Martin Aircraft

Martin JRM Mars

Martin JRM Mars

Transport Aircraft

Martin Aircraft

The Martin JRM Mars is a large, four-engined cargo transport flying boat designed and built by the Martin Company for the United States Navy during World War II

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Martin JRM Mars

The Martin JRM Mars is a large, four-engined cargo transport flying boat designed and built by the Martin Company for the United States Navy during World War II. It was the largest Allied flying boat to enter production, although only seven were built. The United States Navy contracted the development of the XPB2M-1 Mars in 1938 as a long-range ocean patrol flying boat, which later entered production as the JRM Mars long-range transport.

Four of the surviving aircraft were later converted for civilian use to firefighting water bombers. Two of the aircraft still remain based at Sproat Lake just outside of Port Alberni, British Columbia, although neither are operational.


The Glenn L. Martin Company scaled up their PBM Mariner patrol bomber design to produce the prototype XPB2M-1 Mars.[1] The XPB2M-1 was launched on 8 November 1941. After a delay caused by an engine fire during ground runs, the aircraft first flew on 23 June 1942. After flight tests with the XPB2M between 1942 and 1943, she was passed on to the Navy. The original patrol bomber concept was considered obsolete by this time, and the Mars was converted into a transport aircraft designated the XPB2M-1R. The Navy was satisfied with the performance, and ordered 20 of the modified JRM-1 Mars.[1] The first, named Hawaii Mars, was delivered in June 1945, but with the end of World War II the Navy scaled back their order, buying only the five aircraft which were then on the production line.[2] Though the original Hawaii Mars was lost in an accident on the Chesapeake Bay a few weeks after it first flew, the other five Mars were completed, and the last delivered in 1947.

Martin Transport


RoleFlying boat
National originUnited States
ManufacturerGlenn L. Martin Company
First flight23 June 1942
Introduction30 November 1943
Retired1956 (USN)
StatusLimited use
Primary usersUnited States Navy
Coulson Flying Tankers Inc.
Number built7
Developed intoMartin 193


Named the Marianas Mars, Philippine Mars, Marshall Mars, Caroline Mars, and a second Hawaii Mars, the five production Mars aircraft entered service ferrying cargo to Hawaii and the Pacific Islands on 23 January 1944.[3] The last production airplane (the Caroline Mars) was designated JRM-2, powered by 3,000 hp (2,200 kW) Pratt & Whitney R-4360 engines, and featured a higher maximum weight and other improvements. On 4 March 1949, the Caroline Mars set a new world passenger load record by carrying 269 people from San Diego to Alameda, CA.[4] On 5 April 1950, the Marshall Mars was lost near Hawaii when an engine fire consumed the airplane after her crew had evacuated. The remaining “Big Four” flew record amounts of Naval cargo on the San FranciscoHonolulu route efficiently until 1956, when they were beached at NAS Alameda.[1]

Specifications (JRM Mars)

General characteristics

  • Crew: 6 or 7: Aircraft Commander, Pilot, Navigator, Flight Engineer, Radio Operator, 2 Loadmasters
  • Capacity: 200 troops / 123 litter patients with 45 ambulatory patients and 15 medical staff. Maximum payload 74,000 lb (34,000 kg)
  • Length: 130 ft 5 in (39.75 m)
  • Wingspan: 174 ft 1.5 in (53.073 m)
  • Height: 48 ft 3.5 in (14.719 m)
  • Wing area: 2,506 sq ft (232.8 m2)
  • Empty weight: 101,165 lb (45,888 kg)
  • Gross weight: 185,000 lb (83,915 kg)
  • Max takeoff weight: 194,500 lb (88,224 kg)
  • Fuel capacity: 11,128 US gal (9,266 imp gal; 42,120 l) ; 2x 30 US gal (25 imp gal; 110 l) water/alcohol tanks
  • Powerplant: 4 × Pratt & Whitney R-4360-63A Wasp Major 28-cylinder air-cooled radial piston engines, 3,800 hp (2,800 kW) each with water/alcohol injection
  • Propellers: 3-bladed Curtiss Model C634S-C402, 16 ft 6 in (5.03 m) diameter fully-feathering reversible-pitch constant-speed propeller

General characteristics

  • Crew: four (with accommodations for a second relief crew)
  • Capacity: JRM Mars – 133 troops, or 84 litter patients and 25 attendants or 32,000 lb (15,000 kg) payload, including up to seven Willys MB jeeps
  • Water/foam load: Mars waterbomber – 60,000 lb (27,000 kg)
  • Length: 117 ft 3 in (35.74 m)
  • Wingspan: 200 ft 0 in (60.96 m)
  • Width: 13 ft 6 in (4.11 m) Hull beam
  • Height: 38 ft 5 in (11.71 m) afloat, 48 ft (15 m) beached
  • Hull draught: 5 ft 6 in (1.68 m)
  • Wing area: 3,686 sq ft (342.4 m2)
  • Empty weight: 75,573 lb (34,279 kg)
  • Gross weight: 90,000 lb (40,823 kg)
  • Max takeoff weight: 165,000 lb (74,843 kg)
  • Fuel capacity: Hawaii Mars: 6,485 US gal (24,550 l; 5,400 imp gal) Philippine Mars: 13,200 US gal (50,000 l; 11,000 imp gal)
  • Powerplant: 4 × Wright R-3350 Duplex-Cyclone 18-cylinder radial engines, 2,500 hp (1,900 kW) each
  • Propellers: 4-bladed Curtiss Electric, 15 ft 2 in (4.62 m) diameter variable-pitch propellers


 . Maximum speed: 221 mph (356 km/h, 192 kn)

 . Cruise speed: 190 mph (310 km/h, 170 kn)

 . Range: 4,900 mi (8,000 km, 4,300 nmi)

 . Service ceiling: 14,600 ft (4,500 m)

 . Drop speed: 138 mph (120 kn; 222 km/h)

 . Landing approach  . speed: 115 mph (100 kn; 185 km/h)

 . Touchdown speed: 92 mph (80 kn; 148 km/h)

 . Fuel consumption (cruise): 420 US gal (1,600 l; 350 imp gal) per hour

 . Fuel consumption (operations): 780 US gal (3,000 l; 650 imp gal) per hour

 . Operations duration (normal): 5 1/2 hours

 . Area covered, single drop: 3 to 4 acres (1.2 to 1.6 ha)

 . Drop height: 150 to 200 ft (46 to 61 m)

 . Full water tank load: 7,200 US gal (27,000 l; 6,000 imp gal)

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