Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Doberman on February 22, 2002, 02:37:14 PM
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There's been several threads lately in which commonly held "facts" are stated. Unfortunately, alot of the common knowledge is incorrect or at least only partly true. Plenty of it is based on ancedotal evidence, half remembered stories, misconceptions, etc.
Here are a few planes I'm planning on touching on over the next coupla days:
P-51
Corsair
Me-262
I'm not gonna post a huge list of references, but everything I'll state has been culled from reputable written sources which can be verified if there's some sorta huge disagreement. (Which there'll likely be. :) ) If you're gonna refute claims with "common knowledge" back it up.
I already commented in another thread on what seems to be an embellishment of Butch O'Hare's escapade in the "Ghosts" calander. Not having this years calander, I donno how much more of their stuff is similarly exxagerated or wrong. :( Hopefully not too much.
D
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P-51: Several of the most widely held and patently false myths of WWII involve the P-51 Mustang.
Everyone knows that the British approached North American Aviation about building the Curtiss P-40 on license in January of 1940. The story goes that NAA told the British they'd produce a better fighter using the same engine within 120 days. Unfortunately, there's no confirmation of the "120 days" claim anywhere. It's certainly not in the contract for the prototype.
Even more misunderstood is the performance expectations & development of the Mustang, particularly with the US military. Supposedly the 51 was a dog and uninspiring to everyone until some British wizard stuck a Merlin engine in it.
Facts don't support this. First off, the US military was interested in the Mustang from the start. So much so that the production contract stipulated that 2 of the early aircraft would be held back from Britian and sent to Wright Field for testing. At the time, the Pursuit division of the US Army simply didn't have the money to purchase the airplanes themselves. So, in effect, Britain bought the Army 2 planes which they hoped to use to convince the government to finance more.
The AAC was, in fact, so interested in the Mustang that they ordered all that the Pursuit Office could afford (150) even before the first text aircraft arrived at Wright Field. Tests eventually justified the expenditure, when it was shown that the 51 was a superior plane to the current best the AAF had to offer, the P-40.
The AAC wanted P-51's so badly that despite not having any more money in the budget for fighters, they found a way to get more Mustangs. The AAC never saw much use in dive bombing but they asked NAA to design a dive bomber version, which became the A-36.
(Yet another myth about the P-51 is ties up in the name of the A-36. The US Army orginally wanted to name the P-51 the "Apache." Britain had already named their version of the plane "Mustang" and that stuck with Americans who were woking on the plane. The A-36 was commonly called the "Apache", but it never had any offical nickname. "Invader" had been proposed by the Army, but it didn't take and that name was eventually applied to another aircraft.)
To return to the performance topic...both the designers & the military were very familair with the Allison engine that was to be used in the P-51. To claim that they were suprised by its lackluster high altitude performance is foolish. They knew that the Allison's performance dropped off over 15K in the configuration that the 51 would use. Which is why 2 of the original US order were slated for testing with the Merlin. This was ordered before the US had even begun testing on the planes they received from the British order. Original plans were for the Allison engined versions to be lower altitude fighters (where they outperformed the Merlins) while the Merlin powered planes would be used for high altitude missions.
People cry, "the Mustang sucked at high alt until the Merlin was installed." Which is true. What you don't hear from them is," the
Mustang sucked at low alt when the Allison was taken out." Which is relatively true. The Allison Mustang simply performed better at low alts than the Merlin. (Can you imagine an early US P-51 in AH MA where most combat takes place at less than 15K alts? The original US order of 150 P-51's were equipped with 4 20mm cannon. Perked for sure. :) )
And finally, there's the myth that the 51 won the war in the West by allowing bombers to fly escorted to Berlin. As has been brought up here recently in another thread, it's simply not true. P-38's had the range to escort bombers deep into Germany from the outset. Ira Eaker, who was in command of the 8th AF at the time, didn't believe the bombers needed escort though. He thought that the bomber's gunset was enough defense. P-38's sat around in England for a while with nothing to do, watching their bomber brethern get shot up day after day. Most of them were eventually reassigned to Africa. It wasn't until Jimmy Doolittle replaced Eaker that the bombers got the escorts that they so sorely needed.
D
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The Allison Mustang simply performed better at low alts than the Merlin
The flight test data (USAAF and NAA) do not support this claim.
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One of the books I've read over the years recalled a German pilot saying "We knew we were in for an easy day when we say the double tail of the P38"...I think he was regarding the early F models. Sorry, been some years since I read it, but I do recall that part clearly.
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Originally posted by funkedup
The flight test data (USAAF and NAA) do not support this claim.
Point me to this data or sources that quote this data. Everything I've read says that the Allison was equal or better than the Merlin down low.
D
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"America's Hundred Thousand" by Francis Dean, has performance charts for most major variants of US wartime fighters.
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Originally posted by funkedup
"America's Hundred Thousand" by Francis Dean, has performance charts for most major variants of US wartime fighters.
In other words..."The Fighter Pilots Bible" :D
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My copy is currently out on loan (and has been for some time. :( I'm beginning to worry about ever getting it back.) so I'm working from a coupla other sources.
