Martin 170 Mars / JRM-1
On 23 August 1938 the US Navy ordered from Martin a single prototype of the Martin 170 design for a patrol bomber of flying-boat configuration.
The tip of the tail is almost 50 feet above water level while the wing span is 200 feet, greater than a Boeing 747, and the two level interior is as big as a 15 room house with a long circular staircase connecting the two decks. The control surfaces are all fabric covered.
Designated XPB2M-1, it was the world's largest flying-boat when flown for the first time on 3 July 1942, but by then the United States had become involved in World War II and it was decided not to proceed with procurement of the type as a patrol bomber. Instead, the boat was modified for use in a transport role, becoming re-designated XPB2M-1R and entering service in December 1943. It remains the largest flying-boat to have been operated by the US Navy and an early demonstration of its capability came in 1944, when a 9299kg cargo was delivered to Hawaii in a 7564km round trip completed in only 27 hours 36 minutes, resulting in a US Navy order for a production version under the designation JRM-1 Mars. This covered 20 aircraft to be completed specially for the transport role, but the end of World War II brought contract cancellations and only five were built, plus a single JRM-2 for operation at a higher gross weight. When the five JRM-1s were later modified to this latter standard they became redesignated JRM-3. These 60.96m span aircraft were powered by four 1715kW Wright R-3350-8 engines, and an appreciation of their capacity can be gained from the fact that on 19 May one of them, Marshall Mars, carried a total of 301 passengers, plus its crew of seven.
In ten years of military service between 1946 and 1956 and the five logged some 87,000 accident free hours. They estab-lished the world flying boat lift record of 30,992 kg (68,327 pounds) and carried a record 350 troops.
The propellor driven Mars were declared obsolete in 1956 and Forest Industries Flying Tankers Ltd, Canada, purchased four, the other having been lost in a fire.
With a fibre-glassed Douglas Fir plywood 6.000 gallon tank installed in the cargo area it could scoop up the 32 tons of water within 22 seconds while the flying boat skimmed the surface at about 70 knots.
Martin 170 / JRM Mars
Engines: 4 x Wright R-3350-18 Cyclone, 1620kW / 2170 hp
Max take-off weight: 67130 kg / 147997 lb
Empty weight: 34300 kg / 75619 lb
Wingspan: 61.0 m / 200 ft 2 in
Length: 36.6 m / 120 ft 1 in
Height: 13.6 m / 44 ft 7 in
Wing area: 242.0 sq.m / 2604.86 sq ft
Max. speed: 380 km/h / 236 mph
Cruise speed: 300 km/h / 186 mph
Ceiling: 5200 m / 17050 ft
Range w/max.fuel: 9300 km / 5779 miles
Martin JRM Mars