# Martin P5M Marlin

The Martin P5M Marlin (P-5 Marlin after 1962), built by the Glenn L. Martin Company of Middle River, Maryland, is a twin piston-engined flying boat that entered service in 1951, and served into the late 1960s with the United States Navy performing naval patrols. It also served with the United States Coast Guard and the French Navy. 285 were produced.

## Development

Built as a successor to the PBM Mariner, it had better engines, an improved hull, and a single vertical fin tail. The XP5M Marlin prototypes were based on the last PBM-5 Mariners, the company designation being Model 237. The type was 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).

## Design

The Marlin was designed as a gull-winged aircraft to place the engines and propellers high above the spray. Power was provided 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 mm (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 on 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
### U.S. Navy

The last flying boat operations of the United States Navy were Market Time patrols of VP-40. Maritime surveillance patrols 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 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, D.C. As a display area at Smithsonian did not materialize, the aircraft was later relocated to the National Naval Aviation Museum at NAS Pensacola, Florida where it is currently on display.
The final Marlin flight was carried out by VP-40, to San Diego Bay on 6 November 1967.

### 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 they 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.

### French Navy

The French Navy took delivery of ten former U.S. Navy Marlins between 1957 and 1959 to replace Short Sunderlands in maritime patrol service, based in Dakar, Senegal in West Africa. They were returned in 1964.

## Variants
### Company designations
#### M-237

    Company designation for P5M-1

#### M-237B

    Company designation for P5M-2

#### M-270

    XP5M-1 prototype converted with a revised hull.

#### M-290

    Company designation for P5M-3 which was completely revised into the unbuilt four-engine P7M SubMaster

### Pre-1962 designations
#### XP5M-1

    Prototype converted from a PBM Mariner with modified hull and tail.

#### P5M-1

    Production model for the United States Navy, 160 built, later redesignated P-5A.

#### P5M-1G

    Modified P5M-1 for the United States Coast Guard, seven conversions, later returned to the Navy as P5M-1T.

#### P5M-1S

    Modified P5M-1 with upgraded electronic and anti-submarine equipment, eighty conversions, later redesignated SP-5A.

#### P5M-1T

    Seven former USCG P5M-1Gs returned to Navy as crew trainers and one former P5M-1, later redesignated TP-5A.

#### P5M-2

    Updated model, 108 built for the U.S. Navy and 12 built for the French Navy. The P5M-2 featured a T-tail in lieu of the low mounted horizontal stabilizer used on the P5M-1s. United States aircraft were later redesignated P-5B.

#### P5M-2S

    Most P5M-2s were modified with upgraded electronic and anti-submarine equipment, later redesignated SP-5B.

#### P5M-2G

    Four P5M-2s built for the USCG, later transferred to U.S. Navy as P5M-2s.

#### P5M-3

    Completely revised as four-engine M-313 P7M-1 SubMaster. Mockup built in 1956 but lost to Lockheed P-3 Orion.

### Post-1962 designations
#### P-5A

    P5M-1 redesignated in 1962.

#### SP-5A

    P5M-1S redesignated in 1962.

#### TP-5A

    P5M-1T redesignated in 1962.

#### P-5B

    P5M-2 redesignated in 1962.

#### SP-5B

    P5M-2S redesignated in 1962.

## Operators
### France

* French Navy

### United States

* United States Coast Guard
* United States Navy

## Surviving aircraft

One SP-5B is located at the National Naval Aviation Museum 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, Jane's all the World's Aircraft 1957–58, American flying boats and amphibious aircraft : an illustrated history
General characteristics
* Crew: 11
* Length: 100 ft 7 in (30.66 m)
* Wingspan: 117 ft 2 in (35.71 m)
* Height: 32 ft 9 in (9.98 m)
* Wing area: 1,406 sq ft (130.6 m$^2$)
* Empty weight: 50,485 lb (22,900 kg)
* Gross weight: 76,595 lb (34,743 kg)
* Max takeoff weight: 78,000 lb (35,380 kg)
* Powerplant: 2 × Wright R-3350-32WA Duplex-Cyclone 18-cylinder air-cooled radial piston engines with water injection, 3,450 hp (2,570 kW) each
* Propellers: 4-bladed fully-reversible constant-speed propellers
Performance
* Maximum speed: 251 mph (404 km/h, 218 kn) at sea level
* Cruise speed: 150 mph (240 km/h, 130 kn) at 1,000 ft (300 m)
* Range: 2,050 mi (3,300 km, 1,780 nmi)
* Service ceiling: 24,000 ft (7,300 m)
* Rate of climb: 1,200 ft/min (6.1 m/s)
* Wing loading: 60.5 lb/sq ft (295 kg/m$^2$)
* Power/mass: 0.13 kW/kg
Armament up to 8,000 lb (3,600 kg) internally in nacelle bomb-bays + up to 8,000 lb (3,600 kg) externally under the wings
* 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 × Mark 90 nuclear bomb nuclear depth charge
Avionics
* AN/APS-44 radar (later replaced by AN/APS-80 radar)
* Julie echo-ranging active sonar
* AN/AQA-3 Jezebel acoustic search passive sonar