Service.. ......... 24
Arrangement of Equipment in Photographic Trucks ------- ----- ·-···· ·---- ---- -- __ 26
Switchboard and Generator Control on Photographic Truck ................... .... ....... ........ .. 27
Allison Four-Engine Transmission for Liberty ... _ .... ......... ............. .......................... ... . 28
Internal Views of Allison Four-Engine Transmission .. 30
Bullet-Perforated Wing Fabric After Wind Tunnel Test ----- --- ·--·-·----------------- -- ------ - 32
Variation of Engine Power with Altitude ... ............ .. . 33
Morehouse Blower Engine ........ ...... .......... ........ .......... ......... . 37
Schematic Arrangement for Mercury-Vapor Turbine ..... . 38
Airplane Wheel and Tire- Size 64x14 .... .............. ......... . 41
I. Boeing XC0-7B (Inverted Engine. )
2. Atlantic XC0-8 (Loening COA-1 Wings.)
3 . Engineering Division TP-t .
.4 . Cur\iss X0-1 with Liberty.
AIRPLANES IN OBSERVATION COMPETITION-LIBERTY ENGINE.
8. Douglas X0-2 with Liberty.
9. Atlantic A0-1.
10. Fokker C0-4.
5. Engineering Divislilon XC0-5.
6. Engineering Division XC0-6 (Upright Engine.)
7. Engineering Division XC0-6 (Inverted Engine.) JI. Cox-Klemin (Heinke!) CK C0-2 (Liberty.)
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AIRCRAFT DEVELOPMENT
ON ENGINEERING DIVISION PROGRAM
AIRPLANES
Observation Airplane Competition (Liberty Engine.)
The observation airplane competition held at McCook Field during November and De­cember,
1924, under direction of the Chief of Air service resulted in the selection of the Douglas
X0-2 airplane with Liberty engine to succeed the DH-4B as the standard observation type. The ·
selection was made after comparative tests of eleven types of airplanes by a board of seven Air
Service officers having pertinent knowledge of the requirements of the type.
The problem involved the selection of a general utility airplane of a design affording ease of
production and maintainance that would be particularly suitable for cross-country service in all
kinds of weather as well as for observation and attack training. This implied the necessity of select­
·ing a type which would have a performance equal to or greater than the present DH-413, and
which would combine the best possible flying qualities with serviceable construction. Specifically
interpreted, this meant an airplane possessing the following characteristics to the best possible de­gree:
abi lity to operate safely from small fields with inexperienced pilots; safety features and ease
of control in flight; good vision and large fuel capacity for long cross-country flights in inclement
weather; provision for carrying variable loads in airways service without change of balance in
flight; a rear cockpit incorporating the most desirable features for the purposes involved; struc­tural
ruggedness and accessibility of parts; adaptability for skis and pontoons-in fact all things
required in a reliable general purpose 'plane.
Eleven different types of airplanes shown on the opposite page participated in this competition
as follows:
Atlantic A0-1 (Revised C0-4.)
Atlantic XC0-8 (DB-4M2 with Loen'ing COA-l wings.)
Boeing XC0-7B (DH-4Ml with tapered wings and inverted engine.)
Cox-Klemin (Heinke!) CK C0-2. ·
Curti ss X0-1 (With Libertv installati.on.)
Douglas X0-2 (With Libe1:ty installation.)
Engineering Division XC0-5.
Engineering Division XC0-6 (Inverted engine.)
Engineering Division XC0-6 (Standard engine.)
Engineering Division TP-1 (Standard engin~ without supercharger.)
Fokker C0-4.
Each airplane in the competition was subj ected to a regular standard performance test by the
Engineering Division (provided the performance was not a lready known) and then flown as many
times as possible by each member of the competition board acting first as pi lot and then as ob­server
to properly ascertain its behavior and suitability in all maneuvers and conditions of flight.
To further compare the relative merits of the var ious competing types. comparison flights were
made for speed . climb and maneuverability whenever possible. All flights were made with full
military load of 1615 pounds as taken from the latest prescribed list for observation airplanes.
This load included the armament installation, equipment, camera. radio. crew and 91 gallons of
fuel. The flight test data were supplemented by detailed reports on the structural details and de­sign
of the airplane. the general arrangement and in stal lation of armament, equipment and power
plant. and the facility of maintenance and production.
From the results obtained . it was very evident that two airplanes, the Curtiss XO~ 1 and .the
Douglas X0-2. were superior to the rest. The Curtiss airplane possessed a remarkably high per­formance
coupled with excellent flying qualities and maneuverability comparable to a pursuit type.
It had certain disadvantages, however, in regard to structural features and material, size and loca-
8 TECHN IC A L BULLETIN No. 41
tion of cockpits, fu el capacity, safety of personnel in event of crash, arrangement of equipment
and armament for obser vation purposes, and change in balance with variable loads, all of which
rendered · its suitability for use as a general utility 'plane doubtful. The Douglas airplane proved
without doubt the logical successor to the DH-4B. In addition to simplicity of design, rugged
construction and excellent accessibility, it possessed exceptional safety features, perfect balance
with or without load, ample baggage space, very good performance and fl ying qualities especially
desirable for observation and attack training and cross-country service.
In its final decision, the Board unanimously recommended the adoption of the Douglas X0-2
design with Liberty engine as the new standard observation type to supersede the DH-4B. It
also recommended that a sufficient number of Curtiss XO-l's be purchased for service test.
The competing airplanes, all of which are of biplane construction mounting the Liberty en­gine.
are briefly described in the order of merit in the fo llowing:
Douglas X 0-2. This design incorporates a simple single bay, wire-braced construction with
conventional wood wings, wire-trussed tubular fuselage of welded chrome-molybdenum steel, and
wide tread axleless chassis of the tripod type readil y adaptable to pontoons. The engine mount
and rear portion of fuselage are removable. One of the chief safety features is the location of
droppable fuel tanks in the lower wings away from the fu selage. The total fuel capacity of 170
gallons is sufficient for crui sing about 950 miles. There is no center section. Both wings are of
equal span-39 ft. 8 in.-and are symmetrically built on the Clark "Y" airfoil section to give an
effective supporting sur face of 411 sq. ft. Fully loaded. the airplane weighs 4426.8 lb.
Cu.rtiss X0-1. T hi s airplane utilizes a single bay, wire-braced biplane cellule with wood wings
of Clark "'Y" section. The outer panels of the Upj)er wing are supported by N-struts and sweep
hack from the center section . The fuselage is of ri veted duralumin construction quite new in this
country. and this same metal is used in the empen'nage strncture. The engine mount, a welded
steel tube unit. is readily removable making the airplane adaptable to the in stall ation of a Lib­erty,
Packard l .'\-1500 or Curtiss V-1400 engine without appreciably affecting the balance.
The chassis with rubber disc shock absorber is similar to that used on the Curti ss pursuit. All of
the fuel is carried in a single droppable of 119 ~allons capacity in side the fuselage. The overall
span is 38 ft ., supporting area 349.6 sq. ft., and the total weight 4075 lb. or about 300 pounds
lighter than the next lightest competitor, the T P-1.
E11gi11ceri11g Diz1isio11 XC0-6. The special features o( this airplane include a transparent
floor below the cockpits formed of duralumin slat s and celluloid through which pilot and observer
can view the ground. two duralumin strut axleless chasses . one with and one without shock ab
sorbers. and two interchangeable nose structures. one for inverted engine with nose radiator and
the other for uprig'ht engine with tunnel radiator. All fuel is carried in one droppable tank with­in
the fu selage. The design invoh·es a double bay. wire-braced cellule with symmetrical wood
wings of RAF-15 section and welded chrome-molybdenum steel tube fu selage. The span is 48 ft ..
supporting area 481.4 sq. ft .. and total weight 4607 lb. with standard engine in stallation. Practic­ally
the only difference in performance between the standard and inverted engines is that the
aeroclynarnical balance with inverted engine is not affected by throttle position.
Atla11tir AO-l . T his airplane was built by th e Atlantic A.ircraft Corporation as a revision of
the Fokker C0-4 to eliminate objections observed · in service test. The design follows the usual
Fokker type of construction with welded steel tube fu selage and thick canti]eyer wings. The main
fuel tank is placed in the fu selage and the reser ve supply in the large single piece upper wing.
T he chassis is fitted with a quickly detachable ,:hock absorber. The O\•erall span is 39 ft. 6 in ..
which with the narrow chord lower wing gives a total supporting surface of 397.2 sq. ft . The
airplane weighs 4525 lb. gross.
E 11qi11ceri 11g Division X C 0 -5. In this single bay. externally braced biplane. the large chord
USA-35B wing is placed above the narrow chord Gottingen 387 wing to increase vision down­ward.
The wings are of conventional wood and fabric construction braced externally by steel N­struts
and streamline wires whereas welded low carbon steel tubing is used in the fuselage struc­ture
which is fitted with a split-ax le chassis having duralumin struts. The main fuel tank is placed
in the fuselage and a gravity tank in upper wing. The airplane has a span of 43 ft .. supporting area
of 438 sq. ft. , and a total weight of 4427 lb. It is of the same general construction as the En­gin
eering Division TP-1.
Atlantic XC0-8. This airplane consists of a DH-41\f2 fuselage. a welded steel tube structure
designed by A.tlantic Ai rcraft Corporation. fitted with Loening COA-1 (amphibian ) wings. It rep­resents
an irnprO\·ecl DH-4B with metal fusebge. The span is 45 ft., supporting area 495 sq. ft.,
and total weight 4680 lb.
AIRCRAFT DEVELOPMENT 9
Cox-Klemin (Heinllel) CK C0-2. This airplane was built by the Cox-Klemin Aircraft Cor­poration
from a design by Heinke!, a German aircraft designer. It is similar to the Atlantic A0-1
in general construction and maintenance features and utilizes a thick cantilever wing construction
and welded low carbon steel tuhe fuselage fitted with a continuous axle chassis. The wings are set
at a considerable stagger with the larger above, and are braced by single I-shaped struts to carry
torsional stresses. A droppable tank in the fusebge and gravity tank in upper wing carry the fuel
supply. The overall span is 42 ft. 4 in., supporting area 419.6 sq. ft., and total weight 4485 lb.
This airplane is noteworthy for its quickly detachable features.
Engineering Di·z:ision T P-1 . This_ airplane incorporates the same type of construction as the
XC0-5 aforementioned except that the position of the wings is reversed. A Gottingen 387 section
is used in both upper and lower panels which have the same span-36 ft. The wing area (375
sq. ft.) and total weight ( 4363 lb.) are less than those of the XC0-5.
Boeing X C0-7B. This model consists of a Boeing DH-4Ml fuselage (steel tube) fitted with
special tapered wings of Gottingen 436 section to form a two bay, wire-braced biplane cellule. The
principal features ii1clnde an inverted engine, extra wide tread chassis with shock-absorbing struts
mounted outboard under the lower wing, and sectional wing panels with the entire fuel supply in
upper center section. The upper span measures 45 ft. and the lower 38 ft. 9 in., giving a total
supporting surface of 440 sq. ft. The airplane weighs 4652 lb., fully loaded.
Fokker C0-4. This airplane has been service tested and its design reworked as represented
in the Atlantic A0 -1. This design is characteristic of the usual Fokker construction with thick
cantilever wings and welded tube fuselage. The . overall span is 39 ft. 6 in., supporting area
407.6 sq. ft. and total weight 4694 lb.
New Records by Barling and Curtiss Bombers.
New weight-carrying records for altitude and duration were established by Engineering Division
pilots in the reconditioned Barling Bomber (XNBL-1) and the supercharged twi.n-Liberty Curtiss
NBS-1 night bomber during the Air Races at \Vilbur vVright Field last October. These records
have been homologated by the Federation Aeronautique Internationale as follows :
Useful Load
4000 kg. (8818.48 lb.)
4000 kg. (8818.48 lb.)
3000 kg. (6613.86 lb.)
2000 kg. ( 4409.24 lb.)
CLASS C-AIRPLANES.
Altitude Duration
BARLING BOMBER (XNBL-1)
. . .. . .... 1363 m. ( 4472 ft.)
. .... ........ . ............ . . .. . . . 1 hr. 47 min. 10.5 sec.
. . . . .. . . .. .. ... . ....... .. . . .. . .... 1 hr. 47 min. 10.5 sec.
... . . .. .. .... . .. . . . .. . . . .. ....... 1 hr. 47 min. 10.5 sec.
CURTISS NBS-1 (SUPERCHARGED)
* 1500 kg. ( 3306.93 lb.) . . .. . . .. . 4953 m. ( 16,250 ft.)
1500 kg. (3306.93 lb.) .. ............ .. ................. 2 hr. 13 min. 49.6 sec.
1000 kg. (2204.62 lb.) ... .... . .... ...... . ... .. .. ... . ... 2 hr. 13 min. 49.6 sec.
The above records were established in single flights, one by Lt. H. R. Harris (pilot) and
Douglas Culver ( mechanician) in the Barling Bomber on October 3, 1924, and the other by Lt.
J. A. l\Tacready ( pi lot) in the supercharged Curtiss NBS-1 on October 2, 1924. The flight of the
Barling formed part of a series of standard performance and special load-carrying tests with vari­ous
engine combinations as outlined on page 10, T echnical Bulletin Z\T o. 40. A design study of this
airplane incorporating a centralized power plant installation with four Liberty engines geared to a
single propeller has been concluded.
*This record unofficially reported as exceeded by Pilot Bottala at Turin, Italy, on December 2.4, 1924, in a flight to
an altitude of 5400 m. (17,716 ft.) .
10 TECHNICAL BULLETIN No. 4 1
Douglas 0-2 to Supersede DH-4B.
T11e Douglas airplane with Liberty engine has been adopted by the Air Service as the new
standard observation type to succeed the obsolescent ~H-4B .as previously stated, the service model
to be designated "0-2". The Douglas X0-2, the experimental model herein described, was built
and submitted by the Douglas Cprnpany, Santa Moni ca·, Californi a . as a sample airplane for par­ti
cipation in two Air SerYice competitions for observati on airplanes, one type powered b y the
Lihert v engine and the other by the new Packard engine. Thru the use of interchangeable mounts
to accommodate these respective engines, this airplane became eligible for both contests.
