Allison Engine development

[Wolfala]

One thing i'm trying to figure out, why did Allisons get such a bad rap compared to the Packard Merlins during 41-45? And why post 45 did Packard Merlin all but disappear from the engine market? i.e. with the F-82 being Allison powered instead of Packard Merlin.

[Captain Virgil Hilts]

1. Ignorance. And the fact that the War Production Board never allowed a better supercharger (two speed two stage).

2. Because the manufacturing license ran out. And the Allison used in the P-82 was a really nice piece.



Oh yeah, a Packard or Rolls Royce Merlin never won the Unlimited Class at Reno until someone figured out how to use an Allison V-1710 connecting rod in a Merlin. Merlins couldn't finish a race because you couldn't keep the rods in them if you ran them hard enough to keep up with an Allison or a radial.

[Wolfala]

So in a strange twist of fate, the V-1710 timebomb monicer was applied to the Packard Merlin during Reno?

Didn't know it was a licensing issue - were there enough Merlins on the market at the time to keep the F-51s spare sourced without issue through Korea?

Wolf

[TimRas]

Originally posted by Captain Virgil Hilts
And the Allison used in the P-82 was a really nice piece.

From the "Mustang Designer" buy Ray Wagner:
Schmued describes the central problem:
"The engine we had intended for this design [P-82] was  a Merlin. The United States  Air Force was tired of paying a $6,000 royalty to England for each Merlin engine built in this country for Packard, on a royalty basis. So they decided, then, to substitute an Allison V-1710 for the Merlin.
Now the Merlin engine had a very high rating, 2,270 hp with 90-inch manifold pressure, and the Air Force told the Allison people they had to duplicate this performance. It was obvious that the way their engine was built was not suitable for these high manifold pressures. The British built a backfire screen into their engine, which made it run properly . But the Allison people refused to do that.
To help the situation along, we actually modified an Allison engine with a backfire screen that worked fine. But then, the secretary of defence was powerful enough to override the Air Force and told Allison not to do anything. Which, of course, left the F-82 with a rating far below that of a good trainer. The manifold pressure was reduced to 60 inches to keep this thing from backfiring into the blower case and damaging the engines. This was a very sad situation, because it really ruined the project. The secretary of defence [James Forrestal] favored General Motors and, I think, he had a good idea to protect the Allison people.
The Allison people were already on the way to build jet engines and did not really like to go back and build reciprocating engines. That very nearly ended the project. We flew these airplanes with the Allison engine at high manifold pressure and pretty nearly every flight, we lost the engine for sure and sometimes it was dangerous enough to lose the airplane and the pilot. It was really pathetic to see a good design simply ruined by politics and the lack of cooperation by the Allison people in building a good engine.
We had demonstrated the Allison engine with backfire screens, but it didn't make any difference, because Allison never agreed to install them. We just couldn't get any support form the Department Of Defence. The secretary completely failed to support us in this particular endeavor, and therefore the airplane didn't meet expectations. It was a great airplane and it was ruined by personal interests. It was pathetic."

[Krusty]

I've also heard that Allisons were technically complex, and were not easy to repair and maintain in the field. This probably ties in to reliability (if you can't repair/overhaul it in the field, it won't run as well??).

That might have had some part in it.

[Captain Virgil Hilts]

Never needed a "backfire screen?" in an Allison. We ran them over 85" of boost. I have no idea what that guy is talking about, I've seen Allisons run at 100" before and never heard of nor seen a "backfire screen".

The Allison powered twin Mustang was able to exceed 470MPH, and to this day still holds the distance record for a prop driven piston engine fighter with no refueling.

The Allison is no more complex than the Merlin, and is easy to work on. The only difficult Allison to work on is in the P-38, and that is due to the cramped installation and the extra plumbing for the remote oil coolers, radiators, intercoolers, and turbocharger. In fact, the Allison can be reversed in the field relatively easy, I've never seen anyone reverse a Merlin. In the P-82, being able to reverse an engine is critical, since the engines are "handed", and rotate in opposite directions like the P-38.

The Allison was also certainly designed for high speed and high manifold pressure, as the P-38L engine was rated at 3200 RPM and 80".

[storch]

iirc correctly the P82 used allison143/145 they were derated to 1600hp for the P82  this allison was a monster of an engine.

[Debonair]

i always wondered why F-82 were never sent to pwn at Reno, but i just got my copy of

in the mail, so maybe i'll learn soon enough.
do any F-82s still exist?

