Martin P6M SeaMaster: Difference between revisions
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{{Short description|US Navy strategic bomber flying boat}} |
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{|{{Infobox aircraft begin |
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{{Use dmy dates|date=March 2017}} |
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{{Infobox aircraft |
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|name= P6M SeaMaster |
|name= P6M SeaMaster |
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|image= File:Martin P6M Seamaster in flight c1955.jpg |
|image= File:Martin P6M Seamaster in flight c1955.jpg |
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|caption= |
|caption= |
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}}{{Infobox aircraft type |
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|type= Patrol [[flying boat]] |
|type= Patrol [[flying boat]] |
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|manufacturer= [[Glenn L. Martin Company]] |
|manufacturer= [[Glenn L. Martin Company]] |
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|designer= |
|designer= |
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|first_flight= 14 July 1955 |
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|introduction= |
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|introduced= |
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|retired= |
|retired= |
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|status= |
|status= |
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|primary_user= [[United States Navy]] |
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|more_users= |
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|produced= |
|produced= |
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|number_built= 12 |
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|variants |
|variants= |
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}} |
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The '''Martin P6M SeaMaster''' |
The '''Martin P6M SeaMaster''' was an [[Experimental aircraft|experimental]] [[strategic bomber]] [[flying boat]] built by the [[Glenn L. Martin Company]] for the [[United States Navy]] that almost entered service; production aircraft were built and Navy crews were undergoing operational training, with service entry expected in about six months, when the program was cancelled on 21 August 1959. Envisioned as a [[strategic nuclear weapon]] delivery system for the Navy, the SeaMaster was eclipsed by the [[UGM-27 Polaris|Polaris]] [[submarine-launched ballistic missile]] (SLBM). Due to the political situation at [[the Pentagon]] and weapon system choices made amid budgetary constraints, the Navy promoted the P6M primarily as a high speed [[minelayer]].<ref>{{harvnb|Piet|Raithel|2001|page=148}}</ref> |
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==Design and development== |
==Design and development== |
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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. |
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. |
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Its first attempt to address this came in the form of the {{USS|United States|CVA-58|6}}, a large [[supercarrier]] intended to launch Navy strategic bombers. This was cancelled in 1950 shortly after her keel was laid down, a victim of budget cuts and US Air Force interference. In response, the Navy chose to create a "Seaplane Striking Force", useful for both nuclear and conventional warfare, including reconnaissance and minelaying. Groups of these planes supported by [[seaplane tender]]s or special [[submarine]]s could be located close to the enemy, and being mobile, they would be hard to neutralize. |
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The requirement issued in April 1951 was for a seaplane able to carry a {{convert|30000|lb|kg|abbr=on}} warload over a range of {{convert|1500|mi|nmi km|lk=on|abbr=on}} from its aquatic base. The aircraft was to be capable of a low altitude dash at [[Mach number|Mach]] 0.9 (1,100 km/h). Both [[Convair]] and [[Glenn L. Martin Company|Martin]] submitted proposals, and the Martin proposal was chosen as more promising. An order for two prototypes was issued which was projected to lead to six pre-production aircraft and a projected twenty-four production aircraft. |
The requirement issued in April 1951 was for a seaplane able to carry a {{convert|30000|lb|kg|abbr=on}} warload over a range of {{convert|1500|mi|nmi km|lk=on|abbr=on}} from its aquatic base. The aircraft was to be capable of a low altitude dash at [[Mach number|Mach]] 0.9 (1,100 km/h). Both [[Convair]] and [[Glenn L. Martin Company|Martin]] submitted proposals, and the Martin proposal was chosen as more promising. An order for two prototypes was issued which was projected to lead to six pre-production aircraft and a projected twenty-four production aircraft. |
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Originally the plane was to have a Curtiss-Wright |
Originally the plane was to have a Curtiss-Wright [[turbo-ramjet]] engine,<ref name="Goebel">{{cite web|url= http://airvectors.net/avcmast.html|title=The Martin SeaMaster & Convair Sea Dart|author=Greg Goebel}}</ref><ref>''American Aviation'' 12 Sept 1955 p12: "Navy is planning to use more powerful engines than the four Allison J71s plus afterburners to make the production model of the Martin Seamaster supersonic. XP6M-1 with the J71s will attain Mach .95."</ref> but this ran into problems and a more conventional [[Allison J71|Allison J71-A-4]] turbojet was employed, fitted in pairs in overwing pods to keep the spray out of the intakes. Wings swept at 40° were used; they displayed a notable [[Dihedral (aircraft)#Anhedral|anhedral]] and were designed with tip tanks that doubled as floats on the water. Many features of Martin's [[Martin XB-51|XB-51]] bomber prototype were used, including an [[Stabilator|all-flying]] [[T-tail|"T" tail]] and a rotating [[bomb bay]]—pneumatically sealed against seawater in the P6M. |