Simplicity p redominates thruout the Douglas sample design which follows a standard type of
construction, unusually well built and very accessible- commendable features from standpoints of
production and maintenance. T he design involves a single bay wire-braced biplane construction
with conventional wood and fabric wings of Clark "Y" section. conventional welded tube fuselage
of chrome-molybdenum steel and wide-tread axleless chassis. The easily rigged cellule utili zing
upper and lower wings of equal span and chord consi sts of four symmetrical panels extermdly
braced by single streamline wires and two intt"rplane struts at their extremities. Four short
cabane struts connect the upper panels with the fuselage. There is no stagger or center section. The
upper panels are joined to each other at the center whereas the lower ones a re hinged to short
proj ecting stubs of steel tube construction wt"lcled integral with the fuselage structure. All four
panels carry un balanced ail erons inserted in the outer trailing edges.
T he fu selage is a wire trussed tubular steel structure of rectangular shape, measuring 2 feet
9 inches wide by 4 feet 6 inches deep at its maximum cross section. It is well arranged and incor­porates
several stru ctural features such as the detachable all-metal engine mount which permits in­terchangeability
of power plants, the asbestos-faced aluminum fi rewall at which the detachment is
made. and the well located cockpits which provide maximum visibility for both pilot and observer.
Aluminum cowling in conveniently removable sections supported by channel-section duralumin
suj)erstructure gives ready access to all parts of the power plant. The tail portion supports a set of
conventional control surfaces of the unbalanced type having a detachable fin and a wire-braced stabi­li
zer adjustable in flight thru a devi ce incorporated in the tail post. A t ubular tail skid of the
swivel type is used.
Extending under the lower wing well out from the fuselage are two 32" by 6" pneumatic
t ired straight-side wheels carried on a wide tread axleless landing gear of steel construction. The
landing gear is composed of two tripod chasses hinged at the center of the fuselage and lower wing
butts. the outer or shock-absorbing members which extend from the wing being detachable to
facilitate rewinding of the cord.
Disposition of fuel is especially good in that it assures extraordinary safety to per sonnel in
event of crash by carrying the main supply well away from the fu selage in two droppable 60-gal­lon
tanks placed in the lower wing panels near their points of attachment. The main supply is
augmented by a JO-gall on gravity tank placed in upper right wing panel and a 40-gallon auxiliary
tank in the fu selage. making a total of 170 gallons capacity which is sufficient for a cruising range
of approximately 950 miles.
The power plant with Liberty in stallation comprises a standard engine equipped with Zenith
carburetors. gear type fuel pump, 12-volt Delco ignition and a JO-foot detachabl e blade aluminum
alloy propeller . Fuel is suppli ed to the carburetors by means of a C-5 pump dri ven directly from
the engine and provided with a B-1 pressure relief valve. A hand pump is provided for emerg­ency.
Oil is carried in a 13.5-gallon tank suspended by straps at rear of engine. F or cooling is
provided a closed type water system uti lizing a 9-inch core radiator mounted in side the cowling
under the engine. Temperature is regulated by means of radial shutters of rather complicated
design controlled from the cockpit.
T he airplane as equipped for observation purposes provides for the in stallation of one .30 cal.
or one .50 cal. synchronized gun forward and two fl exibly mounted Lewis gun s on rear ring mount.
T he cockpits are fitted with dual controls and adjustable seats with provision fo r camera, radio
and oth er observation equipment.
In the standard performance tests conducted at the Division. the Douglas X0-2 with Liberty
engine attain ed a high speed of 137.2 m. p. h. at ground and a service ceiling of 16,900 feet. An
outstanding characteri stic of this airplane is the perfectly-at-home feeling experienced by different
pilots who have flown it. The fine fl ying qualities coupl ed with excellent visibi lity and ample
baggage capacity render it particularly adaptable for both obser vation and airways service.
AIRCRAFT DEVELOPMENT
DOUGLAS OBSERVATION X0-2.
(Liberty "12" Engine.)
11
_j
12 T E CHN I CA L B ULLETI N No . 41
The production model which will be known as the " 0 -2" will incorporate several mmor
changes to improve construction , chief among which are the fo llowing : substitution of double flying
wires in the external wing bracing, use of tubing for external bracing of stabilizer, radiator shutters
of simplified design and the elimination of gravity tank from upper wing which will be compen­sated
for by increasing capacity of aux iliary fuselage tank to 50 gallons in order to retain same
total tankage. In addition, all .of the production models of which seventy have been ordered will
be provided with detachable wing tips interchangeable with landing lights for night flying.
Curtiss XNBS-4 on Acceptance Test.
In per fo rmance trials at the E ngineering Division, the new Curtiss XNBS-4 twin-Liberty
night bomber with a gross loading of 13.795 pounds attain ed a high speed of 103.6 m. p. h. at
ground and a ser vice ceiling of 11 ,100 feet with the bomb bay covered. \Vith the bomb bay open,
the high speed was reduced about 3 m. p. h. at ground and the service ceiling about 350 feet. These
performances Were made with Curti ss-Reed duralumin propellers and new engine cowling in stalled
on the airplane. The rotational speed of the metal propellers proved too high to give efficient per­formance,
and as a result it will be necessary to increase the pitch to hole\ the propeller speed within
l 700 r. p. m. befo re the tests are continued.
Upon the acceptance of the fir st airplane, several changes recommended by the Di vision will be
incorporated in the second article which is about ready for delivery. The Curtiss XNBS-4, a view
of which appeared jn the preceding Bul!ctin, represents quite an ad\'ance in design of bombardment
aircraft since the Martin Bomber.
XLB-1 Test Fuselage Received.
A static test fu selage for the new single-engined light bomber. :\foclel XLB-1, under construction
by H uff, Dalancl & Co .. Ogdensburg, N. Y., from a design suhmiteed in the light bombardment com­petitions
last April ( 1924), has been received anc\ tested. Several structural changes were founc\
necessary, anc\ a study was made to determine the feasibility of in stallitig dual controls for the
pilot and bomber. It was previously announced that this airplane would be constructed around the
\ i\T right T -3 engine but under a subsequent agreement to increase performance the new SOO-h. p.
geared Packard engine will be substituted.
New Pursuit Design Based on Boeing PW-9.
The E ngineering Division has made a design study fo r a new experimental single-seater pur­suit
airplane ba·sed upon the Boeing pursuit. The new design contemplates the use of an inverted
Packard l A-1500 engine, an auxiliary fuel supply carried in a cl roppable tank attached to bomb
rack beneath fu selage, and two synchronized machine guns mounted at the fl oor level. T he study
also includes a side-type supercharger installation and the feasibility of locating two additional
machine guns on the upper wing far enough outboard to avoicl necessity for synchronization.
Changes in Curtiss Pursuit.
The Curti ss pursuit, Model XPW-8A, which participated in the P ulitzer Race at \Vilbur
\ i\T right Field last October as stated on page 11 T eclmical Bulle! in No. 40, has been furth er changed
by the Curtiss Company. The revised airplane, now designated XP\tV-8B, is provided with special
tapered wings of smaller area and a tunnel type radiator. Combat performance tests wlll be made
with the Boeing pursuit to compare their relative maneuverability.
Standardization of Detachable Propeller Blades .
.A. joint conference was held by representatives of the Standard Steel Propeller Company, the
\1\Testinghouse Electric Company, the Navy Department and Army Air Service to di scuss stand­ardi
zation of both micarta and duralumin blades for adjustable pi tch propeller s. As a result the
Engineering Division has und ertaken the design of a proposed standard detachable blade of alumi­num
alloy fo r use by both Army and Navy Air Services.
Designs have been completed for detachable blade propellers fo r use on the Curtiss D-12 engine
at speeds of 1 SO and 175 miles per hour.
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GENERAL DESCRIPTION.
Airplane .. ...... Doug las X0-2
Type .... ... . . ........... Observation Biplane
St a tus .. .... ..... .. Experimental (firs t article)
Manufacturer .... : .. ...... ... The Doug las Company
Power P lant .. ........... ..... .. Liberty "12" Engine
Supporting Surface .... .. .. 411 square feet
Gross Weight ...... .. .... .... .. 4426.79 pounds
Usefu l Load 615.12 pounds
Wing Loading ... ... ... ... .... 10.77 lb ./sq. ft .
Power Loading .. .......... ..... I 0.31 lb. / h. p.
i---- ------ ----J:J'-8" ~ r--------- - ----z, '.... .:;"- ------
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GENERAL ARRANGEMENT OF DOUGLAS X0--2 WITH LIBERTY ENGINE.
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14 TECHNICAL BULLET I N No. 4 1
ELIAS NIGHT BOMBER XNBS-3
(Two Liberty "12" Engines.)
Elias XNBS-3 Below Performance Requirement.
The fir st XNBS-3 night bomber delivered to the DiYision hy G. El ias & Bro .. Inc., Buffa lo, N.
Y., on experimental contract failed to meet the specified per fo rmance. The contract req uired a
high speed of 100 m. p. h. at ground and a service ceili ng of 12,000 feet with load. T he best per­formance
attainable in the trials with the original H a rt zel I propel lers gave a high speed of 99. l
111. p. h. at 1648 r. p. m. at g round and a service ceiling of only 7.530 feet with load. This per­fo
rmance was later increased by the use of Douglas \Vor ld Cruise type propellers to 100.5 m. p. h.
at 1720 r. p. m. high speed at ground and 8,680 ft. service ceiling. Since there appeared to be no
possibility of increasing the service cei ling to come within the specifi cation without a complete re­design.
the second article was cancelled and the first retained at the DiYision for further tests.
The El ias night bomber presents a clean appearance quite superior to the usual twin-engined
type of airplane. The design incorporates an externally braced biplane construction with sectional
wing cellul e. duralumin tube fuselage, engine nacelles on lower inboard wing, wide-spreading axle­less
chassis. and semi-biplane tail structure utili zing a twin rudder arrangement with the upper
stabili zing plane adjustable in fl ig ht. The wings are symmetri cal ; the round-tipped outer panels
with long narrow unbalanced ai lerons inserted in the trailing edges fo rming a single bay tru ss. The
upper center section contain ing two 22-gallon g ra vity fue l tanks is carried well above the fu selage
by means of short N struts ri sing from the nacelles whi ch rest upon the lower inboard panels
directly above the chassis. Each nacelle, neatly cowled, houses a tractor Liberty engine equipped
with a ten-foot fo ur-inch propeller and a cartr idge core nose radiator. The main fuel supply is
contained in 157-gallon cylindri cal tanks mounted in the nacelles at rear of engines. The tankage
REAR VIEW OF ELIAS NIGHT BOMBER.
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GENERAL DESCRIPTION.
Airpl;::ne
Type
Status
Ma nufactu rer
.. .. El ias XNBS-3
...... S hol't Dis t a nce N ig h t Bomber
.... Expel'im ental (first artic le)
.. G. E lias & Bl'o., Inc.
Power Plan t. ____________ Two Liberty "12" Engines
Supporting Surface .. 154 1.!J square feet
Gross W eig ht ........... 14 ,443 pounds
U s efu I Load ..... .
Wing Loading.
Power Loading .
.. 5,634 pounds
. 9 .37 lb. /sq. ft.
.. 17 .24 lb. / h. p .
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GENERAL ARRANGEMENT OF ELIAS XNBS·3.
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16 TE C I-JNICAL BULLETI I No . 41
totals 358 gallons including that in upper wing tanks. The fu selage follows the usual arrangement
for bombardment airplanes. T hi s includes a bomber's cockpit in nose, a double cockpit for pi lot and
navigator , and a long deep bomb compartment extending beyond the trailing edge to the gunner's
cockpit in the tail. Beneath the bomb bay a wide unobstructed space between the single-wheeled
chasses facilitates the droppi ng of bombs. The arrangement of armament is the one outstanding
fea ture in this airp lane which elicited much commendation.
Skis for Winter Flying.
T hree sets of metal ski s, types A-1, B-3 and C-1 , having capac1 t1es of 1500, 2000 and 2500
pounds respectively have been constructed and fit ted to yarious ser vice ai rplanes for winter fl ying in
regions where snow and ice prohibit the use of wheels. T he smallest ski, type A-1, is designed for
use on J N-4H. l\ID-3A, MB-31\1 and P\ i\T-8 ai rplanes whereas the larger sizes, types B-3 and C-1.
are intended for use on the DH-4B. Two skis of still larger capacity have also been designed for
heavy aircraf t- a 4,000-lb. ski for the Douglas \ i\Torld Crui ser and L-\V-F transport and an 8,000-
lb. ski fo r the NBS-1, XNBS-3 and XNBS-4 bombers.
All of these skis are of metal construction consisting of a co rrugated cluralumin bottom or
runner, 1/ 16-inch thick" supported by a welded steel tube structure which carries a hub fitted with
bronze bushings fo r receiving the axle. T he super struct.ure is streamlined with 16 oz. cluck fabr ic
fastened to the runner w'ith rawhide lacing. The ski is held in proper position by means of two
safety retaining cables running from the ends of the ski to the front and rear landing gear strut
fitt ings on the fu selage. A shock absorber of 5/ 8-inch rubber cord is fastened to the forward cable
to preveM the nose of the ski from digging into the snow as well as to hold it in proper position
during flight. T he rear cable limits the movement of the ski. T he ski s are so designed that
they can be easily mounted upon the chassis axles after removal of the wheels, using the same
thrust collars as in the wheel installation.
DH-48 FITTED WITH METAL SKIS, TYPE C-1.
A IR CRAF T DEVELOPMENT 17
AIRSHIPS AND BALLOONS
Improvements to Terry Mooring Masts.
Sketches haYe been made by the E ngineering Division to accompany an Air Ser vice technical
order cover ing the req uired improvements to all Terry mooring masts now in the service in order
to preclude any repetition of the accident which resulted in the destruction of the TC-1 air ship at
\\' il bur \ \/ right F ield several months ago. T he proposed improvements which have been de­Yeloped
and prm·ed are as fo llows:
n. i\ brake band to restrain oscillation of the buffer a rrangement during the mooring pro­cess.
b. Shroud castings covering sheaye at base of mast to preyent displacement of the mooring
cable.
r. A new drum shaft whi ch enables the drum to ];e tnrnecl at hand -cranki1w speed.
d. Gusset plates and bolts for reenfo rci ng the joints of the wooden A-frame mounting for
the hand winch. T hi s reenfo rcement prevents di sto r tion and possible fa ilure when the mast
is being rai sed to the vertical position after its assembly on the ground.
