U.S. Army Air Service Information Circulars
and Other Documents

The period between the end of WW1 and the middle of the 1920s was extremely important to the development of aviation in the United States. This was in large part due to U.S. Army and Navy-sponsored research into all aspects of flight, particularly engines. When the U.S. became involved in WW1, its military was grossly under prepared to procure and deploy aircraft, and all things necessary to build, operate and maintain quantities of them. The U.S. military and Congress realized this and set upon an unprecedented effort to improve the situation.

Work done by the U.S. Army Air Service is particularly well documented in a series of Technical Bulletins and Information Circulars, some of which are presented here. In an all-out assault on the development of engine technology, the Air Service—

• Tested foreign and enemy engines to catalog their power, design features, materials and manufacturing techniques used;
• Developed standardized testing procedures and established standards that new engines had to meet;
• Tested various engine installations to determine what factors produced the lowest cooling drag and operational utility;
• Experimented with new propeller designs, materials and construction techniques;
• Invited industry and lone inventors to supply a variety of new engine designs for testing, documented the best and worst features of each, and encouraged that subsequent designs incorporate lessons learned;
• Developed and tested new metal alloys and processing techniques for melting, casting, aging and heat treating;
• Addressed the problems associated with high altitude operation, including mixture controls, superchargers and intercoolers;
• Invented, developed and improved numerous accessories, including carburetors, magnetos, starters and gun synchronizers;
• Invented and developed testing apparatus, such as in-flight thrust recorders, torquemeters, and torsional vibration detectors;
• Investigated fuels, fuel additives, and their effects on fuel economy, engine operation and detonation.

The Air Corps (and Navy) even tried their hands at designing engines, none of which was serially produced. By the end of 1925, the political climate had changed and the Government money that had financed these experiments had dwindled significantly. However, by using lessons learned from the Air Corps experimental work, Wright had introduced the J-5 Whirlwind and Pratt & Whitney had run the first Wasp.

As one views pictures of broken parts from these early tests one is tempted to think, "No wonder it broke — anyone can see it was a stupid design." But one must bear in mind that our eyes of today are calibrated by looking a lots of successful designs. Early engine developers did not have that luxury, and were left with a single methodology: "Run ‘um, bust ‘um, fix ‘um." This is how engines evolved into light, reliable, fuel efficient machines.

The pages listed below are available only to AEHS Members. You must join the AEHS in order to view them. Members: Please click on an article title; you will then be presented with a Login page.

The following Information Circulars were provided by Robert J. Neal and William Lewis

