Shipbucket

Designed by Martin,a company with experience in hydroplanes,the P6M Seamaster was reveiled in 1955.After two serious accidents in test flights,Martin redesign the tail in the second prototype creating the XP6M-2 which first took off in 1958 with great success.However,the greatest flaw of the P6M were its engines:the Allison J71 was both underpowered and unreliable and only when they replaced by PW J75 the P6M found an engine allow it to show its capabilities.The aircraft entered service in late 1960 with USN which order 164 airframes,of which 48 went to the Marines.Its very good performance in low height and 13.5t weapons load attracted interest of export customers,with Canada being the first.Canadair manufactured 94 total (CL-70,among them a SAR variant and a fire fighting variant).Next export customers were Norway and Hellenic Kingdom which ordered 24 each and finally Japan ordered 64 which were made by lisence from Kawasaki as K-6M.South Korea received 16 airframes from USN in 1991.
Except from nuclear weapons the P6M can be used as a fast minelayer (this option were available from the beginning of the program),as a Maritime Strike aircraft even as a bomber with Mk80 family Iron Bombs.Also a tanker aircraft was developed for US Marines (20 units) with an 15000lt tank in bombay and the hose and drogue system from the KC-130.Rest 28 could deliver up to 80 marines or Seals below enemy radars with ten specially designed self-inflate inflatables.These were used in Vietnam War landing on Megonq river but suffered 6 losses from enemy fire during the war.Marines P6M were also capable of minelaying.
The unique feature of the Seamaster is an on top hatch with access directly in the bombay from above,giving the hydroplane the capability to rearmed without leaving water.However,the P6M is not amphibious and require a purpose built trolley to come out of water.First trolleys were manually connected to the hydraulic system of the aircraft,second generation was automatic with their own water-tight hydraulic system.This last trolley came together with all export Seamasters,while Canadians modify it for use in colder water.Norwegian P6M were built by Martin,but had several of the Canadian modifications for use in cold weather, plus the Canadian modified trolley.
Last P6M built by Martin were the 24 HU-40M for US Coast Guard,a SAR variant which proved useful in several cases,since it could cope with 9ft(2.7m) waves.Another variant of the P6M came from Canada,the CL-72 Fire Bomber.Powered by more powerful J75-PW-13B engines of 16980lbf dry thrust,it features a 16000lt water tank and the same water-scoop system from the Canadair CL-215/415.Canada also built its own SAR version,designated as CL-71 for the Canadian Coast Guard.These engines replaced the J75-PW-2 of 15800lb in many other P6M during 1980's,offering as a modification kit.
Australia received 24 CL-70 from Canada in late 1980's,from which 6 were modified to fire bombers,due to severe wildfire problem.In Norway the main mission of the Seamaster were minelaying (as the Heinkel He115 back in 1940) and Maritime Strike with Penguin Mk3 and Harpoon missiles.After the end of Cold War some were
modified for SAR missions painted in Kystwakt (Norwegian Coast Guard) bright colors.Some Norwegian P6M are being modified for using the NSM missile.

Note that the P6M is used by Navy in USA,Canada and Hellenic Kingdom while in Australia and Norway aircrafts
belong to Air Force.

In Hellenic Kingdom the hydroplane was first used from a joint Air Force-Navy Squadron in 1970's and passed completely into the Royal Hellenic Navy in early to mid 1980's,as also P-3H Mk2 Orion in early 2000's,but the main base remained the same in Elefsis from both aircrafts.From all Seamaster users only two built bases into secret caves with directly access to the sea,Norway and Hellenic Kingdom.Latter bases are unique because they are a straight tunnel with a specially desighed hinged door to look like rock when close and inside among other there are a dry dock for maintenance which can rotate 180 degrees..The idea for cave-based hydroplanes in Hellenic Kingdom comes from the 1930's when one large such base built in mainland Ionian Sea coast for SHAF K-33 hydroplane (based in Blackburn Iris) and enlarged to accept the Seamaster.Back then this hydroplane base had also the rotator. One base more was built in an Aegean Island and in Cyprus near RHN Naval
Base there.In Hellenic Kingdom the P6M was the largest ever aircraft ever used from armed forces until the delivery of the first B707KH in 1986.