The Terrv mooring mast is designed for outdoor use in mooring non-rigid air ships up to
200.000 cubic feet capacity. The mast is constructed of st ructural steel shapes and plates in eigh­teen7f
oot sections which may be assembled to give a height of either 54 or 72 feet depending upon
the number of sections used. T he mast step of the bottom section is pinned to a fo rked foot
block resting upon a timber grillage on the ground . The other section·s are bolted together and
brace by reenforc i1ig ropes attached to the top casting and mast step. T he top casting which carries
a 13-foot counterbalanced ring buffer is pivoted on the mast in such a manner that the whole ar­rangement
is frte to swing in a horizontal plane with the motions of the moored air ship except
when restrained hy the brake band during the mooring operation. The mooring cable runs from
TC-5 AIRSHIP MOORED TO TERRY MAST.
18 T EC HNICAL BULLETIN No. 41
the buffer over guarded sheaves downward thru the mast column to a hand winch mounted upon
an erection frame built integral with the mast it self. This winch al so serves as a hoist in erecting
the mast which after erection is held upright by means of eight double wire guy lines, radiating
at 45 degrees from the top of the mast and secured to Mathews Scrulix anchors buried in the
ground.
The mooring process is simple. It requires no large ground crew or personnel at the top of
the mast. It consists in simply connecting the drag line from the air ship to the mooring cable
which is then wound on the winch drum until the nose of the air ship is drawn into the buffer. The
cable is then securely anchored at the winch.
vVith the improved mast, mooring can be accompli shed with a high degree of safety in reason­ably
high winds with onl y a few men. Aside fr om their military utility, mooring mast s of this
type erected at suitable places will aid greatly in the early establi shment of transcontinental a ir­ship
routes.
RS-1 Airship Completed.
The construction of the Army's semi-rigid air ship , the RS-1. has been completed by the
Goodyear T ire & Rubber Company, Akron, Ohio. with the exception of a few minor detail s. and
the Yarious units shipped to Scott F ield. Illinois, for assembly and erection. Special cribbing de­signed
by the DiYi sion will be constructed at Scott Field to support the keel during its erection .
Hydrostatic tests on a water model of the RS-1 envelope with keel attached were conducted at
\Vilbur \i\.right F ield under the supervi sion of Professor Hovgaard of Massachusetts Institute of
Technology before the air ship sub-committee of the National Adviso ry Committe for Aeronautics
to determine the bending stresses under verti cal loads and with pressure changes in the e1welope.
The results obtained were so. promising that further tests will be made to ascertain the effect of
tran s\'erse and torsional loadings.
\ \Tith a view to increasing the range and endurance of this air ship. the E ngineering Divi sion
is preparing an alternate design of power car incorporating a single Packard l A-2500 engine by
which design it will be possible to substitute two light weight power cars each containing a P ack­ard
engine for the two heavy power cars containing two Liberties each as at persent. This substi­tution
of power plants would effect a saving of approx imately 3.0GO pounds which could be carried
as add itional fuel.
Construction on TE-1 Airship Started.
Construction on the all-metal car for the one-man training air ship is in progress at the plant
of the Aircraft Development Corporation. Detroit, Michigan. subcontractor to Air ships Incor­porated.
Hammond sport , N. Y . The design and stress analysis for the envelope. suspension and
control surfaces have not yet been approved. The envelope patterns as submitted were di sap­proved
and re\'ised because the panel widths were found too great for standard fabric. The car
will be equipped with a landing wheel and rudder bar control, of which the landing gear design has
been approved.
The TE-1 as this air ship has been designated is designed by the E ngineering Divi sion for
helium ·inflati on with a capacity of 80.000 cubic feet. Propul sion will be furni shed by two 60-h. p.
Lawrance :'.\fodel L-4 engines mounted upon outriggers. Only one model is being built for ex­perimental
purposes.
ARMAMENT
New Beams for NBS-1 Bomb Racks.
New and stronger beams have been designed a nd constructed for the NBS-1 bomb racks.
In static test, the new beams sustained a load of 7205 pounds in a hori zontal position and 7560
pounds in a vertical position. In compari son, the old beams 1tested under the same conditions
failed under a loading of 4165 pounds in the fir st position and 41 90 pounds in the second. The
new beams will be capable of supporting heavier bomb loads.
AIRCRAFT DEVELOPM ENT 19
The Oscillograph.
The oscillograph is a testing device developed by the Engineering Division for comparing
relatiYe merits of bomb sight stabilizers by duplicating on the ground the disturbing motions of
an airplane in flight. By artifically imposing different combinations of motions such as pitch, roll,
bank, acceleration , deceleration and centrifugal force on bomb sight stabili zers and photographicallv
record ing their oscillations, it is possible to obtain very accurate data on their behavior without the
expense of flight testing.
The apparatus is composed of three main parts : namely. an electrically operated camera
which records the oscillations of the stabilizer a tilting table on which the stabili zer is subjected
to pitching and banking, and the turntable which carries the entire testing equipment and re­produces
acceleration, deceleration and centrifugal force. The peripheral speed of the turntable at
the w rti cal axis of the tilting table can be varied from 1 to 10 feet per second and the velocities re­co
rded. The entire apparatus is electrically driven.
THE OSCILLOGRAPH.
(Insert) Close-up of Recording Camera
look ing into Tilting Table with bomb­s
ig ht s tabilizer ready for test.
20 TE CH N I C ,\ L BULLET I N No . 4 1
Gun Improvements on MB-3A Airplanes.
Jn order to eliminate interference between the center section brace wires and the gun synchro­ni
zer generators on MB-3A airplanes . the brace 1Nires ha,·e been replaced by rods and spreader s. a
few sets of which will he made and sent to Selfridge Field. fi chigan. fo r in stallation on the air­planes
at that station.
The Engineering Division has also devised some wire cage a111111 u111 t1on ejection chutes for
use on the fixed Browning gun s in these a irpla nes. These cages were purposely constructed to
deflect the clips and ejected shells from the cockpit without impeding flow of air thru the side radi­ator
s. Two sets of chutes have been fo rwarded to Selfr idge F ield fo r c;ompleti on of tests to de­termine
the feas ibi li ty of adopting thi s type of chute for the Sen·ice.
EQUIPMENT
Night Illumination for A. S. Flying Fields.
The Engineering Division has prepared lighting layouts and cost estimates for the night il­lumi
nation of several Air Service fl ying fi elds including Boll ing . Chanute. Langley. l\'[itchell.
Pope. Scott and Selfridge in contin ental United States as well as F rance F ield. Panama Canal
Zone. and \ \/ heeler Field. H awaiian I slands. The equipment at Bol ling F ield will be used jointly
hy the Army and N"avy Air Services.
36-INCH BEACON EQUIPPED WITH INCANDESCENT LAMP AND DONNELLY DOOR.
AIRCRAFT DEVELOPMENT 21
Substitution of the incandescent lamp for the arc light mechanism in searchlight beacons is
under observation and test at the Division. For this purpose the large 36-inch rot.:1.ting search­light
beacon at McCook F ield has been equipped with a 10-kilowatt, 110-volt incandescent lamp, an
automatic time light relay device and a new design of facto ry-ribbed wire-glass diverging door to
supersede the arc-light mechani sm and ground op ti cal glass door previously used on this long range
beacon. T he factor y-ribbed or "Donnelly" door costs a great deal less than the regular ground
glass door and gives satisfactory beam divergence as a floodlight in night landing.
Several A. G. A. gas beacons belonging to the Division hut located at Wilbur Wright F ield
have been electrified by replacing the gas mantles with 3-kilowatt, 110-volt incandescent lamps.
T hese lamps are automatically controlled by means of a new time limit relay device similar to that
in stalled in the McCook F ield 36-inch rotating searchlight beacon. Three new types of gas flashing
traffic beacons have been in stalled at McCook Field fo r night flight observation, in accordance with
the night landing trail scheme in use by the Post Office Department. This method of lighting
was suggested by the American Gas Accumulator Company.
New Night-Flying Equipment for Airplanes.
P hotometric tests on three new designs of airplane landing lights submitted by the Westing­house
Lamp Company have been completed. O ne of these, a special V-shaped fi lament lamp.
shows promise of giving more efficient results in beam di 1·ergence than the present Type A landing
light.
The Division has in progress the study, con struction and in stallation of night navigation
equipment on the Curti ss pursui t, NBS.-1 night bomber and standard DH-4B airplanes. Tests on
the fir st production model night-fl ying DH-4B to be thus eq uipped pro\red sati sfactory with the
exception that the glare from the short exhaust manifolds seriously interfered with the pilot's
vision in night landing. Long exhaust manifolds wi ll be used as soon as available.
Ground Temperature Compensated Altimeter.
T he ordinary service altimeter is calibrated to read correctly when the mean temperature of
the air column is plus 10 degrees Centigrade. Consequently its indications vary higher or lower
than the actual altitude depending upon the sea­son
of the year. In winter, for in stance, the alti­meter
may read 1,100 feet too high at 15,000 feet
making an error of 8 per cent . . At 30,000 feet
this er ror increases as high as 12 per cent, that
is, the in strument indicates approximately 3,600
feet higher than the actual altitude reached. The.
error s are less in the summer at high altitudes.
This seasonal variation explains to a large extent
the inconsistencies between indicated and cali­brated
altitudes in altitude flights.
If, however , the yearly average decrease in
temperature with altitude is incorporated in the
calibration formula, these errors would be reduced
to 4 per cent at 15,000 feet or a plus or minus
600 feet and to 3 per cent at 30,000 feet or a plus
or minus 1,000 feet according to the season of
the year. Accordingly a service altimeter was
compensated fo r seasonal changes by means of
an adj usting knob to change the magnifi cation
ratio. Since t he seasonal temperatures varied
ALTIMETER COMPENSATED FOR GROUND widely in different parts of the country, the use
TEMPERATURE. of the seasonal altimeter was limited to a compara-tively
short ra nge of latitude (central United
States.) Therefore by simply changing the magnification ratio and calibrating the adj usting knob
to compensate for ground temperatures from min us 10 to plus 30 degrees Centigrade in stead of
seasonal variations, it was found that the accuracy of the in strument could be held within a plus
or minus 2 per cent and its usefulness extended to all parts of this country.
22 TECH r I CA L BUL L ET I N No. 41
H ence the ground temperature compensated altimeter shown herewith gives an accuracy within
2 per cent anywhere in this country ir respective of climatic changes but it does not, however, cor­rect
the altitude for the ordinary changes in baro metric pressure during flight.
Mayall Airplane Engine Heater.
\ i\Then an .airplane_ in ever~day winter fl ying service is housed in an unheated hangar, it is
usually necessa ry to either dram the water from the cooling system of the engine or keep it
warm enough to preyent freezmg with resultant damage. Several types of heaters haYe been de­veloped
fo r this purpose but the Mayall heater di s­cussed
in this arti cle affords an easy and practical
means of keeping the engine warm where orcli­nary
electric current is available.
This beater is an electri cal device which may
be in serted in the water line near the engine. I t
consists of a short brass tube about eight inches
long surrounded by electric beating elements
which transmit heat thru the walls of the tube.
thus setting up a circulation of warm water ·within
the system. T hese elements or coils are care fullv
in sulated and jacketed on the outside to preve1{i
injury and loss of beat. T he heater is connected
to the power source by means of an ordin ary elec­tric
light plug.
During the winter of 1923. a few of these
heating units were purchased and ·tested at the
Division for current consumption and heating ef­fi
ciency under actual sen ·ice conditions. T hese
tests demonstrated that a well blanketed Libertv
engine housed in a hangar where there are no ex­cessive
dra fts can be kept warmed at least 24 de­grees
Centigrade above room temperature with an
energy input approximating 750 watts. At 5 cents
MAYALL ELECTRIC HEATER per ki lowatt-hour, it would cost about 60 cents to
As Insta lled in Waterline of Airplane Engine. operate this heater over night, that is, from 4 p. m.
to 8 a. m. or about 16 hours. Before placing a
heater of this type in sen-ice, however, tests should be made to locate " cold" spots caused by the
interference of the water pump and other parts which retard the flow of the water.
Altho· the Mayall heater proved satisfacto r y, 1t was concluded that an immer sion type of
electric heater in which the heating element is placed directly in the water in stead of enconipassing
the pipe thru which it flows would impart more heat and prove even more efficient and economical.
Handbook on New Direct-driven Generators.
A handbook covering the operation and maintenance of Air Service T ypes lL and 2L direct­driven
generators for aircraft bas been published by the Division and di st ri buted to the Service.
Jn product ion, the nomenclature of these generators with slight modifications will be known as
Types B-1 and C-1 respectively. T he principal diffe rences are enumerated below :
a. T ypes lL and 2L generators have a friction clutch at the base of the generator, which
slips under the torsional whip of the generator drive. T hi s slipping protects the driving
splines. In the production models, T ypes B-1 and C- 1. the driye will be taken thru canti­lever
sp rings which will also absorb the to rsional s tresses.
b. T he negative armature line of the produ ction generators will be grounded. T his applies
to all generators manufactured after July 1, 1924.
c. The control boxes for production model generators are smaller than the control boxes used
in connection with T ype lL and 2L generator s.
The in structions given in the handbook apply to all fo ur types of generator s.
A IRCR A FT DEVELOPME N T 23
New Parachute Designs- Maintenance Transferred to F. A. I. D.
A new back type parachute, built and tested by the Division, is being worn by various pilots
to compare its comfo rtabl eness with that of the present seat type pack. A new fixed type silk para­chute
has al so been built and drop-tested successf ully from a kite balloon. This parachute is de-signed
fo r use in lighter-than-air craft. ·
T he Division has recondition ed a number of service type parachutes of both the seat and lap
types fo r issue to the Service, some of which will be sent overseas. T en parachutes have also been
tes ted and made ready for the Air Mail Service. The repair and replacement of parachutes which
work has been clone entirely at the Division during the past few yea rs will be tran sferred to the
Fairfi eld Air Intermediate Depot in the near futur e.
