Martin P4M Mercator

The Martin P4M Mercator was a maritime reconnaissance aircraft built by the Glenn L. Martin Company. 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.

P4M Mercator
P4M-1 Mercator in flight
United States Navy P4M-1
Role Patrol bomber
National origin United States
Manufacturer Martin
First flight 20 October 1946
Introduction 1950
Retired 1960
Status Retired
Primary user United States Navy
Number built 21

Design and development

Work began on the Model 219 in 1944, as a replacement for the PB4Y Privateer long-range patrol bomber, optimised for long range minelaying missions, with the first flight being on 20 October 1946.[1] 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 Allison J33 turbojets were fitted in the rear of the two enlarged engine nacelles, the intakes being beneath and behind the radial engines.[2] The jets, like those on most other piston/jet hybrids, burned gasoline instead of jet fuel which eliminated the need for separate fuel tanks.

A tricycle undercarriage was fitted, with the nosewheel retracting forwards. The single-wheel main legs retracted 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 (.79 in) 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.[3]

Operational history

Martin P4M-1 Mercator of VP-21 in flight in the early 1950s (NH 101801-KN)
P4M-1 of VP-21

The US Navy chose the smaller, simpler, cheaper and better performing P2V Neptune for the maritime patrol requirement, but nineteen aircraft were ordered in 1947 for high-speed minelaying purposes. The P4M entered service with Patrol Squadron 21 (VP-21) in 1950, the squadron deploying to NAS Port Lyautey in French Morocco.[4] It remained in use with VP-21 until February 1953.[5]

From 1951, the 18 surviving production P4Ms were modified for the electronic reconnaissance (or SIGINT, for signals intelligence) mission as the P4M-1Q, to replace the PB4Y-2 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 antennae.[6]

Martin P4M Mercator VQ-2 06.09.56
P4M-1Q Mercator of VQ-2 electronics reconnaissance squadron in September 1956 - note extra radar 'bulges' on this variant

Starting in October 1951, electronic surveillance missions were flown from U.S. Naval Station Sangley Point in the Philippines, later from Naval Air Station Iwakuni, Japan, and Naval Air Station Atsugi, Japan, by a secretive unit that eventually gained the designation Fleet Air Reconnaissance Squadron One (VQ-1). Long missions were flown along the coast (about 30 NM offshore) of Vietnam, China, North Korea and the eastern Soviet Union, and were of a highly secret nature; the aircraft sometimes masqueraded as regular P2V Neptunes in radio communications, and often flew with false serial numbers (Bureau Numbers) painted under the tail. Operational missions were always flown at night, during the dark with the moon when possible, and with no external running lights.[7]

One Mercator was shot down near Shanghai by Chinese fighters on 22 August 1956, with its crew of 16 all killed.[8] Another P4M-1Q was attacked by two North Korean MiG-17s on 16 June 1959 with heavy damage and serious injury to the tail gunner.[9] The aircraft were also operated out of Morocco by VQ-2; one aircraft was intercepted near Ukrainian airspace and shot down, crashing into the Mediterranean Sea with the loss of all crew.[10] Another, on 6 February 1952, ditched north of Cyprus at night, out of fuel, with no power, losing only the Aircraft Commander/pilot after they were in the water (See United States Naval Institute, Naval History, March/April 1997). The crew was rescued by HMS Chevron. One P4M-1Q of JQ-3[11] crashed at Ocean View, Virginia, on 6 January 1958,[12] when it lost an engine on approach to NAS Norfolk, Virginia, killing four crew and injuring three civilians.[13]

The Mercators were replaced by the EA-3B Skywarrior, which, being carrier-based, had a greater degree of flexibility and the larger Lockheed WV-2Q Warning Star. Final withdrawal from service was in 1960 after which all of the remaining P4Ms were scrapped.[14]


Two prototype aircraft with two R-4360-4 engines.
Production aircraft with two R-4360-20A engines, 19 built.
P4M-1s redesignated when modified for radar countermeasures.