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==Operational history== |
==Operational history== |
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The first pre-production '''YP6M-1''' was completed about a year later, with testing resuming in January [[1958 in aviation|1958]]. |
The first pre-production '''YP6M-1''' was completed about a year later, with testing resuming in January [[1958 in aviation|1958]]. |
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Five more were built in 1958 when the Navy announced that [[ |
Five more were built in 1958 when the Navy announced that [[Harvey Point Defense Testing Activity]] in Hertford, North Carolina, would serve as the testing grounds for the fleet of Martin P6M SeaMasters. These aircraft were fitted with test versions of the full combat equipment suite and were used for bombing, mine laying and reconnaissance evaluations. The J71 engines were unreliable and the aircraft had spray ingestion problems at higher gross weights, which limited takeoffs to ideal conditions.<ref>{{harvnb|Piet|Raithel|2001|page=98}}</ref> The P6M-1 also had a serious control deficiency due to porpoising under some trim settings.<ref>{{harvnb|Piet|Raithel|2001|page=107}}</ref> These deficiencies resulted in the P6M-1 program being cut as it was no longer considered possible for it to be successfully developed. |
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The Navy and Martin felt that a new version, the '''P6M-2''', would provide a useful aircraft. The first was rolled out in early 1959. Changes included new, more powerful [[Pratt & Whitney J75]] engines, an [[aerial refueling]] probe, improved avionics, and a canopy with better visibility. A ''buddy refueling'' drogue kit had also been developed to fit in the bomb bay. Three had been built by summer 1959 and Navy crews were moving them through operational conversion when the program was abruptly canceled in August of that year. |
The Navy and Martin felt that a new version, the '''P6M-2''', would provide a useful aircraft. The first was rolled out in early 1959. Changes included new, more powerful [[Pratt & Whitney J75]] engines, an [[aerial refueling]] probe, improved avionics, and a canopy with better visibility. A ''buddy refueling'' drogue kit had also been developed to fit in the bomb bay. Three had been built by summer 1959 and Navy crews were moving them through operational conversion when the program was abruptly canceled in August of that year. |
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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 {{convert|1|in|mm|abbr=on}} 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 |
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 {{convert|1|in|mm|abbr=on}} thick. The normally docile and pleasant handling characteristics of the P6M-1 were replaced by some severe [[Compressibility#Aerodynamics|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.<ref>{{harvnb|Piet|Raithel|2001|page=117}}</ref> 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. Seaplane operations were a small component of U.S. naval aviation, and the P6M was significantly over budget and behind schedule and competing with aircraft carriers for funding. The Navy had also developed a potentially superior system for the nuclear strike role, the [[ballistic missile submarine]]. |
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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 {{As of|2004|alt=in 2004 dollars}}) and could not be justified without the strategic mission. |
In the age of the ICBM and SLBM, {{citation needed span|date=August 2023|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 {{As of|2004|alt=in 2004 dollars}}) and could not be justified without the strategic mission.|reason=Statements that bombers are "expensive and unreliable" and that the SeaMaster lacked a "strategic mission" seem like [[MOS:EDITORIAL]], and the unexplained budget figures also deserve a citation.}} |
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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]].{{ |
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]].{{Citation needed|date=October 2016}} |
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Martin tried unsuccessfully to market the technology in the civilian market, with a version called the '''SeaMistress''' but there were no takers,<ref>"SeaMonsters of the Navy, by Mark Wolverton, ''Air & Space'', Feb/Mar 2012, pp. 62-63</ref> and the company soon abandoned the aircraft business entirely to focus on missiles and electronics. The P6M was the final aircraft |
Martin tried unsuccessfully to market the technology in the civilian market, with a version called the '''SeaMistress''' but there were no takers,<ref>"SeaMonsters of the Navy, by Mark Wolverton, ''Air & Space'', Feb/Mar 2012, pp. 62-63. [https://www.smithsonianmag.com/air-space-magazine/cancelled-the-navys-seamaster-21166697/]</ref> and the company soon abandoned the aircraft business entirely to focus on missiles and electronics. The P6M was the final aircraft built by the Glenn L. Martin Company. |
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==Variants== |
==Variants== |
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==Specifications (P6M-2)== |
==Specifications (P6M-2)== |
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[[File:Martin YP6M-1 Seamaster 3-view line drawing.png|frameless|right|3-view line drawing of the Convair YP6M-1 Seamaster]] |
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[[File:P6M-1 from below NAN11-55.jpg|thumb|Martin P6M-1 from below]] |
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{{Aircraft specifications |
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{{Aircraft specs |