Supercharger Gage.
T he supercharger gage is a compact combination in strnment of th e vertical scale type by
means of which a pilot can compare the fuel and air pressures at the carburetor on a supercharged
airpla ne. It was designed by the E ngineering Division to supplant two in struments heretofore used
on supercharged engines: namely, a fuel pressure gage with sealed case and an engine altimeter,
a sealed mechani sm connected to the carburetor air intake to indicate apparent altitude at whjcl1 the
engine is operating.
T he unit (see sketch ) consist s of an air-tight case connected to the carburetor air intake mani­fo
ld . a fu el pressure gage A of the ordinary Bourdon tube type in serted in the fuel line at the car­buretor
. and an evacuated Bourdon tube B fo r mea suring the absolute p ressure of the supercharged
air at the carburetor (a simple altimeter mechanism may be used for this purpose also.) Becanse
the fu el gage is exposed to the pressure of the supercharged air in the case, its indication gives the
differenti al p ressure of the fu el and air at the carburetor of the supercharged engine. The in stru­n1ent
has no adjustments. It serves simply as a gage whereby the pilot is enabled to regulate
and maintain the supercharged air at sea-level pressure at the carburetor, and thus keep the engine
developing full power at altitude.
T en units have been manufactured for service test by the P ioneer In strument Company under
E ngineering Division specification s. These gages are fitted with an altimeter mechani sm in stead
of an evacuated Bourdon tube for indi cating carburetor air pressure.
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SUPERCHARGER GAGE SHOWING ARRANGEMENT OF PRESSURE UNITS.
24 TECHNICAL BULLET I N No. 4 1
Photographic Trucks.
The making of aeri al photographs in the fie ld grea tly exped ites the work of observation
squadrons and other photographic missions during peace or wartime. It enables them to prod uce
photographs quickly at the scene of operation and thereby save much Yaluable time that would other­wise
be consumed in having this work performed at the base laborato ry. To fulfill this specific
purpose. the E ngineering Di vision has developed a dual unit motori zed photographic laboratory, de­scribed
in this article. se \·eral units of which a re now undergoing sen·ice test.
PHOTOGRAPHIC TRUCKS READY FOR FIELD SERVICE.
AIRCRAFT DEVELOPMENT 25
This traveling laboratory comprises two dark roorn s, one for developing negatiYes and the
other fo r printing them, mounted on two Class B (3- 1/ 2-ton) U.S. Military chasses equipped with
10-kilowatt electric generators. These dark rooms or bodies are of all wood construction, 13 feet
long by 80 inches wide by 76 inches high , with a 36-inch overhang above the driver's seat. In
general design the bodies are practically identical differing only in the interior arrangement and
eq uipment. Each body has two windows, one on each side. and a door in the rea r. The windows
are ca ref ull y shuttered both inside and out to prevent light entering, and every p recaution is taken
to in sure light tightness thruout the roorn. Several brackets on the outside of the body provide
for the attachrnent of a shelter tent with fly and for the support of a drying reel and motor.
The interior of the body is finjshecl in battleship gray and white enamel. In the overhanging
portion is ample space for two supply cabinets and a n 18-inch exhaust fan which ma intains a
continuous change of air in the room. The fresh air is drawn in thru light-tight ventilato rs placed
in the sides of the hody near the floor and is finally expelled thru a thermo-controlled ventilator at
the back of the fan. The fan is of the self-cooling type controlled by a switch and rheostat. The
floor of each truck is covered with heavy tan battleship linol eum, varni shed on both sides before
heing laid. SeYeral receptacles are conveniently placed along the walls to accommodate ruby or
plain electric lights. T he room may be heated in cold weather from the engine exhaust or by an
electric heater.
Inside at the front of each body is placed a large 120-gallon tank for storing water. This
tank is filled by means of a portable electric-driv en pressure pump controlled from in side by an
automatic relay which cuts in when the pressure falls to 20 pounds and out when the pressure
reaches 50 pounds per square inch.
The interior of the printing truck is divided into two compartments entered thru the door at
the rear of the truck. The print-developing room. in the fore part of the body is fitted with de­veloping
sinks along both sides and encl. Each sink is equipped with two water faucets and a
drain board. At the encl of the sid e sinks which extend fully two-thirds the length of the bodv
a partition is placed to separate the print-developing room from the printing compartment at the
rear. A heavy rubber curtain in this partition forms a lighf-tight door between these cornpartments.
The printing room contains a large storage cabinet for paper and negatives and an air trap for
yentilation. On top of this cabinet and air trap, two electric printing mac;hines are mounted. As
soon as the prints are exposed, they are passed thru a safety slide in the partition into the develop­ing
room where they are developed and washed and then passed outside thru another slide into
the drying and mounting tent.
In the filrn-cleveloping truck, a small sink is in stalled across the front above the supply tank.
wlith two faucets for water. Receptacles are placed above the spla sh board and elsewhere about
the room fo r use of Brownie safe lights. The floor is covered with grating or cluck boards over
the linoleurn and is provided with light proof drains for carrying away the waste water from the
developing tanks.
For field operation, a small lean-to shelter tent with three "Bobbinetted" windows is erected
at the side of each truck. A canvas fly stretched over a ridge pole on top of the truck shelters
both truck and tent in hot weather. The tent not only serves as a place for drying negatives and
prints but also provides sleeping quarters for the personnel.
The equipment consists of a motor-driven water pump rnountecl on a portable base, a col­lap
sible drying reel belt-driven by a small electric motor, collap sible tanks fo r storage of surplus
water. two K-1 electric printing machines in the printing truck and one K-1 fi lm developing ma­chine
in the cleYeloping truck.
The water pump can be easily carried about by two men . suffici ent hose and cable being sup­plied
for its operation at 150 feet from the trucks. A short hose, 15 feet long, is atta,ched to
the suction encl so that water may be taken alongside a stream or the whole unit lowered into a well
if necessary. The pump is driven thru a flexible coupling by a small 1 h. p., 110-volt D. C. motor
capable of delivering 16 gallons of water per minute against a p ressure of 60 pounds per square
inch at a speed of 1150 r. p. m.
The collapsible reel for drying roll film is mounted on the side of the truck body in side the
tent. It is made of wooden slats fastened around two encl di sks and is rotated abot1t 80 r. p. m.
by a belt drive from a small 1/ 6-h. p., 110-volt D. C. motor. The reel like the collapsible water
tanks occupies very little space when di sassembled and stowed away in the truck body.
1. Interior of Developing Truck.
2. Entrance to Printing Compartme nt.
3. Interior of Printing Truck.
K-1 Film Developer and Drying Reel.
Electric Cables a nd Light-lig ht Ventilator.
6·. Portable Water Pump and Hose Connections.
ARRANGEMENT OF EQUIPMENT IN PHOTOGRAPHIC TRUCKS.
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AIRCRAFT DEVELOPMENT 27
SWITCHBOARD AND GENERATOR CONTROL ON PHOTOGRAPHIC TRUCK.
T he electri c current for operating the water pump, exhaust fan, drying reel and printing ma­chines
is suppli ed by a 10 k. w. , 125-volt, 60 ampere direct current generator suspend ed in the
chassis di rectly behind the engine by which it is dri ven. The generator is compound wound of
special design. The armature shaft is bored out to permit the propeller shaft to pass thru it. T he
rear encl of the propeller shaft is splined and fitted with a clutch which may be shi f ted backward
by a lever in the driver's floor to drive the t ruck or fo rward to engage the generator . There is
no neutral position except as provided in the truck transmission. A fan on front end of the arma­ture
shaft cools the generator when the covers a re open. \Vhile driying the generator the engine
is automatically th rottled to prevent dangerous overspeeds by means of a vertical centrifugal gover­nor
driven by a spiral gear on the side of the generator clutch. T he trucks a re connected by elec­tric
cables so that it is only necessary to operate one engine at a time in order to supply current for
both units.
A ,switchboard enclosed in a fire-proof cabinet in the cowling facing the dr iver permits him to
regulate the generator load without leaving his seat. On the switchboard are mounted an auto­niatic
overload circuit breaker, field rheostat, ammeter. voltmeter, light receptacles, and two single
throw switches, one a single pole line switch and the other a double pole fie ld switch.
The service test models described in this article were bui lt for the Air Service bv the Glenn
L. ~fa r t in Company, Cleveland, Ohio, and incorporate many improvements over the ,fir st experi­mental
units designed and constructed at the E ngineering Di vision. Several new units have been
di stributed to various observation squadrons for service test under actual fie ld conditions.
\ i\Tith a view to further increasing the mobili ty of photographic trucks as well as other motor
tran sportation units, the E ngineering Divisioll" is advocating the mounting of all such equi pment on
the new six-wheel Class "C" (3-1/ 2-ton ) pneumatic-tired l'. S. Military chassis. Greater mobil­ity
is of paramount importance in all motor transport of the future if close liaison with the va!·ious
squadrons is to be mai ntained in the field of operations.
New Camera for High Altitude Photography.
A new long range, high altitude camera, Model K-7, is under development at the Division. It
is proposed to so mount this camera that its optical axis will be parall el to the fong itudinal axis of
the airplane, and in a rotary frame mount a prism or mirror thru which may be taken either
oblique or vertical photographs. By mounting this frame in tegral with the camera and rotating the
prism, or the prism and camera together, pictures may be obtained in practically all directions.
28 T ECHNICAL BUL L E T IN No . 41
ALLISON FOUR-ENGINE (LIBERTY) TRANSMISSION.
A IR CRAFT DEVELOPMENT 29
Universal Camera Mount.
A uni versal camera mount is under preliminary development whereby it will be possible to
automatically manipulate an aircraft camera to take overlapping Yerti cal and oblique views, the
latter alternating to right or left thru openings in the sides of the fu selage. This will permit the
taking of both verti cal and oblique views with the same camera and. in addition. offers a possible
aid in obtaining contours by taking both verti cal and oblique Yiews of the same obj ect. This mav
he accompli shed by making parall el and 50 per cent o\·erlapping flight s.
POWER PLANTS
Division Builds an Air-Cooled Liberty.
The latest mod ifi cation of the Liberty engine is the new air-cooled model designed and as­sembled
by the E ngineering Di vision from new parts manu factured by the Allison Engineering
Company. T he air-cooled Liberty has a bore and stroke of 4-1 / 8 inches by 7 inches, respectively.
giving a di splacement of 14 11 cubic inches. It incorporates a standard Liberty engine crankc:ise
fi tted with twelve Type L air-cooled cylinders. new pistons and special O\'erhead camshaft hous­ings,
all of a special cast aluminum alloy. Cooling is accompli shed by the propeller slip stream.
part of which is directed into the vee of the engine by means of a semi -circular tapered cowling
or scoop hinged to each camshaft housing and arched aboYe the vee in such a manner that the air
is pocketed and caused to escape between the finn ed cylinder s. A feature of the design is the
rotary induction system dri ven from the rear encl of the engin e.
In preliminarv power runs on the dynamometer . the air-cooled Liberty deYeloped 400 h. p. at
1800 r. p. m. with a specific fuel con sumpti on of .56 lb. per h. p. hour. A standard 50-hour en­durance
test wi ll be conducted.
Allison Four-engine Transmission.
T he Alli son fo ur-eng ine transmi ssion is a reduction gear thru which four standard Libert \·
eng ines d riw one large propeller. This tran smi ssion was desig ned and built by the Alli son E n­gin
eering Company, Indianapoli s. Indiana. fo r u se by the Air Sen·ice in connection with a pro­posed
long range night bomber utili zing a cen tra li zed power plant. The gear pro,·ides for a re­duction
ratio of 53 to 18 thereby reducing the normal eng in e speed of 1700 r. p. m. to 577 r. p. m.
at the propeller.
The tran smi ssion consists of a large rectang ul ar cast aluminum case carrying four driving
pi nions. one in each corn er. grouped around a la rge spur gear on the propell er shaf t. Each pini on
is driven by a standard 400-h. p. Liberty engine thru a· sliding tooth clutch in such a manner that
any engine may be thrown in or out of gear at wi ll. The case with its corner mounting brackets
parts vertically in the plane of the gear s ; the fr ont half carries the propeller shaft with its gear
and bearings and the rear half , the four dri ving pini ons. clutches and generator mounting . In as­se1rrbly.
the two hal ves a··e bolted together along the flange s. the hell-shaped opening in the rear
half recei ,·ing the rea r bea ring on the propeller shaft. Thrust stresses are taken by se\reral large
thru -bolts spaced near the periphery of the large ge:ir which clri,·es a 600-watt electric generator
in the top of the casting . An independent oi l system operated by a pump supplies oil fr om an out­side
tank to the gear s and hearings. The pump al so scayenges the case and return s oil to the tank.
In the in stallation. the transmi ssion is mounted by means of the corn er brackets. no other
supports being necessar y. T he engines are placed in pairs on different levels with one pa ir
coupled close to the upper gear pinions by short hollow shafts and th e oth er pair mounted to the
rear and connected to the lower pinions by long hollow shafts passing under the forward engines.
The distance between the pinions, however. is such that either the front or rear pair of engines
may be placed on the upper or lower level as desired. The transmission complete with propeller
huh. dri ve sha ft s. coupling and adapters exclusive of generator weighs 875 pounds.
For the 50-hour test which was run at the m::mufacturer's plant, each eng ine was equipped with
a tachometer . oil pressure gage. switches and ammeter, spark and throttle controls. and a clutch
~ hiftin g lever for engaging the gear. The temperature of the oil fr om the tran smission as well as
that of th e oil and water fr om each eng ine was observed during the test whi ch was made in fiw­hour
run s. four hours at 90 per cent power and one hour at fu ll power.
30 TECHNICA L BULLETIN No. 4 1
To begin the test, one engine was fir st engaged with the transmission and then started by
m.eans of the electri c starter. This engine th rottled to about 700 r. p. m. continued to operate the
gear until the other engines had been started out of gear , th rottled to approximately the same
speed and th en engaged. After starting, any engine could he engaged without difficulty by simply
bringing it to the same speed as the others before shifting into gear. As the test proceeded it was
found possible to throttl e, di sengage or stop any particular engine at any time or speed .
INTERNAL VIEWS OF ALLISON FOUR-ENGINE TRANSMISSION.
