https://en.wikipedia.org/wiki/Martin_P6M_SeaMaster
The Martin P6M SeaMaster, built by the Glenn L. Martin Company, was a 1950s
strategic bomber flying boat for the United States Navy that almost entered
service; production aircraft were built and Navy crews were undergoing
operational conversion, with a service entry about six months off, when the
program was cancelled on 21 August 1959. Envisioned as a way to give the Navy a
strategic nuclear force, the SeaMaster was eclipsed by the Polaris
submarine-launched ballistic missile. Due to the political situation at the
Pentagon, the Navy promoted the P6M primarily as a high speed minelayer.
In the immediate postwar defense climate, the United States Air Force's
Strategic Air Command was the linchpin of the United States' security as the
sole means of delivery of the nation's nuclear arsenal. The Navy saw its
strategic role being eclipsed by the Air Force and knew both its prestige and
budgets were at stake. Its first attempt, the United States (a large
supercarrier to launch Navy strategic bombers from) having been a victim of
budget cuts, the Navy chose instead to create a "Seaplane Striking Force" useful
for both nuclear and conventional warfare, including reconnaissance and
minelaying. Groups of these planes supported by seaplane tenders or special
submarines could be located close to the enemy, and being mobile would be hard
to neutralize.
Originally the plane was to have a Curtiss-Wright turbo-ramjet engine, but this
ran into problems and a more conventional Allison J71-A-4 turbojet was employed,
fitted in pairs in overwing pods to keep the spray out of the intakes. Wings
tip tanks that doubled as floats on the water. Many features of Martin's XB-51
bomber prototype were used, including an all-flying "T" tail and a rotating bomb
Role
Patrol flying boat
Manufacturer
Glenn L. Martin Company
First flight
14 July 1955
Primary user
United States Navy
Number built
12
The P6M-2 was an impressive aircraft; its Mach 0.9 (1,100 km/h) performance "on
the deck" could be equaled by few aircraft of the time. The aircraft were
heavily built, with the skin at the wing roots over 1 in (25 mm) thick. The
normally docile and pleasant handling characteristics of the P6M-1 were replaced
by some severe compressibility effects above Mach 0.8. These included rapid
changes in directional trim, severe buffeting, and wing drop requiring high
control inputs to counter. Until those problems were fixed, the P6M-2 could not
be considered for use by the Fleet. The problems were identified as being caused
by the larger engine nacelles required for the J75s. There were also problems on
the water, including a tendency for the tip floats to dig in under certain
situations, and engine surges. These problems were eventually solved, but time
had run out just as the first crews were training for its operational debut.
Eisenhower's administration was making major defense budget cuts that forced the
Navy to make choices. In August 1959 Martin was told to halt operations and the
program was about to be canceled. Seaplanes were a small community in Naval
Aviation, and the P6M was significantly over budget and behind schedule and
competing with aircraft carriers for funding. The Navy also had a potentially
superior system for the nuclear strike role, the Ballistic Missile Submarine.
In the age of the ICBM and SLBM, the manned bomber had become an expensive and
unreliable nuclear weapon delivery system. The P6M program had already cost $400
million (about $2.5 billion in 2004 dollars) and could not be justified without
the strategic mission.
All examples were scrapped although some tail sections were retained for
testing, and one of these is now in the Glenn L. Martin Maryland Aviation
Museum.
Specifications (P6M-2)
General characteristics
Crew: 4
Length: 134 ft 4 in (40.94 m)
Wingspan: 102 ft 7 in (31.26 m)
Height: 33 ft 10 in (10.31 m)
Empty weight: 97,439 lb (44,198 kg)
Useful load: 86,841 lb (39,390 kg)
Loaded weight: 162,932 lb Combat / 184,280 lb T.O. (73,905 kg Combat / 83,588 kg
T.O.)
Max. takeoff weight: 190,000 lb Calm water / 160,000 lb Rough water (86,183 kg
Calm water / 72,575 kg Rough water) **Allowable 6 ft to 9 ft (1.8 m to 2.7 m)
swells**
Performance
Maximum speed: (Sea Level) 596 kn (686 mph, 1,104 km/h) - (20,000 ft) 564 kn,
(35,000 ft) 520 kn
Cruise speed: 465 kn (535 mph, 861 km/h)
Stall speed: 132.2 kn (Power off, flaps down, T.O. wt) (152 mph, 245 km/h)
Range: 1,810 nmi (Combat) (2,083 mi, 3,200 km)
Combat radius: 750 nm (863 mi, 1389 km) (Carrying 30,000 lb / 13,608 kg payload)
Service ceiling: 50,000 ft (15,240 m)
Rate of climb: 7,380 ft/min (37.5 m/s) - Sea Level, T.O. wt, Military Power
Thrust/weight: 0.368
Armament
Mines: 28 x MK36 Mod 1 (1,001 lb/ea, 454 kg/ea) - 28,028 lb/Tot (12,713 kg)
Mines: 15 x MK25 Mod 2 (2,030 lb/ea, 921 kg/ea) - 30,450 lb/Tot (13,812 kg)
Mines: 36 x MK50 Mod 0 (504 lb/ea, 228 kg/ea) - 18,144 lb/Tot (8,230 kg)
Mines: 15 x MK52 Mod 0,1,2,3,4,5,6 (1,348 lb/ea, 611 kg/ea) - 20,220 lb/Tot
(9,172 kg)
Mines: 8 x MK39 Mod 0 (2,025 lb/ea, 919 kg/ea) - 16,200 lb/Tot (7,348 kg)
Mines: 15 x MK19 Mod 2 (540 lb/ea, 245 kg/ea) - 8,100 lb/Tot (3,674 kg)
Mines: 5 x MK10 Mod 9 (1,960 lb/ea, 889 kg/ea) - 9,800 lb/Tot (4,445 kg)
Reconnaissance: High Altitude Reconnaissance Camera 4,050 lb/Tot (1,837 kg)
Reconnaissance: 27 x M120(T9E8) Photoflash (154 lb/ea, 70 kg/ea) 4,158 lb (1,886
kg)
Bomb: 2 x MK91 (3,500 lb/ea, 1,588 kg/ea) - 7,000 lb/Tot (3,175 kg)
Bomb: 1 x MK28 (1,800 lb/ea, 817 kg/ea) - 1,800 lb/Tot (817 kg)
Fire-Control System: Aero X-23B AGL Tail Turret, ASQ-29 Automatic Navigation &
Minelaying System
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