Martin P-6M Seamaster
(The following is partially a fictional history.)
With aircraft carriers unable to carry bombers capable of carrying the large nuclear bombs of the 1950s, the US Navy found itself unable to assist the USAF in providing a nuclear deterrent during the Cold War, with the result that it found itself in danger of losing a great deal of funding and possibly even its carriers. Though the latter problem never materialized, the US Navy nonetheless proposed a mobile strike force of jet seaplane bombers, operating from ships on the open ocean—a force that would be nearly impossible to detect or destroy in a preemptive attack.
The design parameters for such an aircraft were very complicated, but Martin, which had provided seaplanes to the Navy since the 1930s, won the competition with its XP6M-1 Seamaster design, based loosely on a combination of two of Martin’s already flying designs: the failed XB-51 bomber, and the successful propeller-driven P5M Marlin ASW/SAR aircraft. The Seamaster retained the upswept T-tail of the Marlin and a broadly similar flight deck, while incorporating the rotating weapons bay of the XB-51. The Seamaster was otherwise a radical departure from traditional flying boats, as it needed to be capable of a high-speed run to and from a target to deliver a nuclear weapon. The fuselage was long and sleek, while it sat low to the water with a thick, anhedral wing tipped with floats. On the water, the floats acted as stabilizers on landing and takeoff, and retracted upwards to become the wingtips in flight. To keep the engines free of water spray, the four Allison J71 turbojets were mounted above the wings. Since the only threat to the Seamaster would likely come from behind, defensive armament consisted of a remote twin 20mm cannon barbette.
The XP6M-1 first flew in mid-1955, but almost immediately ran into trouble, resulting in the destruction of two out of four prototypes. While the aircraft losses were due to problems with the tail that were easily fixed, the unreliable engines still had a tendency to ingest water in all but calm water conditions and had a tendency to depart controlled flight in certain situations. With the program in danger of cancellation, Martin responded with the P6M-2, which replaced the troublesome Allison engines with proven Pratt and Whitney J75 turbojets, along with a better canopy for improved visibility, improved avionics, and inflight refuelling capability.
Despite greatly improved performance, it still had problems. These included engine surging, severe buffeting above Mach 0.8, and a tendency for the wingtip floats to dig in (risking a catastrophic water-loop). Though Martin proposed design changes that would solve the problems, and despite 12 aircraft already built, the US Navy cancelled the Seamaster in August 1959. This was less due to the aircraft—which despite the aforementioned problems, had proven itself to be an excellent basic design—as it was the expansion of the aircraft carrier fleet (which could now launch bombers heavy enough to carry nuclear weapons, which themselves were getting smaller) and especially the development of the Polaris SLBM. With submarine launched missiles, there was no need for the Seamaster. With the exception of one tail section, the entire Seamaster fleet was scrapped; it was the last Martin design for the US Navy.
In one of the strangest incidents of aviation history, the Seamaster’s story was not to end there. One of the engineers on the Martin project, Glenn Powell, was to become one of the founders of Predator Propulsion in August 1978. The FIRAF and FIRNAA had issued a joint requirement for a maritime patrol aircraft capable of both antisubmarine warfare and on-site search and air rescue. The latter requirement precluded the acquisition of the P-3 Orion, and it was understood that the services intended to buy the ShinMeiwa US-1 flying boat. Powell, however, thought that a resurrected Seamaster might also fit the bill, and his proposal came at a time when the FIR Congress begun to request that the armed services begin buying aircraft built in the FIR, to provide jobs and make the Republic’s fledging aircraft industry competitive. A new-build Seamaster would not be as large as the US-1, but it would outpace it in all respects in performance. High speed was deemed to be useful not only in being able to arrive at a rescue quickly, but also to evade any interception—something to be considered, given that whatever aircraft acquired would likely be operating in Alaska, where the FIR had oil interests and had joined with the US Coast Guard to combat illegal whaling.
The FIRNAA was reluctant to dust off a 20-year design for the same reason the Seamaster had been cancelled in 1959—it needed money for carriers—but the FIRAF liked the idea and commissioned Predator Propulsion to build a proof-of-concept aircraft in November 1979, with Powell in charge. Plans were acquired from both museums and permission obtained to build the aircraft from General Dynamics, which had acquired the Martin company. The new design was designated XP-6C by Predator Propulsion, but changed midway through redesign to the YP-6M to honor the old design.