At the completion of the test, the tran smiss ion was examined and found to be in excellent
condition, the only indi cation of wear bei ng a sli ght poli shing of the gear teeth at the pi tch lin e.
There was practi cally no wear on the bearings fr om which it was evident that the tran smission
would be long-lived. The method of engaging the engines with the gearing thru slidin o- tooth
clutches appears to be highl y sati sfactory. and it is thought that any inexperienced operator would
have no difficulty in throwing any engine in gear e\·en at a difference in speed as high as 50 r.p. m.
Shifting in all cases was accompli shed with the same fac ility as in an ordin ary automobil e.
First Curtiss R-1454 Radial Accepted.
T he new Curti ss R- 1454 radial engine recently delivered to the Division has passed the ac­ceptance
tests. T his engine is the fir st of three la rge experimental radials to be built by the Curti ss
Aeroplane & Motor Company. Buffalo. N. Y .. from a design based upon the impro,·ement of an
earlier engin e, Model R-1. constructed for the A ir Service by the Allison E ngineering Company
and the more recent developments in large bore a ir-cooled cylinders carried on at the E ngineering
Division.
The new product is a 9-cylinder fi xed type a ir-cooled radial engine designed to de,·elop 400-
h. p. at 1650 r. p. m. It has a bore and stroke of 5-5/ 8" and 6- 1/ 2" respecti vely. Its construction
incorporates many improvements over the original R-l engine to lighten weight and increase per­formance.
chief among which are the introduction of light pi stons. imp roved crankshaft and con­necting
rods. and rotary induction system. Another innoYation is the dual magneto embodying
the di stributor dri ,-e within the magneto itself. To hold the weight of the engine within the con­tract
limit of 760 pounds req uired careful workmanship and the use of the new alloys of alumi ­num.
Such parts as the cylinder heads. pistons and p iston pin bushings were supplied by the
Division.
Several fa ilures occurred during the 10-hour acceptance tests due to trouble with an intake
valve, the connecting rod bronze bushings and the piston pin light a lloy bushings. On a short run
of 30 minutes, the engine deYeloped 405 h. p. at fu ll throttle ( 1650 r. p. 111.). A SO-hour endur­
·ance test is now in progress.
RESEARCH AND EXPERIMENT
I
RESUME OF ENGINEERING DIVISION
SERIAL REPORTS.
Serial R eports m~rked with an astemk \ *) wiil
be issued by the Chief of Air Service as "Afr
Sen1ice Jnfor111atinn Circulars."
AIRPLANE SECTION.
Resume' of Deveiopment of Gallaudet DB-1. Serial No. 2369
T he advance in the constructive technique of aircraft represented abroad by the achievements
of Junker and Dornier with the internally braced metal monoplane and later typified in t his country
by the remarkable demonstrations of the Junker L-6 metal airplane induced American aircraft de­signers
to attempt to incorporate the characteri stic features of this type of construction, such as the
all-metal structure and the intern ally braced wing, in the design of military aircraft. Subsequent
in vestigation of the Junker monoplane by the E ngineering Division. particula rly in respect to
material and structural resea rch, eventually leacl to the solicitation of designs from the industry. the -
most promi sing of which was the Gallaudet DB-1 bomber tendered by the Gallaudet Aircraft Cor-poration.
·
T he report gives a comp lete hi stor y of the de velopment of this airplane from the ini tial design
to its present stage and di scusses in detail the various diffi culties encounte red and the recommeilda­'
ions fo r future development.
General Procedure in Airplane Design. Serial No. 2405
This report gives the proposed revisions on general procedure in ai rplane design fo r use in
the new edition of the Air Ser vice handbook, Stn1.ct11ral A 11alysis and Desi_r;n of A irplanes, which
it is hoped will soon be ready for publication. T he co ntents includ e Chapter IV and Part IV of
the appendi x. The new edition. a part of which wi ll he publi shed in 1925. will probably be issued
nncler the title "Airplane Design."
Resistances of Streamline Fuselages of Racing Airplanes. Serial No. 2406
T he res istance of three streamline racer fu selages designed by .the Division were determined
and compared with that of the Army Curtiss Racer fu selage. T he model fu selages with and with­out
cockpits and dummy pi lots were tested in the l\TcCook F ield 5-foot wind tunnel fo r resistance
and drag at speeds from 40 to 250 m. p. h_ The three streamline fo rms proposed for future racers
showed an aerodynamical excellence that is rare ly attained in actual design. T he results of the
tests, however . indicated that this excellence had been approached to some extent in the fu selage
of the Army Curtiss Racer.
Aerodynamical Characteristics of TP-1 and C0-2 Fuselages
With and Without Chassis. Serial No. 2413
T he aerodynamical cha racte ri stics of two model fuselages, the Engineering Division TP-1
two-seater pursuit and the E ngin eering Division C0-2 two-seater observation, as determin ed in the
McCook Field 5-foot wind tunnel for various angles of attack and airspeeds demonstrate that the
chassis contributes a la rge percentage of the total drag- at small angles in both cases and that the
drag coeffi cient decreases and the positive moment increases with speed.
32 TECHKIC A L BULLETIN No . 4 1
Collection of Unrelated Model Airfoil Tests. Serial No. 2416
In this report will be found a coll ection of aerodynamical data on miscellaneous airfoil tests,
exclusive of those given in Serial No. 2340 on du ralumin and wood model airfo il s. T he data have
been taken from tests on different airfoils in different wind tunnels at varioiis airspeeds so that
the results are not directly comparable. T he in fo rmation, however, is particularly ya]uable for
reference purposes.
High Speed Test of Wing Section with Bullet Holes in Fabric. Serial No. 2419
In order to determine whether or not the fab ric of a 'Aring section pierced by one or more
bullets will tear off at high speed as encountered in diving a 'p lane, a section of an MB-3A pursuit
wi ng was subjected to a wind tunnel test at an air speed of 240 _m. p. h. F or the test. the section
was covered with new fabric and fr esh elope and three holes made in both sur faces between the
spars. These holes were further extended by cut ting slits one inch in length at right angles. A
similar sli t, one inch long. was also made in the fabr ic OYer the veneer on the leading edge. Ordi­nary
bull ets passing thru the fabr ic would not leave as severe tea rs as those that were made artifi c­allv
for the wind tunnel test.
BULLET-PERFORATED WING FABRIC AFTER WIND TUNNEL TEST.
An ai rspeed of 240 m. p. h. was maintained thruout the test with the section set at two posi­tions
of attack, a minus 2 and a plus 5 degrees. The fabr ic showed no tendency to tear in either
case. Following these tests, the leading edge was cru shed as shown in the photograph and the air­speed
run up to 200 m. p. h. without any evidence of the fab ric tearing off.
Al tho ·it was impossible in this test to reproduce the actual stresses induced by acceleration in
free Right. it is thought that the fabric will not tear off the wi ng even tho perforated by several
bullets provided the intern al structure of the wi ng is of suffic ient strength to withstand the fo rces
encountered in maneuvers at high speed. From the results of this test, it is safe to assume that
if the ten sil ~ strength of wing fabr ic is high eno ugh to with stand all normal stresses in nnneuvers
at high speed. the addition of several bullet hol es will not cause failure. In cases where the
fa bric has torn off of airplane wings during flig ht. the trouble can usually be attributed to failure
of the internal structure of the wing or of the le<tding edge under high locali zed stresses. to im­proper
spacing of the ri bs. or to the age and rott en condition of the fab ric itself.
Application of "Method of Least Work" to Redundant Structures. *Serial No. 2420
In this report a nevv application of the "l\Tethod of Least \!\Tork" to redundant structures is
presented in order to evolve a more efficient method of attacking problems and tabulating results
'The development of working equations and their solutions is carried out with the aid of a new
method of tabulation which is believed to be mo r e efficient than those methods ordinaril v em­ployed
in connection with the "l\fethod of t east \ \To rk." th ereby saving much labor in S'olving
several simultaneous equations and by precluding the introduction of errors.
R ESEA R CH AND EXPE RI MENT 33
T he framework of the Lepere (USA-C-11 ) airplane wings is used as an example in this re­po
rt, and an analysis of the structure fo r low incidence condition of flight is carried out in detail.
Determination of Engine Power at Altitude from
Propeller Characteristics. Serial No. 2422
It is shown in this investigation that the power of an aircraft engine at altitude can be com­puted
from the characteristics of the propeller since the propeller must absorb all of the power cle­li
\·ered by the engine, the power so absorbed being directly proportional to the density. The varia­tion
of engine power and the revolutions of the propell er with altitude, two factors required in air ­plane
perf ormance calculations, were determined by fl ig ht tests at given altitudes under average
conditions with airplanes whose engine power curves had been p reviously determined on the dyna­mometer.
T he results of this flight-test method of determining engine power from propeller
characteri stics appear to more truly represent the actual, per fo rmance of the engin e at altitud e than
those obtained in the altitude chamber or by oth er methods.
F or comparison, the accompanying chart gives the variation of engine power with altitude as
determined by four diffe rent methods of computation. The flig ht-test method represented in
curve N o. 1 shows that the percentage of engine horsepower is consistently lower than that ob­tained
by any of the other methods. T he use of this curve in connection with the curve repre­senting
the revoluti ons per minute at constant airspeed is th erefore recommended fo r performance
calcul ation.
VARIATIO!f Or Nt6!11t f'OrfL!i' W!Tlf (ILTITIJ!Jc
(R.P.n. CO/f5TAIYT)
-+----< ,A5 DcTO'i'/'1/liCO 8 Y f---+----1 i rL/6/fT Tc5T OATA.
f'OWt:/f f'L/l/'/T ;</CTl/tJOS (~D. SERI/IL 1743).
llYD. /i.P. ~t//IT!Olt /OR t.!fJOfTY.
B. S. /ILT!Tt/Oc (/1/11'/IJC/i' ll'.fT-6 Of(j/lfcS.
zoooo~"lr-__,f-"<-'<c--+~-+-~-+-~-+-~+----1~-+-~-+-~--+.,-~+-----i
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/9000 t;
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/6000~.-+--~-+-->-...._..,.+->.-_.,l--+-l~-l-~-+-~-+-~-l-~-+---4-~--I I ~ ,,
/4<100~-+-~-+-~+---........---<rt~~~-r--~;--~r-----t~-+-~------1
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..35 40 45 50 S5 60 65 70
VARIATION OF ENGINE POWER WITH ALTITUDE.
34 TECI-lNICA L BULLETIN No. 4 1
Resistance of Center Section Type Radiator. Serial No. 2421
This investigation was made for the purpose of obtaining the resistance of the center section
core type radiator hy means of a wind tunnel te st so that the data thus obtained could be com­pared
with re sistance values submitted by the Curtiss Aeroplane & Motor Company on a similar
radiator in free flight. The results checked very close! y with those obtained by the Curtiss Com­pany.
An effort was made to measure the lift of this type of radiator but no correct estimation
could be obtained owing to the small aspect ratio of the test section.
The center section core type radiator is und er consideration as a substitute fo r the wing sur­face
type radiator fo r use on the Curti ~s pursuit.
Wing Analysis of Lepere (USA-C-11) Airplane. Serial No. 2425
f\ ltho the primary purpose of this analysis was to determine whether the lower external drag
wire which broke in flight fai led on account of overstressing, the real value of this analysis lay in
the technique gained in the application of the method of least work to a complex structure with a
minimum expenditure of energy, which method is di scussed under the foregoing seri al No. 2420
on the preceding page. In addition. a fairly up-to-elate stress analysis of the Lepere wings was
obtained. and the necessity of including certain add itional data in stress analyses of ser vice aircraft
became apparent.
The Power Plant Problem in Heavy Bombardment Airplanes. Serial No. 2427
This discussion treats the power plant problem in heavy bombardment airplanes by a com­parison
of the three common arrangements of engines ( that is, the single engin e, multiple engines as
separate units and multiple engines as single centra lized unit) upon the basis of performance. main­tenance.
arrangement, reliability and cost. To simplify the discussion and make the conclusions
comparable. it was assumed that all three arrangements employed reduction gearing, that each had
the same total horsepower . and that the individual power uni ts in each arrangement had the same
weight per horsepower.
T he use of geared power plants in heavy born bardment airplanes appears to be t he only logical
means of obtaining the necessary propulsive efficiency in the take-off and rate of climb at the
ground. The in stallation of a high speed engine in a slow and heavily laden bombing airplane
results in poor performance at these critical speeds. Hence the geared engine which keeps the
propeller r. p. m. relatively low is more efficient and improves both take-off and climb to an extent
that warrants its use in airplanes of this type.
The various phases of the power plant prob lem as applied in present aircraft and as proposed
in future in stallations are intensely interesting and form the basis for much careful deliberation.
Static Tests Conducted at the Division.
The fo llowing serial reports contain complete accounts of the static tests conducted at the En­gineering
Division on va rious airplanes and a irpl ane parts to determi ne their structural fitness for
fli ght. Each report is replete with detail drawings and photographs of the structure and the results
and discussion of the test.
Seri al No. 2338-Second Proof T est of Gall audet DB-1 B Control s.
Seri al No. 2401-Kerber-Boulton E xperimental Wing Beam.
(This beam is an Engineering Division design in duralumin and steel tubing·.)
Seri al No. 2403-L. \V. F. NBS-2 Engine Nacelle and Chassis. ~
Serial No. 2410-Proof Test of E lias NBS-3 Hori. Tai l Surfaces.
Serial No. 2412-Curti ss P ursuit v\T ings (Second set fo r PW-8.)
Serial No. 2430-Eng. Div. Wood Box Wing Beam (Second Arti cle.)
Serial No. 2432--Boeing XC0-7B Hori. Tail Surfaces and Control s.
Serial No. 2433-Third Proof Test of Gallaudet DB-lB Aileron and Hori. Tail Surfaces.
Seri al :-.Jo. 2434-Boeing Experimental Wing Beam (Second Article.)
(This beam is a steel structure, electr ically welded.)
RESEARCH AN D EXPE RI MENT 35
Wind Tunnel Tests in McCook Field Five-Foot Tunnel.
T he following serial reports contain aeroclyn amical data on two airplanes as determined by
tests in the :McCook F ield five-foot wind tunnel.