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|plane or copter?=plane |
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|ref={{citation needed|date=June 2019}} |
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|jet or prop?=jet |
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|prime units?=imp |
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General characteristics |
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|crew=4 |
|crew=4 |
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|capacity= |
|capacity= |
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|length |
|length ft=134 |
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|length |
|length in=4 |
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|length note= |
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|span main=102 ft 7 in |
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|span |
|span ft=102 |
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|span in=7 |
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|height main=33 ft 10 in |
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|span note= |
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|height alt=10.31 m |
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|width ft=<!-- if applicable --> |
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|area main=1,900 ft² |
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|width in=<!-- if applicable --> |
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|area alt=176.52 m² |
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|width note= |
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|airfoil= |
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|height ft=33 |
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|empty weight main=97,439 lb |
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|height in=10 |
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|empty weight alt=44,198 kg |
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|height note= |
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|loaded weight main=162,932 lb Combat / 184,280 lb T.O. |
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|wing area sqft=1900 |
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|loaded weight alt=73,905 kg Combat / 83,588 kg T.O. |
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|wing area note= |
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|useful load main=86,841 lb |
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|aspect ratio= |
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|useful load alt=39,390 kg |
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|empty weight lb=97439 |
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|max takeoff weight main=190,000 lb Calm water / 160,000 lb Rough water |
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|empty weight note= |
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|max takeoff weight alt=86,183 kg Calm water / 72,575 kg Rough water |
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|gross weight lb=184280 |
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|max takeoff weight more= **Allowable 6 ft to 9 ft (1.8 m to 2.7 m) swells** |
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|gross weight note=(at take-off) |
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|engine (jet)= [[Pratt & Whitney]] [[Pratt & Whitney J75|J75-P-2]] |
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::::{{cvt| 162392|lb|0}} (in combat) |
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|type of jet= [[turbojet]]s |
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|max takeoff weight lb=190000 |
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|number of jets=4 |
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|max takeoff weight note=in calm water |
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|thrust main=17,500 lbf |
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::::{{cvt|160000|lb|0}} in rough water ({{convert|6|to|9|ft|m|abbr=on}} swell) |
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|thrust alt=77.8 kN |
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|fuel capacity= |
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|max speed main=(Sea Level) 596 kt |
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|more general= |
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|max speed alt=686 mph, 1,104 km/h |
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|max speed more=- (20,000 ft) 564 kt, (35,000 ft) 520 kt |
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Powerplant |
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|cruise speed main=465 kts |
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|cruise speed alt= 535 mph, 861 km/h |
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|eng1 number=4 |
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|never exceed speed main= |
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|eng1 name=[[Pratt & Whitney J75-P-2]] |
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|never exceed speed alt= |
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|eng1 type=turbojet engines |
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|stall speed main= 132.2 kt (Power off, flaps down, T.O. wt) |
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|eng1 hp=<!-- prop engines --> |
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|stall speed alt= 152 mph, 245 km/h |
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|eng1 shp=<!-- prop engines --> |
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|range main= 1,810 nm (Combat) |
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|eng1 lbf=17500 |
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|range alt=2,083 mi, 3,200 km |
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|eng1 note= |