No. 005: Hispano-Suiza Engine, Model E and I, Ignition Timing Instructions and Chart; Dixie Type 800 Magneto
No. 008: Destructive Whirling Test of Micarta Propeller (Westinghouse) and Rubber-Covered Propellers with Hard and Soft Rubber Leading Edges
No. 009: Test of Monel Metal Valves in Liberty Single Cylinder Engine
No. 011: Modified Hart Adjustable Pitch Propeller
No. 012: Micarta Liberty Propeller
No. 017: Comparative Merits of Dixie Magnetos and Delco Battery Ignition System When Used on Liberty 12 Aero Engine
No. 020: Effect of Reduced Engine Compression Pressure on Pre-Ignition with Mica Plugs
No. 022: Preliminary Test of Bijur Ignition End Starting Motor for Liberty 12
No. 028: Vibration Characteristics of the 300 HP Hispano-Suiza Engine
No. 035: Comparative Test of Special Homogeneous Gasoline and Commercial Aeronautic Gasoline
No. 041: Standard Engine Report on the Six-Cylinder Benz Aeronautic Engine Rated at 200 HP at 1,400 RPM
No. 042: Power Required to Drive Aeronautic Engine Magnetos and Generators
No. 046: Aeronautic Gasoline, Specifications and Methods for Testing
No. 047: Universal Test Engine
No. 048: Storage and Preservation of Rubber Goods, Tires and Tubes, Liberty Ignition System Instruction Board
No. 060: Airplane Tachometers
No. 064: Standard Report on the 300 HP Hispano-Suiza Aviation Engine with Steel Cylinders
No. 066: Foster Modification in Liberty Delco Switch Assembly
No. 116: Standard Test of Hercules Spark Plugs
No. 118: Lubricating Oils-Specifications and Method for Testing
No. 122: Standard Fifty-Hour Endurance Test of Three-Cylinder Lawrance Aviation Engine
No. 124: Test of Revisions in Cooling Systems for Air-Cooled Cylinders
No. 126: Starting Torque on Liberty, Hispano-Suiza, and other Aviation Engines
No. 127: Standard Engine Report of Hall-Scott Engine, Type L-6, Rated at 200 HP at 1,700 RPM
No. 130: Standard 50-Hour Endurance Test of Packard Aviation Engine Model 1A-1116
No. 131: Torque Stand and Flight Test of Compression Relief Device on the 300 HP Hispano-Suiza Aviation Engine
No. 134: Flight Test of Packard Fuelizer on Liberty 12
No. 135: Standard Fifty-Hour Endurance Test of Packard Model 1A-744 8-Cylinder Aviation Engine
No. 137: Destructive Whirling Test of Aero Marine Propeller
No. 138: Calibration of Six Cylinder 185 HP BMW German Aviation Engine Prior to Bureau of Standards Altitude Test
No. 143: Report on Performance and Design of Five Representative Geared Aviation Engines
No. 145: Investigation of Steel Propeller X-14849
No. 149: Fifty-Hour Endurance Run of Hall-Scot Model L-6 Aviation Engine
No. 151: Report on the Delco Automatic Generator Cut-Out
No. 157: Standard Engine Report on the British 450 H.P. Napier-Lion Engine
No. 158: Test of Stromberg Inverted Carburetor Model NA-L5 on the 12-Cylinder Liberty Aviation Engine
No. 159: Test of Hispano-Suiza Model K (Cannon Model) 300 H.P. 8-Cylinder Engine, Rated at 300 H.P. at 1,800 R.P.M.
No. 160: Air Service Technical Orders No 18
No. 161: Air Service Technical Orders No 19
No. 162: Air Service Technical Orders No 20
No. 163: Air Service Technical Orders No 21
No. 167: Standard Engine Report on ABC Wasp Radial Aeronautical Engine Rated at 170 H.P. at 1,800 R.P.M.
No. 168: Test of Lucas Electric Engine Starter
No. 170: Fifty-Hour Endurance Test of 300 HP Hispano-Suiza Aviation Engine at High Speeds
No. 175: Instructions for Installing 85-A Mixture Control in Zenith US-52 Carburetors
No. 177: Test of Issotta-Fraschini 6-Cylinder Model V-6 Aviation Engine Rated at 250 H.P. at 1,650 R.P.M.
No. 179: Report of Wind-Tunnel Test of the Effect of Rake Angle on Suction in Exhaust Stubs
No. 190: Test of Odier Portable Engine Starter
No. 191: Standard Engine Report on Rausie Model E-6 Aviation Engine Rated at 175 H.P. at 1,650 R.P.M.
No. 192: Ten-Hour Endurance Test of Lawrance All-Aluminum Cylinder
