Official first flight for XP-82

[Jhieminga]

After the unplanned circuit during what was supposed to be a high-speed taxi-run only, here is some footage from the official first flight that took place this week.
https://www.youtube.com/watch?v=wEJwLcj6qEU

[treadigraph]

Getting twin-engined Merlin-powered aircraft airborne again seems to be becoming a trend - great! Wonderful work by Tom Reilly and his team.

Shame that Wizzard Investments Allison-powered F-82E G-BXEI, never made it here for restoration - now being restored for an American customer at Anoka, MN.

[DaveReidUK]

Wasn't the XP-82's first flight in June 1945 ?

[Jhieminga]

Point taken. Make that 'official first post-restoration flight'.

Alternatively, we can also change it to 'first flight of a Twin Mustang in the 21st century' ;)

[PAXboy]

What was the intention for this craft? Fighter? Bomber? Experiment?

[DaveReidUK]

https://en.wikipedia.org/wiki/North_American_F-82_Twin_Mustang

[tdracer]

What was the intention for this craft? Fighter? Bomber? Experiment?

Long range escort fighter.

https://en.wikipedia.org/wiki/North_American_F-82_Twin_Mustang

Initially intended as a very long-range (VLR) escort fighter (https://en.wikipedia.org/wiki/Escort_fighter), the F-82 was designed to escort Boeing B-29 Superfortress (https://en.wikipedia.org/wiki/Boeing_B-29_Superfortress) bombers on missions exceeding 2,000 miles (3,200 km) from the Solomon Islands or Philippines to Tokyo, missions beyond the range of the Lockheed P-38 Lightning (https://en.wikipedia.org/wiki/Lockheed_P-38_Lightning) and conventional P-51 Mustangs.

The war ended before it became operational, although it was used in Korea.

Edit: - I see DR responded while I was grabbing a bite to eat...

[FlightlessParrot]

I assume the attraction of this arrangement was that it was quicker than designing a proper more conventional twin based on the Mustang, but the Wikipedia article claims there was a lot of new design, beyond, presumably, the new centre section. And by the way, it looks as though the guns would have needed to be synchronised in that position--is that so?

EDIT: I've found a three-view, which shows the guns located just outside the propellor disks, which would be the obvious way to do it: but it's a tight fit.

I'd be really interested in more information about the reasoning that led to this odd, but evidently successful, aircraft.

[Jhieminga]

I think Tom Reilly explains in one of the videos about the restoration that there are two or three parts that are interchangeable between the P-82 and P-51 families, the rest is all different. So much for it being a quick way to design a twin! :p

[SPIT]

Would the Pilot require a Twin Engine rating ???

[Jhieminga]

You certainly do, you even need one for a Cessna 337 (as you would need one for a Do-335 'Pfeil' if there would be an airworthy one). Although you used to be able to get a 'limited' multi engine rating on a 337 (it may still apply), that is, limited to 'centerline thrust only'.

[bafanguy]

Although you used to be able to get a 'limited' multi engine rating on a 337 (it may still apply), that is, limited to 'centerline thrust only'.

The FAA regs may have changed over the years but circa 1970 when I got my initial ATP in a DC9, the MEL rating thrown in said, MEL(limited to centerline thrust)...useless for GA flying. It had to do with the Vmca being below the stall speed...or something like that. This completely ignored the "foot full" required in the initial stages of a V1 cut. It didn't change to a full MEL until I added the B737 rating.

Regs are funny.

[megan]

From "Mustang Designer - Edgar Schued and the P-51" by Ray Wagner

The design for what culminated in the P-82 began on 21 Oct '43 when Ed Schmued requested Howard Evans & Julius Villepique to investigate a twin fighter design, one conventional & the other the P-82 arrangement. Villepique says of the conventional arrangement, but does not elaborate, "it could not compete with the manifold possibilities offered by the dual fuselage arrangement".

Schmued wrote, "Many people think the F-82 is nothing else but two P-51 fuselages joined together by the wing. This is not the case. It was a completely new design. Nothing of the P-51, except the design principles and power plant group, was used on this new venture".

General Arnold during a visit to the plant on 7 Jan '44 gave the go ahead when shown the proposal. Contracts were approved 30 Jun '44.