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|combat radius main=750 nm |
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|power original= |
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|combat radius alt=863 mi, 1389 km |
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|thrust original= |
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|combat radius more=(Carrying 30,000 lb / 13,608 kg payload) |
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|eng1 lbf-ab= |
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|Extended radius main = 1,500 nm (1,726 mi, 2,778 km) Buddy in-flight refueling from P6M-2 tanker transferring 42,000 lb fuel |
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|ceiling main=50,000 ft |
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Performance |
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|ceiling alt=15,240 m |
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|climb rate main= 7,380 ft/min |
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|max speed mph=686 |
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|climb rate alt= 37.5 m/s |
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|max speed note=at {{cvt|20000|ft|0}} |
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|climb rate more=- Sea Level, T.O. wt, Military Power |
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|max speed mach=<Mach 0.89408 |
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|loading main=100 lb/ft² |
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|cruise speed mph=535 |
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|loading alt=310 kg/m² |
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|cruise speed note= |
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|stall speed mph=152 |
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|stall speed note=(Power off, flaps down, T.O. wt) |
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|never exceed speed mph= |
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|never exceed speed note= |
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|minimum control speed mph= |
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|minimum control speed note= |
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|range miles=2083 |
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|range note= |
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|combat range miles=750 |
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|combat range note=(Carrying {{convert|30,000|lb|kg|abbr=on}} payload) |
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::::{{cvt|1726|mi|nmi km|0}} with one AAR from a P6M-2 tanker |
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|ferry range miles= |
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|ferry range note= |
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|endurance=<!-- if range unknown --> |
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|ceiling ft=50000 |
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|ceiling note= |
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|g limits=<!-- aerobatic --> |
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|roll rate=<!-- aerobatic --> |
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|climb rate ftmin=7380 |
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|climb rate note= |
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|time to altitude= |
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|wing loading lb/sqft=100 |
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|wing loading note= |
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|fuel consumption lb/mi= |
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|thrust/weight=0.368 |
|thrust/weight=0.368 |
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|more performance= |
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Armament |
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--> |
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|armament= |
|armament= |
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*'''Guns:''' 2 × [[20 mm]] [[autocannon|cannon]] in rear remote operated [[ |
*'''Guns:''' 2 × [[20 mm]] [[autocannon|cannon]] in rear remote operated [[Aircraft gun turret|turret]] (1,000 RDS/20mm) |
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*'''[[Naval mine|Mines]]:''' 28 x MK36 Mod 1 (1,001 lb/ea, 454 kg/ea) - 28,028 lb/Tot (12,713 kg) |
*'''[[Naval mine|Mines]]:''' 28 x MK36 Mod 1 (1,001 lb/ea, 454 kg/ea) - 28,028 lb/Tot (12,713 kg) |
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*'''Mines:''' 15 x MK25 Mod 2 (2,030 lb/ea, 921 kg/ea) - 30,450 lb/Tot (13,812 kg) |
*'''Mines:''' 15 x MK25 Mod 2 (2,030 lb/ea, 921 kg/ea) - 30,450 lb/Tot (13,812 kg) |
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*'''Mines:''' 5 x MK10 Mod 9 (1,960 lb/ea, 889 kg/ea) - 9,800 lb/Tot (4,445 kg) |
*'''Mines:''' 5 x MK10 Mod 9 (1,960 lb/ea, 889 kg/ea) - 9,800 lb/Tot (4,445 kg) |
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*'''Reconnaissance:''' High Altitude [[Aerial reconnaissance#Cold War|Reconnaissance Camera]] 4,050 lb/Tot (1,837 kg) |
*'''Reconnaissance:''' High Altitude [[Aerial reconnaissance#Cold War|Reconnaissance Camera]] 4,050 lb/Tot (1,837 kg) |
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*'''Reconnaissance:''' 27 x M120(T9E8) [[Photoflash bomb|Photoflash]] (154 lb/ea, 70 kg/ea) 4,158 |
*'''Reconnaissance:''' 27 x M120(T9E8) [[Photoflash bomb|Photoflash]] (154 lb/ea, 70 kg/ea) {{convert|4,158|lb|kg}} |
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*'''Bomb:''' 2 x [[Mark 11 nuclear bomb|MK91]] (3,500 lb/ea, 1,588 kg/ea) - 7,000 lb/Tot (3,175 kg) |
*'''Bomb:''' 2 x [[Mark 11 nuclear bomb|MK91]] (3,500 lb/ea, 1,588 kg/ea) - 7,000 lb/Tot (3,175 kg) |