No. 199: Test of a Standard Liberty Cylinder Mounted on a Universal Engine Crankcase
No. 205: Standard Engine Test of Almen Barrel Type Engine
No. 209: One Hundred Hour Endurance Flight Test of Model 1-A Brewster-Goldsmith Spark Plugs
No. 216: The Use of Commercial Low-Test Automobile Gasoline in Aviation Engines
No. 218: Report on the Performance of the 5.5-inch by 6.5-inch Smith Cylinder Unit
No. 222: A Metallurigical Report on Materials Used in Foreign Aeronautical Engines
No. 223: Induction System Pressures in Liberty 12 and 300 HP Hispano-Suiza Aeronautical Engines
No. 227: Operating Liberty 12 and Wright-Hispano 300-HP Engines on Automobile Gasoline
No. 239: The 1920 Model Hart Reversible Propeller Manual and Parts List
No. 245: Cooling System Flight Tests of the VCP-1 with Annular Radiator
No. 246: Metal Tipping of Aircraft Propellers
No. 249: Report on the Standard Test of the A.C. Spark Plugs
No. 251: Standard Report on Walker Radial Engine
No. 252: Standard Engine Report on ABC Dragonfly Aviation Engine Rated at 320 HP at 1,650 RPM
No. 257: Instructions to Pilots for the use of Mixture Controls
No. 261: Performance of the Twelve-Cylinder Liberty Engine with a Compression Ratio of 6.5 to 1
No. 265: Report on Tests of A.B.C. "Dragonfly" Cylinder
No. 269: Test of Packard 12-Cylinder Model 1A-2025 Aviation Engine Rated at 550 H.P at 1,800 R.P.M.
No. 272: Fifty-Hour Endurance Test of Curtiss Model C-6 Aviation Engine
No. 273: Report on Standard Test of Mosler Spark Plugs, Model M-1
No. 279: Fifty-hour Endurance Test of Hispano-Suiza 300 HP Model H Engine with Cracked Crankcase
No. 281: The Sylphon Fuel Pump for Liberty 12 and Wright Model H Engines
No. 284: Performance of the Packard Model 1A-1116 Aviation Engine with 6.5:1 Compression Ratio
No. 291: Instructions to Designers of Aircraft Carburetors
No. 293: Comparative Flight Performance of Liberty Engines Equipped with 5.42 and 6.5 Compression Ratios
No. 308: Investigation of the Effect of Doped Fuels on Fuel System
No. 309: Test to Improve Fuel-Consumption Characteristics of the Stromberg Type NA-D6 Carburetor on the 300 HP Hispano-Suiza Engine
No. 314: Instructions for Stromberg NA-L5 Double Venturi Inverted Type Airplane Carburetor
No. 317: Method for Estimating Power and Fuel Consumption of Normal Compression Aviation Engines in Flight at Various Altitudes
No. 319: Elimination of Detonation by the Addition of Xylidine, Ortho-Toluidine, Benzol, and General Motors Anti-Knock No. 1
No. 324: Fifty-Hour Endurance Test of Rausie E-6 Aviation Engine
No. 325: Standard Engine Report of Aeromarine Model U-8-D Aviation Engine Rated at 180 HP at 1,750 RPM
No. 326: Fifty-Hour Endurance Run of Model W-1 Engine
No. 329: Standard Engine Report on Curtiss Model C-6 Aviation Engine Rated at 160 HP at 1,750 RPM
No. 330: Standard Engine Report on Curtiss Model C-12 Geared Aviation Engine Rated at 400 HP at 2,250 RPM
No. 333: Report of Test of 300 HP Hispano-Suiza Model H Engine Fitted with Pistons Which Give a 6.5:1 Compression Ratio
No. 336: Effect of Fuel Head at Carburetor on Brake Horsepower and Brake Specific Fuel Consumption
No. 344: Report on the Performance of the Wright Model H-2 "Superfighter" Engine
No. 347: Air Service Technical Orders No 22
No. 348: Air Service Technical Orders No 23
No. 349: Air Service Technical Orders No 24
No. 350: Air Service Technical Orders No 25
No. 351: Air Service Technical Orders No 26
No. 354: Variation in Performance of a Hispano-Suiza (Model E) Engine with Degree of Throttle Opening
No. 356: Variation in Volumetric Efficiency of an Engine with Valve Lift
No. 357: Report on Test of Bijur Ignition End Starter for Airplane Engines
No. 361: Carburetion, Heat Rejection, and Weight Data of U.S. Model W-1 Engine
No. 368: Tests of Back Suction and Air Bleed Type Mixture Controls in Flight
No. 369: The Bellows (Sylphon) Fuel Pump for Liberty 12 and Wright Model H Engines
