The Martin JRM Mars was the largest flying boat ever to enter production. The US Navy contracted the development of the Mars in 1935 as a massive transport aircraft.

Navy service

The Martin Company effectively scaled up their successful PBM Mariner patrol bomber design to produce a prototype designated the XPB2M-1R Mars. After flight tests with the XPB2M between 1941 and 1943, she was passed on to the Navy which ordered 20 of the new JRM Mars based on the XPB2M. The first, named Hawaii Mars, was delivered in June 1945, but the with the end of World War II the Navy scaled back their order to just 5 more boats. Though the original Hawaii Mars was lost in an accident on Chesapeake Bay, the other 5 Mars were built with the last delivered in 1947.

Named the Marianas Mars, Phillipine Mars, Marshall Mars, Caroline Mars, and a second Hawaii Mars, the 5 production Mars aircraft entered service ferrying cargo to Hawaii and the Pacific Islands. On May 5, 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 cargo on the San Francisco-Honolulu route efficiently until 1956, when they were parked at NAS Almeda.

Civilian use

In 1959, the remaing Mars were sold for scrap. A consortium of British Columbia lumber companies' representative, Dan McIvor, recognized their potential value as water bombers and had them converted. A company called Flying Tankers Inc. was formed, and purchased the "Big Four" for aerial firefighting. The Marianas Mars crashed in 1961 and the Caroline Mars was destroyed in a hurricane while parked onshore in 1962. The remaining Hawaii Mars and Phillipine Mars had their conversions to water bombers accelerated and entered service in 1963. The airtankers are still operated by Flying Tankers Inc., now a subsidiary of TimberWest Forest Ltd. and are based at Sproat Lake, near Port Alberni, British Columbia. When converted, the original powerplants were replaced with four Wright Cyclone R-3350-24WA engines of 2500 hp (1860 kW) each. The aircraft can carry up to 7,200 US gal (27,250 litres) of water, enough to cover an area of 4 acres (1.6 ha). They are used to fight fires along the coast of British Columbia, and even sometimes on the interior. They also make appearances at local airshows, demonstrating their water-dropping ability.

Specifications (JRM-2 Mars)

General Characteristics

• Crew: 7
• Capacity: 133 troops, 84 litters + 25 seats, or 16 tons (15 metric tons) of cargo.
• Length: 117 ft 3 in (35.74 m)
• Wingspan: 200 ft 0 in (60.96 m)
• Height: 38 ft 5 in (11.71 m)
• Wing area: ft² ( m²)
• Empty: 75,573 lb (34,279 kg)
• Loaded: 165,000 lb (74,800 kg)
• Maximum takeoff: lb ( kg)
• Powerplant: 4x Pratt & Whitney R-4360-4T Wasp Major 28-cylinder 4-row radials, 3,000 hp (2,240 kW) each

Performance

• Maximum speed: 221 mph (356 km/h)
• Range: 4,300 nautical miles (5,000 miles or 8,000 km)
• Service ceiling: 14,600 ft (4,450 m)
• Rate of climb: ft/min ( m/min)
• Wing loading: lb/ft² ( kg/m²)
• Power/Mass: hp/lb ( kW/kg)

External link

• Additional History (http://www.vectorsite.net/avmars.html#m5)
• Flying Tankers Inc's homepage with information on the Mars. (http://www.martinmars.com/)

Related content

Related development: PBM Mariner

Comparable aircraft: Blohm & Voss BV 222

Designation sequence: JRM