Technical bulletin no. 35

              ?117 // μ
AIR SERVICE INFORMATION CIRCULAR
VOLUME V
(AVIATION AND AEROSTATION)
BY DIRECTION OF CHIEF OF AIR SERVICE
JULY, AUGUST, 1923
TECHNICAL BULLETIN
No. 35
NUMBER 428
DEVELOPMENT OF MILITARY AIRCRAFT MATERIAL FOR UNITED STATES
AIR SERVICE UNDER SUPERVISION OF ENGINEERING DIVISION.
' ..
1.'UBLISHED BY
ENGINEERING DIVISION, AIR SERVICE
MCCOOK FIELD, DAYTON, OHIO
1923
McCook Field-9-10-23-IM
Ralph Brown Draugh n
LIBRARY
MAY O 9 2013
Non·Depoitory
Auburn University
CONFIDENTIAL
The information contained herein is confidential and therefore
must not be republished, either in whole or in part, without
express permission of the Chief of Air Service, U. S. Army.
1
AIRCRAFT DEVELOPMENT
AIRPLANES
The Barling Bombers (NBL-1) with views and description ------------------------------------------·- 14
Cooling Troubles on, NBS-l's-New Curtiss PW-8-Speed Trials of TW-3-.............. .
New Huff-Daland TW-5 and Thomas-Morse Training-Tests on A-1 Ambulance
Model in McCook Field Wind Tunnel-Exp&imental Wings for Messenger........ 15
Propeller Development on Aluminum Alloy and, M'icarta Propellers·-·--·-·-·-·-·-· --·------·-- 16
AIRSHIPS AND BALLOONS.
Gypsy Moth Experimeillt with OA-1-Increase Capacity of OB Airships-The RS-1.. 16
Additional TC Airships-Packard Engines for Zod'iac-Tractive Units for Balloon
vVinch ·-······ ·········-······ ····················-·····-·········-········································ ··· ·-··· ·················-··- 17
ARMAMENT.
Langley Bombing Project Equipment-Bombing Target-R-3 Release Handles for
Martin Bomben-New Synchronizer Drive for Hispano ..................... .. ... .... ·-·········· 18
EQUIPMENT.
Wash for Battery-Starting by External Source Current-S. T. Ae Cinimo-Derivo­metre-
Earth Inductor Com.pass-Theodolites and Bamberg Speed-Measur-ing
Station -·········-····················--············· ······· ·· ··-········-············-·-····-·-·-······-··········-·-·· ·······18-19
New Airship Water Ballast Gage, Model 1923 ........ ·-··························-········-··········-···· ······· 20
The New Vertical Scale Instrument and Compact Board (Illustrations) ......... .......... 20-23
Specifications for Instrument Boards-H/A Parachute Replaces Stevens 'Chute.... 23
Eastman Graflex Aircraft Camera-Vertical View-Finders for the Service-Type
M Printing Machine for Mosaics-Investigation of Photographic Eimulsions.... 24
Field Servicing Truck for, Hot Oil and. Water.·-···-··-······ ················ ··················-······:. ... ...... 25
POWER PLANTS
Investigation of Curtiss D-12 Engine -···················-··· ······ ·· ········-·····························-··-·········· 25
Improvement of Lawrance J-1-Liberties for St. Louis Races-Navy Modified
Liberty Cylinder -·-·········---·············-·-······-······ ········---···· ·-··-·············-··-···----·········· ··········· 26
Shortage of Bellows Fuel Pumps-Variable Speed Reduction Gear for Liberty........ 27
RESEARCH AND EXPERIMENT.
RESUME' OF ENGINEERING DIVISION SERIAL REPORTS.
Revision of "Structural Analysis-........... ."-Static Tests on MB-3A-Study of
Parasite Areas ·································-··············-· ·······-······ ····· ·············· ····· ·········· ·-········· ····· 28
Tests and Comparison of Aerofoils-Engineering Features of T-2 Transcontinental
Flight ········-······· ·-·············-···· ··----····· ········--···· ····························-·-···· ·--·······-············-·· ....... 29
Bombers w'ith Different Power Plants-Resistance Coefficients-Flare Bracket E-2
-Installation of Pyrotechnics on JN-6H, NBS-1, and MB-3A-Wind Vane and
Ring Sight (X-1) for, Browning Gun ___ ---·-· ···-···-·--····-··---·-·-··-··-·--·-··-·-·----·-·····-··--··-··· 30
Wind Vane Sight D-1-Performance Report on MB-3A-SeJection of Landing
Fields-Lift of Gases in Balloon and Airship Operation ........................................ 31
Replacing Iron by Manganese-Comparison of Naval Gun Factory and A. S. Alloys
-Properties of Routine Melts -·-·-····-··· ·····-···· ··· ·········--·-·· ························-··-·· ···········-·-··- 32
Fatigue of Duralumin Bar Stock-Flooding Test of Stromberg NA-S6B Carburetor
-Cooling Tests of Cox-Klemin TW -2 ··-·-·-···················-·····················-·--······-··-·-········ 33
INVESTIGATION OF MATERIALS.
Re,instatement of Insignia Specification-Investigation of A-6 Airship Fabric ...... -... 33
Cements for Airship Fabric-Inspection of Plywood and Glue-Airplane Dope­Engine
Cooling with Ethylene Glycol-Alloys for Battery Terminals-Mag-nesium
Metal ········ ·············-···············-·-··· ·······-········· ············· ············ ······· ··-········ :······ ······ 34
Heat Treatmernt of Al-Cu Alloy-Corrosion, of Cast Aluminum-Hardness Test on
Irregular Shapes-Tes t of Duralumin Wing Ribs ........................ ·-···-····-·····-···--···-··-·-· 35
NEW BOOKS AND DOCUMENTS.
Documents Added to Engineering Division Reference Files ........................... ................ - 36
4 T E CH N I CA L B U LL ET I N N o. 35
THE BARLING BOMBER- AIR SERVICE NBL-1
(Six L iberty "12" Engines .)
-1
AIRCRAFT DEVELOPMENT
ON ENGINEERING D!VISION PROGRAM
AIRPLANES
BOMBARDMENT
Barling Bomber (Air Service NBL-1).
The initial flight of the Barling Bomber, conceded to he t\ie
day, occurred on August 22, 1923, at "Wilbur 'Nright Field.
engineering effort to a successful culmination.
_<
largest airplane in the world to­thereby
bringing three years o:i
The contrad for the NBL-1 airplane, popularly called the "Barling Bomber" after its de­signer,
was awarded to the vVitternan-Lewis Aire-raft Company, Tnc .. Hasbrouck Heights, N. J .,
by the Engineering Division in June, 1920. A few months before the letting of this contract, the
Engineering Division had engaged the services of \i\Talter l:-T. Barling, an English aircraft designer,
ior the purpose of making preliminary studies on a large night bombardment airplane. During his
employment-, a feasible design was originated which warranted the Air Service calling for bids on
construction of two experimental airplanes.
Bids were received from three firm s, namelv: G. Elias and Bro .. Inc., \,Vitteman-Lewis Air­craft
Company, and Curtiss Aeroplane and I\lotor ·corporation, from lowest to highest in the order
named. On account of inadequate manufactming facilities at that time, the lowest bid ( G. Elias
and Bro.) was rejected and a contract for two airplanes was awarded to \i\Titteman-Lewis. As con­struction
progressed, supplementary contracts were issued which reclucecl original contract to com­pletion
of only one airplane.
The con struction of the Barling was completed at the contractor's plant in October, 1922, from
whence the airplane was shipped to vVilbur \ iVrig!1t Field, ·where it remained in storage until spring
of the present year. Owing to its large size, consid,erable difficulty was experienced in furnishing
transportation of the assembled units and in selecting a suitable field for the initial flights.
The assembly and erection of the Barling was consummated under government supervision at
Wilbur \,\fright Field in July by using an improvised hangar in which the airplane was partially
:1ssembled and then drav..-n out part way for complete erection.
The fir st taxying tests were made at this Field by the Engineering Division oi1 August 16 for
purpose of testing landing gear anc! operation of controls. During these tests a take-off was made
with nine persons aboard for short hops and straight-away flight. Three hops were made at a
maximum altitude of 20 feet, the take-off being effected within a distance of 360 feet in just 14
seconds with wind Yelocity from 6 to 8 m. p. h. As a result of -these tests, several changes were
found necessary in order to improve engine control and eliminate vibration of tail surfaces before
undertaking actual flight.
The first flight lasting 28 minutes was made on August 22, 1923, to an altitude of 2000 feet
v,·ith a crew o[ four persons and 350 gallons of gasoline. The take-off was made in 14 seconds in
a distance of 360 feet at an indicated air speed of 60 rn. p. h. The airplane was found to balance
in climb, at ful! throttle, and with hands, off controls. at indicated air speed of 75 m. p. h. with
horizontal stabilizer setting of 2-2/ 3 degrees. Cooling of engines was found to be inadequate and
some vibration was obsenred in tail surfaces which ceased as soon as tail was removed from slip­stream
or in gliding which occurred at an indicated air speed of 93 m. p. h. A very smooth land­ing.
due to excellent shock absorbing qualiti.es of _ Oleo gear and to slow landing speed, was made in
6 T E CH N I CA L B UL LET I N N o. 35
31 seconds from time of contact to encl of roll. The flying qualities of this airplane appear to be
excellent insofar as could be determined in this short flight. Perfect stability was apparent both
laterally and longitudinally. Considerable effort was required to actuate rudder control as these
surfaces appear to be too small. Response to elevator control is rather slow at reduced speed with
throttle off, which is very likely clue to size and weight of airplane rather than to inadequate elevator
surface.
The Barling Bomber, Air Service designation NBL-1, is a large triplane with span of 120 ft.,
length 65 ft., and height 27 ft., designed for long distance night bombardment. It is powered by
six Liberty engines, has a tail group larger than the wing surfaces of a DH-4 airplane, and
weighs over 20 tons, six of which are carried as fuel. The specifications call for a high speed of
100 m. p. h. at ground, climb to 7000 feet in 20 minutes, and service ceiling of 10,000 feet, with fuel
supply sufficient for 12 hours sustained flight at ceiling. The bomb load is limited to 2-1/2 tons
and is to be carried only with reduced fuel.
PRINCIPAL CHARACTERISTICS.
DIMENSIONS
Overall span ........................................... 120' 0''
Overall length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65' 0"
Overall height ......................................... 27' 0"
Span of wing ( upper and lower) . ............... ...... .. .. 120' 0"
(Intermediate) .. ... .................. ... .. ..... .... 114' 0"
Chord of wing ( upper and lower) . . . . . . . . . . . . . . . . . . . . . . . . . . 13' 6"
(Intermediate) ............. . . ..... .... , . . . . . . . . . . . . 8' 0"
Dihedfal ( upper wing) . . . ....... .... . ... ........ .. . .... . 0°
(Lower wing) ...... . ...... .... ... 0° at fuselage, 3° outer bay
(Intermediate wing) .......... 6° 2' at fuselage, 1 ° 30' outer bay
Incidence ( upper and lower wir.gs) . . . . . . . . . . . . . . . . . . . . . . . . . 3 ° 30'
(Intermediate wing) ................................ 3° 16'
Gap ( mean gap between upper and lower wings) ........... 19' 5"
Stagger ( intermediate wing only) ........... ...... .... .. ... 1' 1/2"
Sweep back .. , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . None
Aerofoil (upper and lower) .. · ............................. RAF-15
(Intermediate) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . RAF -15 (modified)
AREAS.
Total supporting surface (incl. ailerons) ..... . ........... . .4017.72 sq. ft.
Upper wing ........................ · ... .. ... 1420
Lower wing ................................ 1356
Intermediate ............................... 861.72
Ailerons incl. balance ( 4@95) ............................ 380 sq. ft.
Elevators ( uper 68.82-lower 81.78) ....................... 150.6 "
Fins ( 4@37.65) .......................... . .. . . ......... 150.6 "
Rudders incl. balance ( 4@18.36) .......................... 73.44 "
Stabilizers (2) ................ . .. ... . ....... . ..... . .... 411.23 "
WEIGHTS
Empty including water . ...... .. . . ....... ..... .... . . ...... 27,132 l):>.
Useful load ........................................... 15,437 lb.
Armament . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444
Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 917
Crew ( 4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 720
Fuel (2000 gal.) ............................ 12,000
Oil ( 181 gaU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,356
Gross weight ....... . ....... ........ .... ..... ... ....... . 42,569 lb.
Weight per sq. ft. of supporting area. . . . . . . . . . . . . . . . . . . . . . . 10.6 lb.
Weight per horsepower (6 Liberties@400)................. 17.75 lb.
AIRCRAFT DEVELOPMENT 7
\i\Tood forms the fundamental material used in the construction of this triplane into which has
been incorporated the good features of the biplane thru use of the narrow chord middle wing. The
particular features of construction are given in greater detail in the following:
Wings.-The wings form a large three-bay, externally-braced triplane cellule having an over­all
span of 120 feet and a mean gap of nearly 19-1/2 feet between the upper and lower planes ·which
constitute the main supporting surfaces. The middle wing stag~ered inward between ·the main
panels, is of much narrower chord and shorter span, thus giving this airplane the appearance of a
2-1 / 2 planer.
The arrangement of airfoils combines many advantages of both biplane and triplane types
of construction in that it lowers the overall height of the conYentional triplane with increased
safety in taxying and in landing, furnishes a better engine support with controls routed along
narrow chord wing, and facilitates assembly and erection in cramped quarters. Another advantage
inherent in the narrow chord mid-plane is that its ·use precludes any possible interference with inter­aileron
controls ( ailerons are attached to main planes only) and _permits a shorter overnll span for
the triplane and consequently a narrower hangar dimension than would otherwise be possible with a
biplane of the same size.
The upper wing is continuous and symmetrical in plan to the lower except that it has no dihedral.
The camber of the main surfaces conforms to the RAF-15 airfoil curve whereas a modification of
this same profile produced a desired thin section for narrow chord center wing. All _three wings
are nearly square at the tips which round slightly into each edge. Four large ailerons of the Hand­ley-
Page balance type are inserted in the outer trailing edges of the main wings. Each aileron has
a chord of 3 feet, 8 inches and span of 27 feet, 11 inches.
Vv ood construction emplo?ing spruce as principal material is used almost exclusively for the
wings, each of which is built in sections for facility of transportation, erection, or replacement.
