The Martin P5M (P-5) Marlin was developed from the successful PBM Mariner, and was the last operational flying boat to serve with the US Navy.
Work on the Marlin began in 1946. The Martin Model 237 used the wing and upper hull from the PBM-5 with a new hull with a length-to-beam ratio of 8.5:1. Martin was given a contract to produce a prototype XP5M-1 on 26 June 1946. This was produced by modifying a PBM-5, and the prototype made its maiden flight on 30 May 1948. This aircraft had radar operated nose and tail turrets, a power operated dorsal turret, a low-set tailplane and was powered by two 3,250hp Wright R-3350 radial engines. It kept the Mariner’s distinctive wing, which had dihedral on the centre section to raise the propellers above the water and level outer sections, with stabilising floats that retracted into the wing tips.
The Marlin wasn’t ordered into production until July 1950. A number of changes were introduced on the PBM-1. The dorsal turret was removed. The nose turret was replaced with a radome for the APS-80 search radar. The flight deck was raised above the level of the fuselage to improve visibility. Finally more powerful R-3350WA engines were installed in longer nacelles that also included weapon bays.
The first production aircraft were delivered to Patrol Squadron VP-44, starting on 23 April 1952. The -1 was followed by the P5M-2, which had a ‘T’ tail and more powerful engines. The first -2 flew in August 1953 and began to be delivered to the Navy squadrons on 23 June 1954.
The P5M remained in service into the mid 1960s. On 6 November 1967 a search and rescue SP-5B Marlin from VP-40, based at Naval Air Station North Island, made the last operational flight of a US Navy Flying Boat. Although several more modern designs were produced, with the Martin P6M SeaMaster reaching the prototype stage, none actually reached operational status.
The P5M-1 was the first production version. It had the nose turret replaced with a radome for the APS-90 search radar, a raised flight deck, no dorsal turret and two 3,400hp -30WA engines. 160 were built. The revisions to the nose gave it a rather odd look, with the radome resembling a ‘nose’, jutting out in front of the boat hull, and the
The -1G designation was given to seven aircraft produced for use by the Coast Guard
The P5M-1S/ SP-5A was the designation given to aircraft that were given AN/ ASQ-8 Magnetic Anomaly Detection (MAD) equipment, Julie active echo-sounding, Jezebel passive sono-buoy equipment and other electronic equipment, for use in the ASW role. About eighty were produced.
This was the designation give to the old coast guard aircraft when they were taken over by the Navy and used as crew trainers.
The P5M-1/ P-5B was the second production version. It had a modified hull, a ‘T’ tail with the horizontal tail surfaces mounted high on top of the tail, improved crew accommodation and 3,450hp R-3350-32WA engines.
Different sources give different production figures for the P5M-2, ranging from 108 for the US Navy and 12 for the French up to 145. However that higher figure comes from a source than underestimates the number of -1s built, and many be confusing some of the aircraft that were built as -1s and upgraded to the -2 standard with
The -2G was the designation given for four aircraft produced for the US Coast Guard. These later became standard -2 aircraft in US Navy service. In Coast Guard service the ASW gear was replaced with air-sea rescue equipment.
The P5M-2S was the designation given to most -2s when they were given Julie active echo-sounding and Jezebel passive sono-buoy equipment, as used on the P5M-1S, for use as ASW aircraft.
Engine: Two Wright R-3350-32WA turbo-compound radial piston engines
Power: 3,450hp each
Span: 118ft 2in
Length: 100ft 7in
Height: 32ft 8.5in
Empty Weight: 50,485lb
Maximum Take-off Weight: 85,000lb
Maximum Speed: 251mph at sea level
Range: 2,050 miles
Bomb load: Four torpedoes or four 2,000lb bombs or mines or 8,000lb of smaller weapons internally and eight 1,000lb bombs or mines externally