XPB2M-1 / JRM-1 Mars
By the 1940 s flying boats like the PBM Mariner and the PBY Catalina had proven the concept of amphibious air operations for both transport and combat. The Glenn Martin Company of Baltimore Maryland capitalized on existing technology by creating the world s largest operational flying boat, second only to Howard Hughes H-4. With a wingspan of 200 feet, length of 117 feet, and the capability of lifting 25 tons of cargo and carrying that over thousands of miles, the JRM-1 Mars was one of the most spacious and comfortable transport seaplanes to ever get airborne.
Design work for the Martin "Mars", the largest active-duty flying boat the world would ever see, started in 1935. After reviewing proposals submitted by Consolidated, Boeing, Vought-Sikorsky and Martin, Martin received a contract for a long-range patrol bomber. On 23 August 1938 a contract was issued to Martin for one Martin 170 experimental aircraft, a flying boat which was intended to use as a patrol bomber, designated XPB2M-1. This was to be the Martin Mars, a 140,000-pound behemoth that was the largest plane in the US military inventory until the arrival of the B-36 intercontinental bomber in 1947.
Martin really wanted government support for an even larger flying boat. Plans for the 250,000-pound Model 163, projected back in 1937, were dusted off and modernized. Building five hundred six-engine Model 193's could win the war, declared Glenn Martin, and company ads frequently depicted it as a postwar airliner.
The Mars was originally conceived as a "sky battleship" or "flying Dreadnought," armed with multiple gun turrets, capable of flying long distances with huge bombloads (and Marine paratroopers as well). In speeches and articles, Glenn Martin predicted that a single Mars could capture an enemy island or "totally destroy" a rail center or shipyard. A squadron of them, he wrote, could "devastate Tokyo in one trip."
The XPB2M-1 was accordingly treated like a warship. Its keel was ceremoniously laid on August 20, 1940, with Glenn Martin driving the first rivet. Its launching into Dark Head Creek on November 5, 1941, was stern-first, after a bottle of champagne had been duly smashed over its bow. The plane's interior was laid out with separate mess rooms, berths, and washrooms for officers and enlisted men. Its commander had a private stateroom and issued his orders from a desk behind the pilots' seats. A huge bomb-bay, located in the hull underneath the wings, contained racks capable of holding five 1,000-pound bombs each. When it came time to drop them these could slide out on either side along the lower edge of the wing.
Launched in November 1941, the Mars came very much in the limelight when that high-speed builder of surface ships, Henry J. Kaiser, voiced his desire to produce the type in large quantities by turning over nine of his shipyards to aircraft production. There were many in America's aircraft industry who openly questioned 'Kaiser's ability to repeat his shipbuilding " miracle " in terms of flying boats. Kaiser, however, went straight to the fountain head at Washington. with the ultimate result that he was given an order to build 100 Mars-type cargo flying boats. The order, however, was later cancelled, and Glenn Martin himself said that the Mars was not really up to date now. Kaiser, therefore, transferred his energies to another even larger type.
Powered by four Wright Duplex Cyclone engines of z,ooo h.p. each, it has tapered, high aspect-ratio wings of no less than200ft. span. a deep, slab-sided hull, and is very much like a scaled-up Mariner, of which it is is a development. The slightly tapered dihedral tailplade of moderate aspect-ratio is mounted across the top of the iull's rear extremity, and carries inclined twin "end-plate" fins and rudders symmetrically oval in shape. Fixed stabilising floats are attached beneath the wings by " V " struts about 50 ft. inboard from the rounded tips. Of all-metal construction with stressed-skin covering, the tail end of the hull, which tapers to the dimensions Af a gun-turret, is upswept on its top surface as well as from the second step.
Initial taxiing tests in Middle River came to an abrupt end on the Friday before Pearl Harbor when one of the giant laminated-wood propellers threw a blade. Repairs took more than six months, by which time the plane's mission had undergone a complete re-evaluation. The first flight of the prototype, which received designation XPB2M-1, took place 03 July 1942.
The solution about the re-equipment of aircraft into the transport was accepted. Initially intended as a patrol plane, the XPB2M-1 four-engine flying boat was later converted to the PB2M-1R Mars transport and served as a prototype for the JRM series of flying boats. It underent conversion into a transport, and was stripped of its "tactical equipment" to make room for bulky and heavy freight. In December 1943, a new flying cargo boat, the Martin XPB2M-1 (Mars) completed its first war mission in the Naval Air Transport Service. It flew from Patuxent River in Maryland to Natal in Brazil, in a nonstop trip of 4,375 miles, carrying 13,000 pounds of Christmas mail to the armed forces. From Natal, the Mars returned to Patuxent with three stops, and carrying from Belem to Port-of-Spain a record cargo of 35,000 pounds of war materials. Propelled by four 2,000 h.p. engines, this sea monster had a wingspan of 200 feet, a length of 117 feet and a height of 36 feet. Its weight was 140,000 pounds. As a troopship it could carry 150 men and a crew of 11.
The Naval Air Transport Service [ NATS ] operated without a Ferrying Service. It operated several hundred planes including a number of flying boats over routes aggregating 50,000 miles. The largest of the flying boats was the spectacular Mars (Martin XPB2-MO1) which made its first war mission to Natal in Brazil in December 1943. Navy transport planes were flown by former airline pilots or by graduates of Naval Aviation schools in transport flying.