First attempts at flight on a number of successive days were unsuccessful, later found to be caused by the centre section being stalled due to prop rotation direction. First flight was 12 Jun '45 in the unmodified state. Engines/props were removed and installed in the opposite location and the aircraft flown ten days later.

[FlightlessParrot]

@megan: thank you. The Wikipedia entry suggests it was a lot more complicated than gluing two P51Ds together (but you don't trust Wikipedia).

You have to wonder whether a revamp of the P-38 (with a couple of Merlins) might not have been more cost effective? But still, the P-82/F-82 worked.

[megan]

You have to wonder whether a revamp of the P-38 (with a couple of Merlins)That was looked at and an aircraft was sent to Rolls Royce for conversion, but Washington on hearing of the fact ordered the aircraft to be returned to the USAAF immediately. It has been assumed that political pressure was applied by Allison because of a potential loss of business, having already lost supplying the P-51 with its switch to Merlins. Lockheed themselves also looked at the possibility, but didn't proceed.

[BEagle]

Post-war, RR was asking very high licensing costs for the Packard Merlin, so the decision was made to use Allison engines for the F-82.

[megan]

Each Merlin was costing the Air Force $6,000 in royalty payments. It was they who opted for the Allison, which had problems because it was not fitted with backfire screens, so limiting power produced. The Secretary of Defence James Forrestal forbade modification of the engine to have screens, even though NA had demonstrated the modified engine. The Allison -82 had very poor serviceability, requiring 33 hours maintenance per flight hour, mostly due to engine issues. During 1949 serviceability was less than 50%. The troubles with the Allison increased program costs from $35 million to $50 million and the aircraft was a year late getting to service. Might have been cheaper to stick with the Merlin, but as Ed Schmued commented, "Ït was a great airplane and it was ruined by personal interests. It was pathetic. It was really pathetic to see a good design ruined by politics and the lack of cooperation by the Allison people in building a good engine".

All the Allison airframes were completed by 30 Apr '48, but non availability of Allison engines didn't see the last aircraft delivered until 12 Apr '49. Non availability of spares from Allison contributed to the poor serviceability noted above.

[dduxbury310]

Why would the Secretary of Defence get involved in forbidding modifications being incorporated in an engine that the manufacturer's of said engine had decided were necessary? Sounds quite daft, unless it was simply a case of forbidding further modifications because so many had already been incorporated at government expense. I am always suspicious of reasons given for seemingly daft decisions made that are usually blamed on some politician or bureaucrat - often there is a long and convoluted story behind these things, so rather than go through all that rigmarole, it is much easier and less likely to reveal more persons with skin in the fight by simply blaming one convenient person. Time and again, this sort of quick blame game has been revealed over the years, and the real truth, no matter who is implicated, is outed. Also the stated cost of obtaining a license to build the American Merlin, seems outrageously expensive in this case, and I could only guess that the Americans were desperate enough to agree to that amount in 1941, then regretted it later (or yielded to pressure from GM Allison, now rather bizarrely owned by Rolls Royce!)
David D

[megan]

Allison was owned by General Motors and Ed Schmued states that the SoD favoured GM, and knew how to protect Allison. Production of Whittles I-40 (J33) and the axial J35 were taken from GE and given to Allison, Allison having the benefit of operating largely from government owned facilities and had a large workforce available with the downturn in V12 production, so could produce jet engines in quantity more quickly and cheaply. Allison getting into jet production in '45 (J33) and '47 (J35) and not supporting the V12, the reason for Schmueds fulmination at SoD and Allison is understandable. It wasn't Allison who said the backfire screens were necessary, it was North American. I guess Allison had little interest in the V12 once they were committed to jet design and production, allocation of resources perhaps. George Gehrkens, the project engineer, feels the characterisation of the political situation by Schmued is very overdrawn, but doesn't enlighten any further. My post #17 re $6,000 is a quote from Ed Schmued, it seems the royalty was imposed post war, prompting the Army to go with Allison. Post war a market for Packhard Merlins is doubtful in any event, a cash strapped UK would want any market for themselves.

There is also some suspicion about the first flight, George Gehrkens has a different memory to that stated in the book, again without elaboration. Seeing as the interviews with the people involved took place in '85 some suspicion has to lie over the respective memories.