The Martin JRM Mars was the largest Allied production flying boat ever built — a four-engine, long-range transport conceived for the U.S. Navy's transoceanic logistics requirements and ultimately converted into the most capable aerial firebombers in history. Online Aviation Library has assembled the surviving primary-source technical documentation spanning the full JRM family, from the original Navy transport operations through the civilian Forest Industries Flying Tankers conversions that kept the Mars flying into the 21st century.

What This Collection Covers

Pilot's Handbooks

• AN 01-35CA-1 — Pilot's Handbook for Navy Model JRM-1 Airplane. Published under joint authority of the Commanding General, Army Air Forces, and the Chief of the Bureau of Aeronautics. Dated 15 January 1946. Formerly classified Restricted. Supersedes AN 01-5CA-1 dated 1 September 1945. Note: Appendix I of this publication was not to be carried in aircraft on combat missions or when there was a reasonable chance of its falling into enemy hands.
• AN 01-35CA-1 (Revision Notice) — Pilot's Handbook for Navy Model JRM-1 Airplane, Revision Notice. Dated 15 May 1946; Revised 15 November 1947. Supersedes AN 01-35CA-1 dated 15 January 1946. Includes the in-flight photograph of the JRM-1 in U.S. Navy markings over clouds — one of the most iconic surviving primary-source images of the aircraft.
• Pilot's Handbook — JRM-3 Mark II, CF-LYL — Civil-registered Pilot's Handbook for the JRM-3 Mark II in Canadian registration CF-LYL, as operated by Forest Industries Flying Tankers Ltd. The distinctive royal blue binder with typewritten label is a rare surviving example of the civilian firebomber operational documentation.

Aerodynamic Reports & Wind-Tunnel Studies

Official wartime testing focused heavily on ground effect and water taxiing configurations:

• 1/25-scale powered model testing: NACA/NASA historical wind-tunnel tests evaluating aerodynamic forces close to the water surface, including stalling characteristics of the modified wing profile
• Tip float aerodynamics: lateral and directional stability studies for the outboard tip floats, protecting the massive 200-ft wings during high-speed water taxiing
• Hull design variations: comparative reports evaluating modified hull designs for larger gross weights, tracking the transition from the prototype XPB2M-1 to the optimized production JRM with its longer, more aerodynamically efficient nose

Engine Technical Notes

Propulsion documentation covers all production variants and their retrofits:

• Wright R-3350 Duplex-Cyclone (JRM-1 / JRM-3): Four 18-cylinder engines producing 2,200–2,500 hp each. Technical notes focus on managing cylinder head temperatures during long, low-altitude flights.
• Pratt & Whitney R-4360 Wasp Major (JRM-2 Caroline Mars): Four 28-cylinder engines yielding 3,000 hp each, with fully reversible propellers on the inboard engines for backward water taxiing and shortened landing distances.
• Water operations start protocol: flight engineer notes detailing the staggered engine start sequence (engine 2 or 3 first in calm water) to establish immediate directional hydrodynamic control over the 165,000 lb vessel.

Handling & Stability Studies

• Longitudinal control: wind-tunnel data confirming the elevator design's exceptional authority across all specified CG envelopes in landing configuration
• Hydrodynamic stability: rear fuselage width and keel depth adjustments engineered to mitigate porpoising (uncontrolled longitudinal pitching oscillations) during water step acceleration
• Water scooping sequence: handling reports documenting the critical pilot/co-pilot coordination when hull scoops are lowered at speed — the co-pilot must rapidly advance throttles to counter sudden hydrodynamic drag while the aircraft takes on over a ton of water per second

Engineering Bulletins & Modifications

• XPB2M-1 to JRM conversion: bulletins covering removal of defensive turrets, replacement of twin slanted tail fins with a single large vertical stabilizer, and rear fuselage widening
• JRM-3 upgrade standard: post-WWII bulletins detailing conversion of surviving JRM-1 aircraft to JRM-3 standard, including upgraded Wright R-3350-24WA powerplants
• Civilian fire tanker conversions (1960s): Forest Industries Flying Tankers blueprints covering removal of cargo decking, installation of the four-section 7,200-gallon water tank matrix, internal gel-mixing concentrate tanks, and retractable pneumatic hull scoops

Performance Data Reference

Document Manifest

⚠️ Regulatory Notice: Under FAA 14 CFR § 43.13 and EASA Part-M, any mechanic performing maintenance on an active aircraft must use current, manufacturer-approved revision-controlled data. This archival document does not satisfy that requirement.

This is an archival, static-copy edition fixed at its original publication date. Intended for historical reference, flight simulation, museum restoration, and educational use only. Not approved for active airworthiness maintenance under FAA 14 CFR § 43.13, EASA Part-M, or equivalent international regulations. Operators of active aircraft must use current, revision-controlled publications from the Type Certificate holder or an authorized distributor.

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