Seri al No. 2392-Barling Bomber.
Seri al "\To. 2404-Huff-Dalancl Duster Airplane.
MATERIAL SECTION.
Babbitting Direct to Steel. Serial No. 2351
T his report gives a satisfactory method for babbitting directly to steel as used on the bearing
shoes of the Almen "Barrel" engin e. The requi s ite steps fo r the success of the process are specifi c­ally
described and are applicable to any case of dir ect babbitting .
Mechanical Properties of Magnesium-Zinc-Aluminum Alloy Castings. Serial No. 2353
The design and size of castings such as those used in internal combustion engine parts. as well
as the founclrv method of prod ucing them are known to have an appreciable effect on the me­chanical
properties of the alloys. T he strength p er unit of heavy secti ons in general is lower than
that of light sections. the diffe rential magnitude varying with the alloys. In this investigation, the
mechani cal properties of a magnesium base all oy commercially known as "Elektron AZ" in di f­fe
rent sections of a representati ve casting embody ing various thi cknesses are determined and com­pared
wi th those of several aluminum base alloys cast from the same pattern.
From the results of the i1westigation, it app ears that magnesium alloy is a possible substi tute
for the more widely used aluminum 92-copper 8 a lloy in aircraft engine crankcase, since the cast­ing
diffic ulties a re offset by the saving irt weight. Its use, howe1·er . in aircraft engines is ma inly
applicable to parts where the foundry restri ctions limit the size or thickness of the section rather
than the stresses.
SeYeral photographs are appended which show the crankcase casting, the location and appear­ance
of the specimens taken therefrom and the m eta llographic structure.
Column Strength of Duralumin Tubing With Fixed Ends. Serial No. 2376
T his investigation is supplementary to a pre vious one as publi shed in A. S. I. C. No. 470,
(Serial :>Jo. 2302) on the column strength of duralumin tubing with kni fe edge bearings. T he same
kind of material was used in both inYestigations so that the results which are analyzed graphically are
directly comparable.
T he tubing was furni shed by the Aluminum Company of America in diameters varying from
2.25 to 0.75 inches and in thi cknesses varying fr om 0.125 to 0.035 inches. A photograph shows
the typical appearance of the fixed encl columns after test.
Application of Load in Testing Fabrics. Serial No. 2411
T his series of tests was made to obtain pertinent in formati on on the behavior of standard air­plane
and balloon fab rics under a varying rate of application fo r test load and also the relationship
between the magnitude of the dead load and the ti me of its appli cation to the point of fa ilure.
In the investigation the time-dead-load effect was measured, that is, the length of time a
standard one-inch test specimen will sustain a dead load before fa ilure, and the general reaction
indicated by the following fo rmula fo r the hyper bola:
L=aTb C
where L = load in pounds
T = time in m.inutes load is sustain eel
C =constant co rresponding to load whi ch specimen sustains indefinitely.
F rom the natural hyperbolic cur ve f or eac h fabri c, the constant "C" or "endurance limit"
appears to be approximately one-half the indicat ed tensile strength of the fab ric as tested under
standard methods. T his evidently indicates th at the factor of eight generally used by aircraf t
designers for breaking strength is in reality a factor of only four on the basis of endurance limi t.
I t shoul d also he hom e in mind that this factor does not take into consideration the aging of the
fabr ic, whi ch may explain to some extent the short service Ii fe of unrubberized fabrics.
36 TE CHN I CA L B U LLETI N l o . 4 1
Laboratory Tests Made Sole Basis for Accepting· Spar Varnish. Serial No. 2415
T hi s investigation was in itiated to develop supplementary tests for A rmy Quartermaster Corps
Specification No. 3-16A, whi ch is 'identical with Federal Board Specification No. 18, in order that
the specification for spar varnish could be revised to incorporate such additional requirements
that would insure a product superior to that now procured under the present Quartermaster and
Air Ser vice specifications. The proposed revisio ns include a gas test or exposure to exhaust gases,
a viscosity test and a baking test. The weather ex posure test formerly required has been deleted,
thereby ma king laboratory tests the sole basis for acceptance or rejection.
The assurance of a constant supply of spar varni sh of the highest quality is of fundamental
importance to the Air Service since it is imperati ve that nearly all aircraft parts be protected from
corrosion and decay by its use. The present practice is to have the manufacturers submit samples
of thei r products to the E ngineering Division for test, and if the varni sh sati sfies the req uirements
of the specification in every respect, the maker of it is placed on the approved li st. It occasionally
happens. however, that subsequent lots of a previously approved brand of varni sh will not strictly
conform to the specifi cation owing to va riance in materials and methods of manufacture with the
resul t that the manu facturer's name is dropped from the approved li st.
The basis for fina l rejection of a varni sh formerly depended upon the resul ts of atmospheric
exposure tests in comparison with a standard sample of the proven varnish. T his method of test
proved undesirable for the reason that by the ti me the resul ts of the exposure test were knoW11,
the varni sh in question had been used. U nder the new specifi cation . this exposure test has been
dropped and other test s substi tuted whereby it will be possible to accept a ircraft spar varnish
solely upon the basis of laboratory tests.
POWER PLANT SECTION.
Salt-Cooled Valves and Hardened Guides for Aircraft Engines. Serial No. 2328
T hi s report deals with certain experiments conducted by the Engineering Division over a
period of eighteen months on exhaust valves fo r a ircraft engines. in which the problems of cooling
large exhaust valves, preventing the burning and scaling of the valve head and stem and elimi­nating
the wear of the valve stern . sea t, tip and guide were sati sfactor ily solved thru the develop­ment
of salt-cooled va lves and guid es.
In the salt-cooled valve as developed by the E ngineering Division, internal cooling is obtained
by par tially fi lli ng a hollow valve with a mixture of fu sible salts. usually nitrates of sodium and
potassium, in the proper eutectic proportion which has a boi ling or decomposition point well above
any temperature attained by the va lve in contact with the burning mix ture. This fluid substance
whi le it is being kept in a high state of turbul ence by the motion of the valve rapid I y transfers
heat fr om the hotter to the cooler port ions of the valve. that is, from the head toward the tip , thus
sharply reducing the maximum vah·e temperatt.tr e. Altho the salt-cooled valves are des igned pri­marily
for use in la rge high-power air-cooled cylin ders, their use is equally appli cable to cyli nders
cooled by water or other liquid s.
The use of salt fillings for cooling avoids di ffic ul ties in retaining the cooling fluid within the
vah·e such as those ex perienced with mercury-coo led valves in· thi s country and with water-cooled
valves in E ngland. T he pressures produced in the interi or of the valve stem a re so low that
they are easily retained by means of a dri ve- fit pl 11g in the tip of the stem making welding unneces­sarv
as a fi nal seal.
T he development of hard valves and guides in conjunct ion with a means for reducing side
thrust eli minates wear on both valve stem and guide. particul ar I y in the case of large exhaust valves
which open early in the firi ng stroke thus requirin g large forces to actuate them.
J\ verv compl ete account of these experiments and the results obtained was publi shed in Thr
Jo11mal of The Socirty of Auto111otive Engineers for A ugust . 1924.
Power Plant Laboratory Standard Test Methods and Computations. Serial No. 2343
In this report are given the present standard test methods and computations used in the power
plant laboratory at the E ngineering Division. Specific in structions are given for the test, opera­tion.
and computations necessary in determining engine performance including the testing of
equipment and accessories.
RESEARCH AND EXPERI1'1EN T 37
Description and Test of Morehouse Blower Engine (First Design.) Serial No. 2350
The Morehouse blower engine was designed by Mr. H . E . Morehouse and manufactured by
the Steel P roducts Company of Springfi eld , Ohio, fo r the purpose of operating an air blower used
in inflating airship hallonets. It is rated at 12 ho rsepower at 2,000 r. p. m. a nd is so designed that
it may be operated in either a vertical or a horizontal position.
MOREHOUSE
BLOWER ENGINE
(First Des ign)
This engine may be oper ·
ated in e ither a vertical
or horizontal position.
Thi s engin e, whi ch weighs 51 .4 pounds is a small a ir-cooled two-cylinder opposed type, hav­ing
a 3-inch bore and stroke and utili zing the cra nksha ft. counterweights and connecting rods of a
Harl ey-Davidson motorcycle engine. It has aluminum pi stons and cast iron cylinders with cooling
fi ns over the combustion chamber and upper portion of the cylinder. T he lower encl . of the
cylinder is piloted into the aluminum crankcase w here it is cooled by the circulating oil. T he crank­case.
oil sump and cylinder pilots are cast integr al, with the carburetor fl ange and intake bends
cast in the oil sump. T he cam housing is bolt ed to the rear of the crankcase. Two oil pumps
are provided ; a scavening pump for vertical oper ation and a circul ating pump fo r horizontal oper­ation.
In the latter position, the oil drains by gr avity from th e crankcase into the sump from
whi ch it is taken by the circulating pump and discha rged to a four-way fi tting. two lines going to
the cvlinder, one to the relief valve which di scha rges into the cam housing and the fourth to the
oil pressure gage. The accessories include a R ob ert Bosch high tension magneto driven by a fl ex­ible
shaf t and an aluminum Stromberg Model OS-1 ca rburetor with hori zontal outlet.
T he engine was found to be well adapted to blower service in lighfer-than-air craft in view
of its low weight, good power and lack of vibration at high speed. A complete description of the
engine and the results of the test, together with several photographs and drawings, are given in this
serial.
Crank Pin Bearing Pressures on Liberty 1-Inch Connecting· Rod Bearing. Serial No. 2377
In view of the sati sfactory results obtained in a 112-hour test of a connecting rod crank pin
bearing· whose effective bearing surface had bee n reduced to one inch, in the Liberty single
cylinder testing engine, a determination of the bearing pressures was made in accordance with the
method outlined in E ngineering Division Serial No. 2038 "Standard Methods of E ngine Calcula­tions,"
and the results set forth in this report.
38 TECHN I CAL BULLETIN No . 41
Test of Rockwell Slotted Head Liberty Valves. Serial No. 2378
The serYiceability of slotted head valves for the Liberty engine as submitted by Roch.rwell
Field were investigated at the Division and fou ncl to be comparable to standard Liberty valves
under ordinary service. U ncler condition s, however. where extremely high valve temperatures are
encountered, th e slot in the head undoubtedly acc elerates collapse of the valve because of the re­duced
section close to the stem. The use of slotted head valves in the Liberty engine was there­fo
re not recommended unless there can be demonstarted a very definite superi ority of the screw­driver
method of valve grinding over the present procedure. Photographs of both slotted and
standard head valves are appended.
The Mercury-Vapor Turbine as an Aircraft Power Plant. Serial No. 2379
The possibilities of the mercury-vapor turbine as an aircraft power plant are herein discussed.
The use of mercury as a suitable working fluid for aircraft turbines has been suggested because of
its high boiling and condensation temperatures and its low vapor pressure at any given tempera­ture.
H owever it is not claimed that mercury is in a ny way superior to water as a working
medium. except insofar as its working temperatures and density are concerned. The latter prop­erty
aids in the design of the mercury-vapor turbine in that a low peripheral velocity may be ac­compli
shed without an excessive mtmber of stages. Most of the calculations advanced in this
report. however, are inaccurate for the reason that the heat constants. for example. are quite dif ­fe
rent than those usually encountered in engineering literature. Furthermore no data were avail­able
on the physical constants of mercury vapor without which no accurate calculation for the
nozzles could be made. It is believed that this in formation is in possession of the General E lectric
Company which has clone some investigation on this subj ect.
The rei)ort gives an account of the general scheme for the proposed turbine, the thermal
properties of mercury, the problems involved. and the general feasibility of the project. It ap­pears
possible to construct and successfully operate a mercury-vapor turbine of the multiple stage
type having an efficiency less than the present aircraft combustion engine but possessing other ad­vantages.
Such a turbine would weigh about 1670 pounds and develop from 400 to 1680 h. p.
with a fuel consumption of .76 to 2.11 pounds per horsepower hour.
A purely schematic arrangement for a merc ury-vapor turbine is given below, in which a boiler.
condenser and turbine blading system constitute a single rotating unit, the rotor. T he stationary
blades are carried by a wheel 'vV which is rigidly attached to the shaft S and which is held by a
SCHEMATIC ARRANGEMENT FOR MERCURY-VAPOR TURBINE.
RESE A R CH AND EXPER I MENT 39
clamp ( not shown ) so that it cannot rotate. The moving blades are fa stened directly to the
wai st of the rotor which rotates in the bearings B, the propell er being attached to the condenser
end. It must he borne in mind that thi s arrangement is purely imaginatiYe and may not resemble
the final product in any particular.
Behavior of Three Standard A. S. Spark Plugs in High
Compression Liberty Engine. · Serial No. 2390
Pertinent in formation on the behavior of three standard :\ ir Service spark plugs, the A. C.,
the Mosler M -1 and the B. G.-1 XA, in a high compression Liberty engine :is contained in t hi s
seria l. From the test results. it appears that the A. C. and B. G. plugs gives an equally good per­formance,
the latter make of plug being preferable from a mechanical standpoint. T he use of
the Mosler l\1-1 plug is not recommended for severe service.
Performance Curves and Sectional Views of Aircraft Engines. Serial No. 2407
T his large report gives in a concise manner the general cha racteristics. sectional views and
performance curves of 52 different aircraft engines. both domestic and foreign. as fo llows :
A. B. C. "\i\!asp" and "Dragonfly" Liberty "Thomas-l\1orse "6," BX-5 , "8," " 12"
Aeromarine U-8-D LeR hone T ype "R"
J\ !men A-2 "Barrel" M avbach "300"
Tiri stol "Jupiter" Me;·cedes "200"
Bently Rotary BR-2 Morehouse I3lower
Beardmore-I-lalford-Pullinger B. I-I. P . "200" Napier "Lion"
Bentz "200".. Packard l A-744, 825, 1116. 1237, 1500 and 2025
B. '.\1. W. "6-Cvlinder" R-1 Radial
Curti ss C-6, C--12, CD-1 2, D-12, and OX-5 Rausie E-6
Fiat A-12 bis Roll s-Rovce "Eagle VIII"
Galloway "Atlantic" Salmson 9z
Hall-Scott L-6 S iddeley "Jaguar"
Hispa no-Suiza E and I \Vright Hispano
Isotta Fraschjni "250-h. p." \Vright H-2. H-3, K-2 (Cannon), and T -3
Lawrance l\1odels : L-4. J-1 and R-J l\1odel "\i\!-1 "
Lorraine Dietrich "8-Cylinder"
50-Hour Reliability Tests of Two Rock Island Arsenal "Liberties." Serial No. 2389
F ifty-hour tests on two 1odel 1921 Liberty engines which had been overhauled at the Rock
I sland Ar senal proYed conclusively that there sh ould be no cause for anxiety on the part of pilots
when using these engines. There were no forced s tops during the test and what minor difficulties did
occur were such as might be expected of any Lib erty engine under similar conditions. Even the
"Tear-clown" inspecti on af ter the test failed to re veal any unusual fa ults.
