|U.S. Coast Guard Martin P5M-2G Marlin|
|Manufacturer||Glenn L. Martin Company|
|First flight||30 May 1948|
|Primary users||United States Navy
United States Coast Guard
|Developed from||PBM Mariner|
The Martin P5M Marlin (P-5 Marlin after 1962), built by the Glenn L. Martin Company of Middle River, Maryland, was a twin-engined piston-powered flying boat entering service in 1951 and serving into late 1960s in service with the United States Navy for naval patrol. It also served in the U.S. Coast Guard and with the French Navy. 285 were produced overall.
Built as evolutionary successor to the PBM Mariner, it had better engines, improved hull form, and more conventional tail. The XP5M Marlin prototypes were based on the last PBM-5 Mariners, the company designation being Model 237. It would be heavily improved again leading to the P5M-2 (Model 237B), which was redesignated SP-5B. A number of P5M-1 models were also used for training, designated TP-5A (after 1962).
The Marlin was designed as a gull-winged aircraft to place the engines and propellers high above the spray. Power was by two Wright R-3350 radial engines. The rear hull did not lift sharply from the water at the tail, instead rising up steadily, a Martin innovation; this gave the aircraft a longer base of flotation and reduced "porpoising" over waves.
The prototype had nose and tail turrets with twin 20 millimetres (0.79 in) cannon in each, as well as a dorsal turret with two 0.5 in (12.7 mm) M2 Browning machine guns. The cockpit area was the same as the Mariner's. It first flew in 30 May 1948.
The first of 167 production P5M-1 aircraft was produced in 1951, flying on 22 June 1951. Changes from the prototype included a raised flight deck for improved visibility, the replacement of the nose turret with a large radome for the AN/APS-44 search radar, the deletion of the dorsal turret, and new, streamlined wing floats. The engine nacelles were lengthened to provide room for weapons bays in the rear.
The P5M-1 was followed by 116 P5M-2 planes. These had a T-tail to put the tail surfaces out of the spray, an AN/ASQ-8 MAD boom at the rear of the tail-tip, no tail guns (the gun position replaced by the antenna for the AN/APN-122 Doppler Navigation Set), better crew accommodation and an improved bow to reduce spray during takeoff and landing.
Operational history 
The last flying boat operations of the United States Navy were Market Time patrols of VP-40. Maritime surveillance began in February 1965 to locate small craft transporting supplies from North Vietnam to Viet Cong units in South Vietnam. VP-40 operated from seaplane tenders and patrolled off the Mekong delta between Phú Quốc and Vung Tau. The last U.S. Navy P5M, redesignated as an SP-5B, was flown to NAS Patuxent River, Maryland on 12 July 1968 for interim storage pending construction of display area at the Smithsonian Institution in Washington, DC. As a display area at Smithsonian did not materialize, the aircraft was later relocated to the National Museum of Naval Aviation at NAS Pensacola, Florida where it is currently on display.
U.S. Coast Guard 
Seven P5M-1Gs and four P5M-2Gs were built for the United States Coast Guard for air-sea rescue service, but the service found the planes difficult to maintain and surplus to requirements. They were subsequently transferred to the U.S. Navy, which redesignated them as TP-5As and used them as training aircraft, since they had no provision for armament.
The French Navy took delivery of ten former U.S. Navy Marlins in 1959 to replace Short Sunderlands in maritime patrol service, based out of Dakar, Senegal in West Africa. They were returned five years later.
- Prototype converted from a PBM Mariner with modified hull.
- Production model for the United States Navy, 160 built, later re-designated P-5A.
- Modified P5M-1 for the United States Coast Guard, seven conversions, later returned to the Navy as P5M-1T.
- Modified P5M-1 with upgraded electronic and anti-submarine equipment, eighty conversion later re-designated SP-5A.
- Seven former USCG P5M-1Gs returned to Navy as crew trainers and one former P5M-1, later re-designated TP-5A.
- Updated production model, 108 built for the U.S. Navy and 12 built for the French Navy, United States aircraft later re-designated P-5B. P5M-2 featured T-tail in lieu of low mounted horizontal surfaces in P5M-1.