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*'''Bomb:''' 1 x [[B28 nuclear bomb|MK28]] (1,800 lb/ea, 817 kg/ea) - 1,800 lb/Tot (817 kg) |
*'''Bomb:''' 1 x [[B28 nuclear bomb|MK28]] (1,800 lb/ea, 817 kg/ea) - 1,800 lb/Tot (817 kg) |
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*'''[[Fire-control system|Fire-Control System]]:''' Aero X-23B AGL Tail Turret, ASQ-29 Automatic [[Inertial navigation system|Navigation]] & Minelaying System |
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|avionics= |
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*'''[[Fire-control system|Fire-Control System]]:''' Aero X-23B AGL Tail Turret, ASQ-29 Automatic [[Inertial navigation system|Navigation]] & Minelaying System |
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}} |
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*[[Shin Meiwa US-1A]] |
*[[Shin Meiwa US-1A]] |
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|lists= |
|lists= |
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*[[List of flying boats and |
*[[List of flying boats and floatplanes]] |
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*[[List of United States Navy aircraft designations (pre-1962)]] |
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*[[List of military aircraft of the United States]] |
*[[List of military aircraft of the United States]] |
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|see also= |
|see also= |
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==References== |
==References== |
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===Notes=== |
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{{Commons category}} |
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'''Notes''' |
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{{Reflist|2}} |
{{Reflist|2}} |
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===Bibliography=== |
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*{{cite journal |last1=Allen|first1=Francis J.|title=Poseidon's Giant: The Story of the Martin P6M SeaMaster |journal=Air Enthusiast |date=March–April 2001|issue=92|pages=16–27 |issn=0143-5450}} |
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{{refbegin}} |
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*{{Cite |
*{{Cite magazine|last=Nicolaou|first=Stephane|title=Master of the Seas: The Martin P6M Flying Boat |magazine=Wings |publisher=Sentry Publications|location=Granada Hills, California|date=December 1986|volume=16|issue=6}} |
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*{{Cite book| |
*{{Cite book|first1=Stan|last1=Piet|first2=Al|last2=Raithel|year=2001|title=Martin P6M SeaMaster|location=Bel Air, Maryland |publisher=Martineer Press|isbn=0-9700662-0-1}} |
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{{refend}} |
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==External links== |
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{{Commons category}} |
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*[https://www.smithsonianmag.com/air-space-magazine/cancelled-the-navys-seamaster-21166697 ''Cancelled: The Navy’s SeaMaster,'' Smithsonian Air & Space Magazine, 2012] |
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{{Martin aircraft}} |
{{Martin aircraft}} |
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{{USN patrol aircraft}} |
{{USN patrol aircraft}} |
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{{Authority control}} |
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{{DEFAULTSORT:Martin P6m Seamaster}} |
{{DEFAULTSORT:Martin P6m Seamaster}} |
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[[Category:Martin aircraft|P6M]] |
[[Category:Martin aircraft|P6M]] |
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[[Category:United States patrol aircraft |
[[Category:1950s United States patrol aircraft|Martin PM6 SeaMaster]] |
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[[Category:Flying boats]] |
[[Category:Flying boats]] |
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[[Category:Jet seaplanes and flying boats]] |
[[Category:Jet seaplanes and flying boats]] |
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[[Category:Cancelled military aircraft projects of the United States]] |
[[Category:Cancelled military aircraft projects of the United States]] |
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[[Category:T-tail aircraft]] |
[[Category:T-tail aircraft]] |
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[[Category:Aircraft first flown in 1955]] |
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Latest revision as of 01:31, 14 December 2024
| P6M SeaMaster | |
|---|---|
 | |
| General information | |
| Type | Patrol flying boat |
| Manufacturer | Glenn L. Martin Company |
| Primary user | United States Navy |
| Number built | 12 |
| History | |
| First flight | 14 July 1955 |
The Martin P6M SeaMaster was an experimental strategic bomber flying boat built by the Glenn L. Martin Company for the United States Navy that almost entered service; production aircraft were built and Navy crews were undergoing operational training, with service entry expected in about six months, when the program was cancelled on 21 August 1959. Envisioned as a strategic nuclear weapon delivery system for the Navy, the SeaMaster was eclipsed by the Polaris submarine-launched ballistic missile (SLBM). Due to the political situation at the Pentagon and weapon system choices made amid budgetary constraints, the Navy promoted the P6M primarily as a high speed minelayer.[1]
Design and development
[edit]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 to address this came in the form of the USS United States, a large supercarrier intended to launch Navy strategic bombers. This was cancelled in 1950 shortly after her keel was laid down, a victim of budget cuts and US Air Force interference. In response, the Navy chose 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, they would be hard to neutralize.