The internal structure with its built-up truss type spruce spars and ribs follows conventional prac­tice
with rib spacing varying from about 15 inches in the slipstream to about 20 inches near the
tips. Contour of wing along leading edge is maintained by numerous short false ribs inserted be­tween
the main ones. Practically all wing fittings were made of 60,000 lb. low test, thick gage steel.
Interplane bracing comprises a system of streamlined wooden struts and steel external brace
w'ires. Vertical members of the wing truss include four spruce struts in center section between
upper wing and fuselage and twenty-four struts, also of spruce, in the outer bays. The latter are
arranged one above the other between the wings in the vertical planes of their respective spars.
Double lift and single anti-lift wires intersecting in the edges of the middle wing, together with the
incidence wires furnish the bracing between the upper and lower wings. A double system of brace
wires is used in the center section also.
Fuselage .-The fuselage, a large imposing structure about 65 feet long, is of the semi-mono­coque
type built in sections of circular cross-section, bolted together, the largest of which has a
maximum diameter of 10 feet 3/16 inches. The carefully streamlined shell is formed of two-ply
spruce planking or strips, 3/16 inches thick, laid diagonally with each other along longitudinal axis
of fuselage and held together with casein glue. On the inside, the shell is reinforced by circular
bulkheads or rings and light spruce longerons faced with mahogany plywood. The outside sur­face
is protected by fabric covering and weather-proof paint.
For convenience in description, the fuselage may be subdivided into four main sections, namely:
the nose, the engineer's cabin, the fuel and bomb load section, and the tail. The nose section is
bisected horizontally .by a floor separating the gunner's and pilots' cockpits above from the bomb­ing
compartment below. The gunner's cockpit made circular in shape for mounting flexible ma­chine
guns rises out of the very nose. Directly behind this cockpit and communicating with it is
the pilots' cockpit (*Fig . . 5) which accommodates two pilots, dual flight controls of the wheel type,
a navigating· instrument board mounted in center between pilots, and a master throttle control lever.
The seats are placed close to outside of fuselage at such a height that pilots may look out thru two
openings in top of cockpit, protected by triangular-shaped windshields. The bomber compartment
(Fig. 8) which occupies space below floor is provided with V-shaped openings and sighting win­dows
at the front end and with magazine racks and a large circular hole thru bottom at the rear for
installation of front floor guns. The bomber's seat of the bicycle type is mounted in center of com­partment
directly hehind the bomb-sight which is suspended above the V-shaped opening in nose by
an adjustable bracket fastened to side wall.
* Figures ref er to illustrations on page 9.
s T E C H N I C A L B U L L E T I N N o. 35
The e11gineer's cabin occupies a full-diameter transverse section of the fuselage which is large
enough to enable engineer to stand erect in operating the large upright engine-control boards (Figs.
4 and 6) erected on each side of pasageway that opens into the nose section. Light and ventilation
are furnished by two windows, one in each side wall and a large opening in the top. This opening
which is slightly to rear of e ngineer's cabin and over front end of fuel tank forms a large open waist­deep
cockpit containing two seats separated by an instrument table. for use of the rad io operator and
the nayigator .
. Connecting with the engineer ·s cabin at the rear is the [uel and bomb load section ( Fig. 1)
extending entire length of wing chord from edge to edge. T his position allows the heavy fuel and
bomb loads to he centered over the center of gra1·ity which li es about 50.4 inches to rear of leading
edge of lower wing and 10.42 inches below the propeller axis. The main fuel tank for carrying 6
tons of gasoline is rigidly supported aiJoye the hori zontal center line of the fuselage leaving ample
space beneath for three large bomb racks and hoists supported by longitudinal members holding the
bomb rack hangars at their lower ends. The hottom of the fu sel<1ge below these racks is equipped
with several bomb trap doors which a re opened automatically by t he falling bombs. \ Valk-ways
;:dong each side of ftt el tank, giYe crew access to all parts of fuselage .
The tail section consists of an enormous cone (Fig. 2) supporting the biplane tail group at
the small encl and mounting the rear gunner's cockpit (Fig. 3) in the top of the fu selage just aft of
the wings. Openings for the rear set of floor guns are cut in bottom of fuselage m.idw,ay between this
cockpit and tail group. These guns are reached hy a walk-way clown the center.
For safety of the crew, two parachute openings a!·e provided, one in bomber's compartment on
left side of fuselage am! the other on t!1e right side below the rear gun ner's cockpit. Each opening
is fitted with doors hinged to in side of fu sehige.
1Vaccl/rs.--Fonr nacelles carrying six Liberty engines, two in each inboard and one in each out­board
nacelle, are perched in the outer bays betwern middle and lower wings on rigid steel tubnlar
mountings anchored to lower wing spars. The engines in the inboard nacelles are arranged in tan­dem,
one operating as a tractor and the other as a pusher. whereas both outboard engines operate
as tractors.
Since the nacelles are built almost entirely of meta l. no fire walls are required. The cowling
is aluminum supported by members of the nacelle structu re and attached by wing nuts for easy re­moval.
Inspection doors are provided on the sid es of the cowling but the tops of the engine cyl in­ders
are left exposed to the slipstream.
Tail Group .-The tail group is a biplane structure with :idjustal Jle incidence, having a total span
of 39 ft. 2 in., chord of 7 ft. 11 in ., gap 8 ft. 6-3/ 4 in .. and height of 11 ft. with tail skid on ground.
Area 0£ horizontal surfaces is 572 sq. ft. or 132 SC[. f t. greater than total wi11g area of a standard
DH-4B airplane. The weight and balance of such a large tail structure naturall~, presents quite
a problem owing to its great di stance from center o r grcn•ity of the airplane. All surfaces are of
metal construction except fo r the wooden ri bs and fabric covering. Good a spect ratio and dampen­ing
effects were attained by use of thin p1'ofi le section with nar row chord elevator s.
The biplane tail consists of four large balanced rudders of equal area with corresponding fins
that furnish the interplane bracing between the upper and lower stabili zers to which the narrow
chord balanced elevators are hinged. The entire tail structure is carried by the inboard section of
the stabili zer consisting of two center vertical fins and center sections of the upper and lower hori­zontal
stabili zing surfaces. The inboard section is attached as an integral part of the fuselage tail
by means of steel tubular V-strut bracing a nd brace wires and its incidence may be varied by pilot
during flight bv means of an adjusting mechani sm consisting of three cable drums, two in an in­clined
plane and one in a verti,al plane. Facility with which adjustment can be made, was demon­::
trated bv static test to reciuire a load of only 4 lb. per sq. ft. to change the setting of the stabili zer.
This was considered fairly satisfactory in view of area to he moved.
No horns are used on the rudder s. control of which is effected by means of a double svstem
of control linkage and master ribs.
The following dimensions give a general idea of the size of the tail unit:
Horizontal surfaces . . . . . . . . . . . . . . . . . . .............. . ..... area 575 sq. ft.
Vertical surfaces .. . . . . .. .... ..... ........ ... .... ......... . area 250 sq. ft.
Elevators-Chore! 2' 0" , span 35' 10" pins balance 3' 3" .
Fins-Chord 5' 11", vertical span 8' 6-3/ 4".
Rudders-Chord 2' 0", vertical span 8' 6-3/ 4" plus bal. l' 7-1 / 2".
Stabilizers-Chore\ 5' 11", area 435 sq. f t.
STRUCTURAL VIEWS OF BARLING BOMBER
Figs. I , 2 and 3· - Interior of Fuse lage. Fig. 5- Pilo t's Cockpit-Master Control in L eft Fore.ground.
Figs. 4 and 6-Control Board s in Eng ineer's Cabin. Figs. 7 a 11d 9-Chassis s howin~ Oleo a nd Rubber Shock Absorbers.
Fig. 8-Bomber's Cockpit Looking Forward.
10 TE CH N I CAL B UL LET I N No. 35
Tail Skid.-The tail skid
steel tubular mounting affixed
TAIL SKID.
illustrated herewith is of all-metal construction and consists of a
to fuselage and an aluminum alloy shoe designed to ride over the
ground like an earth boat. The shoe boat is pro­vided
with a steel keel armored with steel straps
and is mounted so that it may sW!ivel freely on a
support appended to a cross-axle, the vertical mo­tion
of which is damped by means of rubber shock
absorber cord wouml about axle and the apeces
of the rigid tubular members extending from
fu selage. Tension on the rubber cord is about
same as that used on DH-4 chassis.
Landing Gear.-The airplane is supported on
two sturdy chassis or four-wheeled trncks an­chored
to- lower wing directly below inboard
nacelles, thus providing an exceptionally wide
tread of 37 ft. 7 in. A str'31l two-wheeled auxiliary
gear is fitted to bottom : f fuselage beneath en­gineer's
cabin for preventing damage in case of
bad landing.
Each main chassis (Figs. 7 and 9) is of steel construction incorporating a combination rubber
and long stroke Oleo shock absorbing gear. Each truck is fitted with four Air Service standard 54
by 12-inch straight-side wlheels and tires, two on each a,s:le, so arranged that rear wheels take load of
airplane when at rest on ground. The front axle carrying two closely coupled wheels is suspended
forward of center of gravity by means of radius rods projecting outward from rear axle and is
connected to lower wing by the cylinders of the Oleo gear. In landing it is possible for pilot to
lower front wheels by means of a lever so that this energy will be a~sorhed by the oil cylinders of
Oleo gear. It was found, however, that when airplane is in flying position, these wheels hang clown
of their own accord, automatically absorbing the shock and distributing the weight over entire eight
wheels in landing or taxying.
Steel having an elastic limit of 130,000 lb. per
sq. in. is used for the main axles which have a
diameter of nearly 4 inches ( 3.9). The strengths
of the steel struts supporting chassis vary from
55,000 to 110,000 lb. per sq. in.
Two shock absorbing mechanisms are em­ployed;
that cushioning the front wheels is of the
well-known Oleo type consisting of two · long­stroke
oil cylinders whereas the absorber for the
rear wheels is of rubber cord type incorporated in
the rear st ruts. The unusual features about the
latter device v.1hich is shown ~n the accompanying
ililustration is that it is wrapped with 3/ 4-inch
rubber cords, known as T urner individual shock
absorbing ring. Each ring is made in proper
lengths to slip over the shock absorber saddle. The
use of individual rings is excellent for two rea­sons,
fir st, because breakage of one r ing does not
release the entire shock absorber as in the case of
the one-piece continuous cord and second, be­cause
broken rings may be easily replaced.
The NBL-1 chassis was originally equipped
with eight Palmer (British) clincher wheels and
tires, 1500 mm x 300 mm, arranged in such a way
that entire load of airplane on the ground rested
on only four (rear) wheels, this weight being dis-tributed
over the entire eight wheels only during REAR SHOCK ABSORBER WITH TURNER RING.
A IRCR A FT DEVELOPMENT 11
take-off or in landing. It was found by tests conducted by the Division that the Palmer wheels
which had been obtained from British war stocks were not strong enough since failure occurred
at a loading of 20,000 lb. or a factor of safety of only '.? under full load ( 40.000 lb.) whereas the
new Air Service 54 x 12-inch wheel withstood a factor of 3.5 under same conditions. As a result
of this investigati on. the entire Palmer equipment was replaced by new Air Service straight-side
wheels and tires. The new straight-side wheel has a hub diameter of 4 inches and length of 12
inches and weighs complete with tire 165 lb.
Power JJ/nn t.-Six standard Liberty "12" engines, four operating as tractors and two as
pushers, constituting the 2400-horsepower power plant, are carried in nacelles between the middle
and lower wings, one tractor and one pusher being placed in tandem in each inboard nacelle and
a single tractor in each outboard nacelle. The tandem nacelle is placed far enough out on wing to
enable an 18-foot propeller to be used in future installations if necessary. The wing structure sup­porting
nacelles is extra strong in that vicinity thereby affording greater rigidity and freedom from
vibration at idling speeds and possible in stallations of heavier power plants.
The engines which are standard, have been partially converted into 1921 models awl are
equippecl with standard Liberty U . S.-52 carburetors, Delco ignition, ancl Bijur electric starters.
The tractors are fitted with standard exhaust headers and the pushers ·with short individual exhaust
st;i.cks and extra long carburetor air intake pipes which extend upward t:hru middle wing. Al!
ignition wiring is encased in flexible metal conduit leading from the batteries which are clamped
in acid-proof metal boxes beneath each engine. Starting batteries are placed at sides of the engines
for accessihilitv.
REAR VIEW OF INBOARD NACELLE.
12 1' I~ C I-i N I C~ ~\ I"' B U L, L E 1"' I N N o. 35
\Nater cooling is effected by means of six side radiators with standard 9-inch core providing
285 sq. ft. of cooling surface and frontal area of 3.2 sq. ft. Temperature is regulated by means of
aluminum vane shutters operated by levers on engineer's control board. Brass expansion tanks are
carefully streamlined into the interplane struts over each nacelle. 1\ltho the original radiators al­lowed
a flow of 74 gallons of water per minute. they apparently possessed ~nsufficient surface for
proper cooling, thereby necessitating the install ation of extra N BS-1 radiators before initial flight .
F uel system comprises one 2,000-gallon main tank located in fu selage and four 25-gallon
gra vity tanks streamlined between interpla~ ~truts above engine nacelles. The main tank is made
of terne plates of 18. :?O, and 22 gages ,vith lt.mr separate compartments for gasoline. A level
gage is in serted in the side of each compartment. Overflow from g ravity tanks empties into the
two center compartments. The system is opernted iiy gravity in series with electrically-driven pumps
placed near bottom of main tank . the supply of fuel being controlled by gate \'alves for each engine.
by which any or all engines, pumps, or hand purnps, or any ot!1er combination of same may be
cut 0ut of the svsten,. !\ large size wobble hand pump is in stall ed in engineer's cabin for emergency
use.
!\mple lubri cation i,; f:,m1 ishecl from six 35-gallon oil tanks. one for each engin e, the tank,; in
the inboard nacelles being placed between the engines. Copper tubing of 1-2-inch diameter is
used for oil lines with the oil vent line opening into the engi)1e breathers. Oil is cooled hy radiating·
tubes extending thru each oil tank.
Originally. this airplane was equipped with two-bladed propellers designed to give a good range
of actirm . crui sing speed and economy consistent with fair per formance at the following r. p. m.'s :
Outboard tractors .. . . ........ ... ... . .. . .. .... . .. ... 1700 r . p. 111.