- Most P5M-2s were modified with upgraded electronic and anti-submarine equipment, later re-designated SP-5B.
- Four P5M-2s built for the USCG, later transferred to U.S. Navy as P5M-2s.
- P5M-1 re-designated in 1962.
- P5M-1S re-designated in 1962.
- P5M-1T re-designated in 1962.
- P5M-2 re-designated in 1962.
- P5M-2S re-designated in 1962.
- P5M-3 (Model 313) was revised as P7M-1 Model 313 SubMaster with a single turbojet engine mounted. Mockup built in 1956 and lost out to Lockheed P-3 Orion.
One SP-5B is located at the National Museum of Naval Aviation at Naval Air Station Pensacola, Florida. This aircraft, BuNo 135533, is believed to be the last remaining example of the Marlin. It is now displayed inside the new hangar (as of the spring of 2010) and much of the exterior has been restored. The restoration is being financed by the museum and the Mariner/Marlin Association.
Specifications (P5M-2) 
Data from United States Navy Aircraft since 1911.
- Crew: 11
- Length: 100 ft 7 in (30.7 m)
- Wingspan: 117 ft 2 in (35.7 m)
- Height: 32 ft 9 in (10.0 m)
- Wing area: 1,406 ft² (130.1 m²)
- Empty weight: 50,485 lb (22,900 kg)
- Loaded weight: 72,600 lb (33,000 kg)
- Max. takeoff weight: 85,000 lb (38,600 kg)
- Powerplant: 2 × Wright R-3350-32WA radial engines, 3,450 hp (2,570 kW) each
- Maximum speed: 218 kn (404 km/h, 251 mph)
- Cruise speed: 130 kn (242 km/h, 150 mph)
- Range: 1,783 nmi (3,300 km, 2,050 mi)
- Service ceiling: 24,000 ft (7,300 m)
- Rate of climb: 1,200 ft/min (6.1 m/s)
- Wing loading: 60.5 lb/ft² (287 kg/m²)
- Power/mass: 0.081 hp/lb (0.13 kW/kg)
- 4 × 2,160 lb (980 kg) torpedoes or
- 4 × 2,000 lb (907 kg) mines or bombs or
- 8 × 1,000 lb (454 kg) mines or
- 16 × 500 lb (227 kg) bombs or
- 16 × 330 lb (150 kg) depth charges or
- 1 × Mk.90 "Betty" nuclear depth charge
- AN/APS-44 radar (later replaced by AN/APS-80 radar)
See also 
- Related development
- Aircraft of comparable role, configuration and era
- Related lists
- Roberts 2000, p,663.
- "Longer Hull Safer Landing." Popular Science, August 1948, p. 90.
- An Illustrated Guide to The Air War Over Vietnam by Nalty, Bernard C., Watson, George M., and Neufeld, Jacob: Arco Publishing (1981) pp.106-107.
- The Naval Air War in Vietnam by Mersky, Peter B, and Polmar, Norman: Nautical and Aviation Publishing Company of America (1981) p.30.
- The Vietnam War by Bonds, Ray: Salamander Books (1979) p.132.
- Flecknoe, Harold J. "Progress". United States Naval Institute Proceedings, October 1968.
- Andrade 1979 p207
- Andrade 1979 p157
- Andrade, John, U.S.Military Aircraft Designations and Serials since 1909, Midland Counties Publications, 1979, ISBN 0-904597-22-9.
- Barth, Bruce D., "The Martin P5M 'Marlin'". Pacific Aero Press, 1994.
- Roberts, Michael D. Dictionary of American Naval Aviation Squadrons: Volume 2 The History of VP, VPB, VP(HL) and VP(AM) Squadrons. Washington DC: Naval Historical Centre, 2000.
- Swanborough, Gordon and Bowers, Peter M. United States Navy Aircraft since 1911. London:Putnam, Second edition 1976. ISBN 0-370-10054-9.
- The Illustrated Encyclopedia of Aircraft (Part Work 1982-1985), 1985, Orbis Publishing, Page 2420
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