Pratt & Whitney R-985 Wasp Junior Aircraft Engine Manuals Collection

This structured collection brings together the essential technical documentation for the Pratt & Whitney R-985 Wasp Junior — one of the most widely produced and enduring radial piston engines in aviation history. Spanning overhaul manuals, service instructions, parts catalogs, organizational maintenance references, and original factory training material, this collection covers the full breadth of variants from the early civilian B-series through the military AN-series and the helicopter-optimised B4/B5 configurations.

Definitive Collection with Free Lifetime Updates

This is a living collection that we continuously expand and refine. As we acquire additional R-985 documentation, technical bulletins, or variant-specific materials, we update this collection and provide free lifetime updates to all purchasers. Your one-time purchase guarantees access to all future additions and improvements to this collection.

Historical Note

The Pratt & Whitney R-985 Wasp Junior first ran in 1929 and received its Type Certificate in January 1930 — making it one of the earliest certificated aircraft engines still flying today. Evolved directly from the larger R-1340 Wasp, it was conceived as a “Wasp of reduced dimensions,” sharing many parts and mounting dimensions with its parent engine while delivering a more compact and economical powerplant for lighter aircraft.

Manufactured by Pratt & Whitney Aircraft Company, the R-985 is a 9-cylinder, single-row air-cooled radial with 985 cubic inches (approx. 16.14 litres) of displacement, a square bore and stroke of 5.1875 in × 5.1875 in, and a compression ratio of 6.0:1. Power output ranged from 300 hp in the initial Wasp Junior A to 400–450 hp in the supercharged B-series variants. Dry weight runs approximately 640–684 lbs depending on model. The engine features a gear-driven single-speed centrifugal supercharger, a one-piece master rod for reliability, and an exceptional power-to-weight ratio for its era. Fuel requirements are 80/87 or 100/130 aviation gasoline.

Production ran from 1929/1930 to 1953, with approximately 39,037 units built. Key variants include the Wasp Junior A (initial 300 hp), the B-series (TB, SB, T1B2 — the most popular, with supercharged versions for altitude performance), and the B4, designed for vertical mounting in helicopters. Military applications were extensive: the Beechcraft Model 18 (C-45 Expeditor), Vultee BT-13 Valiant, Vought OS2U Kingfisher, Boeing-Stearman Model 75, and Sikorsky H-5 helicopter all relied on the R-985. On the civilian side, the engine powered the Beechcraft Model 17 Staggerwing, de Havilland Canada DHC-2 Beaver, Grumman G-21 Goose, and Lockheed Electra.

Today the R-985 remains an active engine. The current Type Certificate is held by Pratt & Whitney (United Technologies/RTX), and active Airworthiness Directives address cylinder head separation and barrel flange cracks.

