Technical bulletin no. 39

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AIR
VOLUME V
CIRCULAR
(AVIATION AND AEROSTATION)
BY DIRECTION OF CHIEF OF AIR SERVICE
APRIL, MAY, JUNE, 1924
TECHNICAL BULLETIN
No. 39 ·
NUMBER 432
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 Divh•ion.
·McCook Field -6 -13-24-1 M
CONFIDENTIAL
The information contained herein is confidential and therefore
must not be republished, either in whole or in part, without
express permission of the Chid of Air Service, U. S. Army.
CONTENTS
AIRCRAFT DEVELOPMENT
AIRPLANES.
Bids for New Day Bombers-ILuff-Daland XLB-1 -- ------ -------------------------- ·--- _________ _____ _______ _
Improving Performance of the NBS-1 -- ----- ----------- ------- --------- --- ---------· ---
,..,
7'
:t~ight Bombers, Model XNBS-2, 3 and 4 ····-- -- -- ------------------ -------- -- --------- ------· 7
First Amphibian Damaged in Acce'Ptance Tests --- ------- -------------- ----------- _____ 9
Performance of Fokker C0-4 with New Wing and Dural Propeller _____ ___ ----·- ------- ·- ------- 9
Engineering Division XC0-5 ------------------- ------- ---- -- -- ---- ---------- - ______ _______________ 9
Engineering Division XC0-6 --- --- ----- ------------- ---- ------ ------ ---- ---- _______ ______ ______ ___ ___ ____ __ __________ 10
Boeing XC0-7 (Thick Wing DH-4M-1) _ ------ -- --- -- ---------- ------ ------------ --------- ·--·--- 11
Experimentation with DH-4B --- ------- ----- ---- --- --------- --- -- ----- ----- - -·--------- -------- -------------------- --------- 11
DH-4M, DR-4M-1 and DH-4M-2 ---- --------- -- --- -- -------------- ----------- ------- ·------------------------------ -- ------- 12
New Type"XO" Observation Airplanes -- ------------------ ----- ---------------- ------ --·----------------------- ·--- -- - 12
Dayton-Wright XPS-1 (Alert) --------- ------- ----- --- ------- -- --- -------------- ------------- -- ·---- ----- __ __ __________ __ 14
Curtiss PW -8 and Changes in "Coast-to-Coast" Airplane ----------------- ------ ------------------------- 16
Boeing XPW-9 --- --------------------------------------- --- --- --------------------- ------ ___________ _____ --- --------- ·----------------- - 16
New Records for Engineering Division XTP-1 -- ---------- -- ______ ---------- --·------- ---- ------- ------ --------- 17
Cox-Klemin to Improve XTW-2 Design------------- -- --·--- -- ··----- ------------ ---- ------- ------------------ -------- l7
Consolidated TW-3 -- ------ ---- --- ---- ---- --- --- --- ---- --- -----------------·----------------- -- --------- --------- -- -- ---- ---- ----- ---- - 17
Huff-Daland TW-5 --- ------------------- ---------------- -- --------- ------ -- -------- ·---- ---- ---- ---- -- --- ------------ ----- --- ------ 17
Improved Center Section for Vought VE-9 -------- -- ----------------- ·--·------ ------- ------·-------------- -- -- --- - 17
Study of JN-4H Training with Steel Fuselage _______ __ ______________ ___ ______ __ ___ ___ ------------ --------- ------ 18
Army Entries in 1924 Pulitzer ----- ----- -- ------------ ----- -- --- ----------------------- ---- ------ ----------- --- ---- -- ------ .. 18
Ambulance 'Plane XA-1 to be Built by Cox-Klemin ----- ---------- --- -- ----- - -------- --- ----------------- -- 18
Tests of Air Mail 'Plane ----------- ---------------------------- -- --- ---------------------- -- ----- ---- ----- -- ----- ---- -- ----- ____ 18
Variable Wings and Airship Attachment Device for Messenger ---------------------- ----- ·- --- --- --- 19
Duster Airplane for Department of Agriculture __ ----- ------------ ------- ----- ·------- --·--·----- ·- ------- 19
Parachute 'Planes ---- --- ---------------------- ------ ----------- --- --- ----- --- ----- -- ---- --- ---- --------------· --------- --·--·- 19
Service 'Planes to be Equipped for Night Flying ___________ __ _____ -·------------ -- ----- ----- ·-----·--- ------- - 19
L-W-F Transport, Model XT-3 --------- -- --- -- ------ --- -- ------- -- ---- -- -·-- -----·-- --------· ·----- ------- --·-----·---- ·---- 20
Study for New Transport Design ___ _______ --------------------· --------------- --------··-- -----------·----- ·-- 22
Propellers with Magnesium Blades --- -------- -- ---- ----- -- ----- ---- -- -------- ---- ----- -- -·-------------·--- ·---- --- ------ 22
Experimental Wing Spars ----- ---- ---- ------- ----- -- --- ------ ------ -- ------ --- ----- -- --- --- ------- ------- --- -- ------· __ _____ ___ 22
AIRSHIPS AND BALLOONS.
Progress on RS-1, TA and TC Airships ---- ----------·- -------- -------- ----- --------- -- ------- -·--- --·------ 23
New One-Man Training Airship, Model TE-1 ------ --· -----·-- ---·- -- --- -·--·----- -- ·---- -- ----- ·--- --- _____ ___ 23
Barrage Balloon -- ------ -- -- ---·---- -- ------------------ --- --···· -- ·--- -···--· ---· ·----- -- ·-·--·--- ____________ ____ __ __ 23
The "Grab-Winch" ·-·------ ------ -------- -- -- -- ------- ----- ---- ---- --- ----- ----- ------·-------------·-- -------------- --- ----·-- -- -- 23
ARMAMENT.
Bomb Racks, Types H-4 and A-3 --- ---------·---------------- ---- ------ --- --- ---- -- -- -·-------- -- ---- ---- -- ----- --------- 24
Bomb Rack Aadapter, Type G-2 --------- ------------- --- --- --- --------- ----- --·---- ------·- ---- ----- -·-- --- -- ---- ------- ---- 24
Bomb Truck Chassis Test ---- -- --- -·-- --- --- --- -- -- ---- -- -------------------------------· ----------------- --- ---- --- --- ---- -- 24
Concrete Bombs for Performance Testing --- -------------···- -·-------- ---- -- ------------- ------ ------------ -- -·----- 24
Browning Guns for DH-4B --------------·----- -··------- -------------------- ----- --·-- ----------------- ______ -------- ·------ -- 24
New Accessories for Lewis Gun ------- --- --- --------- ----------------- ______ -- -- ---- ·--·--· ---- --------·------- --- -----· 24
Davis Non-Recoil Cannon Fired from Martin Bomber ---- --·--·--- --··----- ----- -- ---- -- --- ·--- --- -- 25
Vulnerability Test on Curtiss Wing Radiator ___ __________ ___ -- ---------- ·----- ----- ------- ----------- 25
EQUIPMENT.
Navigation Flights ___ ___ __________ _________________ _________________ ___ ____ : ______ ______ ___ --- ------ ----·----- ------- ------ ·----- --- 2f
36-inch Searchlight as Aerial Beacon and Floodlight____ ____ __ __________________ _____ ___________ 26
Improved Electric Starters with Hand Crank and Overload Release --------- -- ---- ------ -- ---- --- 28
Night Flying Equipment ------- ----- -·-- --- ----- -- -- ----- ·-- ----- ----- ----- --- -------- --·- -----·· -- ------- -------- --- -- -- ----- - 29
Pyralin SheU Running Lights for Aircraft _____ ----- ----------------------------·------------------- ------------- -- 29
Night Airways ------ --------- -- -------·------- --- ---··-·---- -------·------- -- -------------------------- -----·---- ---- -------- ·--------- 30
New Instruments-Drift Sight Used on World Cruise -·····- ---- ---- --- --- -- ------------ ------ -- ---- 30
Altimeter for Record Flights (F. A. I.) --- --- --- ·- -- --- ·- ------ ---- ------ -- -- -- ------------ ------ ------ ----- --- --- ----- 30
Altimeter, Temperature Compensated ------------------- ----------·--------- ----- -- ----- -- -·- ---- ----- -- ------- - 31
Air Logs -- ------ ----- ----- -------------------·-------- --------------·----------------------- -- --·- -- --------------------------- ---- - 31
Earographs for Altitude Balloon Flights ---- --- --- ------------·---- -- --- -·--- --·-- ·------ --- ----- -- -- -- ---- -------- -- - 31
French Tachometer "Precision Moderne" ···-----·-··· --- -- ·-------- ------ -------- -- -· ------- -- --------- -- ----·----- - 31
Stove-r-Lang Shaft-Drive Tachometer ·· ·---·----- ·---· ···------------- --------------- -- ---- -- -- -- --- ------------- ----- - 31
C O N T E N T S - (Cont'd)
New 5-Lens Camera, Type T-3 ---------- ------ ---- ------ -- --------- -- --- -- -- -- --- -- - -- -- --- --------- --- -- ------- -- -- ---- ----- 32
Lens Tests ---- ----- -------- -- --- -------- ------ -- ------------- -------- --- ------------------------- -- -- --- --- -- ----- ------------ --- ----- -- -- 32
Frosting Focal-Plane Plates for T-1 Camera ------------------------ -- -- ----------- ------ --- ---- ----- ----· --- ---- - 32
Mosaic Control Point Indicator ---------- -- --- ---- -- ------- -- -- ---------------------- -------------- ---- ----- ------- ----- ----- . 32
Hot Oil and Water Service Truck --------- --------------·---- -----'---------------------------------------------------- -- ----- 32
POWER PLANTS . .
New Curtiss Engine, Model V-1400 ---------- ---- ---- ----- -- -- --- -- -- -- -- --------------------------- --- ---- ----- ----- ---- 35
Development of Curtiss D-12 Engine -------- --- ----- ----- ----------- -- --- ---- ---- -- ----- ------- -- -- -- -- -- ------ -- ------ - 35
Inverted Liberty Engine --------- ---- ---- -------- -- ---- -- -- --- -- ------------ ----- -- ------------------------------------ ----------- 35
Liberty Engine Parts Test ----------------------- ------- ---- --------------- --- -- ----- -- ----------- ------ -- -- -- --- ---- ----- ·---- - 36
New Method for Reenforcing Liberty Cylinders----- -- ----------- -- -- -- --- -- -------------- --- -- -- --- -- -- --------- 36
New Packard Engines, Models lA-1500 and lA-2500 ------ -- ---- -- --- -- --- ------------ --------- ---- ·-------- 36
Dynamometer Tests on Wright T-3 Engine--------------------------------------------- -- -- -- ------- -- -- --- --- -- --- - 36
New Standard Engine Control Unit ----- ---- -- ------------------ ----- -------------------------------- --- -- --- --- -- -· ----- 36
RESEARCH AND EXPERIMENT
RESUME' OF ENGINEERING DIVISION SERIAL REPORTS.
Dusting Experiments in Louisiana in 1923 --- ---------- -- ----------------------------------------------------------- 38
Methods for Selection of Airfoils ---- ----- ------ -- --- -- -- -- -- --- ------- ------- -- ------------------------------------ -- ----- 38
Revisions to "Handbook for Air plane Designers" --- ---------------- --------- ---- --- -- ----------- ------------ -- 39
Radiator Drag on the Fokker C0-4 Airplane -------- --- ---- ------------- ---- -- -- -- --- ------ ------- -- -- --------- --- 39
Structural Design of Army Racer R-3 Monoplane Wing ------- ---- ---- -- ---·------ --- -- ------- -- -- -------- 39
Inflection on Beams under Various Loads ------------- -- ---------------- ------- -- -- -- -- --- -- -- ----- -----·--- -- --- -- 39
Cooling Test on Curtiss Wing Radiator Section ----- --------- -- -- ---------- ----------- --------- --·---- -- -- -- --- -- 39
Impact Tests on Split-axle Chasses for XC0-4 and XC0-5 Airplanes___ ___ __ __ _______ _______ __ 39
List of Static Test Reports ------------------------------------------- --- ------------- -· -- ---- ---------- --- -- ---- --- -- ---- -- ---- - 40
List of Wind Tunnel Test Reports ------------------------------------------------------ -- -------- --- -- ------ ------------- 40
Service Test Requirements of Type E-2 Cannon Mount ---------- ------- --- -- -- --- -- -- -- -- -- ------------- -- 40
Handbook on External Bomb Rack, Type C-2 ------------------------------------ -- -------------------------------- 40
Chronometric Tachometers ------------------------------------------------------------------------- ---- ------- --- ------ --------- 41
Instrument for -Recording Take-Off and Landing -------------------- --- ------------------------------------- -- 41
Stability Tests in Free Flight-Dynamical Stability --------- ----------- -- ------- ---------- --- ----- ----------- 41
Performance Tests --- ----- ---- ----- ------ -- --- ------ -- --- ---- ---- -- --- ------ ------ --- ------ ------------- --- -- -- -- --- ---- -- -- -- ------ 41
Endurance Limit of Vanadium Steel-Part I _________ _________ __ _______ :__ __ __ _______ ________ _____ _____________ ___ 42
Endurance Limit of Stainless Iron --------------------------- ------- ---- ---- -- -- --- -- -- -- -- -------- --- ----- -- --- ---------- -- 42
Physical Properties of High Phospor Bronze -- -- --- ------ ------- ---- -------- ----------------- ---- -------- -- ----- -- 42
Analyses of Some United States Gasoline Fuels ------- --------- -- -------------------------------------------- ---- 42
Strength of Duralumin Tubing -- --- -- ----- ---------- --- --- --------------------------- -- ------- -- ----------------- ---- ------- 43
Magneto Endurance Tests --- -------- --- --- -- ----- --- --- --- -- --- ----- ---- -- -- -- ----- -- -- -- --- -- --------------------------- -- ------ 43
Cooling Tests on DH-4L Airplane ____ __ __ __ _____ ___ _______ _______ ___________________ :____ __ _______ ____ __________ ___________ 43
Cooling Tests on Two Fokker C0-4's with Nose and. Side Radiators__ ______ _______________ _________ 4~
Fifty-hour Endurance Test of Curtiss D-12 Engine --- -- ------- -------------- -- ---------------- --------- --- 43
Engine-Driven Gear Fuel Pumps, Type "C" --- --- -- --- ------- ---- --- ------------ ------------ -- ----------------- -- - 43
INVESTIGATION OF MATERIALS.