Tnboarcl tractors . . . . . . . . . . . . . . . . . ........ . ... . .. . . . 1500 r. p . m.
Inboard pushers ... . . ... . .. .. ... .. . . . . ...... ... .. . .. 1550 ·r. p .. 111
For the initial fli ght and subsequent performance testing. these were replaced by E.. D. A. S.
propellers having excellent climbing characteri stics ; the tractors being fitted with two-bladed pro­pellers.
10 f t. 4 in . in diameter, to turn at 1650 to 1700. r .. p. 111. and the pushers with four-bladed
propellers, 8 f t. 6 in. in diam'eter to turn at 1750 r. p. 111 : By u,;ing four-bladed propellers on the
pushers in place of two-bladed propellers. the severe ·.ribratiom ordinarily set up lw interf ence of
airflow around the wings are eliminated and a more even di stribution result s.
Co11trols.-AII surface controls are centered in the pil ot,;' cockpit and can be actuated by either
pilot without leaving his seat. Two inter-connected wheels actuate the ailerons and d evators in the
usual manner and a 20° angular moYement each way is a llowed for r udder bar control s. Adj ust­ment
of stabili zer is effected by le\'ers and wire cable. Fo1· ease of operation. the sur face controls
compare favorably with those of a Martin Bomber.
The engine controls are quite complicated but not unnecessarily so for such a large airplane.
T he com.bi nation consists of a master control ( throttle only) operated by p ilot and individual
controls ( th rottl e. spark. and mix ture ) for each engine operated by engineer. T hese individual
controls and other engine instruments a re mounted 0 11 two upright panels bolted to back of the
transverse partition that separates engineer's cabin from pilot's cockpit. Each panel accommodates
the necessary controls for three engines. including the radiator shutter control which is provided
with a micrometer adjustment. All levers are provided with friction clutches so that any particular
engine may be cut off in case.of damage without i1:tcrfering- with the others or t he pil ot's master
c:ontrol.
The n1a ster cont rol as 0riginally in stalled consists 0f a long knob-ended lever mounted on a
universal in such a manner that it can be mo\·cd lw either pilot forward or backward to ri ght or
left, the longitudinal movement operating- engines in usual manner and the hteral movement ac­celerating
engines on either side as desired. independently of the engineer's control s.
Arman,ie11/.--Gun defense from fonr stations within the fuselage covers practical ly the entire
field of protective firing . T he upper hemisphere is protected by four Lewis machine guns fl exibly
mounted in two coclq)its on top of fuselage . one in nose and the other behind wing whereas the
lower hemi5phere is protected hy fl cxibie Lewis floor guns, consisting of one or two guns firir. t;
thru hole in bomber's compartment and two separately mounted guns thru individual openings in
bottom nf fuselage midway between rear cockpit and tail g roup. In an emergency, additional guns
could be mounted in the navigator's cockpit.
A bomb load of 5,000 pounds in \'arious combinations ranging from forty 105-lb. to four
1000-lb. bombs may be carried with corresponding reductions in fuel load. Three internal bomb
racks. two Mark XXII and one Mark XXIV, are in stalled in side fu selage beneath fuel tank with
AIRCRAFT DEVELOPMENT 13
the Mark XXIV rack directly on the center of gravity and the Mark XXII racks at front and
rear of same. Two R-3 handles on bomber's r ight are used to operate these racks. A mechanical
arrow pilot director is provided as a signalling device between pilot and bomber. H inged bomb
trap doors below each rack are provided fo r purpose of reducing parasite resistance and a re in ­tended
to remain closed at all t imes except as they are tripped open by the released bombs striking
them.
Equipmc11t.-Instrurnent in stallations are distri buted at fom different stations thruout the
fuselage. The board in center of pilot's cockpit contains seYeral navigating instruments compris­ing
a Type C altimeter (25,000 ft .), an air speed indicator, clock, turn indicator, and inclino­meter.
The only engine in struments on this board are the six \ ,V eston distance-reading, rnagneto­,
·oltmeter electrical tachometers. One standard Navy Type I compass is installed in plain view of
each pilot but it is thought that two Army Type B compasses placed on instrument board would
eliminate parallax and proye more satisfactory.
Beside the engine controls already mentioned . the two engineers' panels contain one altimeter,
clock. and six electrical tachometers similar to those installed on pilots' board and in addition one
Hartman & Braun electri cal thermometer and one oil pressure gage for each engine. Four over­flow
gages placed on rear wall and two pressure gages near floor register the fuel supply.
:\n altimeter , air speed indicator, clock. compass and levels are placed in bomber's compart­ment
whereas navigator's board displayed above engineer's rabin is p rm·icled with a map case in addi­tion
to altimeter. air speed meter. and compass.
Ample provision has been made in the construction of this airplane fo r future in stallation of
radio, photographic, pyrotechnic, or other night-flying eq uipment. T he present equi pment, includ­ing
Yarious instruments has in several cases been superseded by equipment of more recent design
which would quite logically be used in future a irplanes of this model.
It is proposed to conduct a performance test program on the NBL-1 to include a series of tests
using progressive loads up to maximum called for in the specifi cations. It is probable that these
tests will be made at vVilbur W right Field , where adequate hangar faci lities have been assured
th ru a recent order from Chief of Air Service authori zing the construction of a special hangar for
the Barling, which work is proceeding under supervision of the Engineering Division.
INITIAL FLIGHT OF BARLING BOMBER.
14 T E C H N I C A L B U L L E T I N N o. 35
Cooling Troubles on NBS-1 Airplanes.
Tiwo production contracts for eighty-five NBS-1 bombers recently completed by the Curtiss
and L-W-F corporations· are awaiting termination. Althoall of these airplanes have been accepted
by the Government, a shortage of electrical equipment, particularly storage batteries and starters,
has delayed d~livery of several supercharged models which are to be ferried to destination. ·
Several schemes have been proposed for alleviating cooling troubles on Curtiss supercharged
NBS-l's. One airplane received at McCook Field was equipped with underslung radiators which
were attached below nose of nacelle with new cowling over and around engine. This arrangement
furnishes a better streamline and is being tried out for cooling effectiveness. Another proposal has
been advanced for installing Curtiss wing-surface radiators and for cowling engines to eliminate
the cracking and leaking of the water jackets. Provision for heating the oil or protecting it from
extreme cold has been suggested to improve engine operation.
PURSUIT
Curtiss PW-8.
The. favorable performances of the new Curtiss PW-8 which was designed and built by the
Curtiss Aeroplane and Motor Corporation as the embodiment of their ideas for a fast pursuit air­plane,
have resulted in the awarding of a contract by the Air Service for two additional airplanes
of the same design incorporating such improvements as have been found advisable.
The general characteristics of the experimental model delivered to the Engineering Division
are given in the following table:
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . One place biplane pursuit
Power Plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . Curtiss "D-12" 375-h. p. Engine
Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32'
Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22' 9"
Height . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8' 9"
Gap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4' 6-3/ 4"
Stagger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2' 10"
Wing chord . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5' 1/ 4", upper, 4' 1/4" lower
Supporting surface . . . . . . . . . . . . . . . . . . . . . . 271.78 sq. ft.
Useful load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 943.82 lb.
Gross weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2768 lb.
Wing loading . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.21 lb/sq. ft.
High speed (approx. wiith H. S. propeller). . . 172 m. p. h.
Ceiling (service) . . . . . . . . . . . . . . . . . . . . . . . . 27,150 ft.
Endurance ( at ground) . . . . . . . . . . . . . . . . . . . 2 hr. 48 min.
This airplane was used by Lt. Maughan last July in an attempt to make a daylight transcon­tinental
flight from New York to San Francisco. For this flight numerous alterations were made
to provide sufficient fuel capacity for the "hops" en route. These changes consisted in increasing
fuel capacity from 87 to 167.3 gallons by installing two auxiliary tanks holding 40.3 and 41 gal­lons
respectively, and in installing an additional oil tank bringing capacity to 9-1/2 gallons, and
a reserve supply of water ( 17.5 gallons). Altho both attempts (July 9 and 19, respectively) to
carry out this flight were unsuccessful, they served as a practicaly test of the flying qualities of the
new airplane and the endurance qualities of the new, Curtiss engine and .also the possibility of
rapid concentration of pursuit aircraft in distant areas in wartime emergency.
Several important changes will be incorporated in the second and third airplanes. These will
include a larger radiator surface and a new wing of different airfoil section and of larger area. The
weight will be increased to approximately 3012 lbs.
TRAINING
Dayton-Wright TW-3.
Performance tests are in progress on the TW-3 airplane, two of which were built by the
Dayton-Wright Company under contract for the Air Service Procurement Division, at Washing~
ton, D. C. Results obtained at McCook Field show an average timed high speed of 101.3 m.
p. h. at an observed r. p. m. of 1660 or 1615 r. p. m. corrected.
AIRCRAFT DEVELOPMENT 15
The Dayton-Wright TW-3 is of biplane construction, designed for a vVright 150-h. p. water­cooled
engine. It has a side-by-side seating arrangement and resembles in general construction the
earlier LeRhone-engined TA-3 model built for this Division by the same firm.
Buff-Daland TW-5.
A contract has been recently placed with the Huff, Daland and Company, Inc., Ogdensburg,
N. Y., for the construction of five advance training airplanes, Air Service Type XV, to be de­signated
Model TW-5. These airplanes will be powered by ·wright "E" 180-h. p. engines.
The new T\i\T-5 airplane is to be a modification of the Navy HN-1 tandem training equipped
with Wright E-2 engine and pontoons which was built for the Navy Department by the Huff­Daland
Company. The Army model will be a land 'plane having metal fuselage and wheel type
landing gear.
Some idea of the probable performance of the new TW-5 models may be ascertained from
the following extract taken from the Navy report on performance of the HN -1 seaplane with
Wright E-2 engine.
CHARACTERISTICS
weight enwty ... .. ................. . ........ . ....... .
Useful load . ................... . . . ......... .. ..... . . .
Crew (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360 lb.
Fuel ( 43 gallons) . . . . . . . . . . . . . . . . . . . . . . . 258 lb.
Oil ( 3 gallons) . . . . . . . . . . . . . . . . . . . . . . . . . 25 lb.
Equipment .. .... : . . . . . . . . . . . . . . . . . . . . . . 45 lb.
Total weight .... . -................. . ................. .
PERFORMANCE
1814 lb.
688 lb.
2502 lb.
High speed at ground ..... . .......... . .. . ...... . . .. ... 114 m. p. h.
Take-off ............................. . ... . ..... 45 to SO m. p. h.
Landing Speed . . ..................................... 40 m. p. h.
Climb to 5,000 ft ....................... . ... .. ........ 7-1/2 min.
Climb to 10,000 ft ...................... . ....... . ......... 20 min.
Climb to 14,000 ft .......................... . .. . .......... SO min.
Ceiling ....... . ...... . .......... . ..... . ............ . 14,400 ft.
Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Excellent
The flying qualities are considered excellent with exception of lateral control which is over­sensitive
due to large ailerons. No report is available on the land machine which will be about 17.5
lb. lighter and should give improved performance.
Thomas-Morse Training.
A new side-by-side seater training airplane built by the Thomas-Morse Aircraft Corporation,
Ithaca, N. Y., has been received by the Engineering Division for test. This airplane is powered by
Lawrance "J-1" 200-h. p. air-cooled radial engine loaned to contractor by the Government. It is
of biplane construction w:jth metal fuselage.
MISCELLANEOUS
Ambulance Airplane, Model A-1.
The Engineering Division has completed several wind tunnel tests on a model of the new
ambulance airplane, Type A-1, with highly satisfactory results, the model showing a higher maxi­m,
um value of L/ D than any other biplane model so far tested in the McCook Field tunnel. Work
on the design which embodies a biplane construction mounting a standard Liberty "12" engine,
with provision for a pilot, medical officer, and two patients, has been completed and procurment
data is available for bidders.
_ Wings for Messenger Airplane.
Sever-al sets of wings for the Messenger airplane have been received from the Lawrence
Sperry Aircraft Company, for use in a series of tests in which ,this airplane will be fitted with
different airfoils. The wings conformed to USA-27, USA-35, and USA-35B airfoil sections.
l(i T E C H ~ 1 C A L 13 U L L E T I N N o. 35
ln this connection, the E ngineering Division built a wind tunnel model of the Messenger for
test with six cliffe,·ent wing sections so as to make a compari son of their aeroclynamical char­acteri
stics.
Propeller Development.
Considerable experimental work is being clone by the Engineering Division with metal and
micarta propellers. A drop-forged aluminum alloy ( duralumin) propeller has been designed for
the Liberty engine and manufactured by the Standard Steel P ropeller Company. This propeller
has successfully withstood several whirling tests consisting of two 10-hour runs at 600 and 800
h. p., respectively, a preliminary run at 1000 h. p., and a 20-hour run on a Liberty engine, prepara­tory
to actual flight test on an airplane. Recently, it was fitted to a corps observation airplane and
flown daily with resul tant improved performance OYer same airplane equipped with a conventional
wooden propeller.
A detachable blade micarta propeller built with solid hub and screwed-in blades has been com­pleted
for use on the \Vright " E"' 180-h. p . e1,gine, in either a Curtiss J N-4H or Vought VE -7
airplane. The design of another micarta propeller having an ad justable pitch has been made for
use 0 11 the VE-7 a irplane al so. T his propeller is now under construction.
AIRSHIPS AND BALLOONS
Gypsy Moth Experiment with OA-1 Airship.
The Army airship OA-1, equipped with an in secticide hopper qs descri bed in last issue of
T echnic:i.l Bull etin left \Vil bur \ i\!right F ield on July 4, 1923, fo r · Henni ker, N . H., making the
Right without materi al di fficulty and landing four times at di fferent points en route for the purpos<-'
of re-fueling. T he work at Henni ker whi ch was clone in cooperation with the Bureau of E nto­mology,
Department of Agri culture, consisted o [ liying over two tracts of land, one of level
grourid situated in a na rrow valley and the other alongside of high hill s. at an alti tude of 50 feet
o,·er the tree tops. P owdered ar senate of lead was spre;:,.d thic kly over· the fo liage belovY.
The airship handled very well considering its small size, and the distributing apparatus
functioned in a satisfactory manner, altho from the data obtained on these flights. certain irnpron ­ments
in the distribut ing apparatus will be necessary as well as some changes in method of
maneuvering a irship in future work of t his n;itnre.