Manuals Included in This Collection

• Pratt & Whitney Wasp Jr. (985) B4, B5, and Wasp (R-1340) S1H2, S3H1, S3H2 and S3H1-G Engines — Maintenance Manual — Part No. 118611 — April 1962 / Revised May 1974
• T.O. 2R-R985-5 (formerly T.O. 02A-10A-5) — Overhaul Changes Applicable to Pratt and Whitney R-985 Series Engines — Revision Notice — 1 June 1954 / Revised 1 June 1956
• T.O. No. 02-10AB-1 — Handbook of Operation Instructions — R-985 Series Aircraft Engines — Published by Authority of the Commanding General, Army Air Forces, Air Service Command, Patterson Field, Ohio — December 15, 1942
• AN 02A-10AB-4A — Parts Catalog — Models R-985-AN-1, -3, -6 and -12 Aircraft Engines — Revision Notice — 15 February 1951 / Revised 15 March 1952
• Illustrated Parts Catalog — Wasp Jr. AN-1, -3, -4, -6, -6B, -10, -12, -12B, -14B, B3, B4, and B5 Engines — Part No. 121519 — Pratt & Whitney Aircraft Group, United Technologies — Reissued August 1965 / Revised February 1978
• AN 02-10AC-3 — Overhaul Instructions for R-985-AN-5 and -AN-7 Aircraft Engines — Published under joint authority of the Commanding General, Army Air Forces, the Chief of the Bureau of Aeronautics, and the Air Council of the United Kingdom — Ross-Gould Co., St. Louis — 1 August 1944 / Revised 1 March 1945
• (Navy) AN 02A-10AC-4 / (USAF) T.O. No. 2R-R985-14 — Parts Catalog for Models R-985-AN-5 Aircraft Engines — 1 September 1956 / Revised 1 December 1958
• Overhaul Manual — Wasp Jr. B, Wasp H1 and Hornet E Series Engines — Pratt & Whitney Aircraft, Division of United Aircraft Corporation, East Hartford, Connecticut — January 1938
• TM 1-2R-R985-4 — Department of the Army Technical Manual — Parts Catalog Aircraft Engines — Models R-985AN-1, -3, -6, -12, -14B, -39 and -39A — Headquarters, Department of the Army — May 1962
• T.O. No. 02-10AB-3 — Overhaul Instructions — R-985 Series Aircraft Engines — Restricted — Central Press Inc., Marion, Indiana — June 1, 1940 / Revised September 15, 1943
• (Navy) NAVWEPS 02A-10AB-4A / (USAF) T.O. 2R-R985-4 (formerly AN 02A-10AB-4A) — Parts Catalog — Models R-985-AN-1, -3, -14B, -39, and -39A Aircraft Engines — Pratt & Whitney Aircraft, Division of United Aircraft Corporation — 15 December 1957 / Revised 1 November 1965
• T.O. No. 02-10AB-2 — Handbook of Service Instructions — R-985 Series Aircraft Engines — Restricted — Air Service Command, Patterson Field, Fairfield, Ohio — February 10, 1940 / Revised March 1, 1943 — ex-Lockheed Aircraft Corp.
• TM 55-2810-224-24 — Technical Manual — Organizational, DS, and GS Maintenance Manual — Aircraft Engine Model R985-39A — Headquarters, Department of the Army — 29 October 1970 (includes Changes 1 through 5)
• T.O. No. 02-10AB-1 — Handbook of Operating Instructions — R-985 Series Aircraft Engines — Restricted — Manz Corporation, Chicago — March 1, 1943
• T.O. No. 02-10AB-2 / A.P. 2043A — Service Instructions — R-985-A, -B, -9, -11, -13, -21, -23, -25, -27, -AN-1, -AN-3 Aircraft Engines — Restricted — Ross-Gould Co., St. Louis — February 10, 1940 / Revised March 10, 1944
• AN 02-10AC-2 — Service Instructions — R-985-AN-5 and AN-7 Aircraft Engines — Restricted — Published under joint authority of the Commanding General, Army Air Forces, the Chief of the Bureau of Aeronautics, and the Air Council of the United Kingdom — D.F. Keller Co. — 1 July 1944 / Revised 20 September 1944
• NAVWEPS 02A-10AB-3 / T.O. 2R-R985-3 — Handbook Overhaul Instructions — Models R-985-AN-1, AN-3, AN-14B, -39, and -39A Aircraft Engines — Revision Notice — Published under Authority of the Secretary of the Air Force and the Chief of the Bureau of Naval Weapons — 15 July 1950 / Revised 1 December 1962
• TM 55-2810-224-20P — Department of the Army Technical Manual — Organizational Maintenance Repair Parts and Special Tools List — Engine, Aircraft, Reciprocating (Pratt and Whitney) — FSN 2810-624-0647 (R985AN39) / 2810-624-0648 (R985AN39A) — Headquarters, Department of the Army — September 1970
• NAVWEPS 02A-10AB-2 — Technical Manual — Service Instructions — Navy Models R-985-AN-1, -3, -14B, -39, -39A Aircraft Engines — Pratt & Whitney Aircraft, Division of United Aircraft Corporation — 1 December 1965 (replaces NAVWEPS 02A-10AB-2 dated 1 May 1952, Changed 1 October 1955)
• TM 1-2R-R985-2 — Department of the Army Technical Manual — Service Instructions — Models R-985-AN-1, -3, -39, and -39A Engines — Headquarters, Department of the Army — February 1961
• Overhaul Tool List — For 25 Overhauls Per Month — R-985-AN1, -B3, -B4 & -B5 Engines — Pratt & Whitney Aircraft, Division of United Aircraft Corporation, East Hartford, Connecticut — December 11, 1952
• Pratt & Whitney Aircraft — Service School Handbook — Supplementary training material covering R-985 & R-1340 engine design details, gear-driven supercharger operation, cam and valve operation, ignition systems, pressure injection carburetors, aircraft fuels, engine cooling, ground operation, operating curves, and engine trouble shooting — Pratt & Whitney Aircraft, Division of United Aircraft Corporation, East Hartford, Connecticut — April 1948

This collection spans 22 documents covering the full variant range — from the earliest civilian A/B-series service instructions (1938–1940) through wartime Army Air Forces and joint Allied publications (1943–1945), post-war Navy and USAF dual-authority manuals (1950–1965), Army Technical Manuals (1961–1970), and the definitive United Technologies illustrated parts catalog (1978). The inclusion of the 1948 Pratt & Whitney Service School Handbook provides unique factory-level engineering context available nowhere else.

Engineering Norms and Standards

R-985 documentation follows Pratt & Whitney’s established engineering practices and the military Technical Order (T.O.) system, with civilian manuals conforming to CAA/FAA airworthiness standards of their respective eras. Military variants are governed by Army Air Forces and later USAF T.O. numbering (02-10AB-x, 02-10AC-x, TM 55-2810-x, TM 1-2R-R985-x series), while the engine’s civilian Type Certificate establishes the baseline airworthiness requirements still referenced by the current TC holder. Overhaul limits, torque values, clearance tables, and inspection intervals in these documents reflect the original manufacturer engineering standards — essential reference data for any restoration or maintenance programme.

Specialized Documentation

Active Airworthiness Directives apply to the R-985, specifically addressing cylinder head separation and barrel flange cracks. Operators and A&P mechanics should cross-reference these manuals with current FAA AD records and any applicable Supplemental Type Certificates for modified installations. Service Bulletins issued by the TC holder (Pratt & Whitney / RTX) may supersede procedures in older documents.

Where to Find Additional Documentation

Official Support: Pratt & Whitney (United Technologies/RTX) holds the current Type Certificate and can provide current service data. Historical Archives: The Smithsonian National Air and Space Museum, EAA (Experimental Aircraft Association), and type-specific clubs (Beechcraft Heritage Museum, Stearman Restorers Association) maintain additional historical records. Specialty Vendors: Overhaul shops specialising in radial engines and Online Aviation Library for additional documentation as it becomes available.

Format and Delivery

All manuals are delivered as high-resolution PDF files, organised by document number and variant for easy navigation. Files are print-ready and fully searchable. Instant download upon purchase — no shipping required.

Files are delivered as a compressed archive (RAR/ZIP). You will need a free extraction tool such as WinRAR or 7-Zip (Windows) or The Unarchiver (Mac) to access the PDF files inside.

Disclaimer: These documents are provided for historical reference and research purposes. Always consult the current Type Certificate holder and applicable Airworthiness Directives before performing maintenance on airworthy aircraft. No guarantee is made as to the completeness or currency of any document for active airworthiness purposes. All trade names and designations remain the property of their respective owners. Copyright © Sicuro Publishing.