Protective Coating for Duralumin -- -- --- --- -- -- -- --- -- -- -- --- -- -- -------- --------------· -------- -- -- ---- ---------- --- ---- - 44
Substitute for Aluminum Leaf ----- -------- --- ---------- -- -------------------- -- --- -- ----------- --------- ------- ---- --- --- 44
Effect of Bleaching on Balloon Fabric -------------·-- ---------------- -- ------- ------- ----- --- --------------------- ----- -- 4-1
Lacing for Wing CoveTing ---- -- --- --- -- ------ --------- ---- ------ -----------·---- -- ------ ---- --- --- ----------------------------- 44
Analyses of Gasoline Fuels --------------- ---------------- --------- ---- --------- -- ------------------- ----- ------------ ----------- 44
Freezing Points of Alcohol-Benzol Mixtures --- --- -- -------------------- --- ------------------- ---------- ------------ 44
"Stellarene," a Substitute for Gasoline -- --- -- ----- ---- ------------------ -------------------- --------------- ---- --- ---- 45
lvlagnesium Pistons --------- ----------- -- ---------- ------ ---------------------------------------------- -- -- ---- --- -------- -- -- ----- -- 45
Mater;al for Control Pulleys ------ ----- --------- ---- ------- -- ------- -- --- -- -- -- ----- ------------- --- ---- --------- ------- -- ---- 45
Crushing Effect of Army and Navy Type Washers on Wood ----- ------ ----- -- -- --- ------------------ -- - 45
Redesigned 28x4 Airplane Wheel ---- --- --- ---- -- ------------------------- -- ------------------ -- ---- --------- -- ----------- 45
NEW BOOKS AND DOCUMENTS
Documents Added to Technical Files during Second Quarter of 1924_______ _______ ______ _____ __ ___ 47
•
LIST OF ILLUSTRATIONS
Page
36-inch Searchlight Floodlighting McCook Field Airdrome for Night Landing___ _________ 6
Elias Night Bomber, Model XNBS-3 ---- ---------- ----- ---------- ----- ------ -------- -- ---- ---------------- ------- --- ---- 8
Engineering Division Observation, Model XC0-5 (Revised Model) --- ---- ----------- ---------- ---- 10
Engineering Division Observation, M,od.el XC0-6 with Inverted Liberty________________________ 11
General Arrangement of Engineering Division XC0-6 (Dwg.) ------ -- ---- ------ ------ -- ----- --- -- ---- 13
Dayton-Wright Special Pursuit, Model XPS-1 -- --------- ------ ---- ----,----- -- ------ ------ -- --·-- --------- --- ----- 14
General Arrangement of Dayton-Wright XPS-1 ------------ ·------------------ ------,----- -- --- -------- ----- --- 15
Messenger with Airship Attachment ---- ----- ------ -- ----------- ------ ------ ------- ---- ------ -- ---- --- ---- -----·------ -- 19
L-W -F Transport, Model XT-3 -- -------- ------- ------- ------ ---- ------ -------- -- -- ------ ----- --- ---- -- ----- ----------------- 20
Side View of Transport XT-3 showing Passenger Cabin___ ___ ____ ___ __________________ ________ _____________ 20
General Arrangement of L-W-F Transport XT-3 (Dwg.) ------------------------------ --- ------- ----- -- - 21
36-inch Searchlight Equipped with Spread-Lens Door ----- ---·-- --- ------- --- --- -------- --- ----- -- ---- -- --- -- 26
Modified Lamp Mechanism for 36-inch Searchlight --------------------------·- --- ----- ----- -- --------- ------ -- 27
Straight Beam as Aerial Beacon (36-inch Searchlight) ---- ----- ---- ----- --- --- ---- ----·------- -- ------ -- -- 28
Pyralin Airplane Running Lights ----- ----- --------------- ------------------------------------- -- ------ ----- ----- ----- ----- 29
F. A. I. Altimeter ------------- ---- --- ------- ------ ------ -------- -- -- --------------------------------------------- -- ------------------- - 30
Hot Oil and Water Service Truck ----- -------- ------ ---------- ------------ ---- ------- ---------------- ------ ------ ---- ------ 33
Ringen Burners on Hot Oil and Water Service Truck ------ -- --- -- ---- -----·-- ------- ------ -- -- ----- ---- ----- 34
New Engine Control Unit, Type B-4 ---·--------------------- ------·-- ·----- ------------ -- ----------- --- --------- -- ------- 37
f.edesigned 28x4 Airplane Wheel _____ , __ _____ _________ ------- ------ ----- --· ------ -- -------------------------------- -- --- -·· 46
6 T E C H N I C A L B G L L E T I N N o. 39
36-INCH SEARCHLIGHT FLOODLIGHTING McCOOK FIELD AIRDROME FOR NIGHT LANDING.
I. Floodlight Mounted on Hangar. 2. Illuminated Area .. 3. Approaching the Spread Beam. 4. Night Flying DH in
Floodlight.
(Description on page 26)
AIRCRAFT DEVELOPMENT
ON ENGINEERING DIVISION PROGRAM
AIRPLANES
BOMBARDMENT TYPES.
Bids for New Day Bombers-Huff-Daland XLB-1.
The following aircraft manufacturers submitted designs in the April compehttons for A. S.
Type XI Day Bombardment airplanes, in accordance with Circular Proposal No. 2472.
Barnhart Aircraft Company, Pasadena, California.
Boeing Airplane Company, Seattle, \i\Tashington.
Cox-Klemin Aircraft Corporation, College Point, Long Island, N. Y.
The Douglas Company, Santa Monica, California.
G. Elias & Bro. Inc., Buffalo, N. Y.
Huff, Daland & Co. Inc., Ogdensburg, N. Y.
Wright Aeronautical Corporation, Paterson, N. J.
In this connection, the Air Service has negotiated a contract with Huff, Daland & Company
for the construction of one experimental airplane in accordance with their design. Certain recom­mendations
on the seating arrangement and increases in the supporting and radiating surfaces have
been made by the Division. The incorporation of these changes in the design, however, is optional
with the contractor. The new 'plane is to be built around the \i\Tright T-3 engine and will carry the
model designation, "XLB-1."
Improving Performance of NBS-1.
The Engineering Division is conducting considerable experimentation for the purpose of im­proving
the general performance of the supercharged NBS-1 airplanes recently placed in service.
One supercharged airplane, equipped with underslung radiators, water-cooled oil tanks, new en­gine-
driven fuel pumps, and new cowling has been undergoing performance tests with various
loads at Wilbur Wright Field. On one flight this 'plane 'weighing 13.695 pounds fully loaded.
climbed to 10,000 feet in 75.3 minutes carrying a useful load of 5,846 pounds of which 2,400
pounds were bombs.
It is probable that all NBS-l's will be equipped with the new Type C engine-driven fuel
pumps recently designed by the Division, in which case the use of the present wind-driven pumps
will be discontinued. Ten refueling pumps have been ordered from the Blackmer Rotary Pump
Company for installation in these airplanes.
The Division has also undertaken a complete check and classification of all Martin Bomber
parts to determine their interchangeability among the four models now in the service in order to
facilitate requisition of spares for maintenance.
Night Bombers, Models XNBS-2, 3 and 4*.
On account of financial difficulties, the L. W. F. Engineering Company will be unable to com­plete
their contract for two XNBS-2 airplanes and as a result this experimentql contract together
with another covering ten Model T-3 Transports, one of which has been delivered, has been de-clared
in default. ·
The Elias XNBS-3, received at McCook Field in February, 1924, is the first of three new types
of short distance night bombers to be completed on experimental contracts awarded by the Air
Service to the L. \i\T. F., G. Elias and Curtiss aircraft companies, respectively, on designs submitted
*Hereafter all experimental airplanes will be designated by the letter "X" prefixed to the model symbol in accordance
with Wa-r Department Circular 65-20 issued by the Chief of Air Service under date of May 14, 1924.
8 T E C H N I C A L B U L L E T I N N o. 39
in the April competitions of 1922. These airplanes, carrying designations as Models XNBS-2, 3
and 4, are of externally braced bipfane construction mounting two Liberty "12" engines, as stated
in Technical Bulletin No. 27.
T his twin-engined bomber employs a sectional wing cellule having only one bay in the out­board
·sections. The nacelles, each of which carries a tractor Liberty engine, rest on the lower wing
inboard sections directly over the wheels of a wide tread, divided axle landing gear. Diagonal
struts extending from the nacelles to top fuselage longerons furni sh the bracing for the lower wing
inboard sections which are hinged to the lower fu selage longerons. The fuselage resembles the
usual bombing type with a gun ring on the nose, a double cockpit for pilot and navigator , a long
and deep bomb compartment, and a gun ririg on tail just aft of wings. The empennage comprises
a strut-braced, semi-biplane .structure consisting of two vertical fin s, two balanced rudders, one
main horizontal tail plane or fixed stabilizer, an adjustable stabili zer and an elevator. The adj ust­able
stabilizer or trimming plane is mounted above the main stabili zer between the rudders and is
used to correct balance during fli ght. In the pr oof tests, the trimming plane could be operated
sati sfactorily under a loading of ten pounds per square foot.
Upon inspection, it was found that the inte rnacelle spars and other welded parts of the struc­ture
contained minute cracks near the welds which necessitated their replacement by the con­tractor.
This work caused considerable delay in the assembly and erection of the ai rplan e, which
is now ready for final inspection and flight test.
The Curtiss XNBS-4 was the next of the new Type XII bombers to be delivered. T his air­plane
was flown to McCook F ield in May by an E ngineering Division pilot after preliminary flight
tests at the contractor's plant. Preparatory to performance testing, ne,v engines were in stalled and
minor changes made. A proof load of the hori zontal tail surfaces was carried to ten pounds per
square foot.with only slight defl ection but the stabilizer adjusting mechanism could not be operated
with m0re than five pounds of load. In prelirnin ary flight test, ,this airplane loaded to weigh
13,740. pounds gross attained a high speed of 99.4 m. p. h. and a service ceiling of 9,400 feet.
Martin Bomber propellers were used in this test. F ull performance tests of the XNBS-4 will be
made with newly built propellers of the L. 'vV. F. Transport type which have been in stalled, as soon
as other minor changes are completed.
T he XN BS-4 is a large biplane powered by two Liberty engines carried in nacelles on the
lower wing. The fuselage is offset on each side near the nose, the projections being glazed with
triplex glass to give unobstructed vision for landing. The principal characteristics of the 'plane
are as follows: span 90' 2" , length 46' 5", height 15' 9", landing gear tread 18' , supporting sur­face
1524.4 square feet, gross weight 13,777.7 po unds, and useful load 5972 pounds.
ELIAS NIGHT BOMBER, MODEL XNBS-3.
(Two Liberty "12" Engines.)
AIRCRAF T DEVELOPMENT
OBSERVATION TYPES.
First Amphibian Damaged in Acceptance Tests.
9
·while landing in New York harbor during the 10-hour acceptance tests, the new Air Service
amphibian airplane "XCOA-1" recently completed on experimental contract by the Loening Aero­nautical
Engineering Corporation of New York City, was seriously damaged in accidentally strik­ing
a submerged obstacle. Before the accident however, the 'plane had been flown considerably,
there having been 73 landings made on the wat er and 15 on land. These tests disclosed excep­tional
maneuverability in flight for this type of 'p lane. excellent visibility in landing due to use of
in verted engine, and a performance comparing favorably with that of the standard DHAB. On the
whole, the performance proved very satisfactory for the first article of this design and the air­plane
deemed admirably adaptable for army and coast artillery observation arid surveillance.
The Loening amphibian follows practically the same lines as a seaplane and embodies in­teresting
structural features . The design is of the biplane type with symmetrical wings, inverted
Liberty "12" engine, and seaplane hull fitted with retractable land wheels. The close-coupled cock­pits
afford easy communication and accessibility and a re fitted with a combination control system
utili zing a wheel or Dep control in one cockpit and an ordinary stick control in the other. This
amphibian airplane is readily adaptable for use on land or water as it requires only ten seconds to
raise or lower the retractable land gear wheels. General maintenance features are good.
The damaged 'plane will be shipped to McCook Field for survey and probable static test.
Performance of Fokker C0-4 with New Wing and Dural Propeller.
A production Fokker C0-4 observation airp lane equipped with new nose cowling, propeller
spinner, and new short chord lower wing which were submitted by the Fokker Company as stated
in Tech11ical Bulleti11 No. 38, was flown over the speed course at an average timed speed of 135.63
111. p. h. at 1710 r. p. m. This flight was made with an adj ustable blade duralumin propeller of
Engineering Division design . with blade angles set at 18.3° at 48-inch radius from hub center
and with the retractible side radiators three-fourths extended. This same airplane with standard
chord lower wing attained a high speed of 135.7 m. p. h. at 1725 r. p. m. with blade setting at
18.5° at same radius and with radiators one-fourth out, the speed with radiators fully extended
being only 129.2 m. p. h. Some improvement in performance is noticeable with the new wing and
cowling.
In a later test with new setting of propeller blades, a high speed of 143.5 m. p. h. was attained
with radiators fully retracted and a speed of 134.1 m. p. h. ,vith radiators fully extended. In all of
these tests, an adjustable two-blade duralumin propeller was used.
F light tests for comparing the relative merits of the Fokker C0-4 and the standard DH-4B
have been completed and the data thus obtained will be compared with those on the Engineering
Division XC0-5 as soon as performance results on the latter become available.
Engineering Divisio1.1 XC0-5.
Shortly after the completion of the XTP-1 , a two seater pursuit biplane mounting a super­charged
Liberty engine, the E ngineering Division developed an observation airplane along the same
general lines without supercharger, to carry Air Service Type X equipment, the new airplane being
designated Model "XC0-5."
i\s originally constructed, this ai rplane followed the same general design and type of con­struction
as the XTP-1, being practically identical to it. Both models utilized welded steel tube
fu selage structures and conventional wood and fa bric wings. To rear of fir ewall, the fu selages
were the same except for the equipment whereas in front of firewall, the trussing in the XC0-5
was changed to increase accessibility of the power plant. During development, the appearance of
both models underwent considerable change but the resultant modifications still retained a char­acte
ri stic resemblance which may be readily seen by comparing the accompanying view of the
XC0-5 on the next page with that of the XTP-1 on page 39, Technical Bulletin No. 39.