Due to stretching of fab ric and failing of cement. which resulted in 1 he slipping of seams and
patches nn the en velope, it became nece~san· to defla te the airship two clays after the work was
started, thus bringing the experiment to a premature close before the success of the work could
be fully determined.
It i:; unclerstoocl that the Depar tment of A~1iculture will make an effo rt to continue t his ex­periment
next summer, at whi ch time an improved hopper and distributing apparatus will be em­ployed.
It is helievecl that a larger airship of the TC Typ_e will be used in Yiew of its greater load­carrying
capacity. size, stability, and power. all of whi ch render it better adapted to negotiate the
bumpy air conditions encountered in t his 'Nor k.
Increase Capacity of OB Airships.
The Chi ef .of Air Servi ce has recommended in creasing e1w elnpe capacity of the four OB
airships, Goodyear T ype AB, on the new production schedule fo r Lighter-than-Air equipment to
allow use of helium when latter becomes available in suff icient quantities. T his change, involving
an increase o{ 15,000 cu. ft . with total capacity of 55.000 cu. ft ., together with t he fact that no
drawings or procurement data are in the posession of the Air Service for the rea son that previc us
orders haYe been placed with t he Goodyear Tire and R ubber Company as sole source of supply,
necessitates the making of new specifications and drawings in ord er that these a ir ships may he
procured on a competi t iYe basis.
RS-1 Airship.
It is estimated that work on the new semi-rigid R S-1 ai r ship under construction by the Good­year
Tire and Rubber Company at Akron, Ohio, is approximately one-fourth completed. The E n­gineeri
ng Division bas determined upon the armament instali ation. approved the design and mock­up
for the pilot car and is now checking the design for the pow~r car. T he contractor is con­structing
control surfa ces for test and has agreed to furni sh samples of se\'eral types of seams to
be used in the RS-1 en ,·elope.
AIRCRAFT DEVELOPMENT 17
A series of tests is being conducted on the first power transmission delivered to the Division
by the Goodyear Company under a separate contract for three transmission units for the RS-1.
These tests consist of a SO-hour endurance run at various loadings, a short test of the large balsa
wood propeller, made at McCook Field, a clutch test with one plate removed, aμd final destruction
test of the reduction gear with standard Liberty engines operating at full throtte.
At completion of the SO-hour test, the gears were found to be in excellent condition, the
only discrepancies noted being excessive leakage of oil around propeller shaft and development of
cracks in brackets supporting the gear case. Careful inspection of the mechanism upon disas­sembly
discloses that all parts are satisfactory and strong enough to carry the designed load, with
one minor exception in that the main support brackets require strengthening near the hold-clown
bolt bosses. It was found that the complete transmission was about 20 lh. over the contract weight.
However, a study of the situation revealed that reduction of weight can be effected without chang- .
ing any of the highly-stressed parts, and therefore it is considered unnecessary to repeat the en­durance
test after making the reduction.
The large wooden propeller designed and built by the Division for use on the RS-1 passed
the preliminary tests satisfactorily and is now being tested on two Liberty engines at approxima:tely
750 h. p. This propeller is made of balsa wood and is 17 feet, 6 inches in diameter. It is verv
light, weighing only about 130 lb., whereas a solid wooden propeller of this size would weigh about
300 lb.
Additional TC Airshipi:,.
A contract has been placed with Airships, Incorporated, for construction of three TC airships
(new Class C) under supervision of the Engineering Division. These are in addition to the three
airships, TC-1, 2, and 3, recently constructed by the Goodyear Tire and Rubber Company.
Some difficulty has been experienced in obtaining a complete set of Van Dyke drawings for
this airship from the Goodyear Company without which production could not proceed immediate­ly.
In order to obviate delays in construction of these airships on the new contract clue to changes
or inconsistencies in the drawings, which have been received fro111 Goodyear, the Engineering
Division h~.s stationed a representative at the contractor's plant to make such changes as may be
found necessary.
Two water models of the TC envelope are under construction for test in determining proper
arrangement of ballonets and car suspension in connection with the adaptation of the Military
AC car to this envelope. A wiring diagram and equipment parts list including the design of a
special main line switch and connector panel have also been worked out for this airship.
Zodiac Airship to be Equipped with Packard Engines.
Specifications are being prepared by the Division for installation of Packard "1237" engines in
the Zodiac airship at Scott Field. The proposed plan of installing Liberty "12" engines, choked
to 220 h. p. at 1300 r. p. m. for clirigihle use, as stated in Technical Orders No. 23, has been
abandoned since it was found that this engine did not operate efficient! y when choked to such an
extent.
This work will involve rearrangement of fuel and oil systems, modification of engine bearers,
fitting of adapters and gears to ignition-encl of engine for ·operating Type 1 L generator for charg­ing
stt)rage batteries used for starting and radio pnrposes, adaptation of Renault radiators and
other minor changes. The two propellers which were designed and constructed at McCook Field
for use on the Liberty engines throttled to 317 h. p. at 1300 r. p. m .. can be reworked for use
with the new power plant instailation. Two Packard "1237" e1:gines, rated 300 h. p. at 1800 r.p.m.,
have been calibrated in the Dynamometer Laboratory at McCook Field and provided with car­buretor
settings to give 220 h. p. at 1300 r. p. rn. before being shipped to Scott Field for installa­tion
in this airship.
Highly Mobile Balloon Winch.
The highly mobile balloon winch was designed by the Engineering Division and manufac­tured
by the Freeman Motor Company, Cleveland, Ohio, for use with U. S. Army Type R Oh,,er­vation
balloon. This , transportation unit, which is described and :illustrated in Technical Bulletin
No. 28, is of the four-wheel drive type and was originally equipped with 38-inch pneumatic tires.
18 TE CH N I CA L B U LL ET I N N o. 35
In order to adapt this unit for negotiating soft ground, the Division designed and built a
. caterpiller or track-laying adapter which could be applied within thirty minutes without removal
of the pneumatic-tired wheels. After several extensive tests had been made with the track-laying
device, which appeared to be satisfactory, it became necessary to apply brake lining on inside of
track shoes to prevent slipping. It was then thought that the use of dual tires on the rear wheels
of the vehicle would result in great reduction in weight ( about 2800 lb.) and in unit pressure that
w'ould be sufficient to obtain full performance without necessity of changing tractive units.
Consequently dual tires mounted on standard disk wheels purchased from the Budd Wheel
Company, of Philadelphia, have been applied to the rear wheels of the winch by means of a
special adapter constructed at this station. Comparative tests between the dual wheels and track­laying
adapter are being conducted to determine which is the most efficient method of increasing
mobility of the unit.
In the preliminary tests thus far conducted, very steep banks consisting of loose sand and
gravel have been successfully negotiated, and it is believed that with the dual tire equipment the
winch c;m be operated on any terrain which may be encountered in actual warfare.
ARMAMENT
Bombing Project Equipment (Langley Field.)
Considerable bombing equipment consisting of newly-developed bomb sights, pilot directors,
bomb sight stabilizers, bomb racks, hoists, and releasing mechanisms has been furnished and
shipped by this Division to Langley Field, Virginia, for use in the bombing maneuvers being con­ducted
by the Army Air Service. Included in this equipment were two specially-constructed bomb
yokes capable of carrying a 4,000-lb. bomb for installation in the L-\V-F "Owl" airplane. Satis­factory
ground and flight tests using a 2,000-lb. bomb have been made.
Bombing Target.
A large concrete bombing target is being con"tructed at vVilhur \Vright Field for testing vari-
• ous kinds of experimental bombing equipment. The target consists of a cirrnlar band of concrete,
60 feet in diameter and 6 feet in width, which will be plair.ly visible through bomb-sigr.ts from an
altitmle of 20,000 feet. The target is also dished toward the center to hold shallow pool of water
for observation of gun fire in testing machine gun sights.
R-3 Release Handles for Martin Bomber.
Pursuant to instructions received from Chief of Air Service, fourteen sets of bomb release
handles, chains, and other parts necessary to install Type R-.3 bomb release handles in old Martin
Bombers are being made up on priority order.
Synchronizer Drive Unit for Hispano.
A design has been completed for a new machine gun synchronizer drive unit for use on His­pano-
Suiza (\Vright) engines. An experimental unit will be constructed in Engineering Division
shops.
EQUIPMENT
Wash for Storage Battery.
A chemical test of twelve samples of water for washing electric storage batteries preparatory to
forming disclosed a trace of maltose (sugar) only in the sixth and remaining six washings, thus
leaving the plates thoroly cleansed of other harmful substances. It was con.eluded, therefore, that
nine washings will be sufficient to prepare battery for initial forming.
AIRCRAFT DEVELOPMENT 19
ing by External Source Current.
Portable starting equipment is being develop~d for starting six airplanes simultaneously. This
eat is accomplished by energizing the electric starter on the airplane engine by current supplied
rom an electric generator mounted upon a truck, the connection being made by plugging into a
receptacle installed on side of fuselage. The current for each airplane is controlled by the crew
chief by means of a push-button switch.
Tests have been conducted on a ground speed and drift meter of French design, known as the
"Cinimo-Derivometre, Type T. S. Ae." This instrument which was in stalled in floor of rear cockpit
of an airplane, consists of a circular wooden frame, 28 inches in diamete~ containing a circular glass
mounted in such a manner that it can be revolved in the frame. Engraved on the glass are a
series of lines parallel to a diametrical line having an arrow or index at the end. The fixed rim
or frame is marked off in degrees. The instrument is set .so that the center or diametrical line
coincides with the longitudinal axis of the airplane at the zero reading.
To measure drift, the glass is rotated in the frame until objects on the ground appear to travel
along one of the parallel lines. The number of degrees that the index line has moved from zero is
the drift angle which can be either to right or left. To measure ground speed, the eye is held at
fixed position determined by an eye-piece attached to the fu selage. After setting two lines which
measure distance on the ground, to positions corresponding to altitude, the time required for an ob­ject
to pass between these lines is measured. The angle between the lines and the eye corre­sponds
to one kilometer of distance on the ground. These measurements when converted into Eng­lish
units give readings in miles per unit of time. ·
The in strument is not suited for use in airplanes of the DH-4 type on account of its large
size. The principle is good, however, and it is believed that a smaller model of this design could
be operated successfully in an airplane of this size.
Earth Inductor Compass.
The Aeronautical Instrument Company; of Pittsburgh, Pa., has successfully accomplished the
pro<luction of an earth inductor compass which conforms to contract specifications. The experi­mental
model was tested by the Division several months ago and returned to the manufacturer for
improvement. (S ee Technical Bulletin No. 32.) The greatest difficulty that had to be overcome
in the development of this compass which depends upon induction of electric current from the
earth's magnetic lines of force, was that of commutation. Collection of feeble currents from the
generator proved to be a difficult problem and required construction of several commutator brush
1!,5Semblies before one was obtained that would not leak across the insulation between the seg­ments
after very short periods of running. The present model has been operated almost con­tinuously
for 75 hours without showing any inclination of leaking across the commutator seg­ments.
,vork is now proceeding on construction of ten in struments.
'ftteodolites an.d Bamberg Speed-Measuring Station.
For flight testing purposes, the possibility. of using three theodolites, an astronomical instru­ment
for measuring horizontal and vertical angles, set along a measured base line has been under
consideration by the Engineering Division for several years. The Ford In<;trument Company, Inc.,
of New York, presented a proposal along these lines, wherein the actual ground speed, altitude and
rate of climb would be recorded, provided that the three theodolites were kept trained on the air­craft.
The application of such an appliance was questioned from a practical standpoint, principal­ly
as to whether it would be possible to keep the theodolites properly trained on the aircraft in
flight. It was finally decided not to undertake th ~ir proposition since funds were iimited and de­velopmental
costs considerable. Later, it was fourtd. that a German-made speed-measuring station,
known as the "Bamberg," could be purchased at a reasonable figure. It was accordingly decided to
purchase the German apparatus and try it first, then consider the feasihlity of the Ford Instrument
Company's proposition.
The Bamberg speed-measuring station consists of three photographically recording theodolites,
a chronograph, a contact chronometer and other accessories for recording position of the aircraft
at certain time intervals. From these records, successive positions of the aircraft can be plotted,
20 T E C H N I C A L B U L L E T I N N o. 35
direction and altitude scale off, and speed and rate-of-climb computed. \Vhile exposures of the
verti cal and horizontal scales are being made on motion picttlf"e film as it moves along at equal inter­vals
of time, the telescope of the theodolite is kept tr"ained on the ai rcraft so that its image is kept
in center of field of vision. Movement of the tele.,cope is accomplished hy means of two cranks.
operated by hand. T he Bamberg speed-measuring station has been given preliminary tests and will
be used in regular performance work.
Airship Water Ballast Gage, Model 1923.
Specifi cations have been recently prepared to cover construction of an airship water ballast
gage, Model 1923. The in strument consists of a gage head ,vith indicating dial, a hand-operated
air pump and a connecting ee. T his assembly is used to indicate depth of water in ballast bags
or tanks 0 11 airships.
In the installation, an air line connected to the gage extends to bottom of ballast tank. An
air pump, manually-operated, is connected to the air line also. By working the pump, air is· forced
thru the tnbe to bottom of tank and bubbles out thru open encl of the tube . . P ressure in the system
is consequently proportional to the height of the water above bottom of the tube. This pressure is
indicated on tile gage which is calibrated to indicate rlepth in inches of water.
T he dial is finished in dull black with luminous indicating lines and white markings. Portions
of the two indi cating pointer s, one of which registers the depth of water in tank, whereas t he other,
marked "Full ," is set or held by fri ction in the hub to show capacity of tank, a re covered with
lutninous paint to ma_ke them p lainly vi·sible at a ll times.
MODEL OF INSTRUMENT BOARD USED IN DH-4 IN 1918.
The New Vertical Scale Instrument and Compact Board.
In the past very little thought was directed to the development. of the in strument board of an
airplane or to the arrangement of the in struments, themselves, which were usually placed indiscrimi­nately
on the board as space permitted or facility of connections demanded. No a ttention, what­ever,
was given to the relation of one instrument to another or to the fact that instrument indica­tions
are inter-related and should be read collectively. For in.stance, the engine in struments,
meaning the tachometer, oil and fuel pressure gages, and water _thermometer, which record opera­tion
of the power plant, should be read together as a group. F urthermore, it is just as essential
to group those instruments used in navigating, such as the compass, air-speed meter, and turn indi­cator,
so that all of them can be easi ly read at a glance. The early type of instrument board used on
DH-4 airplanes in 1918, which is shown on this page, exemplifies the iJlogical a rrangement and
crudeness of in struments.
