P4M Mercator
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| P4M Mercator | |
|---|---|
 United States Navy P4M-1 |
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| Type | Patrol bomber |
| Manufacturer | Martin |
| Maiden flight | 1946 |
| Introduced | 1950 |
| Retired | 1960 |
| Status | Retired |
| Primary user | United States Navy |
| Number built | 21 |
The Martin P4M Mercator was an American twin-engined martime reconnaissance aircraft built by Martin. The Mercator was an unsuccessful contender for a United States Navy requirement for a long-range maritime patrol bomber, with the Lockheed P2V Neptune chosen instead. It saw a limited life as a long-range electronic reconnaissance aircraft. Its most unusual feature was that it was powered by a combination of piston engines and turbojets, the latter being in the rear of the engine nacelles.
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[edit] Design and development
Work began on the Model 219 in 1944, with the first flight being on October 20, 1946. A large and complicated aircraft, it was powered by two Pratt & Whitney R4360 Wasp Major 28-cylinder radial engines. To give a boost during takeoff and combat, two J-33 turbojets (Rolls-Royce_Derwent clones) were fitted in the rear of the two enlarged engine nacelles, the intakes being beneath and behind the radial engines. The jets, like those on most other piston/jet hybrids, burned gasoline, not jet fuel.
A tricycle undercarriage was fitted, following Navy preferences, with the nosewheel retracting forwards and the single-wheel main legs into coverless fairings in the wings, so that the sides of the wheels could be seen even when retracted. The wings themselves, unusually, had a different airfoil cross-section on the inner wings than the outer.
Heavy defensive armament was fitted, with two 20 mm cannon in an Emerson nose turret and a Martin tail turret, and two 0.5 in (12.7 mm) machine-guns in a Martin dorsal turret. The bomb-bay was, like British practice, long and shallow rather than the short and deep bay popular in American bombers. This gave greater flexibility in payload, including long torpedoes, bombs, mines, depth charges or extended-range fuel tanks.
[edit] Operational history
The US Navy chose the smaller, simpler and cheaper P2V Neptune for the maritime patrol requirement, but nineteen aircraft were ordered in 1947 for high-speed minelaying purposes; these were modified for the electronic reconnaissance (or SIGINT, for signals intelligence) mission in 1951, to replace the PB4Y Privateer. The crew was increased to 14 and later 16 to operate all the surveillance gear, and the aircraft was fitted with a large number of different antennas.
Missions were flown from the Philippines (and, later, Japan) by Fleet Air Reconnaissance Squadron One (VQ-1) along the Chinese borders and along the eastern Russian coasts, and were of a highly secret nature; the aircraft masqueraded as regular P2V Neptunes in radio communications. One Mercator was shot down by Chinese fighters in 1956, while another was attacked by two fighters in 1959 but escaped with injury to one crewman. The aircraft were also operated out of Morocco by VQ-2, where one aircraft was intercepted near Ukrainian airspace by Soviet MiG's. It escaped by flying under jet power but ran out of fuel and crashed into Mediterranean Sea with the loss of all crew.
The Mercators were replaced by the EA-3 Skywarrior, which being carrier-based had a greater degree of flexibility. Final withdrawal from service was in 1960, and all of the remaining P4Ms were scrapped.
[edit] Variants
- XP4M-1
- Two prototype aircraft with two R-4360-4 engines.
- P4M-1
- Production aircraft with two R-4360-20A engines, 19 built.
- P4M-1Q
- M4M-1s redesignated when modified for radar countermeasures.
[edit] Operators
[edit] Specifications (P4M Mercator)
General characteristics
- Crew: 9
- Length: 85 ft 2 in (26.0 m)
- Wingspan: 114 ft 0 in (34.7 m)
- Height: 26 ft 1 in (8.0 m)
- Wing area: 1,311 ft² (122 m²)
- Empty weight: 48,536 lb (22,016 kg)
- Loaded weight: 88,378 lb (40,088 kg)
- Max takeoff weight: lb (kg)
- Powerplant:
- 2× Allison J33-A-23 turbojets, 4,600 lbf (20 kN) each
- 2× Pratt & Whitney R-4360 Wasp Major radial engines, 3,250 hp (2,420 kW) each
Performance
- Maximum speed: 410 mph (660 km/h)
- Range: 2,840 miles (4,570 km)
- Service ceiling 34,600 ft (10,500 m)
- Rate of climb: ft/min (m/s)
- Wing loading: lb/ft² (kg/m²)
Armament
- 4x 20 mm cannon in nose and tail turrets
- 2x .50 cal (12.7 mm) machine guns in dorsal turret
- Up to 12,000 lb (5,400 kg) of bombs, mines, depth charges, or torpedoes
Avionics
- AN/APS-33 search radar
[edit] See also
Comparable aircraft Avro Shackleton - PB4Y Privateer - P2V Neptune - P-3 Orion
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