[Wolfala]

1951 was the last full year of F-82 operations in Korea, as they were gradually replaced by the jet-powered F-94 Starfire. By summer 1953 the last surviving Korean War veteran F-82's were being flown to Tachikawa, Japan to be upgraded to F-82L models with the addition of cold weather equipment, and additional de-icers. Many of these planes would end up operating with Strategic Air Command from airfields in Alaska where they would serve as escorts for the massive Convair B-36 bombers during long flights over the Arctic, finally fulfilling their original mission as a bomber escort. The F-82 did not disappear from Air Force inventory until 1954, when a lack of parts, and high airtime made them impossible to keep flying. Many were finally scrapped in Alaska.

Three other F-82's are known to exist. One has been a "gate guard" for many years outside Lackland AFB in Texas, while a second F-82B that had been on display next to it was acquired by the former Confederate Air Force in 1966 and was operated for many years by its Midland, Texas squadron. That F-82B stalled and crashed in Harlingen, Texas in 1987. The aircraft was restorable, but its unique props and landing gear were destroyed in the crash, and replacement parts could not be obtained. In 2002 it was included with the CAF's crashed P-38 in a trade for a flyable P-38. The Air Force has stepped in and is demanding the F-82 be returned since it was only loaned to the CAF conditional that they keep it. The matter is still being debated. A single fuselage of the second YP-82 was located for many years on the farm of Walter Soplata in Newbury, Ohio. It was sold several years ago and its current whereabouts are unknown.

[Squire]

"One thing i'm trying to figure out, why did Allisons get such a bad rap compared to the Packard Merlins during 41-45?"

The most direct answer is the lackluster performance of the P-40 and P-39 series at higher altitudes.

The engine itself was a fine design, but the US War Dept made a bad mistake by not insisting on two stage superchargers for those two fighters.

The comparisons made tended to be between the Allison and the Merlin, the "Packard Merlin" was the US built Merlin engine, that came along in 1943, and powered the P-51B.

Also, there were comparisons to the US Pratt and Whitney radials, that were delivering 2000 hp, and high alt performance in the P-47 series.

So compared to the P-38 (which had the extras for the high alt Allison), and the P-47, the P-40 and P-39s came off as "2nd rate" amongst USAAF fighter pilots in the Pacific and ETO.

...then of course, the USAAF goes with the P-51 as its "premier" fighter in 1944-45, and its powered by a Merlin, not an Allison.

...and the Grumman and Voight designs in the F6F and F4U series were all PW radials as well.

So there are several factors as to why the WW2 Allisons are perhaps not remembered in a better light, however unfair that might have been to the actual engine design itself.

[Charge]

U seen this site?

http://www.unlimitedexcitement.com/Miss%20US/Allison%20V1710%20Engine.htm

-C+

[storch]

you pretty much nailed it squire.  the allison was far more robust than the merlin, the addition of superchargers rated to deliver sea level power at altitude was really the only difference and accounts for the engine's "lackluster performance".  the hydroplane racers of the 1960's-80's utilized the allisons over the merlins and griffons by a wide margin.

[storch]

Originally posted by Charge
U seen this site?

http://www.unlimitedexcitement.com/Miss%20US/Allison%20V1710%20Engine.htm

-C+

great site just bookmarked it.  thanks for posting that.

[HoHun]

Hi Squire,

>The engine itself was a fine design, but the US War Dept made a bad mistake by not insisting on two stage superchargers for those two fighters.

I think it would be  highly interesting to see an engine comparison based on shaft power instead of the usual brake power. That would eliminate the supercharger from the equation, emphasizing the performance of the basic engine :-)

Regards,

Henning (HoHun)

[gripen]

Originally posted by Captain Virgil Hilts

The Allison powered twin Mustang was able to exceed 470MPH, and to this day still holds the distance record for a prop driven piston engine fighter with no refueling.

AFAIK the distance record was reached with a P-82B ie a Merlin powered twin Mustang.

From Baugher's site:

"On February 28, 1947, P-82B serial number 44-65168 piloted by Robert E. Thacker and his copilot John M. Ard flew nonstop without refueling from Hickam Field, Hawaii to LaGuardia Airport, New York, covering a distance of 4968 miles in 14 hours 31 minutes 50 seconds for an average speed of 342 mph. This airplane, named *Betty Joe* after Thacker's wife, carried four external fuel tanks under the wings for this flight. This was the longest unrefuelled flight ever carried out by a piston-engined fighter. The record still stands."

Regarding the developement of the Allison; IMHO it was allways too little, too late, specially if compared to the Merlin.

gripen