AIRCRAFT D EVELOPMENT 21
In recent years, an attempt has been made to group related in struments more compactly and as
ore attention was directed to proper grouping and visibility, greater difficulty was encountered
FIRST VERTICAL DIAL
INSTRUMENT.
(The Tachometer. )
in placing the round-dial instruments in the limited space on the
board. vVith the ach·ent of more 'instruments to simplify naviga­tion
or to accommodate special en5ine in stallations, such as super­charger
s, the in strument board became over-crowded, thus mak­ing
it very difficult to locate and read any desired in strument
quickly. After much study as to the best means of overcoming
these difficulties, the instrument with the vertical scale was pro-posed.
·
The introduction of vertical scale in struments by the En­g
·ineering Division dates back to August. 192 1. when the f ir st
drawings and patterns for a verti:al scale tachometer were made.
Immediately following thi s, a combi.nation engine gage unit was
proposed, designed, and construc~ed . This unit consisted of a fuel
pressure gage (0-6 lb. ) placed in the top part of the case, an oil
p ressure gage ( 0-100 lb.) in the lower part and the thermometer
unit graduated from Oto 100 degrees Centigrade in the center with
the tube and bulb protruding thru the top. These two in stru­ments,
which are shown in the accompanying photographs were
the pioneers of all vertical scale in struments designed by the Air
Service for heavier-than-air work. The original models were il ­lumanated
by miniature electric lamps placed in side the case behind
the dial. The face of the case and the dial were curved convexly and verti cally to accommodate the
circular motion described by the long radial indicating arm or pointer.
The new experimental in struments possessed many advantages in that they required much iess
spare on the board and could be set closer together than the old round-dial type. Another ad­vantage
is the use of the vertical scale dial lay in the simplicity with which similar engine instru­ments
could be read in in stallations on multi-en­gined
airplanes. For in stance, all of the tacho­meters
could be placed side by side so as to be
read sim.ultaneously and when the pointers were
in line across the group, the engines were known
to be synchroni zed. This compact grouping de­creased
the size of the in strument board and ren­dered
it possible for the aviator to read at a glance
whole groups of in struments, both engine and
navigation units, without changing the position of
his head.
There have been several important improve­ments
in the 1923 models of these instruments.
Disturbing light reflections have been eliminated
by using a flat dial in stead of the original convex
face. To accompli sh this change into the flat
dial type, it was necessary to introduce a straight
line motion into the indicating mechani sm. Elec­trical
illumination has also been replaced by lumi­nous
dials and pointers.
The next step in th" development after the
first vertical scale units were built and tested , was FIRST VERTICAL DIAL COMBINATION INSTRUMENT
th e commerci·a I manu f actun·n g o f van·o us types (The Engine Unit)
of experimental instrnments for service use. f\ t the E ngineering Division's suggestion, the Pio­neer
Instrument Company undertook constrnction of a vertical scale air-speed meter and a flight
indicator. the latter being the first in strument to be assembled in the new fl at- face, vertical dial
case. This unit consists of a standard bank-and-turn indicator in the upper part of the case and a
gyro-controlled pendulum type fo re-and-aft inclinometer with vertical indication in the lower part,
thus furni shing a combination which serves as an accurate artificial hori zon for fl ying in clouds,
22 T E CH N I CA L B U LL ET I N N o. 35
fogs, or in straight level flight and contains all the indications necessary to maintain an airplane on
a straight and level course. F or cross-country flying, complete navigation equipment is achieved
by mounting a vertical scale air-speed meter and a compass alongside this instrument.
A 1923 '"AIRWAYS" MODEL DH-4B BOARD WITH VERTICAL FLAT DIAL . UNITS.
P reliminary tests have proven that the vertical scale instrument is a much greater improve­ment
over the round dial type that was at fir st anticipated with the result that at present there are
four different kinds of yertical scale in struments either standardized or in the process of standardi­zation.
Specifications and drawings have been completed for the tachometer, engine gage unit and
air-speed meter and the design of the flight indica tor completed also.
AIRWAYS INSTRUMENT BOARD IN DH-4B
(Note Dial of Earth Inductor Compass on Left}
The Airways instrument board shown above was used by an Engineering Division pilot on a recent cross­country
flight from Dayton to Boston. A correct course was flown above dense clouds a·t an altitude of 10,000
feet by aid of 1the newly developed compact instruments, the earth inductor compass, and the aerial sextant~
From the Ohio river to the Hudson no sight of land was possible.
AIRCRAFT DEVELOPMENT 23
From the first, it was seen that the compact instrument board would become a possibility with
th~ use of the vertical scale instrument. With that purpose in view, these instruments were de­signed
and constructed with uniform length of case and mounting lugs so that they could be placed
side by side like books on a shelf and require but little space above and below the instrument
when mounted on the board. The mounting lugs were placed so that the instrument could be at­tached
to back of the metal board with dial flush with the face or mounted from the front of the
hoard without projecting more than 3/ 8. of an ind1.
Three types o.f compact instrument boards made of metal have been produced for standard
DH-4B airplanes, in which vertical scale instruments are used so far as possible. The first de­sign
was completed in April, 1923, and contained in addition to the standard "B-3" compass,
bank-and-turn indicator, altimeter, clock, Liberty ignition switch and vibrating starter button, three
new vertical scale instruments, a tachometer, engine gage unit and air-speed meter, none of which
were mounted flush with the board. The second uesign of compact board, an "Airways" model
which is shown on page 22, was completed a month later. Many improvements w,ere incorporated
in this board on wJuch all instruments were mounted flush. By employing a new special bracket, the
compass was mounted from the rear so that only the lower edge of the bowl protruded thru the
board. An exhibition of this board at the Air Service Display, in ·washington, during "Shrine"
week in comparison with old standard wooden board on page 20 elicited much favorable comment
The third design produced for a DH-4B bombing airplane has all of the characteristics of the second
design or Airways model and, in addition, a pilot director mounted at the top alongside the alti­meter.
An "Airways" board of the second design has been mounted for service test m an airplane
especially equipped for the study of instruments and navigation methods. In addition to several
local cross-country flights for test purposes, a particularly interesting long di$tance non-stop flight
was recently made by an Engineering Division pilot from Dayton to Boston with this equipment.
The greater part of this flight was made above the cloi.tds completely out of sight of land at 10,000
feet altitude. The superiority of the new vertical scale instruments and compact metal instru­ment
board has been definitely established, and steps have been taken to standardize the new in­struments
and instrument boards.
Instrument Boards.
The culm ination of extensive development and expe.,rimentation carried on by the Engineering
Division and commercial instrument makers has resulted in the preparation of specifications for the
purchase of standardized instrument boards using the latest compact instrument arrangements.
These specifications cover six different designs of boards as follows :
No. 110--For corps observation airplanes.
No. 111-For day bombardment, single-engined airplanes.
No. 112-For night bombardment, twin-engined airplanes.
No. 128-For special navigation of long distance, single-engined airplanes.
No. 129-For pursuit airplanes.
No. 130--For special flight instrument board.
These instrument boards are to be made of metal and fini shed in black enamel. The instru­ments
will be for the most part of the new vertical-scale type with dials marked in luminous paint.
Stevens Parachute Replaced by Heavier-than-Air Type.
The Engineering Division has just compieted a series of important tests on standard airplane
or heaY-ier-than-air parachutes in kite balloons. When attached to a dummy man weighing 130 lb.,
both the :.eat and lap type heavier-than-air parachutes opened in less than three seconds, descend­ing
a distance of approximately l.50 f P.et in Lhis time. Ten drops were made on these tyves.
Dummy drops were than made with a standard heavier-than-air parachute placed in a pack similar
to the standard lighter-than-air balloon pack which is used for "fixed-station" pai:-achutes. Dropping
tests from 1,000, 200, and 100 feet were all successful. The parachute in the 100-foot drop opened
and completely checked descent in about eighty feet.
24 T E C H N I C A L B U L L E T I N N o. 35
As a result of these tests, it has been recommended that further purchases of cotton parachutes
of the Stevens type ( designed by A. Leo Stevens) which is the present standard "fixed station"
parachute fo; lighter-than-air purposes be cancelled and that heavier-than-air parachutes be used as
"free" parachutes pending further development. The Engineering Divi sion ''fi xed-station" para­chute
which supersedes the Stevens type has the following characteristics in comparison with the
latter:
Type of 'Chute
Stevens .. .. ......... .
Engineering Division .. .
Weight
30 lb .
15 lb.
Aircraft Film Camera (Eastman Graflex.)
B ulk
3.888 cu. 111.
900 cu. 111 .
Fire Retarding
Cotton-No
Silk-Yes
Anticipating the demand and utiliiy of an aerial film camera that can be operated from any
passenger-carrying aircraft without use of a special mounting, the Eastman Kodak Company is de­veloping
a modified Graflex using film for taking a 5 by 7-inch picture. This camera is small
enough to permit easy handling by an operator during flight particularly when exposed to the swift
blast of the slipstream.
The camera was tested by the Engineering Division at the request of the manufacturer and
was found unsatisfqctory in its present stage of development clue to failure of the film -changing
mechanism, inrnnvenience in sighting and small size of the view-finder. It has been returned to
the Eastman Comp~ny for reworking.
Vertical View-Finders for the Service.
Thirty-two vertical view-finders purchased by the Air Service for use on photographic air­planes
have been fitted with lenses and adjusted. These view~fincl ers were purchased without lenses
as there were enough lenses of requisite quality in :\ ir Service stores for this purpose. The com­plete
assemblies_ have been returned to Fairfield Air Intermediate Depot where they are now a vail­able
for issue to the Service.
Photographic Printing Machine for Mosaics.
After considerable experimental work, the Engineering Division has completed specifications
for a photographic printing machine. known as T ype "M," which is to be used principally for mak­ing
prints of negatives of mosaics. It can also be used for making prints from large glass plate
negatives.
The machine is designed for making co.ntact prints from 20 hv 24 or 24 by 24-inch film . It
consists of a square wooden cabinet about thirty inches high mounted 011 four legs. The top part of
the cabinet contains a light box illuminated hy several electric light bulbs mounted on angle-iron
frame. The film and the sensiti zed printing paper are held in close contact by means of a vacuum
pump driven by an electric motor, the pump and motor being mounted on an angle-iron frame
underneath the light box. A motor-dri ven blower to prevent over-heating is also mounted on this
frame and delivers a blast of air across the under surface of the glass plate placed above the lights.
Two ruby-colored bulbs placed in side the light box and connected in the blower cirn,it serve a
double purpose, one as an aid to the operator in placing paper anrl film in proper positions ancl the
other as a warning that the blowe1· is in ope·ration.
Photographic Emulsions.
Characteristics of photographic emulsions and methods of manufacture have always been care­fully
guarded secrets by manufacturers of the photographic indust ry and for that reason, very little
accurate scientific data on enmlsions are available for use of the public or the Government. It is
believed that the formulas used by manufacturers are for the most part almost entirel_v empirical
and are formu lated 'Nith no ab5olute knowledge as to "'hy certain properties a re produced b_v cer­tain
chemical ingredients, mechanical treatments and processes of manufact~ire. Jn order to obtain
this valuable knowledge for the Government as well as the public, particularly in the advancement
of aerial photography, the Engineering Division has furni shed the funds for a detailed a.nd exten­sive
investigation of photographic emul sions at the Bureau of Standards, the preliminary results
of which are now forthcoming.
AIRCRAFT DEVELOPMENT 25
From the funds thus furnished, the Bureau of Standards has purchased a plate-coating ma­chine,
refrigerating apparatus and other laboratory equipment especially for this work, and has also
supplied competent personnel for conducting the investigation. According to the preliminary re­su1ts
thus far determined, there are at least fourteen factors to be considered in making emulsions
which factors are enumerated as follows: '
1. Concentration of reacting solutions.
2. Ratio of gelatine to formation of silver bromide.
3. Excess of soluble bromide.
4. Addition of iodide.
5. l\Tethod of mixing.
6. Temperature and time of ripening.
7. Addition of ripening agents. such as ammonia.
8. Salt formed as by-product in reaction.
9. Hydrogen in concentration of emulsion ( when ammonia i~ not added.)
10. Quality and temperature of wash water. .
11 . Addition of materials such as chrome alum, intended to improve the gelative film
mechanically or alcohol and citric acid. intended to reduce fog.
12. Conditions of re-melting emulsion after washing and addition of extra gelatine ;it
this point to improve mechanical properties of the film.
13. Temperature, humidity, and air circulation in drying plates.
14. Quality of gelatine used in the emulsion.
In order to formulate definite conclusions as to the quantitaive value of these factors , it will
he necessary to vary them one by one while holding the others constant and making actual auanti­tative
tests on the resultant plate~. Tests on the plates made in this manner will determine ac­curntelv
the results nf expos1.1re to standard light and the effect of various wa,•e-lengths on the
emul sion. The first te~ts have been made on emulsions of known formulas and the results com­pared
with st:rndard commercial products. A number of preliminary tests have been made :-ic­cording
to the above-mentioned procedure and reports are being written on questions demanding
immediate solution.
Field Servicing Truck for Hot Oil and Water.
1,Varming and ~tarting· of aircraft engines in cold weath~r will be greatlv facilitated by supply­ing
these engiri'es with hot oil and waler from a field servicing truck, specifications for which have
just been prepared bv the Engineering Division.
The servicing truck will consist of oil and water tanks mounted on a standard Army two-ton
White automobile truck chassis. The tanks which are fitted with thermometers and gages will
have capacities for 100 gallons of oil and 300 gallons of water respectively and are to be con­structed
so that the oil resenoir will be submerged inside of the water tank which will he heated
by gasoline burners. Oil and water pumps, of the rotary type, will be placed inside the water
tank so that they will be always hot and primed. Adequate hose to convey the fluids to the air­plane
will be carried on reels on side of truck.
Of the hirls rcauested from manufacturers of this kind of equipment for constn 1c1ion of one
nnit. :the truck chassis 1·0 he furnished by the Air Service. only one was received. This proposal
was submitted by the Bowser Company of Fort \ i\Tayne. Indiana. which was awarded thf' contract.