A detailed account of these tests will be found in the report.
Endurance Tests of Curtiss D-12 Engines.
T he two se rial reports li sted below contain de tailed accounts of two standard SO-hour endur­ance
tests conducted at the E ngineering Divisi on on Curtiss D-12 engines. P hotographs of the
parts after test supplern.ent the discussion.
*Serial No. 2348-Curtiss D-12 H igh Compression E ngine.
Serial No. 2428-Curtiss D-12 Low Compr ession E ngin e.
TECHNICAL DATA SECTION.
Competing Airplanes in Air Races (1924.) Serial No. 2417
This report contains complete data in tabul ar form on all ai1;p lanes, including their acces­sories
and equipment, which competed in the International Air l~aces at Dayton, Ohi o, on Oc­tober
2 to 4, 1924. The entrants in each event are li sted in the order of winning.
40 TECHNICAL BULLETIN No. 41
INVESTIGATION OF MATERIALS
Paste Colors for Insignia.
A method of mixing and applying paste colors for in signia has been worked out whereby paste
colors may be substituted for pigmented dope in cases where the application of the latter is un­economical.
This condition ex ists where space is limited. Inasmuch as these colors do not run they
can be applied contiguously without drying. A specification has been prepared for use of the Fai r­field
Air Intermediate Depot which requested the investigation.
"Krachow" and "Ta Sua" Wood from Siam.
The physical properties of sample pieces o f wood . from S iam, known as "Krachow" and "Ta
Sua" have been in vestigated as to their value in aircraft construction. "1'-rachow," which is used
in the Orient as a substitute for spruce in airplane construction was found to be 60 per cent
heavier than domesti c airplane spruce, and to co rrespond more nearly to American birch. "Ta
Sua" resembles mahogany in appearance, but its specific gra \·ity and strength are greater than Hon­duras
or true mahogany. It is used in propeller construction by the Siamese Air Service.
Cadmium and Chromium Plating.
Two types of plating are under investigati on fo r use on a ircraft parts : cadmium plating for
the protection of screws, bolts, nuts and oth er small threaded parts and chromium plating for the
protection of engine parts operating at high temperatures. The cadmium plating can be applied
much thinner than the zinc plating in present usage and gives the same degree of protection. Its
use will permit closer tolerances to be held on screw threads without undercutting the thread.
Effect of Gage Width on Elongation-Standard Test-Piece.
In connecti on with the standardi zation of test procedure practised by the Air Service and the
Bureau of Aeronautics, the E ngineering Di vision has concluded some tests on the effect of gage
width on elongation of flat test specimens. It is proposed to incorporate these results in the new
standardi zed methods.
The establi shment of a standardi zed test-piece is very desirable as its use will permit con­cordant
results by Army and Ka vy inspectors and eliminate duplication of tests by contractors.
World's Largest Airplane Wheel and Tire, Size 64x14.
The largest wheel and tire yet built in this country is the new 64" by 14" straight-side air­plane
wheel and tire developed by the Engineering Division for use on large bombardment air­planes
weighing in excess of 40,000 pounds with fu ll load. This new size completes a line of
standard straight-side airplane wheels and tires which has been gradually evolved by the Division
during the past few years to replace the old clincher type fo rmerly used on service aircra f t.
The new wheel is of the steel wire type with radial laced spokes and truck type rim . The
. latter was manufactured by the Ameri can \ !\Telding Company and assembled with the spokes and
hub by the Dayton \Vire \!\Theel Company. The truck type rim has a fl at base with detachable
flange and locking ring to facilitate the mounting or removal of the tire. It is made of plain cold
rolled carbon steel , 5/ 16-inch gage, and has a bead width of 7 inches or 50 per cent of the sectional
diameter of the tire which in sures sati sfactory p erformance in service. There are 152 steel spokes
laced into the rim and hub. The length of the latter measures 14 inches and the in side diameter
G inches. in suring ade(1uate strength for large pneumatic-tired wheels.
The tire which was built by the B. F. Goodri ch Rubber Company consists of a ten-ply cord
fabric casing, one- hal f inch thick at the side wall and .87 of an inch at the tread, a quarter-inch
heavy rubber inner tube and a flap. It weighs complete about 200 pounds. making the weight of
the entire assembly of tire and wheel about 400 pounds. Altho the total weight is about 100 pounds
more than originally estimated it is thought that it can be reduced by decreasing the thickness of the
tread and inner tube without lowering the strength.
RESEARCB AND EX P ERIMENT 41
P hvsical measurements and tests were made in the usual manner at the E ngineering Division.
The wl{eel with tire inflated at diffe rent pressures was mounted on top of an Olsen testing ma­chine
of 100.000 pounds capacity fo r test and the load applied thru the axle by means of steel
straps attached to the pullirig head of the machine. T ire deAedions were recorded on paper in ­serted
between the surface of the tire which had been inked and th e supporting plate. To test
the breaking strength. the tire was mounted in the machine as befo re with the tread resting again st
a +-inch dirt surface and the pressure reduced enough to just hold the beads in place on the rim .
:\'l easurements were taken dn the di stortion of the wheel under load.
The tests demonstrated that the wheel has a breaking strength of 60.000 pounds and the tire
a worki ng load of 20,000 pounds at 90 to 100 pounds infi ation pressure. The working load is
based on 25 per cent deflection. T he physical properties of the tire pro\·ed superior to those re­quired
in either the Air Service specification or the new tentati\·e specification fo r tires ad vocated
by the Bureau of Standards.
The fo llowing compari son between the new 64x l4 wheel and tire and the 54x 12 wheel and
tire used on the Barling Bomber is in te resting :
\\'eight of wheel and tire in pounds ..... .
\ \I or king load in pounds . . . ..... . .. ... . .
Brea king load in pounds .. . .. .. .. .... . . .
Barling Wli ccl
175
10,000
38,000
AIRPLANE WHEEL AND TIRE-SIZE 64x14.
So far as known this is the largest airplane wheel ever built.
64xl4 W heel
400
20,000
60.000
NEW BOOKS AND DOCUMENTS
REFERENCE DATA ON AERONAUTICAL DEVELOPMENT
AND ENGINEERING IN THE UNITED STATES AND
OTHER COUNTRIES ADDED TO THE TECHNICAL FILES
OF THE AIR SERVICE ENGINEERING DIVISION.
Reference Numbers Refer to Engineering Division Technical Files Only
INTERN A TI ON AL ACTIVITIES.
Great Britain.
Commonsense and aeronautics; by Lt. Col.
H . T. Tizard. Royal Aeronautical Society .
Oct. 2, 192.4. 3 p.
Japa n .
Kinematographic s tudy on aeronautics.
Aeronautical ltes earch Institute. Tokio Im­perial
Univer,ity. Sept., 19 24. 11 p. Illu s .
oiags.
United States.
Thoughts of representative American
c itizens on aviation; compiled by McCook
Fie ld, Aug. 1, 1924. 40 p.
Lecture on engineering problems of mili­tary
aviation; by Maj. General M. M. Pat­rick,
before the Harvard .. ngineering Society.
Nov ., l ~J23. 14 P.
Airplane nomenclature s howing s ymbol
des ignatio n for airplanes being made or pur­chased
b y the Air Service. Office of Chief
Engineer. Oct., 1924.
Reports on catapult launc hings to be s ub­mitted
to Bureau of Aeronautics. N a vy
Dept. Bureau o f Aeronautics . Nov. 6, 192,4.
2 p.
Competitions, Records, Etc.
" Round the World F lig ht" while under
command of Major F. L. Martin. 1924 . 45
p . Photographs.
Official record s up to Oct. 1, 1924. F . A.
. I. In French. 4 p.
Roya1 aero club lig h t airplane competitions.
Royal Aeronautica l Society. Oct. 30, 1924.
~ p.
Description of a irplan es competing for the
Beaumont cup; by J . J. Ide. National Ad­visory
Committee for Aeronautics. July 2,
1924. 5 P. Photographs.
Bulletin of Federation AeronautiQue Inte r ­nationale
for Sept., 1924.
New a lt itude and duration recor<ls with
usefu l load, recognized by conte ~t committee
of the National Aeronautic Association. n.
J. 1 p.
Altitude determination for fli g ht m ade by
Lt. Macready on Sept. 5, 1924, at McCook
F ie ld. Bureau of Standards. Sept. 25,
1924 . 3 p.
Altitude determination for flight made b y
Lt. Macready with load of 1500 kilo ·; on Oct.
2, 1924, at Wilbur Wrigh t Field. Bureau of
Standards . 2 p.
Altitude determination for flight made by
Lt_ H. R. Harri::; with load of 4000 kilograms
in Barling bomber on Oct. 3, 1 92 -J at Wilbur
VY righ t Field. Bureau of Stan <lardR. 2 p .
Map of race course of Int"crnational Air
Races held at Dayton, Ohio. Oct. ~. 3, 4,
1924.
A l O / 227
D00 .12/ 1 84
Vol. 1- No.
Al0 / 226
C50.02/17
D61.2 /3
Oct. 22/24
D52.39/17
C71.6/69
C71.61 /55
52.1/116
Misc.
D52.l /36
M i ~c. French
D00.12 /178
1 924 -Sept.
C71.6 1 /52
C7l.61 /53
C71.61 /50
C71.61 /5 1
D62 /57
T ime and speed con version tab les for 5
miles, 1 5 miles and 50 kilometer courses;
b y G. A. Biehn. Technical Data Sect ion.
McCook Field. Sept. 25, 1924. 41 p.
Formula for computing density altitude
recommended by the Engineering Divis ion.
This method is compared w ith t hat used by
Bureau of Standards ; by Maj._ J. F'. Curry.
McCook Field, Oct. 10, 1924. 3 p.
Methods of measuring "ceiling" altitudeR;
by F. B. Newell. McCook Field. Sept.,
1924. 28 p. Photographs, c harts.
Total n umber of hours flown by tht:>- A"ir
Service for fi sca l vear 1 923 is 65, 750.48;
by R. L. Wals h . Mar. 28, 1924.
AERIAL NAVIGATION.
Airways.
R epor t on fi r !" t a n d s econd trip::; of A laskan
air mail s ervice; by C. B. Eiel son. Feb.,
1 (124. 4 P.
Monthly report of operation and main­t
~ nanc e of air mail service United ~tate :3
Post Office Dept. for July, 1~ 21 . ,
Monthly report of operation and main­tenance
of a ir mail service. Unite61. States
Pos t Office Dept. for Aug., 1 924.
Compilation and reproduction of experi­mental
air navigation maps. Notice to
aviators. Oct. 1, 1924. 1 p.
Meteorology.
Astronomica l met hods in aerial nav igation:
by IL H. Beij . National Advisory Com­mittee
for Aeronautics. R eport No. 1 98.
1924. 52 P. Illus. charts, drawings.
Report regarding mechani sm of cyclones
and anti-cyclones; by Tatuo Kobayas i. In
German. Aeronautical Research Institute.
Tokyo Imperial Uni versity. July, 1924. 23
pages.
Results of magnetic observations m ade by
the United States Coast and Geodetic Surv~y
in 1920. by D. L. Ha:zard. U . S. c'1as t and
geodetic su rvey. S erial No .. 161. Specia l
publication No. 72. 1921. 12 p.
Results of mag netic observations made by
the United States Coast and Geodetic Survey;
by D. L. Hazard. U. S. Coast and GeodEtic
Survey. Seria l No. 205. Special pub lication
Ko. 87 . 1922. 25 p.
Results of magnetic observations made by
the United States Coast and Geodetic Survey
in 1922, by D. L. Hazard. U. S. Coast and
Geodetic Survey. Serial No. 235 . Special
publication No. 94. 1923. 41 .p
Results of magnetic ·observations made by
t he United States Coast Survey in 1923. U.
S. Coast and Geodetic Survey. 1924. 44 p.
A90 / 17
D00.113 /21
D00.113 /20
C7 l.6 /70
El0.2 / 41
El0.2 / 9
1924-July
E l0.2/9
1924-Aug.
AOO I 40
1924-No. 10
A40.3 /27
D00.12 / 184
Vol. 1 -No.
A40 /32
A40 / 43
A40 /35
A4 0 /33
NE\V BOOKS AND D OCUMENTS
Alaska m agnetic tables
charts for 1920; by D. L .
Coast and Geodetic Survey.
Special publ ication No. 63.
Maps .
Regula t ion.
and m ag n etic
Hazard. U . S.
Serial No. 12 5 .
1920 . 31 p .
Data r equired in con nection with t he
{:;:;·anting of a certificate of airwor t h ines5 for
a ty pe of airc raft. Air Board. A ir reg ul a­tion
s, 1 ~2 0. 5 p .
In s tructions governi ng co n du ~t of t~ 6 t ~
for aviator 's cert ifi cate6 a s idsued by Na-tional
Ae ronautic Associatio n . n. d. 2p.
INSTRUCTION.
Air Ser vice Engin ee ring S c hool.
Course in s ing le aerodynamic ... ; for in ­s
pectors . Air Service Engin et-r ing Schoo l.
McCook Fi eld. 1924 -25. 12 ]). D iags.
Chemistry of aircraft m ateria ls . A ir
Service Eng ineering S c hool. McCook Field.
rn24.
RESEARCH.
Aerodynam ics .
Aeronautical R esearc h ; b y J. S. Ames.
From Smit hs onian report of 19i2 . 1924. 8
)). Drawings . Ill us .