The “new” Seamaster was, on the surface, almost identical to the old P6M-2 design, with roughly the same dimensions; the only change there was a slight increase in tail surface and height. The wingtip floats were also slightly redesigned to cure the handling problems. Despite this, however, the similarity was literally only skin-deep, as the YP-6M extensively used composites to save weight, at the time still a radical design feature; the use of composites also reduced the amount of salt corrosion the aircraft would be expected to have. The Seamaster also became a true amphibian: the P6M-1 and 2 had used a unique docking collar, where the crew had water-taxied the aircraft to the partially-submerged collar, docked, and then drove up onto the beach or runway. The YP-6M, however, had integral landing gear. The rotating weapons bay door was also deleted for simpler clamshell doors, and two new hardpoints added beneath the wing for additional weapons, including torpedoes that could be launched while the Seamaster was afloat. Since the YP-6M’s primary offensive purpose was antiship or antisubmarine warfare, the size of the weapon bay was reduced; the twin 20mm cannon was replaced with a single M61A1 Vulcan 20mm gatling cannon in a mount identical to that carried on the B-52G Stratofortress. To cure the engine problems, the Pratt and Whitney J75s were replaced by General Electric F101 engines that powered the B-1B Lancer. Besides being more fuel efficient, the more powerful F101s allowed the YP-6M to carry a bigger warload than the original despite being lighter, and fly higher and further. Reinforcement of the hull allowed the YP-6M to land or takeoff in worse sea states than the P6M-2, but it still required mostly calm waters to land and float.
With the switch to ASW warfare, the YP-6M was fitted with an ASW suite similar to that carried by both the SH-3H Sea King and P-3C Orion. This included AQS-13B sonar, contained in a retractable sonar dome mid-hull, APS-115C search radar, and ASQ-81 MAD detector, in a retractable boom carried in the tail. Sonobuoy ports were also included, once more mid-hull, between the sonar dome and the weapons bay. To operate in the SAR role, the Seamaster was fitted with two large doors in the rear hull where up to four eight-man rafts could be ejected remotely; flare ejectors were also added below the tail that could be used either to mark survivors or evade heat-seeking missiles. The design was considered so successful that the FIRAF cancelled the proof-of-concept demonstrator and placed an order for six production P-6M Seamasters.
The first aircraft was rolled out and began flight testing in July 1982, flying to NAS Patuxent River in Virginia, where the original P6M-1 had begun testing nearly thirty years before. The flight testing was remarkably trouble free, and the FIRAF ordered a full production run of 24 aircraft. The first operational P-6M entered service with the 10th Reconnaissance Squadron in July 1983, with the last entering service in June 1985, though Predator Propulsion finished an additional six aircraft as attrition replacements and technology demonstrators.
(Back in the real world...)
I always liked the Seamaster for its unique profile and mission, and as a birthday gift a few years ago, Dad built and modified the old Revell 1/100 scale (sort of) XP6M-2 kit to my fictional P-6M design. To simulate new sensors, USAF-style refuelling plug and ECM, Dad stuck on various bumps and bulges around the aircraft from the spare parts box. He painted it in World War II US Navy Atlantic camouflage (light gray over white), and used decals from the decal box for a "Free Intelani Navy" P-6M, and added an orca motif on the tail, complete with "whalemouth" on the nose! He had a lot of fun with this one.
Martin P-6M Seamaster
(The following is partially a fictional history.)
With aircraft carriers unable to carry bombers capable of carrying the large nuclear bombs of the 1950s, the US Navy found itself unable to assist the USAF in providing a nuclear deterrent during the Cold War, with the result that it found itself in danger of losing a great deal of funding and possibly even its carriers. Though the latter problem never materialized, the US Navy nonetheless proposed a mobile strike force of jet seaplane bombers, operating from ships on the open ocean—a force that would be nearly impossible to detect or destroy in a preemptive attack.
The design parameters for such an aircraft were very complicated, but Martin, which had provided seaplanes to the Navy since the 1930s, won the competition with its XP6M-1 Seamaster design, based loosely on a combination of two of Martin’s already flying designs: the failed XB-51 bomber, and the successful propeller-driven P5M Marlin ASW/SAR aircraft. The Seamaster retained the upswept T-tail of the Marlin and a broadly similar flight deck, while incorporating the rotating weapons bay of the XB-51. The Seamaster was otherwise a radical departure from traditional flying boats, as it needed to be capable of a high-speed run to and from a target to deliver a nuclear weapon. The fuselage was long and sleek, while it sat low to the water with a thick, anhedral wing tipped with floats. On the water, the floats acted as stabilizers on landing and takeoff, and retracted upwards to become the wingtips in flight. To keep the engines free of water spray, the four Allison J71 turbojets were mounted above the wings. Since the only threat to the Seamaster would likely come from behind, defensive armament consisted of a remote twin 20mm cannon barbette.
The XP6M-1 first flew in mid-1955, but almost immediately ran into trouble, resulting in the destruction of two out of four prototypes. While the aircraft losses were due to problems with the tail that were easily fixed, the unreliable engines still had a tendency to ingest water in all but calm water conditions and had a tendency to depart controlled flight in certain situations. With the program in danger of cancellation, Martin responded with the P6M-2, which replaced the troublesome Allison engines with proven Pratt and Whitney J75 turbojets, along with a better canopy for improved visibility, improved avionics, and inflight refuelling capability.
Despite greatly improved performance, it still had problems. These included engine surging, severe buffeting above Mach 0.8, and a tendency for the wingtip floats to dig in (risking a catastrophic water-loop). Though Martin proposed design changes that would solve the problems, and despite 12 aircraft already built, the US Navy cancelled the Seamaster in August 1959. This was less due to the aircraft—which despite the aforementioned problems, had proven itself to be an excellent basic design—as it was the expansion of the aircraft carrier fleet (which could now launch bombers heavy enough to carry nuclear weapons, which themselves were getting smaller) and especially the development of the Polaris SLBM. With submarine launched missiles, there was no need for the Seamaster. With the exception of one tail section, the entire Seamaster fleet was scrapped; it was the last Martin design for the US Navy.
