American patrol bomber flying boat
The Martin PBM Mariner is a twin-engine American patrol bomber flying boat of World War II and the early Cold War era. It was designed to complement the Consolidated PBY Catalina and PB2Y Coronado in service. A total of 1,366 PBMs were built, with the first example flying on 18 February 1939, and the type entering service in September 1940, with the last of the type being retired in 1964.
A Mariner, otherwise noted for its WW2 and post-War service, was the type that vanished searching for Flight 19. Flight 19 vanished in the Bermuda Triangle, it and the Mariner that searched for it were never found with its 14 crew, though it was thought to have suffered a mid-air explosion. Another noted crash was the 1946 Antarctica PBM Mariner crash in December 1946.
Design and development.
In 1937 the Glenn L. Martin Company designed a new twin-engined flying boat, the Model 162, to succeed its earlier Martin P3M and complement the PBY Catalina and PB2Y Coronado. It received an order for a single prototype XPBM-1 on 30 June 1937. 
To test the PBM's layout, Martin built a three-eighths scale flying model, the Martin 162A "Tadpole Clipper" with a crew of one and powered by a single Chevrolet engine driving two airscrews via v-belts; this was flown in December 1937. This was followed by an initial production order for 21 PBM-1 aircraft on 28 December 1937.
The first genuine PBM, the XPBM-1, flew on 18 February 1939.
The aircraft had multiple gun positions including single mounts at each midship beam and stern above the tail cone. Additional guns were positioned in the nose and dorsal turrets, each fitted with two-gun turrets. The bomb bays were in the engine nacelles. The gull wing was of cantilever design, and featured clean aerodynamics with an unbraced twin tail. The PBM-1 was equipped with retractable wing landing floats that were hinged outboard, with single-strut supported floats that retracted inwards to rest beneath the wing, with the floats' keels just outboard of each of the engine nacelles. The PBM-3 had fixed floats, and the fuselage was three feet longer than that of the PBM-1.
Martin also developed the even larger 4-engined Martin JRM Mars in this period.
Operational history.
The first PBM-1s entered service with Patrol Squadron Fifty-Five (VP-55) of the United States Navy on 1 September 1940. Prior to the USA's entry into World War II, PBMs were used (together with PBYs) to carry out Neutrality Patrols in the Atlantic, including operations from Iceland. Following Japan's attack on Pearl Harbor, PBMs were used on anti-submarine patrols, sinking their first German U-boat, "U-158", on 30 June 1942. PBMs were responsible, wholly or in part, for sinking a total of ten U-boats during World War II. PBMs were also heavily used in the Pacific War, operating from bases at Saipan, Okinawa, Iwo Jima, and the South West Pacific.
The United States Coast Guard acquired 27 Martin PBM-3 aircraft during the first half of 1943. In late 1944, the service acquired 41 PBM-5 models and more were delivered in the latter half of 1945. Ten were still in service in 1955, although all were gone from the active Coast Guard inventory by 1958 (when the last example was released from CGAS San Diego and returned to the U.S. Navy). These flying boats became the backbone of the long-range aerial search and rescue efforts of the Coast Guard in the early post-war years until supplanted by the P5M Marlin and the HU-16 Albatross in the mid-1950s.
PBMs continued in service with the U.S. Navy following the end of World War II, flying long patrol missions during the Korean War. It continued in front line use until replaced by its successor, the P5M Marlin. The last Navy squadron equipped with the PBM, Patrol Squadron Fifty (VP-50), retired them in July 1956.
The British Royal Air Force acquired 32 Mariners, but they were not used operationally, with some returned to the United States Navy. A further 12 PBM-3Rs were transferred to the Royal Australian Air Force for transporting troops and cargo.
The Royal Netherlands Navy acquired 17 PBM-5A Mariners at the end of 1955 for service in Netherlands New Guinea. The PBM-5A was an amphibian with retractable landing gear. The engines were Pratt &amp; Whitney R-2800-34. After a series of crashes, the Dutch withdrew their remaining aircraft from use in December 1959.
On 5 December 1945, a PBM Mariner took off from Eastern Florida to search for a missing Flight 19 (five TBM Avengers on a training flight), and was not heard from again. Twenty minutes after takeoff the airplane vanished from radar. A vessel in the area reported seeing a fireball and found an oil slick, but no remains of the crew or aircraft were found. The aircraft and crew remained missing but it is suspected it suffered from a mid-air explosion.
The 1946 Antarctica PBM Mariner crash occurred on 30 December 1946, on Thurston Island, Antarctica when a United States Navy Martin PBM-5 Mariner crashed during a blizzard. Buno 59098 was one of 4 aircraft lost during Operation Highjump.
One of its replacements in US service was the Martin P5M Marlin.
Prototype. Powered by two 1,600 hp (1,194 kW) R-2600-6 engines.
Initial production version. 5× .50 inch (12.7 mm) machine guns. Two R-2600-6 engines; 21 built.
Conversion of one PBM-1 as experimental catapult-launched long-range strategic bomber.
Improved version. 1,700 hp (1,270 kW) R-2600-12 engines; 32 built.
Unarmed transport version of PBM-3. 18 new build plus 31 converted from PBM-3.
Improved patrol version with twin .50 in machine guns in nose and dorsal turrets, and single guns in tail turret and waist positions. AN/APS-15 radar in radome behind cockpit; 274 built.
Designation for ex-RAF Mariner GR.1A after return to U.S. Navy.
Dedicated anti-submarine aircraft with reduced armament and weight for improved range. Six were prototyped from the PBM-3C with radar and standard armament less the dorsal turret. Later a light weight nose armament was fitted (2× fixed 0.50 in machine guns in nose. Retained were single machine gun in port waist position.; 62 conversions plus 94 built as new plus .
Patrol bomber with increased power (two 1,900 hp (1,417 kW) R-2600-22s) and increased armament (twin 0.50 in machine guns in nose, dorsal, and tail turrets, plus two waist guns). 259 built.
Proposed version with two 2,700 hp (2,015 kW) Wright R-3350 engines; unbuilt.
Version with 2,100 hp (1,566 kW) Pratt &amp; Whitney R-2800 engines; 628 built.
Variant of PBM-5 with improved radar.
Lightened anti-submarine variant of PBM-5.
Improved anti-submarine aircraft with revised radar installation.
Amphibian version of PBM-5, with retractable tricycle undercarriage; 36 built plus four conversions.
British designation for 32 PBM-3B supplied to the Royal Air Force.
Specifications (PBM-1).
"Data from" "Jane’s Fighting Aircraft of World War II"General characteristics* Crew: Seven* Length: ()* Wingspan: ()* Height: ()* Wing area: ()* Empty weight: ()* Gross weight: ()* Powerplant: 2 × Wright R-2600-6
 14-cylinder radial engines
, 1,600 hp (1,194 kW) 
Performance* Maximum speed: (, ) * Range: (, ) * Service ceiling: ()* Rate of climb: ()
Armament
See also.
Related development
Aircraft of comparable role, configuration, and era
Related lists
References.
Notes.
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