No. 370: Test of a Zenith Carburetor, Model U.S. 52, Fitted with Plain Tube and Britton Type Discharge Nozzles
No. 372: Flight Test of Anti-Knock Injector
No. 373: Test of Curtiss Eight-Cylinder Model OX-5 Engine Rated at 90 HP at 1,400 RPM
No. 375: Curves for Estimating Aviation Engine Fuel Consumption Based on Displacement and RPM
No. 377: Air Service Technical Orders No 27
No. 378: Air Service Technical Bulletin (Formerly Technical Orders) No 28
No. 379: Air Service Technical Bulletin (Formerly Technical Orders) No 29
No. 380: Air Service Technical Bulletin (Formerly Technical Orders) No 30
No. 383: The Effect of Doped Fuels on the Fuel System
No. 390: Sediment Deposit in Carburetors
No. 396: Test of Machine Gun Synchronizer Type C-8
No. 399: Test of Supercharger Air Coolers
No. 401: Investigation of the Effects on Cylinder Performance of Variation of Position and Number of Spark Plugs
No. 405: Description of Carburetor Test Chamber and Method of Making Computations
No. 410: Cooling System Flight Test of TW-1 Airplane
No. 421: Standard Method of Engine Calculations
No. 422: Test to Determine Minimum Fuel Head to Operate Liberty 12 Engine on Propeller Load
No. 423: Mathematical Analysis of Liberty 12 and the Packard 2025 Camshaft Drive Gear Stress
No. 439: The De Bothezat Barograph, Type "A"
No. 442: Development of Stromberg Inverted Type Model NA-L5 Carburetors
No. 447: Stress Analysis of the Model W-1 Engine
No. 450: Alcohol-Gasoline Mixtures
No. 451: Comparison Tests of Storage Preparations for Aviation Engine Storage of Less Than Six Months
No. 458: The Bellows (Sylphon) Fuel Pump for Liberty 12 and Wright H Engines
No. 464: Engine Driven Gear Fuel Pumps Type C
No. 504: Instructions for Reinforcing Liberty Cylinders
No. 505: Computing the HP Available from Engines with Two-Bladed Propellers
No. 523: First Full Throttle Endurance Test of Liberty Engine Equipped with Various Experimental Materials
No. 525: Comparison of Piston Side Thrust in the Modified R-1, 400 HP Radial Engine and Single Cylinder Test Engine
No. 550: Standard Engine Tests of Curtiss D-12 High and Low Compression Engines
No. 551: First 50-Hour Test of the Air Cooled Liberty Engine
No. 570: Development and Test of Zenith ED-52 Carburetor for Liberty 12 Engine
No. 572: Development and Test of Stromberg NA-Y5D Carburetor for Curtiss D-12 Engine
No. 575: Air Service Technical Bulletin No 49
No. 576: Air Service Technical Bulletin No 50
No. 589: Power Plant Laboratory Standard Test Methods and Computation
No. 594: Exhaust Equipment Temperature Determinations
No. 595: Comparison of Flight Tests of a Number of Wood Propellers with Wind Tunnel Tests on a Series of Wood Propeller Models
No. 596: Fire Hazard Tests of Ignition Equipment
No. 611: Aircraft Ignition, Recent Developments
No. 630: Dynamometer Carburetion Runs on Curtiss GV-1570 Engines
No. 638: Test of Standard Water-Cooled Liberty 12 Engine with Various Piston Rings and Arrangements
No. 648: Instructions for Assembly of Detachable Blade Propellers
No. 670: The Mechanical Difficulties of Prestone Cooling at 300° F Outlet Temperature
No. 682: Indicator Study of SV-1570 Engine
Air Service Technical Orders No. 1
Air Service Technical Orders No. 2
Air Service Technical Orders No. 3
Air Service Technical Orders No. 4
Air Service Technical Orders No. 5
Air Service Technical Orders No. 6
Air Service Technical Orders No. 7
Air Service Technical Orders No. 8
Air Service Technical Orders No. 9
Air Service Technical Orders No. 10
Air Service Technical Orders No. 11
Air Service Technical Orders No. 12
Air Service Technical Orders No. 13
Air Service Technical Orders No. 14
Air Service Technical Orders No. 15
Air Service Technical Orders No. 16
Air Service Technical Orders No. 17
Air Service Engineering Division Special Report
Air Service Materiel Division Activity Report