POWER PLANTS
Investigation of Curtiss D-12 Engine.
The Engineering Division has recently undertaken dynamorneter investigation of the newly-de­veloped
Curtiss D-12 aircraft engine which, within a comparatively short time, has attained great
success for racing and fast pursuit purposes.
The Curtiss D-12 engine, designed and built by the Curtiss Aeroplane and Motor Corpora­tion
of Garden City, N. Y.. for the U nited States Army and Navy, is a development of the earlier
Curtiss K-12, C-12, and CD-12 engines and follows the same general construction. It is a 12-
cylinder, 60° Vee type, water-cooled engine with two rows of six cylinders en bloc having a bore
of 4.5 inches and a stroke of 6 inches with a total displacement of 1145 cubic inches.
26 T E CH N I CAL B UL LET I N N o. 35
The characteristic feature embodied in its design is the cylinder construction in which the
cooling water circulates directly against the cylinder walls. The cylinders are formed by individual
closed-end steel sleeves screwed directly into the aluminum cylinder head for a depth of approxi­mately
two inches. After the sleeves are in place, the valve port holes are cut thru the upper end
of the sleeve and an aluminum water jacket which is cast in one piece for each block of six cylin­ders
is assembled over the lower ends of the sleeves, the lower water joint being maintained be­tween
the sleeve and jacket by a composition gasket placed under flange of the sleeve and the upper
joint by means of a copper-asbestos gasket. The engine employs two overhead camshafts for each
hlock of cylinders, driven thru bevel gear and shaft from crankshaft and operating four valves per
cylinder. Low weight per horsepower and small frontal area, together with excellent perform­ance
as shown by high mean effective pressure at high speeds and smooth operation over the entire
speed range makes this engine particularly suitable for aircraft use.
In the investigation being conducted by the Engineering Division, two Curtiss D-12 · engines
are used, one being a standard low compression engine rated at 375 h. p. at 2000 .r. p. m. with com­pression
ration of 5.3 to 1 and the other a high compression engine giving 460 h. p. at 2300 r. p. m.
with compression ratio of 5.7 to 1. Dynamometer runs of the low! compression engine have been
completed and the engine calibrated preparatory to a 50-honr endurance test on the torque stand.
The high compres~ion engine, the one used in the Curtiss R-6 Racer piloted by Lt. Maughan
in the 1922 Pulitzer race at Selfridge Field and later in the one kilometer record at ·Wilbur Wright
Field, failed during a fuel and oil consumption run on the dynamometer when a broken master
connecting rod rammed the crankcase. Upon investigation ·this failnre was attributed to cracks
caused during heat treatment and forging. Another high compression engine has been shipped
from McCook Field to the Lawrence Sperry Aircraft factory for installation in the Verville­Sperry
R-3 Racer which has been redesigned and rebuilt for entry in the 1923 Pulitzer Race at
St. Louis. For this race, however, two new Curtiss D-12 engines of larger bore (4.625 in.) and
increased displacement (1209.6 cu. in.) will be used, one in the Verville-Sperry R-3 Racer to re­place
the engine forwarded by this Divi8ion for illstallation purposes and the other in one of the
Curtiss R-6 Racers. These new engines, which were just completed hy the Buffalo plant of the
Curtiss Aeroplane and Motor Corporation are of the high compression type giving -50 rated horse­pow;
er at 2300 r. p. m.
Improvement of Lawrance "J-1" Engine.
Improvement of the Lawrance nine-cylinder, air-cooled, fixed radial engine, Model "J-1," dis­cussed
in last number of Technical Bulletin (No. 34) , is being continued by the Division with a
view of increasing the reliability and performance of this engine for training and light pursuit pur­poses.
Tests of a new oil system with balanced oil outlet line from crankshaft indicate a greatly de­creased
oil consumption which is highly desirable. At full throttle, the engine nsed only 2.6 lb. of
oil per hour as compared to 7 to 8 lb. per hour under the old system. Another advantage is that
the new system also prevents fouling of the cylinders.
The new rotary induction system designed by this Division, in which a single carburetor replaces
the three carburetors formerly used, gave satisfactory idling at speeds as low as 90 r. p. m. and
good ::iccderation on dynamometer test, but failed to deYelop full power even with use of larger
Venturi in the carburetor. Consequently, the standard carburetor setting will be made and the en­gine
installed in an airplane for flight test.
Liberty Engines for St. Louis Race.
Three high compression Liberty engines have been conditioned at this station for installation
in airplanes entered in th(' Natinnal Airplane Races at St. Louis. All of these engines were as­sembled
and calibrated on .th e dynamometer before installation .
Modified Liberty Cylinder (Navy.)
A Liberty engine cylinder has been partiaily reworked in accordance with drawings submitted
by the Na,-7 Departrr.ent for modification of the Liberty engine. These modifications involve re­inforcing
the cylinder by bridging between the valve port elbows. The reinforcement prevents the
cylinder head from flexing under pressure and thus reduces failures of the water jacket.
AIRCRAFT DEVELOPMENT 27
The modified cylinder completed the first SO-hour endurance test on the single-cylinder testing
engine without showing any signs of weaknesses in construction and later completed a second 50-
hour test with compression ratio raised 6.5 to 1, at the end of which it appeared to be in excellent
condition. Further tests are being conducted on three similarly modified cylinders mounted on a
Liberty engine which is undergoing a SO-hour test.
Shortage of Bellows Fuel Pumps (Sylphon.)
A serious shortage of bellows fuel pumps required by the Service for use with Liberty en­gines
has been caused by inability of manufacturers to make deliveries on schedule. As a result
!l large number of airplanes, especially the new DH-4B's recently constructed for the Service, are
being delivered to storage awaiting delivery of this equipment. The Engineering Division has sent
a representative to the plant of the Keuka Industries, one of the manufacturers, to ascertain cause
of delay. The C. B. Kirkham Company is also constructing several hundred pumps.
Variable Speed Reduction Gear for Liberty.
A few months ago, the Engineering Division awarded a contract to the .Allison Engineering
Company, Indianapolis, Incl., for the redesign and reconstruction of a standard Liberty "12A" aero­nautical
engine to incorporate a variable speed reduction gear. According to the specifications, the
geared engine shall be capable of operating at either of the following gear ratios-73 . 36 or 66. 43
and shall not exceed the weight of the standard Liberty engine by more than 220 pounds.
Upon completion, ,it is proposed to subj ect this engine with reduction gear installed to a 10-hour
running test at the contractor's plant with each gear ratio running approximately half of this time.
During the test each gear reduction is to be run at full throttle for at least 30 minutes. The engine
is then to be partially dis-assembled for inspection of the reduction gear after which, if satisfactory,
it will be reassembled and delivered to the E ngineering Division for a SO-hour service test.
RESEARCH AND EXPERIMENT
I
RESUME OF ENGINEERING DIVISION
SERIAL REPORTS.
Serial Reports marked with an asterisk (*) will
be. issued by the Chief of Air Service as "Air
Service Infonnatinn Circulars."
AIRPLANE SECTION.
Revision of "Structural Analysis and Design of Airplanes."
(Chapter I-Airplane Design-Revision of May 17, 1923.)
Serial No. 1954.
This serial constitutes the latest tentative revision of the first chapter of the book entitled
"Structural Analysis and Design of Airplanes." two editions of which haw been published by the
Engineering Division. The present revision supersedes that issued in 1922 under this same serial
number as noted in Technical Bulletin No. 28. page 24.
Tentative revisions of the various chapters of this book which have been issued in report form
from 'time to time will later form the basis for a new edition Comments and constructive criti­cism
from aircraft designers and other interested persons on these proposed revisions or on other
parts of the present book will be welcomed for careful consideration in compiling the final version
of the new book.
Static Test of Tail Surfaces of MB-3A. Serial No. 2124
A static test was conducted by the Division on new tail surfaces for the Boeing Mil-3A
( Thomas-Morse design) airplane to determine structural strength preparatory to installation on
service airplanes. The horizontal surfaces were fonnd to be 43 per cent stronger than required and
1·he vertical surfaces 50 per cent stronger, thus permitting a redesign f0r reduction of structural
weight. A view and brief description of the new surfaces were published in Technical Bulletin
No. 34.
Static Test of Thomas-Morse MB-3 Wings, Serial No. 2127
Static tests of a set of upper and lower wings, designed and built by the Division for use as a
standard two-aileron w\.ing cellule on the new MB-3A airplane, demonstrated that these wings were
structurally satisfactory as based on a total weight of 2485 lb. for the complete airplane in flight.
Construction of the new wing is entirely of wood with exception of drag bracing wires and
fittings. In the upper wing laminated sprucr spars extend from tip to tip making a nne-piece struc­ture
. whereas those in the lower wing panels are joined to sides of fuselage in usual manner. Ply­wond
rihs with spruce capstrips and a plywood-covered leading edge are used but the false ribs and
plywood around the interplane struts in the old desigti have been eliminated. The wing cur\'e con­forms
to the R A F-15 aerofoil section.
Study of Parasite Areas. Serial No. 2140
The object of this study is to determine what factors should be applied to airplane parts ex­posed
to the airstream, in order to calculate the equivalent flat plate area. By equivalent flat plate
area is meant the area of a flat plate ,vhicil would offer a resistance equal to that offered by an
equivalent part of the airplane at the same velocity. This equivalent flat plate area has Leen fre­quently
railed "parasite area," and in the following discussion the two terms are considered as hav­ing
the same meaning. The resistances of struts, wheels, and wires were taken from data given in
RESEARCH AND EXPERIMENT 29
the Navy Handbook and the parasite area determined and tc1.bulatecl. These factors are given for
struts in terms of thickness, fineness, and length; for streamline wire, in terms of size and length;
for cables, in terms of diameter and length; for wheels, m terms of tire size and type of fairing
used. ·
The study was started with the intention of using the fuselage factor given in the Navy Hand­book,
(Vol. 1, Edition of 1919) , but it was soon found that these values did not agree with values
determined from flight test so that the problem became one of determining what value should be
assigned to the fuselage factor for the various airplanes considered. This fuselage factor is not
strictly a fuselage factor, as it is made up of the resistance of the fuselage, the added resistance due
to slipstream and the summation of all resistances due to interference or not otherwise accounted
for, including resistance of cockpits, cutouts, manifolds, guns, tourelles and other obstructions ir.
the airstream. It also includes a factor d~e to position of radiator, that is, whether radiator is ir.
. nose of fuselage or mounted on side or hottom of fuselage or in the wings. It was originally in­tended
in making the calculations to determine factor for radiators in terms of area and depth of
coring, but a more thorn investigation resulted in assigning values to the radiator factor depending
· upon position and factor for fuselage resistance. These factors for radiators are given iii. the
Tables.
The values obtained are not to be considered conclusive. Altho considerable work remains to
be done on this problem, it is thought, however, that a compilation of data from various flight tests
will be of value to those who desire to study this problem from the stand!)Oints sif fu selage de­sign,
radiator design and location, and propeller design.
Wind Tunnel Test of Gottingen No. 387 Aerofoil. Serial No. 2141
Report gives aerodynamical characteristics of a model Gottingen No. 387 aerofoil at 30, 40,
and Wm. p. h. in standard air as determined from tests in the four-foot windt unnel at the Massa­chusetts
Institute of Technology, Cambridge, Mass.
Wind Tunnel Test of USA-27 Aerofoil. Serial No. 2142
Report contains data on aerodynamical characteristics of a model USA-27 aerofoil at 30, 40,
i,tnd 60. m. p. h. as •leterrnined in the M. I. T. wind tunnel above-mentioned.
Test and Comparison of Gottingen and USA Aerofoils. Serial No. 2143
Determination and comparison of aerodynamical properties of four model aerofoils-Gottin­gen
No. 387, USA-35, USA-35A, and USA-35B-were obtained from tests in the M. I. T. four­foot
wind tt:nnel atxl the resultant data tabulated in this report. These tests were run under iden­tical
· condition at 40 rn. p h. in standard air ( 150° C and 760 mm. Hg.)
Engineering Features of the Non-Stop Transcontinental Flight. . Serial No. 2146
In this profusely illustrated and intere;;ting serial of 77 rages is set forth the engineering
prr.hlcms in volved in the preparation of the Air Sen-ice Transport T-2 for that history-making non­stop
transcontinent;:d flight from the time of its conception to its successful consummation. The re­port
is divided into nine parts. each riving in detail an account of the v;:,.rious stages of the -work
necess;i.ry for the eventual accomplishment of the flight, as follows:
I Introduction.
II Aerodynamics and Prediction of Performance.
III Structure.
IV Installation of Extra Fnel Tanks.
V Fuel and Oil System.
VI Cooling System.
VII Engine.
VIII Miscellaneous Modificatio11s.
IX Conclusion.
This report furnishes a clearer conception of the vast amount of preparation required for a
project of such magnitude and a keener appreciation c, i the engineering difficulties to be overcome
before flights of great distance and duration can be attempted with positive assurance of suc::ess.
30 T E CH N I CA L B UL LET I N No. 35
Comparative Study of Bombers with Different Power Plants. Serial No. 2151
This study was originated for purpose of determining effect on performance and bomb-carry­ing
capacity of three new or proposed types of hravy bombardment airplanes by substitution of
various available power plants. The estimated performances with variable factors were determined
for each type by Engineering Division's method of "Simplified Performance Calculation" and
the figures are consistent and practically correct for relative performances for airplanes of the same
type.
Resistance Coefficients of Airship Models. Serial No. 2156
The present test was conductrd in the McCook Field five-foc,t wind tunnel for- purpose of de­trrmining
net resistance coefficients of five small airship envelopes. Models C-1 , C-2. RO, SR-1,
and UB-2A. It differs from an earlier test conducted last vear on these same models for com­parative
resistances only in that corrections for tare have bee~ determined and applied.
Owing to small size of models ( 3 inches in diameter) and forces ant:! the proportionately large
effects of tare and interference which ranged from one-fourth to five times the net model resistance,
it became necessary to depart from conventional methods for streamline shapes and adopt the
methc,d drscri}wd in the earlier test in Serial Report No. 2086-"Comparison of Air Resistance on
Airship Models" on page 18, Technical Bulletin No. 33. The results are plottrd in t_erms of the
product velocity multiplied by linear dimension of the model in order to show effect of scale. The
prc.eision of the test proved to be within 2-1/2 per cent at higher speeds aroμnd 90 m. p. h. and
10 per cent at lower speeds around 40 m. p. h.
