The PBM Mariner never achieved the popularity of the PBY Catalina. Marin's PBM Mariner offered considerably greater military capability at the expense of increase complexity. Unlike the PBY, which had relatively few problems in service, the PBM suffered from a number of problems, many of them related to the engine. These were finally overcome when the more powerful P&W R-2800s replaced the Wright R2600s in 1944.
The Navy contracted for the XPBM-1 in June 1937. Prior to this time, Martin had flown a quarter scale, piloted "flying model," the Martin 162A, to explore the hydrodynamic and aerodynamic characteristics. The XPBM-1 first flew early in 1939 but, in spite of the testing with the 162A, experienced problems both on the water and in flight. Full wings, twin tails, and retractable tip floats were its most distinguishing features. Hull redesign in 1940 and additional dihedral to the horizontal tail, resulting in the veritcal surfaces being canted inward, were major changes introduced to correct the problems in the XPBM-1. They were incorporated in the 20 PBM-1s, which followed. The first of the 1s to enter the fleet was assigned to VP-55 in September 1940.
Along with the PBM-1s, one XPBM-2 was ordered-modified to be a catapult-launched long-range patrol seaplane. While tests were satisfactory, the concept was not pursued.
The next service aircraft were the 3 series, delivered from 1942 through mid-1944. Initially delivered as PBM-3s, they featured improved armamentand engines, and could be easily recognized by the fixed wing-tip floats replacing the retractable floats of the 1s. Many of the early 3 series were converted to unarmed 3R transports. 3C patrol planes went to fleet squadrons, followed by stripped 3s ASW versions and, finally, 3Ds with improved R-2600 engines. Radar had been added in a large radome behind the cabin, starting with the 3Cs. Improved versions of the radar were used as they became available.
With the R-2800 engine, the subsequent PBM-5 series was destined for service long after WWII. Initial 5s were delivered with a new radar in a teardrop radome. A prototype amphibian version of the 5 was proposed in April 1944, but was not flown until December 1945. Thirty-six were produced before production stopped in 1949. Up to that time, 1,366 Mariners had been built.
Improvements in the 5 series led to ASW PBM-5S conversions starting late in 1949, while the 5As were converted to unarmed transports. Both models served worldwide well into the Fifties, the 5Ss being supplanted by 5S2s with updated equipment, before the last fleet squadron, VP-50, relinquished them for P5M Marlins in June 1956. Individual Mariners continued in Navy service to meet special needs for a few more years, the last one flying being a hydro-ski test aircraft. Mariners were also transferred and served with the COast Guard and several foreign countries.
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