 United States

Specifications (P4M-1 Mercator)

P4M-1 3-side drawing
Martin P4M-1 Mercator

Data from United States Navy aircraft since 1911,[15] Naval Fighters #37: Martin P4M-1/-1Q Mercator[16]

General characteristics

  • Crew: 9 (patrol bomber) ; 16 (Electronic reconnaissance)
  • Length: 86 ft 2.5 in (26.276 m)
  • Wingspan: 114 ft 0 116 in (34.749 m)
  • Height: 29 ft 2 116 in (8.892 m)
  • Wing area: 1,311 sq ft (121.8 m2)
  • Aspect ratio: 9.87
  • Airfoil: root: NACA 2417 (17%) ; tip: NACA 2412 (12%)
  • Empty weight: 48,536 lb (22,016 kg)
  • Gross weight: 83,378 lb (37,820 kg)
  • Fuel capacity:
Fuel (115/145 Avgas): 3,500 US gal (2,900 imp gal; 13,000 l) total in 4 wing tanks and 4 auxiliary tanks in the bomb bay
Oil: 216 US gal (180 imp gal; 820 l) in 2 nacelle tanks
Water 9 US gal (7.5 imp gal; 34 l) in 2 nacelle tanks
(XP4M-1: 2,975 hp (2,218 kW) R-4360-4)
(XP4M-1: 3,825 lbf (17,010 N) J33-A-17)
  • Propellers: 4-bladed Hamilton Standard, 15 ft 2 in (4.62 m) diameter reversible-pitch constant-speed propellers


  • Maximum speed: 410 mph (660 km/h, 360 kn) at 20,100 ft (6,100 m)
  • Range: 2,840 mi (4,570 km, 2,470 nmi)
  • Ferry range: 4,230 mi (6,810 km, 3,680 nmi) with bomb-bay auxiliary tanks fitted
  • Service ceiling: 34,600 ft (10,500 m)


  • 4 × 20 mm (0.787 in) cannon in nose and tail turrets
  • 2 × 0.5 in (12.70 mm) machine guns in dorsal turret
  • Up to 12,000 lb (5,400 kg) of bombs, mines, depth charges, or torpedoes


  • AN/APS-33 search radar

See also

Aircraft of comparable role, configuration and era

Related lists


  1. ^ Lake and Dorr 2000, p.139.
  2. ^ Lake and Dorr 2000, pp. 138–139.
  3. ^ Dorr and Burgess 1993, pp. 216–217.
  4. ^ Dorr and Burgess 1993, p.217.
  5. ^ Roberts 2000, p.125.
  6. ^ Lake and Dorr 2000, pp. 141–142.
  7. ^ Dorr and Burgess 1993, pp. 217, 220.
  8. ^ Dorr and Burgess 1993, pp. 220–221.
  9. ^ Dorr and Burgess 1993, pp. 221–222.
  10. ^ Former seaman who served in the Med
  11. ^
  12. ^
  13. ^ Associated Press, "Four Missing In Air Crash", The Anderson Independent, Anderson, South Carolina, Tuesday 7 January 1958, Volume 41, Number 99, page 1.
  14. ^ Dorr and Burgess 1993, p.222.
  15. ^ Swanborough, Gordon; Bowers, Peter M. (1976). United States Navy aircraft since 1911 (2nd ed.). Annapolis: Naval Institute Press. p. 513. ISBN 0870217925.
  16. ^ Ginter, Steve. Martin P4M-1/-1Q Mercator. California: S. Ginter. ISBN 0-942612-37-X.

1Q may refer to:

First quarter of a calendar year

Sirena (airline) (IATA code)

1q, an arm of Chromosome 1 (human)

SSH 1Q (WA); see Washington State Route 505

AH-1Q, a model of Bell AH-1 Cobra

P4M-1Q, a model of Martin P4M Mercator

A3D-1Q, a model of Douglas A-3 Skywarrior

AD-1Q, a model of Douglas A-1 Skyraider

Allison J33

The General Electric/Allison J33 was a development of the General Electric J31, enlarged to produce significantly greater thrust, starting at 4,000 lbf (18 kN) and ending at 4,600 lbf (20 kN) with an additional low-altitude boost to 5,400 lbf (24 kN) with water-alcohol injection.