The revised XC0-5 airplane is distingui shed by the rever sed position of the wings, the larger
wing being placed at the top and the short chord wing at the bottom to give greater visibility and
angle of fire downward. The wings have been made with circular tips and the span increased
10 TECHNICAL B U LLETIN o. 39
ENGINEERING DIVISION OBSERVATION, MODEL XC0-5 (REVISED MODEL).
(Liberty "12" Engine.)
from 36 feet to 43 feet, thereby increasing the supporting area from 375 · square feet to 434 square
feet . The fu selage has been lengthened 80 inches and the overall height of the 'plane raised 7
inches. A split-ax le duralumin strut chassis and an underslung radiator complete the differentation.
Performance data on the original XC0-5 with small area wings in the original position, that
is, with large wing at the bottom, are as follows :
High speed at ground . ... .... . .. . . .. . . . . ... . ...... .. . .... .. 137.3 m. p. h.
Climb to 15,000 feet .... .. ... .. .. . .... .... . . .. . .. .. .. . . .... 30.7 minutes
Service ceiling .................. ... ... .... ... . .. . . .... .. .. 16,200 feet
Absolute ceiling .. . .. .................. . . . . . ............... 18,000 feet
Since no performance data have yet been obtained on the revised model, which has only re­cently
been completed, the above figures cannot be taken as truly indicative of this type of airplane.
Engineering Division XC0-6.
A few months ago, the E ngineering Division undertook the design and construction of a new
observation airplane around the inverted Liberty engine to replace the present standard DH type.
Two airplanes of the new design which is designated "XC0~6" have just been completed, one for
static test and the other for flight test. the formerbeing fi ni shed only in so far as it was necessary
for the test s. One of the features of the design is a releasable fuel tank located in the fuselage.
U nder static test, the hori zontal tail surfaces held sati sfactorily the required loading of 30
pounds per square foot. Failure of the elevator spar occurred when the load was carried to 35
pounds per square foot. The vertical tail surfaces supported a load of 35 pounds per square foot
without failure, 10 pounds over the required loading. A fiber aileron, which had been undergoing
a weathering test of four months, held a load of 60 pounds per square foot, the required loading
in this case being the same as for the horizontal surfaces-30 pounds per square foot.
In constructing the XC0-6, the work proceded in such a manner that any recommendations
or changes resulting from wind tunnel tests of the model could be incorporated in the design with
least duplication of effort. On parts not affected by these aerodynamical tests, the work proceded
without interruption. A study is now being made to determine what modificationos are necessary
to make the present XC0-6 design comply with the new specification recently adopted by the
Air Sen·ice for observation airplanes, due to the fact that when this design was started onlv a
tentative specifi cation was available. Such changes as are considered practical will be incorporated
in the present model.
The Division is now planning the construction of a third ai rplane utili zing a Clark "Y" wing
section and carrying the fuel tanks in the upper wing . to be designated "XC0-6A." The fuselage,
tail surfaces, landing gear, power plant installation, and many other parts are to be identical to
those of the XC0-6 in order to provide for interchangeability.
AIRCRAFT DEVELOPMENT
Boeing XC0-7 (Thick Wing Dlf4M-1).
11
T1he Boeing Airplane Company of Seattle, Washington, which is building a large number of
DH-41\1-1 airplanes on production contract equipped three of these airplanes with special thick
wings and split-axle chassis for experimental purposes as stated in Technical Bulletin No. 38
under A. S. Order 1441-24 on page 22, the experimental models to be designated "XC0-7." As
a result of the tests on the second XC0-7 which failed in flight, the Division has recommended
several changes in the third article. These involve the construction of two detachable engine sections
to accommodate either the upright or the inverted Liberty engine. Drawings for the inverted
engi ne in stallation are being prepared.
Experimentation with DH-4B.
A wind tunnel model of a standard DH-4B airplane at McCook Field is being built by the
Division to obtain aerodynamical data for use as check against actual flight performances of the air­plane
itself. The model will be constructed with forward encl of the fu selage detachable in order
that different types of cowling may be tested as desired. l\foclel radiators of various types will also
be in stalled for the purpose of determining their relative parasite resistances.
The E ngineering Division is preparing installation drawings for use of the Fairfield Air Inter­mediate
Depot, Fairfield, Ohio, in equipping service DH-4B's (wooden fuselage) with side type
superchargers. A study is also being made to determine the feasibility of applying this type of
supercharger to the new DH-4B's with steel fuselages (DH-4M. )
A DH-4B airplane equipped with Curtiss D-- 12 engin e, without military load, developed an
average timed speed of 110.7 m. p. h. at 2060 r. p. m. over the speed course.
A standard DH-4B has been equipped with an adjustable blade duralumin propeller to obtain
performance data in a series of flights for compari son with the Fokker C0-4 and E ngineering
Division XC0-5 airplanes.
The Division is designing and constructing new exhaust manifolds and a set of duralumin
covered tail surfaces for a special DH-4B airplane assigned to the Division of Chemical \ i\Tarfare.
The fini shed parts will be forwarded to Phillips F ield, Aberdeen, Maryland, for installation and
test.
ENGINEERING DIVISION OBSERVATION, MODEL XC0-6.
(Inverted Liberty "12" Engine.)
12 T E C H N I C A L B U L L E T I N N o. 39
DH-4M, DH-4M-1 and DH-4M-2.
The Boeing Airplane Company of Seattle, \ i\T ashington, has completed production contract ( A.
S. Order 1173-23 )for fifty DH-4M steel fu selage airplanes and has another (A. S. Order 1403-
24) for one hundred DH-4M-l's about one-half completed. It was found necessary to reinforce
the bottom bay at Station 3 on all DH-4M-l fu selages with a metal plate to resist the bump of the
tail skid which might otherwise damage transverse members at this station.
The principal design characteristics of the Boeing DH-4M and DH-4M-l airplanes were pub­plished
in T echnical Bulletin No. 36.
Specifications have been drawn and circular proposals issued by the Chief of Air Service to
aircraft manufacturers asking for bids on the construction in lots of 25, SO and 100 airplanes of a
modified DH-4M type to be known as the DH-4M-2. In this connection, the Atlantic Aircraft
Corporation has submitted bids for the construction of 65 DH-4M-2, 25 DH -4M-2-P (photo­graphic),
and 10 DH-41\1-2-S (supercharged) airplanes. The DH-4M-2 design incorporates a
steel tube fuselage and landing gear.
New Type "XO" Observation Airplanes.
In response to circular proposals issued by Chief of Air Service, various aircraft manufac­turers
submitted designs and bids on two new types of obser vation airplanes, one type to be
built around the Liberty engine and the other around the new Packard l A-1500 and the new \ i\T right
T-3 engines.
The following firms and individuals submitted bids on Circular Proposal 2487 for an observa-tion
airplane built around the Liberty engine:
Aeromarine Plane & Motor Corporation.
Atlantic Aircraft Corporation.
Barnhart Aircraft Company.
Boeing Airplane Company.
Cox-Klemin Aircraft Corporation.
Curtiss Aeroplane & Motor Company, Inc.
The Douglas Company.
G. E lias & Bro., foe.
Huff, Daland & Co., Inc.
Mr. Chas. B. Kirkham.
Loening Aeronatuical E ngineering Corporation.
Mr. MacQueen
Glenn L. Martin Company
Thomas-Morse Aircraft Company.
In connection with Circular Proposal 2453 for A. S. Type X two-seater observation airplanes
mounting new Packard and \Vright engines, competing designs were submitted by the fo llowing air­craft
manufacturers.
Aeromarine P lane & Motor Corporation.
Atlantic Aircraft Corporation.
Boeing Air.plane Company.
Cox-Klemin Aircraft Corporation.
Curtiss Aeroplane & Motor Company, Inc.
The Douglas Company.
Fowler Smith Compa ny.
H uff, Daland & Co., Inc.
Loening Aeronauti cal Engineering Corporation.
Glenn L. Martin Company.
Thomas-Morse Aircraft Corporation.
Wright Aeronautical Corporation.
\
F inal decision on the first mentioned type has not been made pending submj ssion and test of
wind tunnel models from designs submitted by the Curti ss, Thomas-Morse, Douglas and Loening
companies. In regard to the second type mounting new Packard and vVright engines, contracts
have been drawn with the Curti ss, Douglas, Wright and Martin companies as follows:
Curti ss X0-1-Packard l A-1500 engine.
Douglas XO 2-Packard l A-1 500 engine.
Wright X0-3-Wright T-3 engine.
Martin X0-4-vVright T-3 engine.
vVith regard to Model X0-4, however, the contract with the Glenn L. Martin Company has
not been signed as this firm desired to complete a large production order for the Navy Deparment
in preference to proceeding with the experimental work.
f------1z'.... tJ "- ----<
_; I
L
~------- ----- ------48'-------- -----------__.,
j'- ll"
6~ 6"
6'
GENERAL DESCRIPTION
Airplane .. ...... ... ..... .... . Eng in eering Div ision XC0 -6
Type.. ..... . .... .. Obs e rvation Biplane
St atus ...... --------- Experimenta l
Manufacturer. . . ... Eng ineering Divis ion
Eng ine ........... In verted Libe rty "12"
Sup porting Area ...... .4 84 s q u a re f eet
Gross W eig ht ........... .4 590 .66 pounds
Useful load ....... ...... ... 1557.5
Wing loading .... .. .. .... 9.42 lb. /sq. ft .
------------Z:J'-tl -"----- - ----
GENERAL ARRANGEMENT OF ENGINEERING DIVISION XC0-6 WITH INVERTED LIBERTY.
H
.....
w
14 T E C H ~ I C A L B U L L E T I ~ X o. 39
PURSUIT TYPES.
Dayton-Wright XPS-1 (Alert).
In June, 192 1, T he E ngineering Division entered into a contract with the Dayton-vVright
Company, a firm which has since di scontinued the manufacture of aircraft, fo r the design and con­struction
of three experimental special pursuit airplanes of the "Alert" type, designated Model
XPS-1 and designed to carry a light milita ry load for airdrome defense. The fir st of these was
subjected to static tests, the second per formance tested to determine contract requirements, and the
third held in reserve. Altho the per formance requirements were not met in these tests and the
flying models therefore not accepted by the Air S ervice, the design exhibited many new and in ­teresting
aerod ynamical features peculiar to this type.
The distingui shing features which characterize this single place alert monoplane mounting a
Lawrance air-cooled radial engine, are its low -hung appearance and hand-operated · retractable
chassis. This latter feature is an original design known as the endless retractable undercarriage by
means of whi ch the wheels can be drawn up into recesses in the side of the fu selage, an operation
requiring about ten seconds to retract the wheels and six seconds to lower them.
In general , the design embodies a continuous monoplane wing of wood and fabric construc­tion
mounted above a welded steel tubular fu selage by means of four pairs of cabane struts extend­ing
upward and outwa rd from the upper and lower longerons to the spar s. The wing panels taper
both in chord and thickness on both sides of the outer struts and carry two ailerons in the trailing
edge at their overhanging ti ps. The hori zontal tail surfaces are built entirely of wood and fabric
whereas the vertical fin and rudder are constructed of steel tubing, oxy-acetylene welded and fabric
covered. T he hi ckory tail skid is connected to the rudder bar by means of cables and tension
springs to enable pilot to steer 'plane in taxying .
The power plant consists of a 9-cylinder 200-h. p. Lawrance J-1 air-cooled fi xed radial engine
fitted with three Stromberg N AS -4 carburetor s, two Dix ie magnetos, and a four-bladed short
diameter propeller. The three lower cylinders are fitted with short exhaust stacks di scharging to rear
of the cowl whereas the rest of the stacks di scha rge in side the cowl, the exhaust gases fi nding their
way out thru the annular spaces between it and the fuselage. In certain positions of the 'plane dur­ini?;
climb, these gases escaped into the cockpit ca using great di comfort to pilot. A new exhaust
system will be necessary to correct this conrlition.
F uel is carried in lealqJroof tanks. The main tank holding 21.5 gallons is placed under the
pilot's seat and a small 7-gallon gravity tank in the center of the wing . The system is operatec!
by an engine-driyen bellows fu el pump providect with an automatic p ressure relief valve.
No electri cal , radio or photographic equipment is carried. T he armament in stallation provides
for either a .30 caliber or a .50 caliber synchroni zed Browning machine gun together with the
necessary ammunition boxes, shell chutes, and sights.
DAYTON-WRIGHT SPECIAL PURSUIT, MODEL XPS-1.
(Lawrance "J·l" 200-h. p. Engine.)
·~
1---......::.1r.=:----1-t-
~
GENERAL DESCRIPTION
Airplane ...... ..... ... Dayton-Wright XPS-1
Type .. ... Alert Purs uit Monoplane
Status .................... ..... 'Experimental
Manufacturer ........... .. Dayton• Wright Company
Engine ... ... ... ............... Lawrance "J..,l" Radial
Supporting Area ...... 143 square feet
Gross Weight .. ...... .... 171 5 pounds
Useful load .... .. .......... 541.6 pounds
Wing loading .. .... ... .... 11.98 lb./sq. ft.
Power loading ....... .. .. 8.58 lb./h. p.
GENERAL ARRANGEMENT OF DAYTON-WRIGHT XPS-1 (ALERT) .
)>
-Ul
16 T E C H N I C A L B U L L E T I N N o. 39
In the performance tests conducted by the Division, the flight model ( second article) attained
a timed high speed in level flight of 145.6 m. p. h. at 1830 r.p.m. with cowling on and undercarriage
retracted. Under the same conditions with undercarriage extended, the high speed was 129.8 m.
p. h. at 1762 r. p. m. High speed at 15,000 feet reached 132.4 m. p. h. and the climb to 20,000
feet ceiling required 36 minutes.
Performance requirements inserted in the cuntract specified a high speed of 145 m. p. h. at
15,000 feet altitude and a climb to 20,000 feet in 18 minutes. In a subsequent agreement, these
figures were lowered to a high speed of 130 m. p. h. at 15,000 feet and climb to 20,000 feet in 25
minutes because of the fact that the Lawrance engine used in this airplane was still in the ex­perimental
stage where its performance characteristics in the altitude chamber as well as in actual
flight were as yet undetermined. In ·comparing the above figures, it can be seen that the per­formance
as specified under the modification have been met for speed but not for climb.
Curtiss PW-8 and Changes in "Coast-to-Coast" Airplane.
The second experimental Curtiss pursuit, views and descriptions of which were published in
the preceding Bulletin, was returned to the Curtiss company for modification of the cooling system.
During the ensuing tests, it was badly damaged, necessitating considerable repair.