Report of Aeronautical R e ·.5earc h Com­mittee
for fis cal yeat· 1923.-24. 50 p .
Forest Products Laboratory Progress Re­port
for Oc t ., 1924.
News bulletin No. 91. R eport on work at
Bureau of Stan dards . Nov. 10, 192 4. 20 p.
Flow p henoma at obstructions ; by G. v. d.
Borne : In German with translation from
Zeitschrift fur . Flugtechn ik und Moto·r ­luftsc
hiffarht. Vol. 3. Tech nical Data s ec­tion.
McCook F ie ld. Oct. 20, 1924. 4 p.
Photos tats.
Genera l theories regardi ng mechan i..: s. of
flu ids : by D. R iabouc hinsky. In French . S.
T. Ae. Bulletin Tech n ique No. 17. Apr .,
1924 . 97 p. Dia gs .
An electrical m et hod of tracing s tream
lint! .:; for two dim ens ion a l motion of a per­fec
t fluid ; by E. F. Relf. Aer c1nautica1 Re­search
Committee. Apr., 1 924. 3 p . I ll us .
drawing, charts .
Simplify ing assum ptions, reduc ing t he
strict application of c la ss ica l h ydrodynam.ics
to practical aeronautical computat ion s : liy
M. M . Munk. National A d v is o!·:1 Com mittee
for Aeronautic s . N ov. , 1924. 16 p .
Meas ur ement of v is cosity by m ean:> of
ca pillary tubes; by Guy Barr. Aeron autical
Research Committee. Mar., ~923. 23 p.
Prediction on Prandtl t hc(HY o f lift and
drag for infi n ite span from mea.; 11 re1n e n t s on
acrofoil ;3 of finite ~pan; by A. } age anU H.
L. Nixon. Aeronauti ca l R cti2arch C..:ornrni t t ce.
Dec .. rn23 . 1,4 p. Ch arts.
Jnd111;ed drag of mu l t i plnn ~.-;. Resu lts of
aerod ynam ic te:.;. t plant at Co1~ tingen, V <> I.
II, 13 2:-!, t rans lated by J . Van ier. Tec hnica l
Data Sect.ion. McCook F ield. Oc t. ii, lu2;J.
~ p. Charts.
Determination of s cale effec t on centl"e
of prc::-.su re of R. A. F. 14, ll. E. 2C biplane
with three value"5 of s tagger ; by Aero~
c.l y 11~1m i c s~ aff. Ae ronautical H.e:>e::l.rch CGm­n,
i!t <·e. Jan., 1924. 23 p. Ch a!·ts .
Design panel on s cale effect on lift, drag
a 1.d «enter of press ure of compl~t~ airμJan e,.; .
Aeronautical Resear ch Committee. Ma r .,
1924. 22 P. Ch arts .
SmoKe producer res u lt s of :i et·odyn.tm ic
test plant at Gott ingen, Vol. :i..l , 1 9:~ 3 . Mc­Co,
1k F ie ld . Oct . 6, 1924. 2 ;i . Ph:.ito­s
tab.
f1i ~ to rtion of a s t iff- j ointed Jllane poly­gonal
irame under loads app lied in i t~ pJ:.i.ne;
b:.- . .\ . J. S. PipparJ and P. F. Fo>ter. Aero­nautic.'
1.I Res earch Co m m it t~ e. Ju ly, l !J2 4.
24 r-. Charts, diags.
A40 /36
B00.6 /8
noo.6 / 7
A l 0.2 / 153
A60 /22
D00. 12/ 117
D00 .12/27
D 00.12 /99
1921-0ct.
D00.12/9 1
T. N. B.
A l 0.2 / 151
D 00.12 / 126
19 24 -No. 17
D J0. 12 /905
R. & M .
A l 0.24/4
D 00.12 / 906
R. & M.
D00 .1 2 /9 03
R. & M.
A l 0.2 / 148
D 00. 12 /899
It. & M.
D 00 .12 /900
R. & M.
A 1 0.2 / 1 4!J
D 00 .12/!!13
R. & M.
Stresses in sti ff - jointed polygonal fram e
under system of parallel loads. Part II ; liy
A. J . S. Pippar d. Aeronautical Rese::i.rch
Coff.mittee. Apr., 1924. 5 p. Dhg3.
Desig n and Computation.
Experiment al test of calculation fonuulas
for b ip lanes , developed from t he Multi.J)l:lne
T heory. Tr. by J. Vanier from t h e A ero ­dyn
amic test pla n t at Gottin:j12 n , Vol. l[,
. 9~ 3. Tec hnical Data Sec t io:'l. ~1 cCook
Field . Sept. 10, 1924 . 10 v. Cha,·to.
T heory and application of logarithmic
p c lar curve to predetermin ation o( airp la ne
pe rfo rmance; by Val. Cronsted t. National
Adv is o r y Committee for Aerona ~Jtics. Oct.,
1924. 20 p . D rawings .
Cr u is ing performance of airplan es ; by Lt.
Comd r s . E. E. Wilson a n d H. n. Leighton.
Navy Dept. Aug., 1924. 60 p. Cha1·t< .
W eig h t data requiremen t s . Navy Dcvt.
Bur eau of Aer onautics. Apr. ?, J 924. (l p .
Stru ctura l W eig ht of a ircraft as affected
by t he s y stem of deE ig n; by C. Vi. Hall.
Nation a l Advis ory Committee for Aero­nautics
. Nov ., 1924 . 2·1 p. P h otographs ,
diags.
I n f o rm atio n for approval of des ig n . Navy
Dept. Bureau of Aeronautic s . Oct . l, 1924.
4 ]).
F ina l corrected informat ion and fina l cor-
1·ected drawings. Navy Bu ?·ea~ of Aero-na
u tics . Oct. 1, 1924. 2 p . .
Calculating the w ings of an airoiane; by
St. N. Mirea. In French with t !"a ns lat ion.
International A ir Congress, L ondon, 1 :)23 .
T ec hnical Data Sect ion. McCoo:< Fiel cl. Sept.
1 5. 1 ~12 4 . 4 p.
Experime nts with cut-ou t sectio ns on
wings; by J . Ackere t. T r . from Vorlau fige
Mitteil ungen Ver s uchsanstalt Zu Gottingen.
Heft 1. Ma r. , 1924. T ech n ical Data Section.
McCook Field. Oct. 22, 1 ~2 4 . '1 p. Ch arts,
d1ag s .
Wings wit h e n d p lates; by J Ackert. Tr.
f r om Vorla u fige Mitte il un gen der Aero ­d
y n a misc h en Vers uc hsan stalt zu Gottingen,
Vol. 2~ July, 1 924 . Tec h nica l Datn Sect ion.
McCook F ie ld . Nov. 4, 1924. 13 11. Charts .
E:xp eriments with rudders on two tv .. ·in ­er.
gi ne a irp lanes; by F. W. Meredith. Aero­n
autica l Re:5 earch Committee . D1~c . . J 923 .
8 p . Ch arts, drawings.
S t udy .of s tatic s tab ility ot air~hip s; by
Frank Rizzo. National Advisory Committee
for ~e r onautic s. Sept., 1924. 5'0 p. Ch arts ,
Craw 1ngs.
E ffect o f rat io between volume and s u r­face
area of a i r ::. hip s ; by G. A. Crncco; tr.
from Note di Tecn ica Aer onava le, l t)2:·L Na­t
io nal Ad v i ~ or y Committee for A e ronautics .
Sept., 1924 . 7 p.
Ca lc ulatio ns for h uJI a n d car- s uspe n s ion
Rystem of a irs h ips ; by R. Verduizio. Tr.
f rom Rendiconti T ec n ic i, A'l i"! r. , l 9'!4. Na-t
ional Advisory Committee fo r A eron a utics.
Oct., 1924. 24 JJ. Ch arts.
Aerofoils .
T heory of thi n ae rofoi ls; by H. li: lauf"rt.
A ~ron aut i ca l R e .5 earch Committee. Feb .,
1924_ 10 p. D raw ings, c harts .
Note on application of vortex th eory of
aerofoi ls to t he prediction of down was h ; b y
L . F . G . Simmo ns a n d E. Ow(•r. Aero­n
a u t ica l Res earch Com m ittee. Apr., 192.:t. 3
P. Charts.
Generalised type of Joukows ki aerofo il;
by H. Glauert. Aeronau t ical R esearch Com ­m
ittee. J an ., 1924. 6 p. Diags .
Ge n eraliation of Sc h ukowas k i method of
p lottin g airfoilc: : b y A. Betz. Tr. Tech nica l
Data Sec tion. McCook Fie ld. Oct. 27, 1924.
3 Jl.
Recen t test data on s lotted a i rfo il ~; b y
G. Lac hm ann. Tr. from t h e German. Tec h­nica
l Data Section. Nov. 8, 1 :)2 ,t. 5 p.
l 'hotostats , d rawings, c harts.
43
D00.12 /912
R. & M .
Al0.2/14G
Al0.2 / 147
D52.1 / 1 51
D52.1 / 157
D52.1 6/46
D52.I6 / 47
D00.12 /2 08
D52.338 /205
D5 2.338 /209
D 52.33 8/210
D00.12 /9 08
R. & M.
Al0.1 / 11
A. 0.1 /IO
D52.7 6/ 12
D0 0.12 / 910
R. & M.
D00.12/914
R. & M.
D00 .12 / 911
R. & M .
D52.338f208
D52.3 38/206
44 TECHNICAL BULLETIN No . 41
Rec;ults of experiments with ~lotted wings;
by G. Lachmann. Tr. from Zeit~c hd ft fur
F lugtechnik und Motorluftsc hiffahrt. May ~6,
1924. National Advisory Committee for
Aeronautics. Oct., 1924. 19 p. Drawings,
charts.
New relation between induced yawing
moment and rolling moment of airfoil in
s traight motion; by 11. M. Munk. National
Advisory Committee for Aeronautics. 1924.
7 p. Chart.
Air force and moment for MT airplane.
Navy Yard. Construction dept. S ~pt. 22,
• 1924. 14 p. Photographs, charts, dra,wings.
E levator hinge moments of Handley Page
control su rfaces. Navy Yard. Construction
Dept. Sept. 17, 1924. 6 P. Photographs,
charts .
AIRCRAFT.
(Heavier-than-Air)
Airplane technical requirements. Navy
Dept. Bureau of Aeronautics . Oct. l, 1924.
4 p.
Miscellaneaous data required b efore demon ­s
tration trials of airplanes Navy Dept.
Bureau of Aeronautics. Oct. 1, 1924. 1 p.
Des ignation and general description of
naval airplanes. Navy Dept. Bureau of
Aeronautics. Oct . 30, 1924. 9 p.
Catalog on Chicago Helicopter entered in
British h e licopter competition, Chicago Heli­copters
, Ltd. 15 p. Illu s .
A tlantic.
Summary of officia l performance te s t of
Atlantic A0-1, McCook Field. Nov. 7, 1924.
1 'p.
Summary of special performance tes t of
Atlantic DH4M2. McCook Field. Nov. 8,
192 4. 1 p.
Consolida.ted.
Specia l s tress computation ruling for
PT-1, manufactu red by Consolidated Aircraft
Company. McCook Field. Oct. 29, 1924.
2 P.
Curtiss.
Summary of official performance test of
Curtiss NBS-4. McCook Field. Nov. 7,
1924. 1 p.
Con · truction photographs of the F4C-1
b u ilt by Curtiss. Navy Dept. Bureau of
Aeronautics. Oct. 25, 1924.
Summary of official performance tes t of
PW-8, equipped with low-compress ion Curtiss
D-12 engine. McCook Field. Nov. 1 8, 1924.
l p.
Surr1mary of officia l p ~ rforman ce tes t of
P. W.- 8, equipped with Curtis s D-12 e n g in e .
McCook Field. Nov. 28, 1924. 1 p.
DeHaviland
Handbook on the DeHaviland 9A. Air
Minis try. Apr., 1922. 27 p. Illus. draw­ings
.
Eng.i.;'neering Division.
Summary of officia l performance tes t of
C0-5, equipped with Liberty 12 engine. Mc­Cook
Field. Nov. 22, 1924. 1 p.
Summary of official performance test of
XC0- 6, e quipped w ith in verted Liberty en ­gine.
McCook Field. Nov . 25, 1924. 1 p.
Summary of official performance test of
TP-1 , equ ipped with Liberty engine. Mc­Cook
Field. Nov. 25, 1U24. 1 p.
Fokker.
Summary of official performance tes t of
Fokker C0-4 , equipped with Liberty e n g ine.
McCook Field. Nov. 10, 1924. 1 p.
Gourdou-Leseurre.
Des cription of Gourdou Leseurre in which
Callizo made al titude record; by J. J. Ide.
Nov. 1 2, 19 24 . 2 p.
D52.3 3 /87
D52.338 /2 07
Dfi2.l/l
MT
D 52 .32 1 /4
D52.l / 156
D00.12/207
D52.l / 114
Misc.
Al0.22/ / 1
Chicago
D52.l 18
C0-4A
D52.l /1
Atlantic
D52.l /l
PT-1
D52.l /8
NBS-4
D52 / 2
F4C-l
052.1 /3 1
PW-8
D52.l /32
PW-8
D52.l / 16
De Haviland-
9A
D52.l / 10
C0-5
D52.l /7
XC0-6
D52.l / 16
TP-1
D52. l /71
Fokker
D52.l / 12
Gourdou
L-W-F.
Summary of official performance tes t of
L. W. F. T-3. McCook Field. Nov. 12,
1924. 1 p.
Navy PN-9.
Detail specification for model PN-9 fl y ing
hoat. Navy Dept. Oct., 1924. 23 P.
Nieuport.
Characteristics of Nieuport Delage in
which Sadi L ecointe made his altitude rec­ord;
by Maj. J. A. Rader. Nov. 22, 1 924 .
1 p.
Rukh.
Report on t he Rukh convertible passen ger
carrving and heavy bombardment airplane;
by R. S. Van Atta. McCook Field. Oct.,
1924. 8 p.
Wren.
D escription of Englis h Electric Company's
"Wren ." n. d . 4 p.
AIRCRAFT.
(Lighter-than-Air)
American airs hip ZR-3, a description; by
L. Durr. Tr. from Zeitschrift des Verei