World War 2 showcased the value of large flying boats in the long range maritime patrol and anti-shipping roles. The Glenn L. Martin Company, established in 1912, had been building aircraft for some time before the Second World War and it sold various global military services on its PBM "Mariner" flying boat design which appeared in 1940. 1,285 of this aircraft were produced with the last retired from Uruguayan service in 1964. In the post-war years, Martin tried its hand at a modernized version of its Mariner which went on to become the P5M "Marlin" (Model 237). An improvement overall, the aircraft was procured in just 285 examples by the USN/USCG and the French Navy.
Design experience produced an elegant flying boat through smooth lines and an aerodynamically refined form. The aircraft carried the usual boat-like hull seen in others of this class. Other traditional features were also retained - the high-mounted wing mainplanes, leading edge engine nacelles, outboard wing pontoon floats. The cockpit sat high in the fuselage for good vision out-of-the-cockpit. There were two engines - Wright R-3350 radials of 3,450 horsepower - fitted to streamlined nacelles. A single vertical tail fin was used with low-set horizontal planes. In its original form, the aircraft carried cannon-armed turrets at both the nose and tail sections for defense and a 2 x 0.50 caliber heavy machine gun dorsal turret emplacement.
First flight of an XP5M prototype was recorded on May 30th, 1948.
The aircraft was adopted by the USN/USCG as the P5M-1 and an initial order was for 167 examples. By this time, the finalized aircraft was revised some from its prototype days - most notably was the deletion of the nose cannon turret (replaced by AN/APS-44 series radar under a cone assembly) and dorsal turret, introduction of a raised cockpit flight deck for improved vision, and extended engine nacelles. Production of this form began in 1951 with formal service introduction occurring in 1952.
Martin engineers were not done with evolving their Marlin design. The P5M-2 variant appeared in 116 examples with the most obvious difference being the switch to a "T" tail configuration which set the horizontal planes high atop the vertical tail fin. The tail turret was also deleted and an AN/ASQ-8 MAD ("Magnetic Anomaly Detector") boom assembly added. Other equipment added included the AN/APN-122 DNS ("Doppler Navigation Set"). The lines of the hull were also redrawn form better water performance.
While the USCG was an initial recipient of the Marlin (to be used in the SAR role), the aircraft did not live up to the requirements of the service which led to some eleven machines being passed on to the USN which reconstituted them as training platforms under the TP-5A designation. Original USCG designations were P5M-1G (seven examples) and P5M-2G (four examples). From the period of 1957 to 1959, the French Navy borrowed (and returned) at least ten USN P5Ms for service over Senegal.
P5M Marlins served during the Vietnam War (1955-1975) with the United States Navy where they undertook maritime patrol and surveillance missions in an attempt to stem the tide of supplies reaching the enemy by water. Operations were flown into the late 1960s.
In 1962, the United States military revised its aircraft designation system which resulted in the P5M-1 becoming the "P-5A" and the P5M-2 becoming the "P-5B". The other variants followed suit (see variants listing for full breakdown).
The P5M-2S mark were upgraded P5M-2Ss outfitted with Anti-Submarine Warfare (ASW) equipment and upgraded electronics. The P5M-3 (Model 313) was a proposed flying boat of 1956 fitted with a turbojet engine. It competed unsuccessfully with a Lockheed proposal which went on to become the P-3 "Orion" series.
Many of the Marlin production stock were scrapped after their flying days were over. The only known preserved examples resides at the National Naval Aviation Museum in Pensacola, Florida, USA. The aircraft in question made a tribute flight to USN flying boat operations on November 6, 1967 when it flew over Naval Air Station (NAS) North Island and landed on the waters of San Diego Bay.
Status Retired, Out-of-Service
Production 285 Units
Glenn L. Martin Company - USA
France; United States
- Ground Attack
- Anti-Submarine Warfare (ASW)
- Navy / Maritime
- Medical Evacuation (MEDEVAC)
- Search and Rescue (SAR)
- Reconnaissance (RECCE)
100.72 ft (30.7 m)
117.13 ft (35.7 m)
32.81 ft (10 m)
50,486 lb (22,900 kg)
85,098 lb (38,600 kg)
(Showcased weight values pertain to the Martin P5M Marlin production model)
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