Due to the fact that the wing construction of the second article differed from that of the
first Curtiss pursuit, the Curtiss company submitted for static test a sample right-hand cellule of
the new design which is used on the forthcoming production articles also. In the static test con­ducted
at McCook Field, the sample cellule withstood satisfactorily a load equivalent to the re­quired
factor of 6.5 in low incidence position but failed in high incidence position at the required
factor of 12 after supporting a load factor of 11.5. In the impact tests, the new landing gear
used on these airplanes withstood the required drop of 48 inches under one-half load.
Two production P\V-8's have been received at the Division. One of these is being fitted with
a side type supercharger and a special propeller designed for 190 m. p. h. at 20,000 feet altitude.
The fifth airplane on the production contract was the one used by Lt. Maughan in his famous
"Dawn to Dusk" transcontinental flight from New York to San Francisco on June 23, 1924. In
this flight, the distance of 2760 miles was covered in a total elapsed time of 21 hours and SO minutes,
the actual flying time being 18 hours and 38 minutes or at an average speed of 148 rn. p. h. Pre­paratory
for the flight, the Engineering Division recommended and procured the necessary equip­ment
for installation in the airplane as well as tools and emergency parts for allocation at the re­fueling
points along the route.
The "Coast to Coast" airplane was equipped with a low compression Curtiss D-12 engine
fitted with reinforced cylinder block, improved vertical drive shaft gear, long exhaust pipes, and
duralumin propeller. Fuel capacity was increased from the normal supply of 77 gal lons to 167
gallons by the installation of two auxiliary tanks of 45 and 47 gallons capacity in addition to the
main tank containing 77 gallon s: A 3-gallon tank of Liquid "X," a radiator compound for pre­venting
leaks, was also carried for injection into the water system. An Engineering Division
earth induction compass was included in the special equipment. Other than the replacement of a
leaky fuel line at McCook Field, no repairs were found necessary on this flight.
Boeing XPW-9.
The Boeing Airplane Company completed their contract for three experimental pursuit a1r­planes
with the delivery of the second and third article to this station. Preliminary observations
in the ihitial flight tests indicate superior performance to the first article described and illustrated
in T echnical Bulletin No . 38.
In a regular performance test, the third article equipped with a high compression Curtiss
D-12 engine and a combination high speed and climbing propeller attained a high speed of 163 rn.
p. h. at 2240 r. p. rn. with a useful load of 962.7 lb. The gross weight of the 'plane in this flight
was 3014.7 lb. Another test will be made to obtain performance data on this airplane equipped
with low compression engine and Curtiss high speed propeller.
Special tail surfaces and split-axle landing gears have been received from the Boeing Com­pany
for installation on these airplanes. The stress analyses furnished by the contractor will be
checked, however, before these parts are installed for test.
AIRCRAFT DEVELOPMENT 17
New Records for Engineering Division XTP-1.
An Engineering Division pilot in the rebuilt XTP-1, a two-seater pursuit of biplane construc­tion
mounting a side-supercharged Liberty engine, established two weight-altitude records for 250
and 500 kilograms which have been homologated by the Federation Ae:-onautique Internationale
as fo llows: on l\1arch 27, 1924. 250 kilograms, 29,462 feet (8980 m. ) and on May 21 , 1924, 500
kilograms. 23,143 feet (8578 111. )
TRAINING TYPES.
Cox-Klemin to Improve XTW-2 Design.
A Cox-Klemin tandem training 'plane which had been delivered to the Division on an experi­mental
contract more than a year ago has been loaned to the Cox-Klemin Aircraft Corporation for
use in the construction of a new airplane of simi Jar design but not identical with the present
XTW-2. Parts of the old airplane that will be used in the new include the fuselage, landing
gear, tail surfaces and power plant, a \ i\Tright Model E engine of 180 h. p. In aclclition, the Gov­ernment
is furnishing a VE-7 propeller and air-cl riven fuel pump for installation in the modified
article which upon completion will be sent to Brooks Field, T exas, for competitive tests with present
service training 'planes.
Consolidated TW-3.
Performance tests of the fir st production model TW-3 airplane built by the Consolidated Air­craft
Corporation , East Greenwich, R. I., on A. S. Order 1079-23, have been completed by the
Division at McCook F ield for the purpose of obtaining data for comparison with prospective
service test reports. The tests were interrupted by failures of the fuel tank and engine mount
brace tubes. The tank has been reenforcecl externallv in an effort to overcome structural weak­ness
caused by use of thin gage walls and in suffi cien't baffle plates. If this method of reenforcing
the fuel tank is successful , it will be applied to the nineteen T'vV-3's at Brooks F ield.
The Consolidated TvV-3 is an improved design of the earlier Dayton-Wright side-by-side seater
training 'plane built about the \ i\T right Model "E" 180-h. p. engine, several of which were con­structed
for the Air Service.
Huff-Daland TW-5.
In recent flight tests of the Huff-Daland T'vV-5 trammg 'plane, a modified design of the Navy
HN-1 tandem training seaplane for land use, the following performance was obtained with a
Wright Model "E" engine equipped with micarta adjustable blade propeller using a blade setting
of 14.9 degrees at a 48-inch radius :
High speed at ground ( 1820 r. p. m.) . . . . . . . . . . . . . . . . . . . . . . . . 116.3 m. p. h.
Rate of climb at sea level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 990 ft./ min.
Service ceiling .. . .................... . ...... . ......... .... 14,250 ft.
Absolute ceiling . ......... .. ....... . ............. ... . .... .. 15,850 ft.
The Engineering Division is making a study of the mounting of the Wright E engine in a
welded steel tubular fu selage for application to this airplane. The original engine mount on the
TW-5 airplane was redesigned along the lines of that used in the VE-9. When the airplane was
flown , the vibration from the engine was transmitted to the pilot's cockpit with such severity that
flight was physically impossible except for very short periods. In order to make the 'plane com­fortable
to fl y, the wooden engine bearers were then replaced by steel channels having rubber
washers set in the tubing around each engine bolt. This resulted in a great improvement. From
the standpoint of engine in stallation. however, this mounting is still inf erior to that used in the
VE-9. and a design study is in progress for the purpose of rai sii,g it to this standard.
Improved Center Section for Vought VE-9.
For the purpose of improving the upward vision and facilitating egress with parachute from
the front cockpit of the Vought VE -9 airplane, the Engineering Division has constructed and in­stalled
a welclecl steel tubular center section in which the rear spar is non-continuous. In the flight
18 T E C H N I C A L B U L L E T I N N o. 39
tests by various pilots, the differences in fl ying chara cteristics between this 'plane and the standard
Vought were considered negligible. The new center section appears to serve the purpose for
which it was designed and is interchangeable with the standard center section.
Study of JN-4H Training with Steel Fuselage.
The study and preliminary design of a tubular fuselage for the J N-4H training 'plane is be­ing
carried on by the Division with a view of substituting this type of fuselage for the present
" stick and wire" type, thereby improving manufacture, accessibility and maintenance.
MISCELLANEOUS PROJECTS.
Army Entries in 1924 Pulitzer.
The Army Curtiss Racer s, Model R-6, which won the Pulitzer Trophy at Detroit in 1922, are
being modified by the Division and conditioned for participation in the International Air Races at
Dayton , Ohio, this coming October. The modifications of the R-6 consist principally in the in­stallation
of diffe rential controls to correct directi onal and longitudinal instability at high speed, and
in the installation of a large bore, high compress ion Curtiss D-12 engine of 500 h. p. fitted with
a racing type duralumin propeller. No ex tensive structural changes will be made.
A Navy Curti ss Racer, Model R-2C, which won the race last year, has been transferred to
the Divi sion and redesignated as the Army Racer "R-8." This airplane will be overhauled and
fitted with a large bore, high compression Curti ss D-12 engine, the same as used in the R-6. The
Engineering Division has designed a special aluminum alloy propeller of the detachable blade type
that is suitable for speeds up to 270 rn. p. h. for in stallation on this airplane. A special hub and
spinner have also been designed for this propeller.
Ambulance 'Plane XA-1 to be Built by Cox-Klemin.
As a result of bids submitted by six aircraft manufacturers on Circular Proposal 2404, a con­tract
was placed on June 25 with the Cox-Klemin Aircraft Corporation for the construction of
two ex perimental ambulance airplanes in accordance with the design made by the E ngineering
Division, the airplanes to be designated Model XA-1.
The design incorporates a biplane construction with steel tubular fu selage mounting a stan­dard
Liberty " 12" engine. P rovi sion is made for carrying a pilot, medical officer, and two
patients, the later to be carried in a new type of litter which can be locked in place. In addition
to the regular fl ying equipment, provision is also to be made for carrying supplies such as medi­cine,
splints, thermos bottles, oxygen fla sks, water bottles and wrecking tool s, including an axe,
wire and bolt cutter s, tow cable, etc. A speaking tube will afford audible communication between
pilot and medical offi cer. The plane will be equipped with landing and running lights and the
necessary electrical equipment to f urnish the current.
In connection with this contract, the Division has completed drawings and stress analyses of
the preliminary design and is constructing a "mock-up" and wind tunnel model for check. Changes
are being made in the design of the engine mount and fuel system in order to bring the line of thrust
nearer the center of gravity, as a r esult of the re cent experience with the Boeing XC0-7 which
embodi ed the same structural features as the XA-1 design.
The contractor is to furni sh additional parts for static test. These include one front upper
wing spar truss complete with fittings and brace wires, one compression rib, and one interplane
strut. Proof tests of the tail and control surfaces will be made at the contractor's plant.
The normal useful load of the XA-1 will aggregate 1800 pounds di stributed as follows:
Crew and passengers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 720 lb.
F uel and oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 729 lb.
Equipment including medical supplies and wrecking tools, etc. . . . . . . . . . . 351 lb.
Tests of Air Mail 'Plane.
An Air Mail 'plane which had been deliver ed to the Di vision for high speed and static tests,
was flown over the speed course at an average timed speed of 122.8 m. p. h. at 1735 r. p. m. (ob- .
served ). No military load was carried. Static tests will be conducted.
•
AIRCRAFT DEVELOPMENT 19
Variable Wings and Airship Attaching Device for Messenger.
A Sperry Messenger (Engineering Division design) has been equipped with variable camber
wings by the Aeromarine P lane & Motor Company and delivered to McCook F ield for t ests. The
top surface and trailing edge of the variable camber wing are so constructed that they may he
moved by the pilot during flight for the purpose of increasing or decreasing the speed of the 'plane
and also varying the other characteristi cs. F light tests are being held in abeyance pending a check
of the stress analysis to be submitted by the contractor.
MESSENGER WITH AIRSHIP ATTACHMENT.
Duster Airplane for Department of Agriculture.
Sometime ago the Air Ser­vice
contracted for the construc­t
ion of a device by which a
Messenger airplane could be at­tached
to or released from an air­ship
in flight. A hook structure
was designed and installed on the
upper wing of this airplane as
shown in the illustration and a
special trapeze built for suspen­sion
from the airship. Both
structures were sent to this sta­tion
for static proof tests.
In these tests, a load equiva­lent
to a factor of 2 was placed
on the airplane, and the hook and
trapeze tested for yaw, roll and
drop. Multiple motion pictures
( slow motion ) were taken to
show the attachme:1t and release
of the hook mechani sm 111 opera­tion.
With the cancellation of the L. vV. F . contract for T-3 transports, the E ngineering Division
transfererd a Liberty engine to the H uff, Da land Company for in stallation in the Duster airplane
under construction by that company for the Department of Agri culture. This 'plane is being
built expressly for use in the extermination of the gypsy moth. boll ,veevil and other pests by
dusting poison insecticide.
A wind tunnel model is to be built and tested by the Division.
Parachute 'Planes.
Two Douglas Torpedo airplanes, Model DT-2, have been transferred to the E ngineering
Division by the Navy Department for use in parachute-dropping tests. One of these 'planes was
wrecked while being flown to McCook Field and extensive repairs were necessary to place it in
flying condition. Each airplane has been provided with a special compartment containing a rack and
rel easing device for dropping the paraclmte-fitted dummies.
Service 'Planes to be Equipped for Night Flying.
The fo llowing service airplanes are to be equipped for night flying in accordance with an
order from Chief of Air Service : 2 J N-6H, 12 MB-3A, 80 DH-4B and 65 NBS-1. All neces­sary
equipment such as landing and running lights, wing tip and parachute fl ares, electric genera­tors.
switch panels, etc., is to be distributed by the Fairfield Air Intermediate Depot to the various
stations making the in stallation s. Instructions relative to the installation of night -flying equip­ment
on these airplanes have been prepared by the E ngineering Division and forwarded to Chief
of Air Service for approval. It will be necessary to provide DH-4B's and KBS-l 's with special
non-glow mani fo lds for this purpose.
•
20 T E C H N I C A L 13 U L L E T I N N o. 39
L-W-F TRANSPORT MODEL XT-3
(Liberty "12" Eng ine .)
L-W-F Transport, Model XT-3.
The L-,V-F Transport, Model XT-3, the only airplane completed by the L. W. F. E ngineer­ing
Company on their defaulted contract for ten articles. is undergoing experimentation at the
Division in an effort to improve per formance in speed and climb. To this encl several propellers
are being tried out. including the Martin Bomber type as well as two experimental designs built by
the Division. It is also contemplated to install a geared Liberty engine, two of which with spring
coupling cle-vices have been requested from the Bureau of Aeronauti cs. A special propeller for
thi s engine is to be built by the Division.
In general , the design incorporates a large two-bay ( a short inner and a long outer), single­engined
biplan<o; of conventional wire-braced const ruction. Its characteristic feature is the pointed
nose of the well streamlined fu selage which exposes the fo re part of the Liberty engine as it widens
rearward to form a spacious cabin accommodating six passengers. The ax les of the wide tread
divided chasses pivot about the lower longerons and then straddle out under the wing as far as
the in ner interplane struts where they are hung on metal V struts attached to the wing spar s. A
wide sha llow unclerslung radiator suspended beneath the nose projects partly in free air.
Both wings are symmetr ical, the upper carrying ailerons in the outer trailing edges and fuel
tanks in the center section. The lower panels are fitted with electric run ning and landing lights
SIDE VIEW OF TRANSPORT XT-3 SHOWING PASSENGER CABIN.
GENERAL ARRANGEMENT OF L-W-F TRANSPORT XT-3 .
GENERAL DESCRIPTION
Airplane ..................... L-W-F "XT-3"
Type ............ .. ............ Tra n s port Biplane
Status
Manufacturer ...
