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Martin P4M Mercator

1950 COLD WAR

Martin P4M Mercator Stories

In the latter part of World War II (1939-1945), the United States Navy (USN) began an active search for new long-range naval patrol bombers to replace the aging fleet of joint PB4Y "private" aircraft in the same role. Two potential candidates emerged from competing companies from Glenn L. Martin and Lockheed, known as P4M Mercator and P2V Neptune.

However, the latter was ultimately selected for mass production and frontline service, while the P4M had limited service and was unable to perform a wide range of electronic reconnaissance missions for the US Navy - which resulted in only 19 aircraft being built.

The aircraft that would become the "Mercator" was known internally as the "Type 219", and work on this type began as early as 1944 (WWII ended in 1945). Prototype made its maiden flight on October 20, 1946, powered by 2 Pratt & Whitney R-4360-4 "Wasp Major" radial piston air-cooled engines, providing the power and performance needed to match the range required by marine type (usually operating on uninhabited, landless terrain).

At this point in the "Jet Age" it turned out to be fairly common for US fighter jets to have a "combined" propulsion scheme, so 2 Allison J33 series turbojets were added to increase the aircraft's performance - or reduce the required runway length or evade the pursuit of enemy interceptors. The injection system relies on the same fuel as the strut drive radially, requiring only a common fuel supply.

Standard mounted armament consists of 2 x 20mm autocannons in the nose, additional 2 x 20mm autocannons in the stern and 2 x .50 caliber heavy machine guns (HMG) in the dorsal turret. In this way, the aircraft can defend almost any position the enemy approaches (except the bottom).

Optional bomb loads may include conventionally dropped bombs, mines, depth charges or torpedoes for a total war load of up to 12,000 pounds.

The top-down profile of the aircraft is very slender, with glass on the nose and tail of the fuselage. The cockpit is located above the tail of the nose section, as in a typical "stepped" arrangement, so this elevated position improves the pilot's view of the aircraft and each engine. The engines of every major aircraft are suspended below, extending significantly forward from the leading edge. The bomb bay buried in the fuselage was the same length as the engine.

Instead of mounting the main landing gear into the engine, the legs are positioned outside the nacelle and embedded in the wings (folded from the centerline). The front wheels are located under most of the nose to complete the tricycle arrangement required for ground travel. The empennage contains an elegantly shaped single rudder fin with a low, upwardly sloping horizontal plane.

The wing main aircraft is located directly amidships and is naturally slender, tapering along the leading and trailing edges from the centerline to the wingtips.

Eventually two prototypes were built to the "XP4M-1" standard with the R-4360-4 engine, followed by the production standard "P4M-1" model, of which 19 and 2 x The 4360-20A R series engine is put into service. The "P4M-1Q" designation was used to denote the P4M-1 airframe converted to a radar countermeasure platform (SIGnals INtelligence = "SIGINT").

When complete, the P4M-1 will carry a crew of nine and will have a total length of 85.1 feet, a wingspan of 114 feet, and a height of 26 feet. Empty weight is 48,535 pounds and maximum takeoff weight (MTOW) is 88,380 feet. Power comes from 2 Pratt & Whitney R-4360 "Wasp Major" radial piston air-cooled engines, 3,250 hp each, assisted by 2 Allison J33-A-23 turbojets, 4,600 thrust each. Performance includes a top speed of 410 mph, a range of up to 2,850 miles, and a service ceiling of up to 35,000 feet.

The aircraft is equipped with an AN/APS-33 search radar.

Even though Lockheed's Neptune design met the original requirements of the US Navy, the Mercator's value as a minelaying platform was not overlooked by the authorities, so production orders for the design followed in 1947 and it entered service in 1950 . Back in 1951, the fleet was rebuilt for the SIGINT role and operated under the aforementioned P4M-1Q designation - these aircraft were equipped with additional mission support equipment and a larger crew to take on the modified role.

Under this guise, Mercatos carried out daring and often dangerous espionage missions in communist areas near countries such as the Soviet Union, China, North Korea and Vietnam. On August 22, 1956, a Mercator was shot down by a Chinese interceptor, killing all on board, followed by another similar incident in the Soviet Union near Mediterranean waters, when the Mercator was captured near Ukraine.

Likewise, a North Korean interceptor shot down a Mercator, although the American fighter jet managed to survive the encounter and limped home.

After its useful life expired (and only the jets have taken over completely), the Mercator line was abandoned in favor of Douglas A-3 "Skywarrior" in "EA-3B" camouflage. Unlike the Mercator, the Sky Warrior was compact enough to operate and stow below the decks of U.S. aircraft carriers at the time.

The last Mercator was decommissioned in 1960, and none of the surviving airframes survived.