Martin PBM Mariner
The Martin PBM Mariner was a twin-engined patrol flying boat built by the Glenn L. Martin Company for the United States Navy. First flown in February 1939 and in squadron service from October 1940, it was larger and faster than the Consolidated Catalina it supplemented, and by the end of the Second World War it had taken over many of the older boat's duties. Mariners hunted U-boats in the Atlantic, flew patrol, bombing and rescue missions across the Pacific, and served on into the Korean War; the last operational Mariner retired from the Coast Guard in 1958. Martin built 1,366, and a single PBM-5A survives, displayed at Tucson on loan from the Smithsonian.
Why It Mattered
The Mariner was the United States Navy's heavy patrol flying boat of the Second World War, designed by the Glenn L. Martin Company to complement the Consolidated PBY Catalina and, in time, to take over many of its duties. It reached its first patrol squadrons in October 1940, more than a year before the United States entered the war, and Martin built 1,366 in all. The National Air and Space Museum calls it one of the least known American patrol aircraft of the war, and also one of the most successful. In the Atlantic its crews hunted German submarines — the museum credits Mariners with ten of the twenty-nine U-boats sunk by American patrol aircraft — while in the Pacific it flew patrol, bombing and rescue missions until the war's end.
Design Notes
Martin proved the design with a piloted three-eighths-scale model, the 162A "Tadpole Clipper", which began testing in November 1937; convinced, the Navy funded development without waiting for a full-scale prototype. The XPBM-1, first flown on 18 February 1939, mounted its gull wing on a deep hull, a layout that held the engines above the spray and did away with the strutted parasol wing of the Catalina. Its bombs rode inside the hull, its wing floats retracted into the wings to cut drag, and two 1,600 hp Wright R-2600 radials gave the much bigger aircraft a speed advantage over the Catalina. Production aircraft canted the tailplane upward, which tilted the twin fins inward and gave the Mariner its most recognisable feature. Later models swapped retracting floats for stronger fixed ones, replaced the troublesome R-2600s with Pratt & Whitney R-2800s, and gained provision for jet-assisted take-off (JATO) bottles. The final variant, the PBM-5A, added retractable tricycle gear to become a true amphibian, and the Pima museum, which displays the survivor, calls it the largest amphibian ever built.
Operational History
The first production Mariners joined squadrons VP-55 and VP-56 in October 1940 and were soon patrolling the Atlantic for the German U-boats threatening the supply of war material to Britain. The Navy ordered 379 improved PBM-3s. In the summer of 1943, as Germany campaigned hard against Caribbean shipping, Mariners sank five of the ten U-boats involved; the boats' heavier anti-aircraft fire shot down three Mariners and damaged eight more. Stripped-down transport Mariners, their armour and armament removed, supplied remote submarine bases that had no airstrips and later flew medical-evacuation missions. Britain took PBM-3Cs under Lend-Lease in 1943 but preferred the Short Sunderland and sent them back, though it was the British who gave the aircraft its Mariner name. The PBM-5, the final version, entered service in 1944 and flew "Dumbo" rescue missions for ditched B-29 crews, night raids against Japanese shipping, and bombing attacks on Pacific island installations. After the war the type supported the early atomic tests in the Pacific and mapped Antarctica under Admiral Byrd. Its swan song came in the Korean War, on essential night patrols along the Korean coast with high-powered searchlights. The P5M Marlin that began arriving in 1952 quickly rendered the Mariner obsolete, and the last operational PBM retired from Coast Guard service in 1958.
Afterlife
Production ended in April 1949, when the last PBM-5A was completed. Of the 1,366 Mariners built, one survives intact: PBM-5A serial 122071, accepted by the Navy in 1948 and retired in 1953 with just 1,326 flying hours. Sold off as surplus, it passed through civilian hands that tried to work it as a fire-fighting tanker and a fish hauler, but the big boat was not economical to run as a civil aircraft. The Smithsonian accepted the aircraft as a donation in 1973, and it is displayed today on loan at the Pima Air & Space Museum in Tucson, Arizona — one of the last Mariners produced. The little 162A scale model that proved the design in 1937 survives with it in the Smithsonian's collection.