ARMAMENT SECTION.
Wing Tip Flare Bracket, Type E-2. Serial No. 2133
A detailed description, history of development, and views of the new wing tip flare bracket,
Type E-2, will be found in this report. The flare is especially designed for use on a monoplane
wing for night landing and differs from the standard Holt tlare in that it holds the Mark I flare
candle in a horizontal position. The particular advantage of the new bracket lies in the fact that
it is fitted with an adjustable shield which effectively eliminates glare from the pilot's eye. Brief de­scription
and photographs of this bracket were published in Technical Bulletin No. 34.
Instructions for Installation of Pyrotechnics-JN-6H Airplane. Serial No. 2136
The Engineering Division presents in this serial complete and detailed instructions, drawings,
and other data for the installation of pyrotechnics on Curtiss JN-6I-I service airplanes. The pur­pose
of each kind oi night-flying equipment and specific instructions for its installation are set forth
under the following headings.
Section I. Mark I Airplane Flare.
Section II. Wing Tip Flares.
Section III. Running Lights.
Section IV. Exhaust Equipment.
Instructions for Installation of Pyrotechnics-NBS-1 Airplane. Serial No. 2137
As in thr preceding report, instructions for installation of pyrotechnics on NBS-1 bomhers are
specifically set forth by the Division in this serial. This equipment includes the Mark I airplane
flare, willg tip flares, running lights, and non-glow exhaust pipes.
Instructions for Installation of Pyrotechnics-MB-3A Airplane. Serial No. 2139
This report contains similar instructions as in the two preceding ones for installation of pyro­technical
equipment on l\,IB-3A pursuit airplanes. The .same kind of night-flying eqnipment is used.
Wind Vane and Ring Sights-Type X-1 (Browning Gun.) Serial No. 2168
Flexible use of the .30 caliber Browning aircraft machine gun has been greatly facilitated by
the deYelopment of two new sights that can be mounted without modification of the gun itself.
RESEARCH AND EXPERIMENT 31
The front sight is an adaptation of the s~andard Norman wind vane sight to the Browning gun.
This is accomplished by mounting the standard wind vane sight up.on a special base and clamp sup­port
which is attached to gun by means of · round head screw and nut. The sight itself is held
in position on the base by standard Ordnance parts. Lateral adjustment of the unit is obtained
by USf of the do ve-tailed slide whicb is also u:;ed on the Lewis machine gun.
The rear or ring sight which performs the same function as the standard Lewis gun ring sight,
consists of an inner ring mounted at upper extremity of the sight post and encircled by an outer
ring, the entire assem\bly being attached to the gun by a bracket bolted thru the rocker shaft hole
in the trunnion. The post is held in position in the mounting bracket by means of a spring.
Service test requirements together with photographs and drawings for proper installation and
application of these sights complete the report.
Wind Vane Sight-Type D-1. Serial No. 2169
This development is a modification of the standard ~ orman wind vane sight to i,ermit ad­justment
without use of tools in compensating for speed of airplane upon which it is mounted. The
moilified si~ht may be u~ed on any .30 Lewis aircraft machine gun in the same manner as the
standard Nor man sight.
The modifications consist in introducing into the standard sight new top and bottom side
plates provided with notches for manual adjustment of the standard Norman front sight post with
vegetable ivory ball by means of special fulcrum pins inserted in the fulcrum holes in the post.
The adj usted position of the front post is maintained by a spring. Other parts of the standard
sight are used unmodified.
FLYING SECTION.
Performance Test on Boeing MB-3A (Special Wings.) *Serial No. 2113
Performance results contained in this report were published in part in Technical Bulletin No.
34 and apJ;>ly to a standard MB-3A pursuit airplane equipped with \V right "H-3" engine, Boeing
special design wings, and old style tail surfaces. This airplane is slightly heavier than the standard
prncluction model upon which no performance data have yet been obtained.
Selection of Landing Fields. *Serial No. 2192
Selection of Government landing fields presents a complex problem which resolved itself into
two antithetical requirements- one, a large field for permament training and. operations, and the
other, an emergency field of much smaller proportions. The location and size of b.nding fields for
these purposes depend upon several factors involving the characteristics of the airplane, the sur­fac
e, surrounding obstructions, and sea-le,·el altitude of the field, and the prevailing winds in that
locality.
From the discnssion, it is evident that permanent fields should be selected for convenience and
safety and have a minimum dimension sufficient to permit a safe forced landing for all directions
of wind. A field one mile square is recommended for this purpose. For an emergency field, the
size of which depends more closely upon the typ~s of airplanes using it and local geographical con­rlitions,
it is recommended that the land be well drained and he situated between sea-:evel and an
altitude of two thousand feet, and have a minimum length of not less than one thousand feet in
the direction of the prevailing wind of that locality. In event of obstructions bordering field on
windward sick ten feet should he added to the minimum lf:ngth for every foot the obstruction rises
in excess of thirty feet, whereas on the leeward side ten feet of field should be allowed for every
foot of obstruction.
The above conclusions are preliminary and are based upon results obtained from actual tests
on three representative types of service airplanes, the l\fartin Bomber, the DH-4, and the Thomas
.Morse.
LIGHTER-THAN-AIR SECTION
Lift of Gases in Practical Balloon and Airship Operation. *Serial No. 2159
The purpose of this report is to provide a pnctical and easy means of calculating rapidly and
accurately static lift or buoyancy of a balioor. or airship under various atmospheric conditions, both
at the giound and at various aititudes; and also to calculate the percentage of envelope fullness
32 T E C H N I C A L B U L L E T I N N o. 35
required at the surface to attain a given altitude at complete fullness without loss 0f gas hy valving.
The four general conditions to he met in practical operation of lighter-than-air craft are: first,
constant volume with envelope full; second, variable volume with envelope partially filled; third,
temperatnre of gas and surrounding air equal; and fourth, temperature of gas and surrounding air
unequal. Proper account has been taken of various correction factors for impnritv of gas, super­heat.
and h1m~iditv. The appendix contains an aerological survey of the U nited States giving vari­ation
of lift with altitude, latitude, and longitude, in atmosphere of different moisture content.
As a result of these inv•:stigations, certain values have been estahlished that are fairly represen­tative
of "standard Ii ft" in " standard atmosphere."
MATERIAL SECTION.
Replacing Iron by Manganese in Ail9y No. 3. Serial No. 2150
This investigation completes the study of the copper-zinc-aluminum alloys containing small
amounts of the following elements-iron, magnesium, and manganese. Previous in vestigations
covered in the following reports resulted in the development of a good high strength shock-resi<;t­ing
alloy (copper 2, iron 1, zinc 10, balance aluminum) known as Aluminum Alloy No. 3, A. S.
c;pecification No. ] 1,019 The results from the present investigation in this report disclosed that
the properties of this alloy were not improved by substitution of manganese for iron and that in
sor.1e Gt5es snch substitution produced an inf erior alloy.
The previous works were as follows :
Serial No. 1426---Investigation of Copper-Zinc-Aluminum Alloys.
Serial No. 1731-Investigation of Effect of Iron on Certain Alloys of the Copper-Zinc­Aluminum
Series.
Serial No. 1773-Physical and l\.fetallographic Properties of Copper-Zinc-Aluminum Al­loys
containing Magnesium.
Comparative Properties and Casting Qualities of Naval Gun Factory
Copper-Manganese-Aluminum Alloy. Serial No. 2152
This investigation was made hy the Engineering Di vision to compare the physical properties
and casting qualities of the Copper-Manganese AJnminum alloy made by the Naval Gun Factory ·
with those of seven.ii standard aluminum alloys used bv the Air Ser-..ice. It was found that this
alloy containing copper 1.4 per cent, manganese 0.00 per cent, balance aluminum. is more difficult
to cast than the Air Service standarrl 8 per cent copper-aluminum alloy but probahly less difficult
than the Air Service copper-zinc-iron-aluminum al!ov. A!tho the Naval Gun Factory's alloy pos­sesses
a verv high elongation as compared to the Air Service standard 8 per cent alloy, it was not
recommended as a substitute for the latter owing to its lower elastic limit.
Average Physical Properties for Routine Foundry Melts. *Serial No. 2153
T his report contains several tables giving the average results obtained by the Engineering
Division in routine foundry melts on test bars cast separately according to standard Air Service
methods. These results represent average physical properties obtained m ordinary production and.
therefore, should not be considered special in a ny sense.
These tests cover the following melts :
Aluminum Alloy No. 1 (A. S. Specification ll ,023).
Aluminum Alloy No. 2 (A. S. Specification ll ,024).
Aluminum Alloy No. 3 (A. S. Specification 11,019).
Aluminum Alloy N'o. 4 (A. S. Specification 11 ,300).
Aluminum Alloy No. 5 ( Aluminum .93- Copper 4--- Silicon 3).
Aluminum Alloy No. 6 ( Aluminum .93-Copper 3-Silicon 4 i.
Aluminum Alloy No. 7 (Aluminum .92-Copper 7-Tin 1).
Aluminum Alloy No. 8 (Copper 4-Nickel 2-Magnesium 1.5 ) .
Manganese Bronze (A. S. Specification ll ,021).
P hosphor Bronze (A. S. Specification ll,022).
Gun Metal (A. S. Specification ll ,020)
Reel Brass (A. S. Specification 11 ,026).
Piston Alloy ( A. S. Specification 11,024).
RESEARCH AND EXPERIMENT
Fatigue Resistance of Duralumin Bar Stock.
33
Serial No. 2165
The fatigne resistance or endurance limit of duralumin was determined by subjecting bar stock
"as received," tempered, or annealed under alteTnating stresses of equal magnitude with the fol­lowing
results:
"As rolled" . . . . . . . . . . . . . . . . . .... . . .......... . . . .... 14,000 lb. per sq. in.
Tempered at 925°F . .................. . ..... . ...... . .. 12,000 lb. per sq. in.
Annealed at 700°F . ... .. .... .. .... .. ........ . ...... . . 10,860 lb. per sq. in.
It was al so concluded that duralumin does not appear to follow the same general law as ferrous
mct:tls when ,;ubjected to alternating stresses. It follows also that the endurance limit does not
seem to be reached with less than 100,000,000 reversals of stress nor does it bear any constant rela­tion
to other physical properties. In plotting the test results, the semi-logarithmic meihod proved
superior to the logarithmic methorl in that it disclosed discrepancies in the results to a better ad­vantage.
POWER PLANT SECTION.
Flooding Test of Stromberg NA-S6B Carburetor. '~Serial No. 2162
This report gives the results of flooding tests conducted with Stromberg NA-S6B carburetors
on the new 18-cylinder 700-h. p., Model W-1 engine to determine what fuel head at the carburetor
is required to cause overflow from carburetor discharge nozzles with the engine running at idling
speed and with the engine stationary. It was found that the fuel head required to flood the car­buretors
with engine running averaged over 16 lb. per sq. in. , and that with the engine stationary, 7.9
lb. per sq. in.
The flooding tests treated in the present serial are only a part of the complete carburetor tests
made on the Model \ i\T-1 engine which were is'med in Serial No. 1899-see p. 30, Technical Bul­letin
\' o. 27.
Cooling Test of Cox-Klemin Airplane "TW-2" with Wright
180-h. p. Engine. Serial No. 2f64
Cooling tests conducted by the Division on an experimental trammg airplane, Model TvV-2,
built by the Cox-Klemin Aircraft Corporation, showed a satisfactory performance for the cooling
system used on this airplane. The report contains description and views of the cooling system
which consists of two side radiators niade of standard extruded seamiess copper tubes with ex­panded
hexagonal ends, 7 inches long, an expansion tank placed above and to rear of e:igine, and
aluminum shutters with vertical vanes; together with ne,:::essary piping and connections.
INVESTIGATION OF MATERIALS
Reinstatement of Insignia Specification.
The Engineering Division has recommended temporary reinstatement of Air Service Specifica­tion
No. 24,106-B, entitled "Colors for Insignia Marking and Coating" which was superseded by
Quartermaster Department Specification No. 3-lA for the reason that the new specification in­volves
use of new pigments which could not be approved without an exposure test of several months.
The old Air Service specification will therefore remain effectiYe until April 1, 1924, and will apply
in all cases where Quartermaster Specification No. 3-1 A is specified.
Investigation of Fabric of A-6 Airship.
A thorn investigation is being made of the fabric the Army A-6 airship, which was deflated
on account of excessive leakage discovered when taking permeability readings on top of envelope
with a portable permeater. The permeability to the right of the center top seam was found to be 600.
Further investigation is being made of the effect of tension in the fabric on permE'.ability and also
the effect of sustained load and temperature on slipping of seams. In this connection the Goodyear
Tire and Rubber Company has agreed to furni sh several types of seams for experimental purposes.
A complete report Vl,jll be issued later.
34 T E CH N I CA L B UL LET I N N o. 35
Cements for Airship Fabrics.
The investigation of cements for airship fabrics has led to the tentative approval of one kind
of cement manufactured by the B. F. Goodrich Rubber Company, known as Goodrich No. 4. Al­tho
seams manufactured from this cement did not hold under elevated temperatures, they were
more satisfactory than seams manufactured from the first sample of Goodrich cement and from
the F irestone product. A new sample of Goodyear cement is now in the Engineering Division
laboratory, together with several seams manufactured· by the Goodyear Tire and Rubber Com­pany
as representative of the seam which is to be used in the RS-1. Complete tests will be made
of these seams and special attention paid to their resistance to slipping under a load applied for
long periods of time at elevated temperatures, as this is one of the limiting factors in judging a good
cement.
Inspection of Plywood and Glue Specimens.
A large number of plywood and glue specimens have been submitted to the Division by Govern­ment
aircraft inspectors at \i\Tashington for examination and test. Some delay has been experienced
in expediting the results due to the length of time required by the specification to complete the
tests. The specification for plywood requires a 24-hour soaking period before testing whereas
that for glue requires a period of 7 entire days. In case results are desired in minimum period of
time, inspectors are requested to send samples by special delivery, i~ possible.
Investigation of Airplane Dope.
Twenty-six formulas have been tested by the Division, using different compounds, such as
benzyl alcohol, triacetine, · diacetin, ethyl phthalate, ethyl lactate, and ethylene glycol diacetate.