The requirement issued in April 1951 was for a seaplane able to carry a 30,000 lb (14,000 kg) warload over a range of 1,500 mi (1,300 nmi; 2,400 km) from its aquatic base. The aircraft was to be capable of a low altitude dash at Mach 0.9 (1,100 km/h). Both Convair and Martin submitted proposals, and the Martin proposal was chosen as more promising. An order for two prototypes was issued which was projected to lead to six pre-production aircraft and a projected twenty-four production aircraft.
Originally the plane was to have a Curtiss-Wright turbo-ramjet engine,[2][3] 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 swept at 40° were used; they displayed a notable anhedral and were designed with 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 bay—pneumatically sealed against seawater in the P6M.
Operational history
[edit]
The first flight of the XP6M-1 came on 14 July 1955,[4] but early tests showed that the engines were mounted too close to the fuselage and scorched it when afterburners were used, leading to angling the engines slightly outward in subsequent aircraft. Flight testing was initially successful, but, on 7 December 1955, a control system fault destroyed the first prototype with the loss of all aboard. The first prototype, BuNo 138821, c/n XP-1, disintegrated in flight at 5,000 feet (1,500 m) due to the horizontal tail going to full up due to a control malfunction, subjecting the airframe to 9 g stress as it began an outside loop, crashing into the Potomac River near the junction of St. Mary's River, killing four crew members.[4]
Eleven months later, on 9 November 1956, the second prototype, BuNo 138822, c/n XP-2, first flown on 18 May 1956, was also destroyed, due to a change made in the horizontal stabilizer control system without adequate evaluation before test flying the design. The crash occurred at 15:36 near Odessa, Delaware due to a faulty elevator jack. As the seaplane nosed up at ~21,000 feet (6,400 m) and failed to respond to control inputs, the crew of four ejected. The airframe broke up after falling to 6,000 feet (1,800 m) before impact.[2][5]
The first pre-production YP6M-1 was completed about a year later, with testing resuming in January 1958.
Five more were built in 1958 when the Navy announced that Harvey Point Defense Testing Activity in Hertford, North Carolina, would serve as the testing grounds for the fleet of Martin P6M SeaMasters. These aircraft were fitted with test versions of the full combat equipment suite and were used for bombing, mine laying and reconnaissance evaluations. The J71 engines were unreliable and the aircraft had spray ingestion problems at higher gross weights, which limited takeoffs to ideal conditions.[6] The P6M-1 also had a serious control deficiency due to porpoising under some trim settings.[7] These deficiencies resulted in the P6M-1 program being cut as it was no longer considered possible for it to be successfully developed.
The Navy and Martin felt that a new version, the P6M-2, would provide a useful aircraft. The first was rolled out in early 1959. Changes included new, more powerful Pratt & Whitney J75 engines, an aerial refueling probe, improved avionics, and a canopy with better visibility. A buddy refueling drogue kit had also been developed to fit in the bomb bay. Three had been built by summer 1959 and Navy crews were moving them through operational conversion when the program was abruptly canceled in August of that year.
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.[8] 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. Seaplane operations were a small component of U.S. naval aviation, and the P6M was significantly over budget and behind schedule and competing with aircraft carriers for funding. The Navy had also developed 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[update]) and could not be justified without the strategic mission.[citation needed]
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.[citation needed]
Martin tried unsuccessfully to market the technology in the civilian market, with a version called the SeaMistress but there were no takers,[9] and the company soon abandoned the aircraft business entirely to focus on missiles and electronics. The P6M was the final aircraft built by the Glenn L. Martin Company.