In January 1945 the Navy ordered twenty more Mars transports, now designated JRM-1. In comparison to the original, their hulls were to be six feet longer and the split PBM-style tail replaced by a single 44-foot vertical fin. The Martin 170 remained the largest flying boat of US Navy. Already in 1944 it demonstrated its possibilities, after delivering payload in 9,300 kg to Hawaii, after covering a distance of 7,564 km in 27:36 hours. After this flight the U.S. Navy ordered 20 series production machines with the designation JRM-1 Mars specially for use as transport aircraft. But the war ended, and only five copies were built , plus the one JRM-2 aircraft with the increased gross weight. On the standard of this last aircraft later were modified five apparatuses JRM-1; they all obtained designation JRM-3. These machines, which had a wing span of 60.96 m, were equipped with the Wright R-8 engines with 2300 hp.
Only five were put into service. These boats operated for years throughout the Pacific from Alameda Naval Air Station as part of Transport Squadron Two, each named for the area covered (i.e. Philippine Mars, Marianas Mars, Hawaii Mars, Marshall Mars, and Caroline Mars). The last production airplane (the Caroline Mars) was designated JRM-2, powered by 3,000 HP Pratt & Whitney R-4360 engines, and featured a higher maximum weight and other improvements.
The Martin Mars flying boats had a near perfect operational record, covering the equivalent of 23 round trips to the moon, and accumulating more than 87,000 accident-free hours before being retired by the US Navy. Only one incident existed as the exception to this record. On April 5th, 1950, the Marshall Mars was carrying out a short test flight for a new number three engine. Only minutes from Honolulu, oil could be seen streaming from the engine nacelle, and a fire had broken out. Unable to extinguish the blaze, LCDR Glenn E. Simmons brought the Marshall Mars down for a safe landing just south of Pearl Harbor, and the crew abandoned ship. Crash boats on the scene were also unable to put out the fire, and the Mars exploded in a spectacular eruption. Fortunately, no lives were lost. The remains of the Martin Marshall Mars now lie 1,200 feet underwater. The bow and forward section of the hull are inverted, the currents slowly scouring sediments from beneath the cockpit. A portion of the wing and three of the four engines rest a short distance to the south.
The remaining "Big Four" flew record amounts of cargo on the San Francisco-Honolulu route efficiently until 1956, when they were parked at NAS Alameda. In 1959, the remaining Mars were sold for scrap. Dan McIvor, who represented a consortium of British Columbia lumber companies, 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. Four aircraft, the Marianas, Philippine, Hawaii and Caroline Mars were ferried to British Columbia where three were fitted with 7,200 gallon (27,000 liters) water tanks and converted to waterbombers.
The Marianas Mars crashed near Northwest Bay, British Columbia on June 23, 1961 during firefighting operations; all four crewmembers were lost. Just over a year later, on October 12, 1962, the Caroline Mars was destroyed by Typhoon Freda while parked onshore.
The remaining Hawaii Mars and Philippine Mars had their conversions to water bombers accelerated and entered service in 1963. When converted, the original powerplants were replaced with four Wright R-3350-24WA Cyclone engines of 2500 hp (1860 kW) each. The aircraft can carry up to 7,200 US gal (27,000 liters) of water, enough to cover an area of 4 acres (16,000 m²). The two remaining aircraft, the Philippine and Hawaii Mars, continued on to provide unsurpassed firefighting protection for thirty-seven accident free years. They have operated on hundreds of fires saving untold thousands of acres of valuable forestlands, delivering foam or water exactly where and when it is needed.
The two surviving tankers are operated by the Coulson Group, based at Sproat Lake near Port Alberni, British Columbia. They are used to fight fires along the coast of British Columbia and the interior. On April 13, 2007, TimberWest announced the sale of both Martin Mars aircraft to Coulson Forest Products, a local forestry company in Port Alberni. The Mars would remain in the Alberni Valley operating from their base at Sproat Lake. On October 25, 2007, Hawaii Mars ("Redtail") arrived at Lake Elsinore in Southern California, negotiated through a private contract, to assist with the firefighting efforts containing the California wildfires of October 2007.
During the fire season, the aircraft are kept in a state of readiness to meet the existing fire hazard conditions. They can be in the air in ten minutes and, based on historical data, each can make a drop every fifteen minutes. Working in tandem, this equates to 7,200 US gallons (27,276 litres) every seven minutes and each drop can cover an area of up to 4 acres (1.6 hectares). It has often been said that the Mars, with a 60,000 pound (27,216 kilogram) payload of foam, is like ""a huge wet blanket". The highly experienced Mars pilots, working closely with the Incident Commander, deliver the water or foam right where it is needed.
Each Mars carries 600 US gallons (2,270 litres) of foam concentrate - enough for 21 drops of a 0.4% solution which is the standard used although it may be decided to use more or less foam as dictated by the Incident Commander. The Mars are also equipped to deliver Thermo-Gel which when mixed with water forms a light gel by encapsulating the water droplets. This product provides a more even coating of the fuels as well as lasting longer on the ground.
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