Ethylene glycol diacetate is a relatively new product in large production, and as it is a good solvent
for both cellulose acetate and cellulose nitrate, a patent application has been filed covering its use in
this type of material. Ethyl lactate is also a good solvent for cellulose acetate and tests indicate that
it can be used to replace cliacetone alcohol in elopes. A patent to cover this has also been applied
for. Ethylene glycol cliacetate, triacetin, and diacetin may be found suitable to replace triphenyl­phosphate,
and tests are now under way to determine thi s.
Engine Cooling with Ethylene Glycol.
Considerable thought has been devoted to the subj ect of cooling an aircraft engine with some
other medium than water, the idea being that by the introduction of some compound into the cool­ing
water or the use of a new cooling medium entirely, which would raise the boiling point and
lower the freezing point, the resultant engine operation would prove more efficient and the· ever­present
dangers of freezing at low temperatures would be eliminated. In this connection, the En­gineering
Division has made several physical tests with ethylene glycol as a medium for cooling an
airplane engine. The specific gravity of water solutions of ethylene glycol at 15 C. varies from
1.123 at 100 per cent glycol to 1.02 at 10 per cent glycol. The viscosity is affected considerably by
variations in temperature. One hundred per cent lycol has a siscosity of 34.8 at 90° C. and 220.4
at 0°C. Ten per cent glycol has a viscosity of 28.2 at 90°C. and 35.6° at 0°C. Practically all of
the so.lutions tend to approach the viscosity of water above 75 °C. Corrosion tests are under way.
'
Corrosiveness of Al1oys for Battery Terminals.
An investigation has been completed by the Division to check the corrosion resistance of several
alloys which were recommended by various manufacturers as ·suitable for storage battery terminals.
It was found that the only metals which did not have a tendency to sulphate in the atmosphere
directly over 1the electrolyte were the lead base alloys, such as Fi-eflo, manufactured by the Cleve- ,
land Brass Company, and Frary metal, manufactured uy the United Lead Company. For this
service in storage batteries the most severe corrosion occurs just above the surface of the liquid.
The alloys which failed to meet the test were Ilium, Stainless Steel, Aluminum Bronze, Phosphor
Bronze,. Silchrome, Mone!, 95 per cent Nickel, and Rezistal Steel.
Developing Magnesium Metal.
The Engineering Division has completed an investigation on samples of extruded magnesium
alloys from the American Magnesium Corporation which is attempting to perfect an alloy of mag­nesium
and aluminum. The properties of the 4 and 6 per cent alloys were found to be comparable
RESEARCH AND EXPERIMENT 35
with the magnesium-zinc alloy which this Division received from Germany, but the 8 and 12 per
cent specimens are hrittle. The 4 per cent aluminum alloys give an ultimate tensi le strength of
38,000 lbs. per sq. i-n. and elongation of 16 per cent in 2 inches. The Engineering Divi3ion at
the present time is making experiments with a 13 per cent copper alloy for castings, and is test­ing
it in the form of wrist pin bearing blocks and pistons. The specific gravity of this new alloy
is about 1.80. compared with 2.85 for the present standard alloy, which contains 10 per cent cop­per
and 90 per cent aluminum.
Beat-Treatment of Aluminum-Copper Alloys.
A report has been completed by the E ngineering Division on experimental work done in con­nection
with heat-treatment of aluminum-copper alloys with and without magnesium. It was found
that the addition of magnesium to the copper-aluminum group gives an alloy which responds bet­ter
to heat treatment. The heat treatment required to develop maximum physical properties for
this new alloy consisting of 4.5 per cent copper, 0.5 per cent magnesium, remainder aluminum, was
as follows :
a. Heat 925° F. for 96 hr.
b. Quench in cold water.
c. Age at 300° F. for 2 to 8 hr.
d. ...\ir cool.
The physical properties developed possessed the following characteristics :
Ultimate strength, lb/sq. in ...... . ........ .
Elongation in 2 in., per cent ............ . . .
Sand Cast
(300°F .-6 hr.)
36,430
5.0
Corrosive Properties of Cast Aluminum. Alloys.
Chill Cast
(300°F.-8 hr.)
42,200
8.5
An investigation on corrosive properties of cast aluminum alloys indicates that Air Service
standard Nos. 1 and 2 alloys, namely : 8 per cent copper and 10 per cent copper, respectively, have
the highest rate of corrosion and that the silicon alloys and alloys containing manganese have the
lowest rate. A heat-treated aluminum-copper-magnesium alloy is about intermediate.
Hardness Tests on Irregular Shapes.
Determining hardness on castings and forgings of irregular shapes has always presented a
difficult problem. The Division, however, has investigated several methods for mounting such
irregular parts as small valves, gears, and the like and found that comparable results on sclero­scope
hardness can be obtained by mounting the specimen in a mold 'made of a low melting solder.
Test of Duralumin Wing Ribs.
An interesting test has been completed by the Division on a set of six wing ribs manufactured
by Huff, Daland and Company. The rib has a chord of 132 inches, is made of 1/ 2-inch, 20-gage
duralumin tubing and weighs 44 ounces. The load-weight ratio at failure was 28, the failure oc­curring
in the duralumin rivets. Altho the load-weight ratio was comparatively low, the ribs sup­ported
twice the load for which they were designed. It is believed that if 3/ 8-inch tubing were
used in place of the l /2~inch size, the rib would be sufficiently strong and also much lighter.
NEW BOOKS AND DOCUMENTS
REFERENCE DATA ON AERONAUTICAL DEVELOPMENT
AND ENGINEERING IN THE l!NITED STATES AND
OTHER COUNTRIES ADDED TO THE TECHNICAL FILES
OF THE ENGINEERING DIVISION, AIR SERVICE.
AVIATION AND AEROSTATION.
GREAT BRITAIN
Rules for Air Ministry's helicopter com­petition.
Air Ministry communique No. 843.
M. l. D. England. n. d. 4 p.
Commercial aircraft and the state; by C.
L. !1alone. International Air Congress . . Lon­don.
June 27, 1923. 2 p.
Priced vocabulary of Royal Air Force
equipment and ;meterological stores. Air
publication 809G, 809H. Amendment No. 7
to Air publication 809. Air Ministry. Mar.,
1923.
Development of commercial aviation; by
F. Handley Page and W. P. Savage. In­ternational
Air Congress. London. June 27,
1923. 5 p.
Appropriation account of sums granted by
parliament for air service for the year ended
Mar. 31, · 1922, together with report of the
comptroller and auditor general thereon and
upon store accounts of air services. 1\1. I.
D. England. Mar. 13, 1923. 114 p.
Information regarding entry
as officer in Royal Air Force.
tion No. 870. Air Ministry.
6 p.
and service
Air Publica­Apr.,
1923.
Strength of British, French, and Belgian
air forces. Dec. 23, 1922. 2 p.
FRANCE
Civil aeronautics in France; by Camera_
man. M. I. D. France. May 16, 1323 .. 21
p. Maps.
List of civilian pilots schools in France
and number of students assigned to each
one. M. I. D. France. Apr. 27, 1923. 1 p.
Duties and organization of Superior Ad­visory
Committee for Military Aviation Con­struction.
M. I. D. France. June 8, 1923.
2 p.
Method employed in France for procure­ment
of military aeronautical equipml?nt, Jn
French wit h translation. M. I. D. France.
June 21, 1923. 29 p.
HUNGARY
Hungary's .Air Service after War; tr. fron1
Luftweg, Aug. 15, ln22. 3 p.
ITALY
· Air Service in Italy; by Schnitzler. M. I.
D. Tr. from Luftfahrt, July-Aug., 1922.
8 p.
Data on procurement of aeronautical
equipment in Italian Air Service. Model of
contract for purchase of aircraft. also model
of offer-contract for securing avi:.-tion lncl­terial
other than aircraft engines or material
purchased in open market . 1v1. I. D. It~ly.
June 9, 1923. 15 p.
JAPAN
Japan's rapid s trides in development o.f
an air force. M. I. D. Engle.nd. Feb. 12.
1923. 3 p .
Al0.22/29
Al0.01/43
D00/9
Al0.01 /H
A00.3/17
C00/2
Gr. Britain
C20.3/8
Al0.01 /3 J
C51.1/1
C3'1.3 /1
D00.13 /34
Al0/1
Hungary
Al0/6
Italy
DOO /36
Al0/8
Japan
Data on
equipment.
2 p.
procurement of aeronautical
M. I. D. Japan. June 13, 1923.
Japan's air force compared to other coun­tries.
M. I . D. Japan. Jan. 15, 1923. 4 p.
RUSSIA
Purchase of fourteen German airplanes fer
Russia. M. I. D. Russia. June 5, 1923.
1 p .
Location of combat units
forces. M. I. D. Germany.
2 p.
in Soviet air
Mar. 10, 1923.
Number and distribution of squadrons in
air service of Soviet army. From Le Matin .
M. I. D. Russia. Feb. 1, 1923. 1 p.
NEW ZEALAND
Ch-il aviation in New Zealand during year
ended Mar. 31, 1923. M. I. D. England.
May 28, 1923. 3 p.
UNITED STATES
Air Service activities of United States
army, giving station reports and Air Service
strength of commissioned regular army and
reserve corps. March 31, 1 :123.
Photostated map s howing Air Service ac­tivities
in United States. n. d.
United States army, navy and post office
Air Service appropriations for 1920-1923 in­c]
u s ive; compiled by L. D. Seymour. Feb.
24, 1923. 1 p.
List of Navy Yards. Bureau of Construc­tion
and Repair. Aircraft Technical Notes
No. 1-115. Navy Dept. Bureau of Aero­nautics.
Circular Letter No. 81. June 2~.
1923. 5 p.
Report for y ear 1922 of National Physical
Laborat ory. 1923. 227 p.
RECORDS, PERSONNEL, ETC.
World's official airplane records, officially
recognized by F. A. I. as of Jan. l, 1922.
This list also includes records made up to
an:.l including- May 7, l!J23, some of which
have not been officially recognized but prob­~
bly w ill be. McCook Field. TP.chnical
Data Section. Memo. report No. 69. May
8, 19 23 . 5 p.
Official timers sheets for speed records
m ade over 500, 1,000, 1,500, 2,000, 2,500,
3,000, 3,500, 4,000 kilometers at Wilbur
Wright Field and McCook Field and endur­ance
fligh t of Lt. Kelly and Lt. Macready.
Mar. 16, Apr. 16-17, 1923. 2.1 p.
Rules and entry blank for international air
races to be h eld in St. Louis, Oct. 1-3, 1923.
Ed. 2. 4 0 p. Illus.
Altitude records of Jean Casale and Bury.
E ntries for second experimental congress
for mctorless aviation. M. I. D. France.
June 15, 1923 . 3 p.
Chart s howing airplane requirements for
training :pilots for eight armies and their re­p
lacements. Mar. 15, 1921.
D00.13/31
C21/1
Japan
D00.13 /29
Al0/4
Russia
Al0/2
Russia
Al0/1
New Zealand
C21/8
1923-Mar.
Al0/5
United States
A00.3/15
C13/36
D00.12/189
C71.61 /29
C71.61 /17
D 52.03/64
C71.61/16
D52.1/131
NEW BOOKS AND DOCUMENTS 37
Hyg iene in r ecruiting with air fi g hting
forces; by Maj. Erms t Koschel. German
and trans lation from handbook of m edical ex­periences
in the World War. 1914-18. 1923.
47 p.
Summary of civil aviation certificates and
licenses issued, <"3nceJled, renewed and s till
in force. Canadian Air Force. Mar. 3 1,
1n3.
Summary of civil aviation certificates and
licenses issued, cance lled, renewed and s till
in force. Canadian Air Force. Apr. 30,
192 3.
Human machine in aviation; by C. E.
Hea ld. International Air Congress. London.
June 27, ln3. 2 p .
INSTRUCTION.
AIR SERVICE ENGINEERING SCHOOL.
Outline of entrance requirements for Air
Service Technical School. War Dept_ 0. C.
A. S. Circular No. 66. June 29, 1 923 . 4 p.
Bomb and
Air Service
Field. June,
drawings.
g un s ig hts; by H . B. Ing lis.
Eng ineering School. McCook
1 ~23 . 28 p . Photog r aphs,
Aircraft cannon. Air
Srhool. McCook Field.
P hotographs.
Service Engineering
April, 1923. 11 p.
Course in flight testing; by W. F . Gear­hardt.
Air Service Eng ineering Schoo l." Mc­Cook
Field. June 18, 1923. 38 p. Draw­ings,
charts.
Lift of gases in practical balloon and afr­s
hip operation; H . Dill. Air Service En­g
ineering School. McCook FiPld. May 3,
192 3, 34 p. -
Non-Rigid ail- ship design. Course in
Lig hter-than-Air EquipmP.nt. Air Servi·.!C
Eng ineering School. McCook Field. n .d.
Aerostatic problems involved in des ign
and navigation of lig hter-than-air craft with­out
:power. Practical effects due to chan ge::;
in barometric pressure, temperature, humid­ity,
superheat, purity, etc. Cource in ligbter­than-
air equipment. Air Service Eng ineering
Sc.hool. McCook Field. June 25, 1923.
Large document.
Ra dio equipment. Air Service Engineering
School. McCook Fie ld. 1923. 5 p .
RESEARCH
GENERAL
Standarrlization of methods of research ; by
R. T. Glazebrook. International Air Con­g
r ess . London. June 25, 1923. 8 p. Charts,
drawings.
Experimental research work in aerody­namics;
wing sections. In French. Mar.,
1923. 14 p. Charts .
Report on Italian Aeronautical Experi­mental
Institute. Series 2A-No. 1. In Italian
with partial trans lation. M. I. D. Italy
Ma r . 15, 1923. 48 p. Charts.
Contents:
1. List of symbols to be employed in
aeronautica l studies.
2. Simplified t heory for study of pro­pellers
; by Pis tolesi.
3. Barometrical altimetry; by TcnanL
Translated.
4. Studies on fr iction of fluids ; by
Pic;tolesi.
5. Airplane fabrics tightening· var­nishes
has ed on ceJlulo;;e e the rs ; by
Core!li.
Firs t annual report of Aeronautical Re­Fearch
Institute. Tokio Imperial University.
In J apanese. 1923.
Forest Products Laboratory T echnical
Notes No. 190-197. May 15, 1923. 18 p.
Contents :
1. Fuel value of · wood waste overesti­mated.
2. Average yields of g roundwood pulp
from various woods.
3. Standard abbreviations.
4. Starved g