Engine ....... .
...... .. Experimental
..... L. W. F. Engineering Co.
........ Liberty " 12"
Crew.......... . ... 2 p i!ots-6 pass engers
Supporting Area ...... 760 square feet
Gross Weight ........... 73 16 pounds
Useful load.. . ..... 2671.25 pounds
W ing loading .... ... ... -~ / 64 lb./ sq. ft .
Power loading .. ... ...... 18.3 lb. /h. p.
hJ
22 T E C H N I C A L B U L L E T I N N o. 30
carefully streamlined in the leading edges near the tips. The tail surfaces follow the usual wire­braced
construction utilizing a double camber stabilizer actuated by a DH-4 type adjusting mech­anism
and a large balanced rudder shaped like that of the J N-4.
The fuselage, a welded tubular structure cove.red with fabric and aluminum ( around engine),
broadens in two dimensions into a nearly square cross-section 80" by 56" at the cabin. At this
place the lateral bracing is carried below the floor so as to leave this entire section free from ob­structions.
The cabin contains six revolving leather upholstered seats and ample space for per­sonal
baggage. Two doors, electric dome lights, and four windows in which the glass can be
lowered afford plenty of light and ventilation. A passage leads to a large open double cockpit
located behind and above the engine in a position affording excellent visibility. Duplicate wheel
and pedal (rudder) controls are provided for the two pilots who have a plain view of the compact
instruments mounted in the center in front of them. Controls for operating the radiator shutter
and the stabilizer adjustment are conveniently placed within the reach of either pilot.
The power plant ·consists of a standard Liberty "12" engine equipped with Zenith carburetors,
12-volt ignition, and Type A-2 oil pump. Oil is carried in a 12.5 -gallon tank underneath the en­gine
and the fuel in two 62.5-gallon tanks, one in each side of the upper center wing section. A
32-gallon compartment in the main tank is reserved for emergencies.
Due to the fact that the contractor has discontinued business, it is not known at present what
arrangements will be made to complete the nine airplanes remaining on this contract.
Study for New Transport Design.
The Division recently completed a study and preliminary design for a new transport airplane
to be built around the new geared Liberty and Wright T-3 engines. From the study of the design
it was concluclecl that the geared Liberty woukl be preferable for meeting the specified perform­ance.
\Vinci tunnel models are being made for determining aeroclynamical efficiencies.
Propellers with Magnesium Blades.
In experimentation with light alloy propellers, the Engineering Division has designed and con­structed
for tests on the Vought VE-9 airplane a split-hub propeller with detachable magnesium
alloy blades. The magnesium blades weigh about two-thirds as much as a similar pair made of
aluminum alloy and are designed for use in a split-hub, the same as that used for detachable
micarta blades. Destructive whirling tests of 10 hours at 300 h. p. and 10 hours at 400 h. p. have
been completed without failure. However, the blades were broken in a test on the Wright 300-h. p.
engine clue to the fact that they were threaded to a sharp edge at the base to take the hub used for
the' micarta propeller. In the redesign this sharp edge will be eliminated.
An aluminum alloy propeller with detachable blades and split hub has been made for use on
the Liberty engine in an effort to develop a simpler type of split hub that will permit the blades
to be changed more easily than in the present t ype. Destructive whirling tests were run for 10
hours at 1,000-h. p. with satisfactory results.
A destructive whirling test of ten hours at 1,000 horsepower is in progress on a three-blade
aluminum alloy propeller manufactured by the Standard Steel Propeller Company for use on ob­servation
airplanes equipped with supercharged Liberty engines.
Experimental Wing Spars.
Experimentation is in progress on a series of experimental wing spars which are being de­veloped
by the Division and various aircraft manufacturers for use in bombardment airplanes. Two
experimental metal spars, one from the Douglas Company and the other from the Aeromarine
Plane & Motor Corporation, failed under a static load equivalent to 5 per cent of the designed
load, the spar submitted by the latter firm supporting 70 per cent of the required before failure.
In the static test of an experimental combination steel and cluralumin spar designed by the
Division, a load equivalent to 110 per cent of the designed load was carried before signs of
failure occurred in one of the steel diagonals. The test was then carried to a loading of 140
per cent of the designed load when failure occurred in fitting at outer end of spar. The spar weighed
only 61.5 pounds and is the lightest one so far tested that has held the desired load.
AIRCRAFT DEVELOPMENT 23
AIRSHIPS AND BALLOONS
Progress on RS-1, TA and TC Airships.
Construction on the RS-1 a irship, the largest semi-rigid on the Air Service building program.
is being rushed to completion at the plant of the Goodyear T ire & Rubber Company, Akron, Ohio.
An improved nose cone structure of a design proposed by the Division will be built. This design
effects a great saving in weight and at the same time increases rigidity. The power transmi ssion
units for the Liberty engines have been completed and accepted, one unit having been tested at
McCook Field and the other two delivered direct to the contractor for installation in the airship.
Drawings and specifications were prepared by the Division and forwarded to the Procurement
Section at Washington, D. C., for use in connecti on with the recent purchase of additional TA and
TC airships and spare envelopes for those now in service. E ngineering data received from Langley
Field on cooling tests conducted on the Army D-3, T A-2, and TC-3 airships will be used in deter­mining
the proper dimensions for cooling surfaces on different airships. A scheme for the ar­rangement
of fuel systems in airships has been evolved to preclude the use of gravity tanks. T his
arrangement may be incorporated in the TA airships recently ordered on Air Service Order 2014-24.
New One-Man Training Airship, Model TE-1.
Airships Incorporated, Hammondsport, N. Y., have been awarded a contract for one experi­mental
one-man training air ship of Engineering Division design to be known as the "TE-1." T he
new aircraft is designed for 80,000 cubic feet capacity with helium, which capacity insures an
adequate cei ling. Propulsion will be furnished by two Lawrance L-4 radial engines.
An alternate design of an airship of the same capacity and for similar purposes was prepared
by the Aircra ft Development Corporation. Al tho this design was not selected, it incorporated some
new features such as an all-metal car and specially arranged control surfaces.
Barrage Balloon.
As a result of preliminary flight and water model tests on an experimental barrage balloon
designated and constructed by the Division, a new and larger model is to be constructed which
will have increased gas capacity, larger lobes and new arrangement of suspensions. It was found
in the water model tests that better trim and di stribution of stresses in the suspensions could be at­tained
by adding a panel forward of the maximum section thus giving about ten per cent increased
capacity and li ft to the nose in counteraction with increased lift resulting from use of larger lobes.
The second experimental model will have a capacity of 24,000 cubic feet for the envelope.
which represents an increase of 4,000 cubic feet over the original design. The large lobes will
have a capacity of 13,000 cubic feet to accommodate expansion of the li ft ing gas at higher alti ­tudes.
Special Grade AA balloon cloth from government stores is to be rubberized into Style 13
fabric for use in the construction. The Division is negotiating for the purchase of 15,000 feet of
extra flexi ble steel wire cable, 3/ 16-inch in diam eter, for use with this balloon. The Division is
negotiating for the purchase of 15,000 feet of extra flexible steel wire cable, 3/16-inch in diameter,
for use with this balloon.
The "Grab-Winch."
The "Grab-winch," a caterpillar type self-propelled vehicle designed by the Division expressly
for the ground-handling and maneuvering of airships, has been completed and delivered under its
own power by the manufacturer, the Steel Products Engineering Company of Springfield, Ohio.
to the Division's Lighter-than-Air operating sta tion at Wilbur \;\!right Field where numerous tests
are under way.
The winch is designed to operate over fairly level ground such as that usually found at
Lighter-than-Air stations. Steering is accompli shed by means of two pedals, both of which when
depressed forward cause forward motion and when depressed rearward, reverse motion. Turns to
right or left are executed by depressing the respective pedal. Depressing the pedals in opposite
directions at the same time causes the machine to turn upon its own center as one track travels
forward while the other travels backward. Exceptional maneuverability is made possible because the
tracks are independently driven. The mechanism which grabs and holds the drag rope from the
24 T E C H N I C A L B U L L E T I N N o. 39
airship consists of two small track layers running in vertically opposed position in such a manner
that the distance between them is automatically regulated by the thickness of the drag rope. The
pressure or "squeeze" between these tracks which .can be instantly separated to release the rope,
is likewise automatically controlled by the load-the greater the tension, the tighter the grip.
Despite minor failures in the preliminary tests such as clutch sticking and gear breakage, the
experimental winch has so far demonstrated to a very satisfactory degree its efficiency and utility
for the purpose-the elimination of large ground crews now required to handle an airship in
taking flight or in landing.
ARMAMENT
Bomb Racks, Types H-4 and A-3.
An external bomb rack, Type H-4, designed by the Division for carrying either a 4,000 or a
2,000-lb. bomb, together with a Type L-12 release handle has been installed on a Martin Bomber
MB-2 for ground :functioning tests with the 2,000-lb. bomb. An emergency bomb wheel was also
installed for use of the pilot or assistant pilot. The rack weighs only 112 pounds and is fitted with
supports and ratchets for receiving the bomb hoist drums, thus serving as a bomb hoist as well.
In the installation, the longitudinal axis of the bomb rack is inclined 4.5 degrees so that the front
end is below the horizontal line of flight. This position has several advantages in that it decreases
parasite resistance of the bomb during climb or at maximum altitude, allows sufficient ground clear­ance
for the bomb stabilizers, and facilitates loading and installation of the rack.
Delivery of 350 production external bomb racks, Type A-3, under construction by G. Elias &
Bro., Inc., of Buffalo, has started. The Type A-~ bomb rack is similar to the Type A-2 or modified
Ordnance Mark XVIII bomb rack but is made of metal thruout and incorporates a new locking
mechanism which precludes premature release of the bombs.
Bomb Rack Adapter, Type G-2.
A combined single and double adapter, Type G-2, has been built for use in attaching one or
two Type C-2 or C-3 external bomb racks to the internal bomb racks, Type G-4 or G-5. The new
adapter complete weighs only 12.4 pounds, whereas the original design, Type G-1 , weighed 80
pounds. The Type G-2 adapter is designed for a factor of seven when carrying 2,200 pounds of
bombs.
Bomb Truck Chassis Test.
A four-wheel-drive cargo truck chassis, Type TTL, received from the Quartermaster Experi­mental
Depot at Camp Holabird, Maryland, has been subjected to extensive road tests at McCook
Field preparatory to being sent to Detroit, Michigan, to receive a special bomb-carrying body. The
truck will be capable of handling and transporting bombs up to 4,000 pounds over all kinds of
terrain.
Concrete Bombs for Performance Testing.
Reenforced concrete bombs are being constructed for use as load in connection with perform­ance
testing of airplanes. The sizes range as follows: One 4,000, one 3,000, one 2,000, one 1,100,
fi £teen 600, and twenty 300-lb. bombs. Their use for this purpose affords an easy method of at­taching
and carrying required test loads.
Browning Guns for DH-4B.
The Engineering Division has prepared for the Field Service Section, F. A. I. D., the neces­sary
drawings and parts lists covering the installation of one .30 caliber Browning aircraft machine
gun on DH-4B airplanes. Firing tests were conducted on a model installation at McCook Field to
insure satisfactory functioning in the Field.
New Accessories for Lewis Gun.
Modified double yoke and duplex trigger controls for the Lewis aircraft machine gun have
been service tested and approved with minor changes. A Lewis double gun yoke, T ype G, mounted
on a DH-4B airplane, has passed both ground and air tests for strength and movement.
AIRCR A FT DEVELOPMENT 25
A new latch assembly for holding twin Lewis guns in fixed position on the standard nng
mounts, Types A and C, proved sati sfactory in both air and ground tests.
New ring mounts, Types C-2 and D-2, are being developed to supersede the earlier Types
C-1 and D-1 .
Davis Non-recoil Cannon Fired from Martin Bomber.
Firing tests of a Davis non-recoil cannon in stalled in a Martin Bomber have demonstrated
that guns up to 3-inch caliber can be successfully fired from airplanes. T wenty shots were fired
from the air without causing any detrimental effects upon the airplane structure or interfering
with the course of flight. The Davis non-recoil gun is a two-ended cannon in which a counter­charge
offsets the recoil from the projectile.
Vulnerability Test on Curtiss Wing Radiator.
Vul nerability tests conducted by the Division on Curtiss wing radiators such as are used on
the Curtiss racer and the Curtiss pursuit demonstrate conclusively that this type of radiator as at
present constructed will not withstand gun fire of any caliber and is ,therefore unsatisfactory for
use on military airplanes. The results of these tests indicate that a radiator similar to that us~cl on
the Curtiss pursuit, containing approximately 15 gallons of water at a mean pressure of 2 pounds
per square inch, would be completely emptied under extreme conditions by leakage caused by a
single raking shot from a .30 caliber gun in less than six minutes, and by a .SO caliber shot in less
than three minutes. Seventy-five per cent of the water was lost within 33 seconds in case of the
.30 caliber shot and within 1 S seconds in case of the .SO caliber shot. H ence, if a shot should
pass thru this radiator at normal flying altitude ( 10,000 to 20 ,000 feet ), it would be necessary to
land the aircraft as soon as possible.
EQUIPMENT
Navigation Flights.
Early in March, a navigation flight was made from McCook F ield to :.\f ineola, L. L. and re­turn
for the purpose of testing new navigation in struments in flight. In the flight to Mineola , all
landmarks were hidden by clouds for a di stance of 450 miles, the airplane flying at an altitude of
13,000 feet and the course being steered by the distant-reading earth inductor compass. For long
periods the 'plane was actually flying in the clouds and the flight indicator was used to maintain
straight and level flight. Aided by a strong tail wind, the distance from Dayton to Mineola was
covered in 3 hours and 45 minutes. T hi s fast time is incidental proof that in spite of the absence
of checks a straight and true course was flown. O n the return flight which was made a few clays
later, a SO-mile cross-wind from the northeast necessitated a 30-clegree crabbing into the wind at
the start. As the 'plane traveled westward , the wind shifted to northwest making progress more
diff icult. On clescencling, the 'plane was only ten miles north of the course. Because of the ad­verse
wind conditions, the return trip which took 6 hours and 8 minutes, three hours of which were
flown over a solid bank of clouds, proved to be an even better test of navigation equipment than the
eastbound trip.
Another successful navigation flight of 2,500 miles was completed in the early part of April,
in which two E ngineering Division aviators made a six -clay cruise from McCook F ield to San An­tonio.