Specifications (P6M Seamaster II)

Type:Hydroplane
Crew : 4 (2 pilots,navigator/weapons operator/acoustic system operator)
Dimensions: Wingspan 31.37m,Length 40.84m,Height (overall) 11.65m,Height (floating) 9.75m
Powerplant: Four Pratt & Whitney J75-PW-13B turbojets,16980lbf (7720kg) each
Weights: Empty 98829lb (44920kg),combat 146960lb (66880kg),max take off 186938lb (84792kg)
Fuel capacity : 7950 us gal. (30090lt) for taking off,in refuelling 10808 us gal.(40910lt)
Speed: Maximum at low altitude 0.99 Mach (654 knots,1211 km/h),max retaining cruise 0.95 Mach (630 knots,
1166km/h),1.04 mach in dive
Operational ceiling 52000ft (15853m)
Combat radius:For Minelaying 750nm (1389km),Hi-Lo-Hi 1500nm
Armament: 1 X M61 Vulcan 20mm controlled by Emerson MD-7 radar in tail
Load: 35140lb (15972kg) of weapons in internal,water-tight rotating,11m long weapons bay including mines,
air to sea missiles,cruise missiles,bombs,nuclear bombs,nuclear or convectional mines etc.

P6M-MS:Maritime Strike variant.
Equipment: APS-80M radar (later APS-116),MAD high in tail,electronics from S-3A Viking.

''One of the best seaplanes ever designed''

LOL, really true? Why didn't it got a real service?

The short answer? Funding being denied due to the Polaris program requiring priority. And yes, this was certainly an impressive machine: Payload of 30,000 pounds (compared to 20,000 for the B-47E). And a very good radius of action; and a rotary bomb bay that could be loaded while the airplane was still in the water.

This airplane features in Friedman's 'The Postwar Naval Revolution'

Likewise it could be asked why Montana wasn't built, even though it would have probably been the meanest bastard ever to take to sea.

P6M was a victim of changing circumstances as much as anything else.

Agreed (about the P6M). That said, it would have been interesting to see it in service. Certainly, it was nuclear capable, and in USN hands, so we can imagine how the USAF would have welcomed that

like this (Montana):

http://wolfsshipyard.mystarship.com/Mis ... united.htm

To add to what's been said, it was believed that flying boats were obsolete. However, unlike say the Montanas its not so much a case of being a solidly white elephant. The P6M was one of the fastest subsonic aircraft around actually and was especially fast skimming the water. It would have had a very fast response speed when hunting subs; one of the things the British liked about the Nimrod and why they even drafted a supersonic ASW aircraft requirement(!), plus speed may not be a total perfect defense but more of it never hurts (we've never had a bomber that was considered "slow" since probably around the time the B-17 and B-24 retired). Moreover flying boats can be positioned anywhere where you have a base and I've yet to see any military capability be able to sink an ocean. But even if the P6M did enter service and enjoy a long service life it likely would've been the last one as the changing military environment would erase any perceived carrier threat.

I have also read that psychophysiological stress for SeaMaster pilots was quite extreme as they needed to endure several day long flights in pretty cramped conditions...
By the way, why this thread is in the Parts Sheets Discussion forums at all?

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Worklist: Portuguese Navy and Barnegat class seaplane tenders

I put it here because of some images I want to post.Site administrators or moderators could move it if nessesary.Here also there is the Planebucket.

Some videos of P6M Seamaster.

http://www.youtube.com/watch?v=QowTqmxYZ1Q
http://www.youtube.com/watch?v=NDia5WJB4Eg
http://www.youtube.com/watch?v=mqhhs5xrGek