In one of the strangest incidents of aviation history, the Seamaster’s story was not to end there. One of the engineers on the Martin project, Glenn Powell, was to become one of the founders of Predator Propulsion in August 1978. The FIRAF and FIRNAA had issued a joint requirement for a maritime patrol aircraft capable of both antisubmarine warfare and on-site search and air rescue. The latter requirement precluded the acquisition of the P-3 Orion, and it was understood that the services intended to buy the ShinMeiwa US-1 flying boat. Powell, however, thought that a resurrected Seamaster might also fit the bill, and his proposal came at a time when the FIR Congress begun to request that the armed services begin buying aircraft built in the FIR, to provide jobs and make the Republic’s fledging aircraft industry competitive. A new-build Seamaster would not be as large as the US-1, but it would outpace it in all respects in performance. High speed was deemed to be useful not only in being able to arrive at a rescue quickly, but also to evade any interception—something to be considered, given that whatever aircraft acquired would likely be operating in Alaska, where the FIR had oil interests and had joined with the US Coast Guard to combat illegal whaling.
The FIRNAA was reluctant to dust off a 20-year design for the same reason the Seamaster had been cancelled in 1959—it needed money for carriers—but the FIRAF liked the idea and commissioned Predator Propulsion to build a proof-of-concept aircraft in November 1979, with Powell in charge. Plans were acquired from both museums and permission obtained to build the aircraft from General Dynamics, which had acquired the Martin company. The new design was designated XP-6C by Predator Propulsion, but changed midway through redesign to the YP-6M to honor the old design.
The “new” Seamaster was, on the surface, almost identical to the old P6M-2 design, with roughly the same dimensions; the only change there was a slight increase in tail surface and height. The wingtip floats were also slightly redesigned to cure the handling problems. Despite this, however, the similarity was literally only skin-deep, as the YP-6M extensively used composites to save weight, at the time still a radical design feature; the use of composites also reduced the amount of salt corrosion the aircraft would be expected to have. The Seamaster also became a true amphibian: the P6M-1 and 2 had used a unique docking collar, where the crew had water-taxied the aircraft to the partially-submerged collar, docked, and then drove up onto the beach or runway. The YP-6M, however, had integral landing gear. The rotating weapons bay door was also deleted for simpler clamshell doors, and two new hardpoints added beneath the wing for additional weapons, including torpedoes that could be launched while the Seamaster was afloat. Since the YP-6M’s primary offensive purpose was antiship or antisubmarine warfare, the size of the weapon bay was reduced; the twin 20mm cannon was replaced with a single M61A1 Vulcan 20mm gatling cannon in a mount identical to that carried on the B-52G Stratofortress. To cure the engine problems, the Pratt and Whitney J75s were replaced by General Electric F101 engines that powered the B-1B Lancer. Besides being more fuel efficient, the more powerful F101s allowed the YP-6M to carry a bigger warload than the original despite being lighter, and fly higher and further. Reinforcement of the hull allowed the YP-6M to land or takeoff in worse sea states than the P6M-2, but it still required mostly calm waters to land and float.
With the switch to ASW warfare, the YP-6M was fitted with an ASW suite similar to that carried by both the SH-3H Sea King and P-3C Orion. This included AQS-13B sonar, contained in a retractable sonar dome mid-hull, APS-115C search radar, and ASQ-81 MAD detector, in a retractable boom carried in the tail. Sonobuoy ports were also included, once more mid-hull, between the sonar dome and the weapons bay. To operate in the SAR role, the Seamaster was fitted with two large doors in the rear hull where up to four eight-man rafts could be ejected remotely; flare ejectors were also added below the tail that could be used either to mark survivors or evade heat-seeking missiles. The design was considered so successful that the FIRAF cancelled the proof-of-concept demonstrator and placed an order for six production P-6M Seamasters.
The first aircraft was rolled out and began flight testing in July 1982, flying to NAS Patuxent River in Virginia, where the original P6M-1 had begun testing nearly thirty years before. The flight testing was remarkably trouble free, and the FIRAF ordered a full production run of 24 aircraft. The first operational P-6M entered service with the 10th Reconnaissance Squadron in July 1983, with the last entering service in June 1985, though Predator Propulsion finished an additional six aircraft as attrition replacements and technology demonstrators.
(Back in the real world...)
I always liked the Seamaster for its unique profile and mission, and as a birthday gift a few years ago, Dad built and modified the old Revell 1/100 scale (sort of) XP6M-2 kit to my fictional P-6M design. To simulate new sensors, USAF-style refuelling plug and ECM, Dad stuck on various bumps and bulges around the aircraft from the spare parts box. He painted it in World War II US Navy Atlantic camouflage (light gray over white), and used decals from the decal box for a "Free Intelani Navy" P-6M, and added an orca motif on the tail, complete with "whalemouth" on the nose! He had a lot of fun with this one.