Texas, and return with landings at Bellev ille, . Illinois, Kansas City, Missouri, and Mus­kogee.
Oklahoma, for the purpose of testing air navigation methods and equipment, especially the
di stant-reading, earth inductor type compass. On this cruise, two long flights were made . one
from Kansas City to San Antonio_:.._710 miles in 6 hours and 50 minutes-and the other from Mus­kogee
to Dayton-685 miles in 6 hours and 15 minutes.
In order to demonstrate that a flight could be made solely by following a compass course, that
is, by using a distance-reading earth inductor compass, and not by the aid of landma rks, a specially
equipped DH-4B airplane was flown from Dayton, Ohio, to Albany, N. Y., by an Engineering
Di vision pilot and an observer without maps and a cross country OYer which neither had fl.own before.
This flight of 600 miles was made "non-stop" in 6 hours and 10 minutes in spite of a strong cross­wind.
26 T E C H N I C A L B U L L E T I N N o. 39
On April 21 , a flight was made in a standard Airways DH-4B airplane from Dayton to Cleve­land
in one hour and ten minutes, or at an average speed of 150 m. p. h. Advantage was taken
of a favorable tail wind which was blowing at a velocity of 60 m. p. h. at 4,500 feet altitude. The
return required twice as long owing to a 30-mile head wind. An earth inductor compass manufac­tured
by the Aeronautical Instrument Company was used on this test.
36-inch Searchlight as Aerial Beacon and Floodlight.
The standard Army 36-inch high intensity arc searchlight developed by the Engineers Corps
during the late war has been modified by the E ng ineering Division to serve both as an aerial beacon
and as a floodlight in the night illumination of airdromes. These changes involve the addition of a
spread or diverging lens door, a rotating mechani sm. and the substitution of a semi-automatic lamp
mechanism, for the automatic type to simplify operation thereby obviating the services of an ex­pert.
In fact. the searchlight can now be easily operated and the arc adjusted by an ordinary me­chanic
af ter brief in struction.
For fl oodlighting, a "spread-lens" door was applied over the plain door of the searchlight to
diverge the straight beam of light into a flat fan - shaped one which when proj ected upon the ground
uni fo rmly illuminates an area large enough to enable safe night landing of all present types of
service airplanes. By rotating the door in the ro ll ers ,vhich are bolted to the rim of the searchlight
barrel, the flat beam can be laid on the ground so that its long edge is parallel to the direction of
the wind. in this way facilitating night landing into the wind. The spread beam has a divergence
of 40 degrees.
\Vhen the searchlight is used as an aerial beacon, the "spread-lens" door is removed and the
straight beam set so that its axis is slightly above the hori zontal. The searchlight is then rotated
in azimuth at about 5 revolutions per minute by means of a small electric motor controlled by a
switch on the base. The rotation can be stopped at any time simply by disengaging the gears, and
the searchlight again converted into a landing light by replacing the "spread-lens" door.
36-INCH SEARCHLIGHT EQUIPPED
WITH SPREAD-LENS DOOR.
(Rotating Mechanism Not Shown.)
AIRCRAFT DEVELOPMENT 27
The lamp mechanism was changed from the Sperry automatic to the General E lectric H -36
form BCL sem~-automatic type illu strated herewith. In the new mechanism, the carbons are fed
to the arc at a rate proportional to their burning rate by means of an electric motor and associ­ated
gearing incorporated in the base of the lamp. The positive carbon ( 1) which is 18 inches
long and 16 mm. in diameter, is rotated continu ally while it is being fed forward whereas the
negative carbon (2), a smaller piece 9 inches long and 11 mm. in diameter, is prevented from
turning during feeding. Silver connecting strips ( 3 and 4) carry the electric current to the ca r­bons,
the feed rollers and gears being carefully in sulated to prevent current reaching the carbon~
thru the gearing in case of fa ilure of the contacts. Both contacts, ( 5 and 6) are made of pure
nickel. These contacts are not rigidly fixed but simply fl oat on the carbons so as to compensate
for small surface irregularities.
\_,
4
14------
10----------
MODIFIED LAMP MECHANISM FOR 36-INCH SEARCHLIGHT.
The ,Uc-feeding mechanism is actuated thru a system of shafting and gearing by an electric
motor in the base of the lamp. The positive carbon is gripped firrnly between two notched and
grooved hardened steel ro ll ers which are pinned to short shafts terminating in spur gears in mesh
with the feed sha ft ( 7) . A worm gear which is pinned to the encl of the drive shaft, is driven by
a worm shaft parallel with the axis of the carbon. A spur gear on the worm shaft rotates with the
feed ing gears and rollers and is advanced during each revolution by being in mesh with a sta­ti
onary gear on the center tube, thus feeding the carbon forward. The negati ve carbon is advanced
toward the arc between two hard toothed rollers carrying at their extremities two worm gears ( 8)
meshing with right and left hand worms (9) driven by the negative feed shaft ( 10. )
The electric motor is the base of the lamp mechani sm has its field and armature connected
across the arc. The negative feed is provided with a hand control ( 11 ) which permits the carbon
to be fed by hand thru a slipping clutch independently of the motor. By this combination of motor
feed and hand contro l, the keeping of the carbons in a constant position relative to their heads, that
is, keeping the arc in proper adjustment, is made possible.
28 T E C H N I C A L B U L L E T I N N o. 39
In starting the lamp, the arc is struck by rota:ting a t,mall handwheel connected to 'the arc
striking lever ( 12) which raises the negative head into posi tion. As soon as the arc is struck,
the position of the carbons may be watched by their images on the ground glass window in the
side of the searchlight d1\1m and maintained by means of the negative hand feed. T he Sperry
thermostat and the arc-length rheostat are not used in the new lamp mechani sm. W hen the arc is
properly adjusted, it draws from 140 to 150 amperes of current. This adjustment is easily main-
STRAIGHT BEAM AS AERIAL BEACON.
tained after a few minutes practice so that an oc­casional
quarter-turn of the negative hand feed is
all that is necessary to keep the arc burning per­fectly.
Experience has demonstrated that it is un­necessary
to stop the beacon during rotation in
order to adjust the arc which has been prop­erly
set before starting as the rate of rotation is
so low that the position of the carbons can be noted
on the ground glass by the operator at each revo­lution
and the negative carbon feel by the hand
wheel with the light in motion. When necessary,
new carbons can be easily inserted by simply pull­ing
the release levers ( 13 and 14) which allow the
gripping rollers to spread.
In permanent installations, the searchlight is
mounted up on the roof of a hangar or on any
building bordering the airdrome that is high
enough for the beam to clear all obstructions when
the searchlight is rotated as an aerial beacon. In
landing with the floodlight, a pilot will find it
easier to land his 'plane just alongside the lighted
area rather than directly in it for the reason
that there will be no disturbing reflections from
parts of the airplane. For temporary in stallations,
the searchlight may be set upon a slight elevation
or if a portable outfit is desired, it may be placed
in the body of a specially equipped automobile
truck.
The estimated apparent beam candle-power
intensity of this light with the arc in proper focus
and the plain glass door is conservatively placed at
300 milli on. Various estimates of the beam in-tensity
of this light have been made as high as 600 million apparent beam candle-power but these
estimates have not been considered very exact.
The beacon is distinctly visible at night for a range of approximately 40 to 1 SO miles depending
upon atmospheric conditions.
Improved Electric Starters with Hand Crank and Overload Release.
T he hand crank for the Bijur rear-end engine starter has been reworked with a ratchet clog
at the end to enable quick detachment when the motor speeds up. Twelve combination hand-elec­tric
starters have been received for service test of the hand-crank adapter. Improved starters were
installed on the "Round-the-World" cruisers.
Preliminary tests of a \ Vestinghouse starter fitted with a friction disk clutch overload release
shows that this type of clutch will function properly. Tests are to be made to determine the num­ber
of bach.rfire releases necessary to cause a change in the friction clutch calibration. The friction
clutch overl0ad release was designed at the Division.
A IR C R A FT D E V E LOPME N T 29
Night Flying Equipment.
Two incandescent searchlights, a General E lectric 18-inch rotating beacon and a Pyle-Na­tional
rotating beacon. are undergoing life tests at McCook Field. The latter has already completed
approximately 300 hour's of continuous operation without serious trouble. Minor changes such as
relocation of the switches, heavi er connecting leads, and different brush material will be , recom­mended
for production. The General Electric beacon has been run approximately 100 hours at 12
revolutions per minute with entire sati sfa ction , as a check upon a similar lamp which has been giv-ing
considerable trouble. •
Photometric tests have been completed on an 18-inch Bausch & Lomb glass mirror in connec­tion
with a series of incandescent projector lamps-the 30-volt 30-ampere, the 12-volt 100-arnpere,
the 1500-watt 32-volt, and the 1000-watt 110-volt lamps. This same series of lamps was al so
tested in a 23-inch Pyle-National reflector and in a Sperry 24-inch searchlight drum with a 24-inch
Bausch & Lomb refl ector. The results indicate that the 1500-watt 32-volt lamp with either the
23-inch Pyle-National refl ector or the 24-inch glass mirror will almost meet the · requirements fo r
a 15-mile beacon range under bad weather conditions. Various combinations will be set up for
Aight observati ons. If these do not approximate the 15-mile requirement, the lamp manufacturer
wi ll then deYelop a 30-volt lamp using from 2-1/ 2 to 3 kilowatts, which should prove sati sfactory.
Sample lenses and lamps for use in airplane landing lights have been received from the Bausch
& Lomb and \ i\Testinghouse lamp companies for photometric tests.
A 24-inch rotating incandescent searchlight has been received from the General E lectric Com­pany.
This searchlight embodies many improvements resulting from service tests conducted at this
Division. This company has submitted two new incandescent lamps of 2.700 wa tts each and an
imprO\·ed base for test.
For the Air Mail service, the Division has completed drawings of a new airplane landing
light. Type A-2. six of which will be built for the use of the E ngineering Di vision.
Two steel navigati on light towers, a new Air Mail type and an Air Service standard type, have
been erected at McCook Field for cm~arative t ests of rotating incandescent searchlight beacons.
Pyralin Shell Running Lights for Aircraft.
The new type of clear vision , demounta ble, py ralin shell aircraft running lights developed by
the Division has given sati sfactory results both in the laboratory and in the field. The red (port
side) and green (starboard side) lights when equipped with standard 21 c. p. 12-16 volt lamps
have an effective range of visibility from 3 to 5 miles in clear weather, whereas the clear pyralin
shell (tail) light has an effective range from 6 to 7 mil es.
The side lights are located at the extreme tips of the lower wing, the red light on the left tip
and the green on the right, and may be used as a irplane-to-ground signal lights when fla shed in
code. The clear tail light is placed on the rearmost portion of the fu selage or on the top of the
rudder or fin as the case may require, to in sure maximum angular visibility. \ i\fhen the side lights
are used in conjunction with T ype A-2 wing-tip airplane landing lights, they are mounted on the
extreme outer edge of the body of each landing light.
Port Side (Red) Tail (Combination) Starboard (Green)
PYRALIN AIRPLANE RUNNING LIGHTS.
30 T ECHNICA L B U LLET! No. 39
Night Airways.
Regular Night Airways are flown between Dayton, Ohio, and Columbus, Ohio, for the purpose
of obtaining observation data on a irdrome and airplane lighting equipment. T he Division has pre­pared
a questionnaire relative to all kinds of night fl ying equipment for use of the pilots in sub­mitting
their comments.
In conjunction with these night flights, obser vations and tests are being made on experimental
lighting equipment for use on airplanes and airdromes in connection with the night flying program
during the International Air Races at Dayton, 0 hio, in October. The lighting in stallations at
McCook Field and also those at London and Columbus (Ohio) are reported as being sati sfactory.
New Ins truments- Drift Sight Used on World Cruise.
The E ngineering Divi sion has started the development of an aircra ft sextant, an improved
chronomet ric tachometer, a strip-map ca se for holding route map in navigation flight s, and a new
drift meter, E ngineering Division Model 3A.
Four dri ft sights, designed and built by the Division, were in stalled on the Douglas ·world
Crui sers for use in conjunction with smoke bombs in mea suring drift over water. In operation, the
smoke from the bomb which has been dropped astern is sighted through a telescope for a couple of
miles over the tail. As this telescope or sighting tube is moved to follow the apparent movements
of the smoke bomb, a pencil, connected by link age with the telescope, traces the ,changes in
azimuth on a hori zontal piece of opaque celluloid . If the 'plane is fl ying straight and level, this trace
will be a straight line. In practice, however, th is trace is an irregular curve thru which a straight
line can be drawn to average the irregularities. In the dri ft sight, a movable wire serves this pur­pose.
No report has yet been received from the World F lyers on the utility of this device.
Altimeter for Record Flights (F. A. I.)
A special altimeter has been developed and calibrated fo r use on high altitude flights. It indi­cates
altitude according to the pressure-altitude relation used by the F ederation Aeronautique In­ternationale
in stead of that used in the calibration
of service a ltimeters. \tVhat the pilot desires to
know in making a flight for record purposes is the
altitude for which he will be given credit and not
his true height above the ground nor what his
height would be if the mean temperature of the
air beneath the aircraft were at plus 10 degrees
Centigrade.
T he F . A. I. altimeter differs from the or­dinary
service in strument not only in the pres­sure-
altitude relation used for calibration but in
the general appearance of the dial. Instead of the
low altitude graduations being marked off on the
outer circle in the usual manner, they are incon­spicuously
marked off on the inner circle, whereas
the higher altitudes graduations a re marked off
on the outer circle and plainly numbered. Great
ca re has been taken in adjusting the mechani sm so
that it will indicate correctly between 35,000 feet
and 40,000 feet, because this part of the scale is
of most interest to the pilot. T here is no dial
shi fting knob on th is instrument because it indi­cates
the altitude above sea level in stead of the
altitude above the landing field.
F . A. I. ALTIMETER.
T he advantage of using this in strument in altitude flights ( as stated by Lt. Macready) is that
it gives the F. A,. I. altitude, and thus saves the p ilot the disappointment of having the height as in­dicated
by the ordinary altimeter lowered af ter calibration.
A IR C R A FT DEV E L OP M EN T 31
Altimeter, Temperature Compensated.
A 30,000-foot altimeter has been modified by the addition of a temperature element so that
it indicates the true altitude above sea level within 2 per cent, regardless of the season. T he tem­perature
element is so constructed that it changes the magnification ratio of the linkage which
transmits the motion of the pressure element to the pointer. This automatically corrects for tem­perature
of free air and thus eliminates the large er rors which are so troublesome in the present
type of service altimeter. T he indication of this modified a ltimeter is not affected by changes in
temperature at approximately sea level pressure.