Blackbushe Airport

Blackbushe Airport (IATA: BBS, ICAO: EGLK) is an operational general aviation airport in the civil parish of Yateley in the north-east corner of the English county of Hampshire. Built during the Second World War, Blackbushe is north of the A30 road between Camberley and Hook. It for a time straddled this road with traffic having to wait whilst airliners were towed across. The southside was used for aircraft maintenance, utilising wartime-built hangars. Today, only the part of the airfield section that lay north of the A30 remains in active use. The traditional name for the flat piece of land on which it is sited is Hartford Bridge Flats. The nearest towns are Yateley and Fleet.

Blackbushe Aerodrome has a CAA Ordinary Licence (Number P693) that allows flights for the public transport of passengers or for flying instruction as authorised by the licensee (Blackbushe Airport Limited). The aerodrome is licensed for night use.It is one of several airfields eclipsed since 1958 by the growth of London Heathrow Airport and London Gatwick Airport. Unless looking at aerial views or maps, it is hard to visualise that this was once a significant airport for passenger and cargo charter flights for the London area.

Currently based aircraft include several corporate jets, two flying schools, a helicopter training facility, as well as Aerobility, a flying charity. The airport is now open to the general public, and is also popular for walks around its perimeter and to see the wildlife in Yateley Common and Castle Bottom National Nature reserve.

Glenn L. Martin Company

The Glenn L. Martin Company was an American aircraft and aerospace manufacturing company founded by aviation pioneer Glenn L. Martin. The Martin Company produced many important aircraft for the defense of the US and allies, especially during World War II and the Cold War. During the 1950s and 60s, the Martin Company moved from the aircraft industry into the guided missile, space exploration, and space utilization industries.

In 1961, the Martin Company merged with American-Marietta Corporation, a large sand and gravel mining company, forming Martin Marietta Corporation. In 1995, Martin Marietta merged with aerospace giant Lockheed to form the Lockheed Martin Corporation.

List of United States bomber aircraft

This is a list of United States bomber aircraft

List of maritime patrol aircraft

The following is a list of maritime patrol aircraft, which are sometimes referred to as Maritime reconnaissance, coastal reconnaissance or patrol bombers depending on the service and the time period, and are characterized by their use in controlling sea lanes.

List of torpedo bombers

This is a list of torpedo bomber aircraft, designed or adapted to carry a primary weapon load of one or more aerial torpedoes in an anti-shipping role. It does not include types equipped for the more general anti-submarine warfare (ASW) role.

Naval Station Sangley Point

Naval Station Sangley Point was a communication and hospital facility of the United States Navy which occupied the northern portion of the Cavite City peninsula and is surrounded by Manila Bay, approximately eight miles southwest of Manila, the Philippines. The station was a part of the Cavite Navy Yard across the peninsula. The naval station had a runway that was built after World War II, which was used by U.S. Navy Lockheed P-2 Neptune, Lockheed P-3 Orion, and Martin P4M Mercator maritime patrol and anti-submarine warfare aircraft. An adjacent seaplane runway, ramp area and seaplane tender berths also supported Martin P5M Marlin maritime patrol aircraft until that type's retirement from active naval service in the late 1960s. NAS Sangley Point/NAVSTA Sangley Point was also used extensively during the Vietnam War, primarily for U.S. Navy patrol squadrons forward deployed from the United States on six-month rotations. The naval station was turned over to the Philippine government in 1971. It is now operated by the Philippine Air Force and Philippine Navy.

Martin and Martin Marietta aircraft
Model numbers
Attack aircraft
Maritime patrol
Military transports
Military trainers
Scout/Torpedo bombers
Reconnaissance aircraft
Martin Marietta
USN/USMC patrol aircraft designations 1923–1962
Patrol Bomber
Patrol Torpedo Bomber


This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.