Martin JRM Mars

Martin JRM Mars
Hawaii Mars
Hawaii Mars

Role Flying boat
First flight : 23 June 1942
Status : only one airplane in service
Introduced : 30 November 1943
Retired: 1956 (USN)
Produced: 1945-1948
Number built : 7
Primary users: United States Navy
Coulson Flying Tankers
List of Martin JRM Mars airplanes

Caroline Mars
Caroline Mars

Hawaii Mars undergoing an overhaul
Hawaii Mars undergoing an overhaul

The Martin JRM Mars is a large cargo transport seaplane intended initially to be used by the United States Navy during the Second World War. With four engines and a length of 35,74 m (117 ft) was the largest of the Allied flying boats. During its 3 years production run only 7 aircraft were built. These were intended to be used as long range ocean patrol flying boats, they've entered production as the JRM Mars long range transport.

The aircraft that survived the war were converted to firefighting water bombers and one of them is still used occasionally for fighting forest fires. This remaining aircraft is based at Sproat Lake near Port Alberni, British Columbia


The prototype XPB2M-1 Mars was luanched on 8 November 1941 and was in fact a scaled up PBM Mariner patrol bomber by the Glenn L Martin Company. The first flight was performed on 23 June 1942 after a delay caused by an engine fire that occured during ground runs. Test flights were conducted between 1942 and 1943 and then it was handed over to the Navy. By this time the original patrol bomber concept was considered obsolete so the Mars was converted into a transport aircraft under the designation XPB2M-1R. After initial trials the US Navy ordered 20 modified JRM-1 Mars.


The first aicraft was delivered in June 1945 and it was named Hawaii Mars. However due to the end of the 2nd World War the Navy decided to downscale and cancelled the order except the five aircraft that were already on the production line. These five Mars were completed and delivered to the Navy in 1947. The original Hawaii Mars was lost just weeks after its first flight in an accident at Chesapeake Bay.

Operational Service

In service with the U.S. Navy

The five production aircraft that were delivered to the U.S.Navy were named Marianas Mars, Philippine Mars, Marshall Mars, Caroline Mars and a second Hawaii Mars. These aircraft were used by the navy primarily for ferrying cargo to Hawaii and the other Pacific Islands. The Caroline Mars the last production aircraft was designated as JRM-2 receiving 3,000 hp (2,200 kW) Pratt and Whitney R-4360 engines and other improvements. The maximum weight of this aircraft was also increased. On 4 March 1949 the Caroline Mars set a new world passenger load record by carrying 269 people from San Diego to Alameda, California. Unfortunately the Marshall Mars was lost on 5 April 1950 near Hawaii due to an engine fire that consumed the airplane (the crew successfully evacuated the airplane). The remaining "Big Four" remained in service until 1956 carrying record amounts of cargo between Honolulu and San Francisco. After they were withdrawn from service they were beached at NAS Alameda.

Civilian service

In 1959 the Navy put up the remaining aircraft to be sold for scrap. Several forest companies from British Columbia formed a new company named "Forest Industries Flying Tankers" (FIFT) and this company bid for the four aircraft and the considerable amount of spares. The bid was accepted and the sale completed in December 1959. The aircraft were flown to Fairey Aviation at Victoria, British Columbia for conversion into water bombers. A large tank was installed in the cargo bay and also a retractable pick-up scoop was fitted on the aircraft. This way the aircraft was able to scoop water while taxiing at a rate of 30 tons in 22 seconds. Some time later further water tanks were installed replacing a few of the hull fuel tanks.


  • XPB2M-1- Model 170 prototype long-range patrol flying boat, powered by four Wright R-3350-8 piston engines. Only one was built and was later converted to XPB2M-1R
  • XPB2M-1R - Prototype, converted in December 1943 as a prototype transport version. The armament was removed, additional cargo hatches were installed, existing hatches were enlarged, further cargo loading equipment were installed and decking was reinforced.
  • JRM-1 - Model 170A, long range transport variant. Out of the 20 initially ordered aircraft only six were to be delivered. Single-tail design with longer hull and fewer bulkheads and also a higher maximum take-off weight. The aircraft was fitted with equipment for overhead cargo handling. The engines were four Wright R-3350-24WA Cyclone engines with 4-bladed propellers. In the end only five were built and the surviving four aicraft were converted to JRM-3
  • JRM-2 - The last JRM-1 on order by the Navy was converted to the JRM-2. The modifications included the new 3,000 hp Pratt and Whitney R4360-4T engines with 4-blade, 16ft, 8 in diameter Curtiss Electric propellers. The gross weight was also increased by 20,000 lb (~9072 kg).
  • JRM-3 - Model 170B. The four remaining JRM-1's were converted to this specification. New 2,400 hp Wright R3350-24WA engines with 16ft, 8 in Curtiss Electric propellers. The two inboard engines were also fitted with reversible-pitch devices.

Aircraft list

  • The Old Lady - Bureau Number (BuNo) 1520
  • Hawaii Mars I - JRM-1, BuNo 76819
  • Phillipine Mars - JRM-1, BuNo 76820
  • Marianas Mars - JRM-1, BuNo 76821
  • Marshall Mars - JRM-1, BuNo 76822
  • Hawaii Mars II - JRM-1, BuNo 76823
  • Caroline Mars - JRM-1, BuNo 76824

Specifications (for version JRM-3 Mars)

General characteristics

  • Crew: four (with possibility to accommodate a second relief crew)
  • Capacity: JRM Mars - 133 troops, or 84 litter patients and 25 attendants or 32,000 lb (15,000 kg) payload
  • Water/foam load: Mars waterbomber - 60,000 lb (27,000 kg)
  • Length: 117 ft 3 in (35.74 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
  • Wingspan: 200 ft 0 in (60.96 m)
  • Hull draught: 5 ft 6 in (1.68 m)
  • Wing area: 3,686 sq ft (342.4 m2)
  • 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)
  • 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)
  • 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


  • Range: 4,948 mi; 7,964 km (4,300 nmi)
  • Maximum speed: 221 mph (356 km/h; 192 kn)
  • Cruise speed: 190 mph (165 kn; 306 km/h)
  • Service ceiling: 14,600 ft (4,450 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)

Further reading

List of seaplanes and amphibious aircraft

Martin PBM Mariner

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