Air Logs.
Air logs complete with anemometer commuta tors, condenser s, and resistance units received
from the Stover-Lang Company of Boston, Mass., are now undergoing acceptance test. T he air
log is a combination of three in struments built into a single compact case. One unit indicates the
true airspeed regardless of the density of the atmosphere through which the airplane is flying,
another indicates the total air-miles flown as well as the air-miles flown on each t rip, and the
third indicates the total number of hours in the air and also the number of hours required for
each flight. An air log is a valuable in strument for air navigation, particularly in cross-country
fl ights. The true airspeed is indicated so that it may be used in calculating navigation in forma­tion
w~thout fir st correcting the reading for air d ensity, as is necessary with the dynamic pressure
types of airspeed indicators. T he pilot is given a continuous indication of the time elapsed so that
he may estimate and check the time at which he should reach a given point.
Barographs for Altitude Balloon Flights.
Two Friez dual-traverse barographs have been adapted to record altitudes corresponding to
an absolute pressure of 100 mm. of mercury ( 2. 93 inches) for use on high altitude balloon flights.
This pressure corresponds to an F. A. I. altitude of 46,600 feet. To accompli sh this, the mag­nification
of the motion of the sylphons was decreased and the in struments equipped with smoked
paper and styluses to produce a fin e, distinct rec ord at extremely cold temperatures. T he styluses
were made interchangeable with pens. The cloc ks have been wound and the cases sealed ready
for use.
French Tachometer "Precision Moderne."
Tests have been completed on a F rench di st ant-reading, centrifugal tachometer , the " P re­cision
Moclerne." This in strument is a combination oil and air pressure unit, oil bei11g fo rced by
a turbine into an air -fill ed chamber which is connected to two manometers graduated in r. p. m.
The range of the in strument is between 500 and 2,000 r. p. 111. T he dials have non-uni form scales.
Indication was found accurate during ordinary cali bration tests but in bell-jar tests serious altitude
change errors were disclosed. On account of its size, weight, leakage of oil , possibi lity of air leak­age
in the lines, and the amount of power consumed . this in strume1it did not prove as sati sfactory
as our present chronometric type.
Stover-Lang Shaft-Drive Tachometer.
A ve rtical, straight-scale, shaft-driven tachometer, manufactured by the Stover-Lang Com­pany
of Boston, Mass., has been received and tes ted by this Divi sion. The chronometric mechan­ism
in this tachometer is similar to that employed in the S tover -Lang electro-chronometric tacho­meter.
except that the electro-magnet and armature of the old model have been replaced by a
cam-operated ratchet, which produces the requir ed reciprocating motion. The cam is dri ven di­rectly
by the shaf t. By means of the ratchet this tachometer can be dri ven in either direction with­out
the use of the customary reversing gears. The case has the same t hickness as the electro­ch
ronometric in strument, that is, 1-3/ 4 inches. It is believed that t his thickness can be decreased
to 1-3/ 8 inches by slightly changing the mechanism, a matter which is being di scussed with the
manufacturer. The accuracy of the sha ft-driven tachometer compa res favo rably with that of the
eletcro-chronometric in strument.
32 T E C H N I C A L B U L L E T I N N o. 39
New 5-Lens Camera, Type T-3.
A new multi-lens mapping camera known asType T-3 is under development at the Division.
The new camera (service model) contains five lenses and differs considerably in construction from
the T-1 and T-2 cameras ( the latter a four-lens type built for experimental purposes) in that it
has a lesser number of parts, a new film punching device and cam-operated pressure plates in place
of the present spring-operated plates. A transforming printer is a lso being developed for this
camera.
Lens Tests.
Two hundred twenty Bausch & Lomb Tessar lenses, 6- 1/ 2 x 8-1 / 2, have been tested on the
special lens testing camera developed by the Division. This same method was used in testing
several lenses of the Tessar type, domestic and foreign, as well as other types such as the Radar
lens and the Cooke "Telephoto" and "Primoplane" special lenses. Tests by this method resulted
in the substitμtion of a special 36-inch B. & L. Protar lens for the Turner-Reich as standard
equipment in general utility cameras.
Several lenses, including Dogmars, Tessars, 20-inch B. & L. and Zeiss Tessars, and a special
36-inch Hawkeye Aerial, have been fitted in a special testing camera and tested in the air. Protar
and Tessar lenses used in the T-1 camera have been measured for focal lengths and the positions of
the nodal points determined on the optical bench. Speed and efficiency of eight types of between­lens
shutters and three types of focal-plane shutters have been determined.
German lenses and optical flats with filters between them have been tested for precision and
planeness of surface. It was found that the filters were made with an accuracy equal to that of the
lens surfaces. One filter in particular was plane to the extent of one-fourth the wave-length of
sodium light, that is. 0.0059 millimeters. The surfaces of the Bausch & Lomb lenses are being tested
preparatory to examination of a number of optical flats supplied by the Eastman Kodak Company.
Frosting Focal-plane Plates for T-1 Camera.
A sand-blasting machine for frosting focal-plane plates for use in Air Service Type T-1
mapping cameras has been developed. T his frosting is necessary for rendering the border of the
plate so that a definite size (50" x6") will appear in the center with index marks on the margin.
Also lettering and numbering of camera and chamber are accomplished on these plates by protecting .
during sand-blasting a portion of the border. Du ring photographing these clear 'portions allow
light to pass and reproduce the marks and figures on the margins of the negatives.
The ordinary sand-blasting apparatus used for cleaning metal parts has never given satisfac­tory
results on these plates. \Vith the new equipment, the Engineering Division will be able to
furni sh new focal-plane plates for replacement to all photographic sections using these cameras.
Mosaic Control Point Indicator.
A simple device has been developed for positioning control points in making mosaic maps. It
consists of a pointer arm mounted on a heavy base and provided with fine adj usting screws and
means of lowering the point for location and then raising it to allow the print to be placed in proper
pos1t10n. In assembling mosaics, the known points of control are laid off on the baseboard and
the photographs then pasted down, the point on the photograph corresponding to the control point
being placed exactly over the marked point. Si nee the prints are opaque, an indicating device is
necessary to locate the position of the points marked on the board.
Hot Oil and Water Service Truck.
A very useful unit has been developed by the Division for supplying hot oil and water to air­craft
engines in order to facilitate starting in cold weather and to shorten the time required to
"warm-up" engine before taking off. The "Hot Oil and \Vater T ruck" as this equipment is desig­nated
was used quite extensively at Langley F ield during the past winter and is now undergoing
service test.
AIRCRAFT DEVELOPMENT 33
The unit consists of a large water tank containing a smaller oil tank, together with the neces­sary
pumps, gasoline burners, hose and other appurtenances, the whole enclosed by a heat-retaining
casing and mounted up a two-ton White automobile truck chassis equipped with pneumatic t ires.
The water tank or compartment is elliptical in shape, being 32 in. high by 43-1/ 2 in. wide by 85 in.
long. Suspended in a horizontal position within this tank so its contents are heated by the water
is the oil compartment. a cylindrical tank, 20 in. in diameter by 85 in. long, holding 100 gallons.
Each tank is also tested to withstand a hydrostatic pressure of at least 25 pounds.
HOT OIL AND WATER SERVICE TRUCK.
Lower View s Show Hose Reel and Cover.
NOT E : A view of this t r u ck with pneumatic tires was publish ed in Technical Bulletin No. 38.
.,,
34 T E C H N I C A L B U L L E T I N J o. 39
The water, and indirectly the oil, is heated by eight Ringen gasoline burners. arranged four on
a side, which are supplied with gasoline fuel from a 30-gallon cylindrical tank mounted at the
rear of the driver's seat. E ach burner plays upon a cast-brass water heater. placed so as to cause
a direct circulation of water thru the tank. The water may be heated to the boiling point and the
oil to a temperature of 185° F. The burners give the best results when operated with an air pres­sure
from 2 to 5 pounds on the fuel tank. and are generated in much the same manner as the com­mon
blow-torch.
Two hand-operated bronze pumps of the rotary type, mounted in a niche in the water com­partment
between the outer casing and the tank proper, discharge the heated oil and water at
the rate of 1 gallon every seven revolutions thru 1-1 / 4-inch hose at rear of truck. Each pump is
of simple and practical design, there being only tw,o moving parts, a large angular, geared rotor
and a sma ll interior idler. There are no valves, sp rings or other fi ttings to get out of order. T he
pumps are connected to 25-foot lengths of hose, one for water and the other for oil , carried upon
reels of sufficient diameter to prevent kinking, each reel being fitted with a hinged heat-retention
cover to keep the hose warm when it is not in use.
Both tanks are provided with two-inch filler s, each of which is fitted with concentric, re­movable
fills having automatic ball vents to accommodate the intake and exhaust of air. F ine wire
gauze strainers are inserted in each filler. A Triumph magnetic gage and a distant-reading dial
thermometer, connected to each tank, give the level and temperature of the oil and water.
A heat-retention cover of 16-gage galvanized steel completely surrounds the tank leaving an
air space of 1-1 / 4 between the upper half and the tank. T he lower half of the cover, which is
hinged to give access to the burners, flares inward to an angle of 170° at the bottom where it is
fastened to the truck floor by hold-down lugs. Both the floor and shell are lined with heavy sheet
asbestos to retain the heat. The top of the cover or casing is provided with vent holes that
terminate in ventilators to permit escape of fumes and create a complete circulation of air within
the jacket. Port holes with sliding covers are placed opposite each burner for convenience in ad­justing
the flame. \~Then the unit is in operation, these holes are opened on the windward side.
RINGEN BURNERS ON HOT OIL AND WATER SERVICE TRUCK.
AIRCRAFT DEVELOPMENT 35
All working parts are readily accessible for inspection or renewals.
Reports from Langley Field where this unit has been undergoing service test state that it has
successfully met the requirements for which it was designed and recommend that one oil and water
heating truck be included as part of the equipment of each squadron that is compelled to operate in
weather of freezing temperature.
POWER PLANTS
New Curtiss Engine, Model V-1400.
The Curtiss Aeroplane & Motor Company has been awarded a contract for the design, con­struction,
and test of four experimental aircraft engines to be designated Model "V-1400." The new
engine will be of the water-cooled 12-cylinder, 60 degree V type, with a bore and stroke of 4-7 /8
inches and 6y,i inches respectively. The displacement will be approximately 1400 cubic inches and
the normal horsepower 500 at 2100 r. p. m., the normal speed. The weight of the complete en­gine
not including exhaust manifolds, fuel pump, generator, starter, booster magneto or switch
is not to exceed 700 pounds.
Fuel and oil consumption when engine is operating at rated output under standard conditions of
temperature and pressure is not to exceed .53-pound and .025-pouncl per brake horsepower hour,
respectively. Provision is to be made for the installation of an electric generator, two Nelson syn­chronizers,
an Engineering Division Type C-5 fuel pump, a tachometer, a Bijur electric starter, and
a Curtiss triplex fuel pump. The design of the induction system will be suitable for operation
with superchargers.
Development of Curtiss D-12 Engine.
A standard SO-hour endurance test of a high compression Curtiss D-12 engine at full throttle
speed (2200 r. p. m.) has been completed. Altho several failures of the ver tical drive shafts and
water jacket leaks occurred, the engine appeared to be in a very good condition at the encl of the
test. A report is being written.
An attempt was made to conduct a standard 50-hour test on a low compression engine of this
same type at full throttle speed of 2400 r. p. m. as stated in T echnical Bulletin No. 38, page 36.
This test was terminated by failure of the connecting rod . After repairs were made. another test
was conducted to determine propeller load and fuel consumption at 2200 r. p. m. for the purpose of
obtaining data for estimating the flight endurance with a given fuel capacity.
Special parts have been built and installed in a standard Curtiss D-12 engine to permit its
cperation in an inverted position. Standard tests will be made.
Inverted Liberty Engine.
Four standard Liberty engines have been rebuilt for inverted operation, special parts being
required to accommodate the mounting of the rearranged accessories. Each engine has been given
an acceptance test including the usual power runs. The fourth engine will be subjected to a SO-hour
test on the torque stand.
Several studies have been made in regard to the best possible combination for re-arrangement
of the accessories on the inverted engine. Four engines were built with special oil pumps mounted
in place of the distributor heads, and the distributors and generators mounted on a special adapter
in place of the oil pump. This arrangement was unsatisfactory because the generator and distributor
adapter extended too far upward and cut clown the visibility which is possible with this type of
in stallation. The water pump was removed from the back of the engine and placed in the "V"
where the generator had been.
An additional design was then laid out with the generator and distributors mounted on the
rear of the engine in place of the water pump drive. This installation, however, proved to be un­satisfactory
for the Loening amphibians due to the increased length caused by this arrangement.
36 T E C H N I C A L B U L L E T I N N o. 39
The final design leaves the engine in practically the same arrangement as in the normal engine, with
the exceptions that the distributor heads are moved backwards about 2" to permit installing a
scavenging oil pump housing, which also prevents the oil in the camshafts going into the di s­tributors,
and the use of redesigned carburetor mani fo lds. The engine with these modifications is
expected to weigh not much more than the standard Liberty, whereas with the other modifica­tion
previously t ried , the weight aggregated 960 pounds.
The particular advantage of the inverted in stallation lies in increased visibility, and as a con­sequence
inverted Liberty engines are being used in the new Loening amphibian and Engineering
Divi sion XC0-6 airplanes.
Liberty Engine Parts Test.
A Liberty engine with compression ratio of 6.5 to 1 is undergoing a SO-hour endurance test
for the purpose of determining the durability of several experimental parts and accessori es. This
engine has been equipped with Allison connecting rod bea rings. Genelite and Durex gun synchro­ni
zer bearings, special modified rocker arm bearings, latest stub-tooth gears, Meisel Press gun
synchronizer gears, navy reenforced cylinder s, silchrome tulip valves, aluminum bronze valve
guides, Rockwell Field water pump modification s, Type A-1 oil pumps, jump-gap di stributor
heads. Alernite lubrication for tachometer drives and rigid fuel connection s.
New Method for Reenforcing Liberty Cylinders.