Variants
[edit]- XP6M-1
- prototypes, two built (BuNos 138821, 138822). Both crashed.
- YP6M-1
- pre-production model, six built (BuNos 143822-143827). All six examples were scrapped when the program was cancelled.
- P6M-2
- production model, eight built (BuNos 145876-145899). 145877-145879 were completed and flown, 145876 and 145880-145883 were completed but not flown. Contracts for 145884-145899 were cancelled.
Specifications (P6M-2)
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Data from [citation needed]
General characteristics
- Crew: 4
- Length: 134 ft 4 in (40.94 m)
- Wingspan: 102 ft 7 in (31.27 m)
- Height: 33 ft 10 in (10.31 m)
- Wing area: 1,900 sq ft (180 m2)
- Empty weight: 97,439 lb (44,198 kg)
- Gross weight: 184,280 lb (83,588 kg) (at take-off)
- 162,392 lb (73,660 kg) (in combat)
- Max takeoff weight: 190,000 lb (86,183 kg) in calm water
- 160,000 lb (72,575 kg) in rough water (6 to 9 ft (1.8 to 2.7 m) swell)
- Powerplant: 4 × Pratt & Whitney J75-P-2 turbojet engines, 17,500 lbf (78 kN) thrust each
Performance
- Maximum speed: 686 mph (1,104 km/h, 596 kn) at 20,000 ft (6,096 m)
- Maximum speed: Mach <Mach 0.89408
- Cruise speed: 535 mph (861 km/h, 465 kn)
- Stall speed: 152 mph (245 km/h, 132 kn) (Power off, flaps down, T.O. wt)
- Range: 2,083 mi (3,352 km, 1,810 nmi)
- Combat range: 750 mi (1,210 km, 650 nmi) (Carrying 30,000 lb (14,000 kg) payload)
- 1,726 mi (1,500 nmi; 2,778 km) with one AAR from a P6M-2 tanker
- Service ceiling: 50,000 ft (15,000 m)
- Rate of climb: 7,380 ft/min (37.5 m/s)
- Wing loading: 100 lb/sq ft (490 kg/m2)
- Thrust/weight: 0.368
Armament
- Guns: 2 × 20 mm cannon in rear remote operated turret (1,000 RDS/20mm)
- 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 pounds (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)
Avionics
- Fire-Control System: Aero X-23B AGL Tail Turret, ASQ-29 Automatic Navigation & Minelaying System
See also
[edit]Aircraft of comparable role, configuration, and era
Related lists
- List of flying boats and floatplanes
- List of United States Navy aircraft designations (pre-1962)
- List of military aircraft of the United States
References
[edit]Notes
[edit]- ^ Piet & Raithel 2001, p. 148
- ^ a b Greg Goebel. "The Martin SeaMaster & Convair Sea Dart".
- ^ American Aviation 12 Sept 1955 p12: "Navy is planning to use more powerful engines than the four Allison J71s plus afterburners to make the production model of the Martin Seamaster supersonic. XP6M-1 with the J71s will attain Mach .95."
- ^ a b Nicolaou 1986, pp. 25–26
- ^ Nicolaou 1986, pp. 26–27
- ^ Piet & Raithel 2001, p. 98
- ^ Piet & Raithel 2001, p. 107
- ^ Piet & Raithel 2001, p. 117
- ^ "SeaMonsters of the Navy, by Mark Wolverton, Air & Space, Feb/Mar 2012, pp. 62-63. [1]
Bibliography
[edit]- Allen, Francis J. (March–April 2001). "Poseidon's Giant: The Story of the Martin P6M SeaMaster". Air Enthusiast (92): 16–27. ISSN 0143-5450.
- Nicolaou, Stephane (December 1986). "Master of the Seas: The Martin P6M Flying Boat". Wings. Vol. 16, no. 6. Granada Hills, California: Sentry Publications.
- Piet, Stan; Raithel, Al (2001). Martin P6M SeaMaster. Bel Air, Maryland: Martineer Press. ISBN 0-9700662-0-1.
External links
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