At present. the procedure be:ng employed by the Engineering Division for welding or reen­forcing
the Li berty cylinder head appea .. s to be more satisfactory than the method used by the
Navy Department. In the latter method, the jig which is used to set up the initial distortion in
the head by drawing the valve ports apart has proved un satisfactory for the reason that it is neces­sary
to clamp the cylinder in the jig by means of the valve port flanges thereby resulting in either
bending or cracking these flanges or the valve port itself under stress. In structions based on the
present procedure used by the Division are being prepared and tl~e new method will be tried by
welders unfamiliar with present methods.
New Packard Engines, Models lA-1500 and lA-2500.
The fir st Packard engine, Model l A-1500, has been completed at the plant of the Packard
Motor Company. Detroit, 1ich. This eng ine developed 518 h. p. at 2080 r . p. m. on acceptance
test and will be shipped to the Douglas Company for installation in the new X0-2 observation air­p!
aioe under construction by that company. The g uaranteed output of this engine is 510 h. p. at
2100 r. p. 111.
Recent reports tram the Packard Company state that the la,·ger Packard Model l A-2500
engine wh; ch weighs 1095 pounds developed 834 h. p. at 2020 r. p. m. during the preliminary cali ­bration
runs. Fuel consumption amounted to .5-pound per horsepower hour. The third engine on
this contract is to be equipped with a reduction gear.
Dynamometer Tests on Wright T-3 Engine.
The first \ I\T right T-3 engine delivered under the \;\!right Ae:·onautical Corporation's contract
for three engines was subjected to dynarnorneter tests with both high and low compression pistons.
In these tests, considerable trouble with preignition occurred al tho different fuel mixtures with 25.
50, and 75 per cent of benzol were used. Even California gasoline failed to overcome the diffi­culty.
Performance curves for the engine with low compression pi stons a re being prepared.
All engines on this contract have been delivered.
New Standard Engine Control Unit.
Ne\v engine control uni ts . designated as T ypes B-2. B-3 and B-4 signif ying two, three and
four levers respectively, have been developed hy the Di,·ision and recently adopted by the Air
Service as standard equipment on all new airplan es. In the new design, interchangeability has
been worked out to a high degree and the cost of manufacture materially reduced thru the ex­tensive
use of stampings and simple screw-machine parts.
AIRCRAFT DEVELOPMENT 37
The new unit combines safe operation and simplicity of ad justment with light weight and ease
of production and maintenance. It is constructed with steel control levers. aluminum frame, spacers
and face plate, and brass friction plates in such a manner that the parts with few exceptions can be
easily assembl ed into two, three or four-lever units. By using steel for the levers in stead of dura­lurnin.
the tend ency to bend is greatly minimized. and besides the harder metal furnishes a better
wearing surface in contact with the brass friction plates. Another advantageous feature not found
in earlier types is the method for regulating the friction to hold the lever in place. This is nicely
accompli shed by means of a simple hex -pointed spring and adju ting nut which are readily accessible
by simply removing the face plate:
All le\'ers are ball ended and plainly marked with luminous paint, the spark and throttle con­trols
being placed above in all units and the mixture control below in the three and fo ur-lever
units. The fourth Jew ;· which is added primarily for controlling the blast gate on supercharged
airplanes is also used for operating the water bi-pass valve on airplanes using Curtiss wing radia­tors,
Type B-4 unit being used on the new production Curti ss P\i\T-8 pursuit airplanes for this
purpose. The Type B-3 unit may be used on the new Engineering Division XC0-6 observation
airplane.
NEW ENGINE CONTROL UNIT, TYPE B-4.
(Four Levers.)
RESEARCH AND EXPERIMENT
I
RESUME OF ENGINEERING DIVISION
SERIAL REPORTS.
Serial Reports marked with an aste1isk (*) will
be issued by the Chief of Air Servzce as "Afr
Service In.f ormati()n Circulars."
AIRPLANE SECTION.
Dusting Experiments in Louisiana in 1923.
(Development of the Unit Airplane Duster)
Serial No. 2271
The airplane dusting experiments conducted at Tallulah, Louisiana, during the summer of 1923
were made principally for the purpose of developing suitable dusting apparatus for the DH-4B air­plane.
The results of the previous year's experiments with Curtiss JN-4H airplanes were used
as a basis.
The problem which presented itself was to build an apparatus for the DH-4B airplane. which
would thoroly atomize the calcium arsenate powder, a poisonous insecticide, so that it would float in
the air and not drop to the earth in small pellets. From the experience gained in these experi­ments,
an effective dusting apparatus known as the "Unit Airplane Duster" was finally developed.
This unit consists of a hopper, 24" by 21-1/ 2" by 44" deep, the bottom of which slopes down­ward
and rearward, and an air duct which takes air from a scoop on top of the hopper and forces
it down and out thru a slot in the bottom of the fuselage. The air duct acts as a Venturi with its
throat at the bottom of the fuselage, into which the powder is dropped. Three sword-shaped
blades sweeping back and forth across the sloping sides of the hopper about eighty times a minute
keep the powder in constant agitation, thereby insuring a steady flow thru the slot. These blades
are actuated by a reduction gear of 50 to 1 ratio, driven by a 10-h. p. 12-volt camera motor which
in turn receives its current from a 300-watt wind-driven heating generator. The hopper was in­stalled
in the rear cockpit of the airplane.
Drawings and photographs of the device are appended.
Methods for the Selection of Airfoils. Serial No. 2282
In considering a new design, the data in this report offer a very simple and rapid means of
selecting the most suitable wing section for any desired purpose. The method employed attacks the
problem from an aerodynamical standpoint only; hence considerations for spar depth and struc­tural
fitness of the section under design should he made independently.
The method consists essentially in the plotting of curves showing the power required to fly
the wings at different speeds, from which curves the most economical section for the desired
condition of flight may be easily selected. Comparisons are made in two ways : first, on the as­sumption
of constant weight and wing loading and second, on the assumption of constant weight
and landing speed. The latter takes into account the relative merits of the airfoils with respect to
their lifting characteristics, which forms the bas is for use in cases where maximum landing speed
is specified.
RESEARCH AND EXPERIMENT 39
Revisions to "Handbook for Airplane Designers."
Tentative revisions have been made by the Division for incorporation in a new edition of the
Handbook for Airplane Design ers. a publication issued to aircraft designers, engineers. and manu­facturers
for use in connection with Air Service contracts and design procedure.
Serial No. 2332-Section II , P art I-Required Loads for Airplanes.
Serial No. 2299- Section II , Part II-Stress Analyses and \i\Teight Data.
\Vork on the new edition is in progress and should be ready for publication in the near future.
Radiator Drag on the Fokker C0-4 Airplane. Serial No. 2311
This is a brief report on the flight tests of the Fokker C0-4 airplane with side radiators in ful1
extended and one-fourth extended positions. The drag for these positions was found to be 973 ancl
931 pounds, respectively, which made a difference in speed of 6.5 m. p. h.
Structural Design of Army Racer R-3 Monoplane iWing. Serial No. 2314
In this report are recorded the data on the structural anal ysis and design of the Army Racer,
l\fodel R-3, monoplane wing (Verville-Sperry. ) The computations of stresses and the design of
the members were effected by the methods found in S tructural Analysis and Design of Airpla11es
and were based upon the load factors required by Air Service Specifications for Type II airplanes.
Inflection on Beams under Various Loads. *Serial No. 2324
T he purpose of this investigation, the results of which are given in both tabular and graphical
forms, was to determine whether or not the loca tion of the points of inflection on a beam changed
materially under different ratios of bending load to axial load and differing degrees of restraint at
the points of support. The problems was studied by computing the location of the sections of zero
moment on a beam under four different lateral loads in combination with fourteen different axial
loads, the same spar and length of span being used to make the results comparable. The results
showed that the position of the points of inflection varies appreciably with diffe rent magnitudes
of encl load and that multiplication of loading on a beam under combined axial and lateral loads by
a given amount would increase the bending moments, and consequently the stresses in the beam, by
more than the given amount.
Cooling Test on Curtiss Wing Radiator Section. Serial No. 2326
A section of the Curtiss wing radiator similar to that used on the Curtiss pursuit PW-8 air­plane
was tested in the McCook Field five- foot wind tunnel in order to secure data for compari son
v,ith results of ground and flight tests of the actual radiator, as a means of indicating at what ~ir
speeds this cooling system performed most effec tively. In general , it was found that the coeffici­ent
of heat transfer checks with results obtained in the 14-inch wind tunnel test of 1921; both tests
showing that the coefficient of heat loss varies ap prox imately as "V" to the 0.655 power. The values
of heat transfer for any given velocity are given graphically.
Impact Test of Split-axle Chassis for XC0-5 Airplane. Serial No. 2330
The structural strength of a duralumin chassis designed and built by the Division for the
XC0-5 airplane was found to be sati sfactory. Drops under hal f -load ( 2,000 pounds) were made
from 6 to 48 inches before failure, the required height of drop with half load being 42 inches.
Drnwings and photographs of the chassis are appended.
Impact Test of Split-axle Chassis for XC0-4 Airplane. Serial No. 2346
This report covers an impact test on a landing chassis of the split-ax le type designed and built
by the Division for use on the F okker C0 -4 airplane. The axles, struts, wires and fittings are of
steel construction with the exception of the alumi.num brackets supporting the rubber cord shock
absorber. The unit without wheels attached weighs only 85 pounds. Drawings and photographs
of the chassis are appended.
40 T E C H N I C A L B U L L E T I N N o. 39
Static Tests.
The following serial reports contain a complete account of static tests conducted at the Division
on various airplanes and airplane parts to determine their structural strength. Appended to each
report are a number of photographs of the test. structural drawings and load deflection diagram~.
Serial No. 215~Engineering Division XTP-1 (Original Design.)
Serial No. 2155-Wing Spar for Elias XNBS-3 Airplane.
Serial No. 2210-Static (Proof) Tests of Gallaudet DB-1 Controls and Surfaces.
Serial No. 2219-Dayton-Wright XPS-1 (Special Pursuit with Lawrance J-1 Engine.)
Serial No. 2251-Wing Spar for Curtiss XNBS-4 Airplane.
Serial No. 2274- Huff-Daland Test Spars (Steel tubes.)
Serial No. 2275-L. \V. F. Test Spars of Duralumin.
Serial No. 2276-Duralumin Wing Spar for L. W. F. XNBS-2 Airplane.
Serial No. 2283-Gallaudet DB-lB Revised Wing.
Serial No. 2298-Duralumin Fuselage for XC0-7 Airplane.
Serial No. 2305-Fiber Aileron for XC0-6 Airplane.
Serial No. 2321-Boeing Experimental vVing Beam (Steel.)
Serial No. 2322-Engineering Division Experimental \ i\fing Beam (Wood Box.)
Serial No. 234~ The "O. W. T." Rudder Bar (Designed by 0. W. Timm.)
Serial No. 2345-Steel Center Section for Vought VE-9 Airplane.
Wind Tunnel Tests.
The following serial reports contain results of wind tunnel tests on vanous airplane models
to determine their aerodynamical characteristics. Each report gives a description and photograph
of the model , airfoil section, data curves and tabulations. All tests were conducted in the wind
tunnels at the Massachusetts Institute of Technology.
Serial No. 2280-L. W. F. Transport Airp lane, Model XT-3.
Serial No. 2287-Elias XNBS-3 Bomber.
Serial No. 2288-Loening XPA-1 Air-Cooled Pursuit Airplane.
*Serial No. 2289- Engineering Divi·sion XA-1 (Amhulance) Airplane.
*Serial No. 2297-Gallaudet DB-1 Airplane (Revised Model.)
*Serial No. 2301-Thomas-Morse MB-3 Airplane. (Original model with Eng. Div. Tail
Surfaces.)
Serial No. 2323-Fokker PW-5 with V-40 and PW-5 Wings.
*Serial No. 2331-Engineering Division TA-4 (Revised Design.)
This report is an appendix to Serial Jo. 225Q published on page 67, Tcc/111ical Bulletin No. 38.
Serial No. 2336-Elias XNBS-3 Bomber (Appendix to Serial No. 2287 above.)
*Serial No. 2337-Gallaudet DB-1 Bomber ( Original Design.)
*Serial No. 2342--Boeing GA-2 Ground Attack Airplane.
ARMAMENT SECTION.
Service Test Requirements of Type E-2 Cannon Mount. Serial No. 2246
The Type E-2 Cannon Mount was developed hy the Division for the purpose of mounting
the 37 mm. semi-flexible automatic aircraft cannon upon the nose of the armored GA-1 airplane.
The cannon is supported by a curved metal shield which forms a part of the armored nose of the
fuselage. This shield in turn is supported by rollers attached to its upper and low.er edges and
borne in channels riveted to the airplane structure, which permit the shield to rotate thru an angle
of 45 degrees on either side of the longitudinal axis of the airplane. The shield is traversed by
means of gearing operating on a rack which is fixed to nacelle. The hand wheel and gears are at·
tached to the movable shield and move with it. The gun is mounted upon trunnion bearings so that
it may be elevated approximately 15 degrees or depressed 60 degrees as it is traversed.
Report contains complete description and views of the cannon and its mounting in addition to
the service questionnaire and installation drawings.
Handbook on External Bomb Rack, Type C-2. Serial No. 2285
This report contains material for use in compiling a handbook on the Type C-2 external . bomb
rack, a modified form of the old Ordnance Mark XIX bomb rack for carrying either 600 or 1100-
lb. bombs. The Division is contemplating publishing this material in the near future.
RESEARCH AND EXPERIMENT
EQUIPMENT SECTION.
41
Chronometric Tachometers. Serial No. 2312
This report contains an account of the study and test of three types of verti cal-dial, straight­scale
chronometric tachometers, the shaft-drive Pioneer-Van Sicklen, the electric drive Stover-Lang
and the shaft-drive Stover-Lang mechanisms. The relative characteristics and inherent errors are
given and the data presented by graphs on the performances of these particular instruments. It is
shown that further improvement in performance, size and weight can be obtained by a redesign.
FLYING SECTION.
Instrument for Recording Take-off and Landing. Serial No. 2223
In performance testing of airplanes it is highly desirable to have accurate in formation regard­ing
the time and di stance required for taking off and landing, as well as the ground speed at which
these are effected. In the past, it required the ser vices of three men from three to five hours to
observe and record the length of roll and the time to lift off, and then the results were only ap­proximate.
For these reasons, it became highly d esirable to develop an instrument that could be
readily installed on any airplane to accurately record take-off and landing measurements.
The report gives a chronological account of the development of the recording instrument from
the early models up to the present one used on the DH-4 airplane. The in strument proper con­sists
of two recording reels