List me some speed & accel data for Allison vs. Merlrin powered early Mustangs at say 10,000 feet?
D
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not sure ripsnort but i think that was in 'the first and the last' adolf gallands book.I seem to recall it too.
If we are talking myths then one such myth is this 'forked tailed devil' claim i see from many AH p38 fliers who go on to claim 'it must have kicked the 109s/190s bellybutton if they called it the forked tail devil!!' but unfortunately the name was given to the P38 by the pilots of the LW transport planes (ju52s) in the mediteranian theatre because they were mauled regularly by them in those poorly protected skies.
It seems people are very reluctant to admit that the P38(early marks) werent as suitable for the Euro theatre as they would wish for.
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Actually the P51 altitude performance was maybe not as good as often quoted. Or letīs say: in AH it is a bit optimistic for the P51B
Interavia No.918.19 page 18, 11.5.1944 reports from official english sources that the maximum speed is 685km/h, 425mph. This is a bit less than here eh?
The speed claim got more or less confirmed in Rechlin where the captured P51B reached 670km/h in ~7-8km
Actually the author from Interavia was so impressed with the speed claim that he assumed that it was for P51 with a 2000hp Griffon installation (info based on "good informed english sources").
niklas
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Good Read Doberman thanks.
But... and here's where it turns out that I'm an amazinhunk. Any chance we could get some citations? Lord knows that we've gone over this in other threads, but statements are simply opinion until backed up by data. In a case like this, where you are attempting to dispell rumors and myths, it helps to have a qualified expert backing up your statement. It could very well be that you are such an expert (I honestly don't know) but if not you should probably cite where you came up with your ideas and/or Data
-Sikboy
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"In other words..."The Fighter Pilots Bible" "
Nope..Shaw's is the Fighter Pilots Bible.
Daff
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Doberman my copy is in a box in storage. Anybody else who has a copy want to look up the numbers?
Niklas, there are various USAAF and NAA tests showing top speeds of P-51D and P-51B at over 440 mph. Of course those aren't as reliable as German and British tests. :rolleyes:
:D
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The charts in my copy of AHT show that the Allison powered P-51 would motor along at about 380mph at 10,000 ft (pg 325) and the P-51B/C would scoot along at just about 400mph at the same altitude (pg 326).
As far as acceleration, there are charts in the back of the book (pg 604) that show linear acceleration at sea level. The P-51 (the allison one) has an acceleration of 2.13 ft/sec/sec. The P-51D (only merlin powered one listed on the table) has an acceleration of 3.85 ft/sec/sec. One thing should be noted, the Allison version started at 250 mph when military power was suddenly selected. The Merlin version started at 250 and combat power was selected. How big of a difference this really causes, I can't say. I think the increase of 570 horsepower from the allison to the merlin would probably be the bigger factor though.
I would scan the charts and attach them, but I am tired and I don't feel like clearing off my scanner for this.
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Originally posted by funkedup
Niklas, there are various USAAF and NAA tests showing top speeds of P-51D and P-51B at over 440 mph. Of course those aren't as reliable as German and British tests. :rolleyes:
Pls tell me where full tests including temperature, and especially speed correction (or at least ias and tas) are avaiable for these both ac. thx
nik
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Gentlemen,
As the project head for a current P-38 restoration, I can give some bearing on the validity that the Allison powered aircraft are superior to the Merlins at lower altitudes. I have worked on a multitude of various WW2 aircraft from the B-25 through to FW-190, and during this time I have on numerous occasions found that supplied data from both the military and other "reputable" sources to be in the wrong.
Given my current vocation, it goes without saying that I speak with quite a few veterans both in pilots and crewman, as well as maintenance personel. As for 38 pilots, the common statement I get from them is that they prefererred the Lightning to the Mustang below 15000 ft, and above that would prefer to have a Mustang, as the Merlin is better matched to it's supercharger than is the Allison / GE combination. The reasoning behind that is supported by the USAAF supplying early aircraft designers with both the power plants, superchargers, and components that were to be used to ensure commonality of spares.
Another interesting fact I have found is that bottomline, the Packard built Merlin is more sought after than the British built RollsRoyce Merlin. Reasoning being in both reliability and better craftsmanship.
So, friends, I caution you to be open to what those who worked on the equipment, and flew it say, as theyu really truly know how those aircraft perform.
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Hi Bodhi,
>As the project head for a current P-38 restoration, I can give some bearing on the validity that the Allison powered aircraft are superior to the Merlins at lower altitudes.
The V-1650-3 engined P-51B tested by the US Navy achieved speeds virtually identical to those of the Allison F21R engined Mustang I tested by the RAF up to the latters full pressure altitude of 4000 ft, and much higher speeds above that. The same Mustang I with an F3R Allison was decidedly inferior even at low altitude.
Have a look at the RAF report on the Mustang I:
http://www.fourthfightergroup.com/eagles/ap222.html
Regards,
Henning (HoHun)
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A couple of points:
Dutch Kindelberger had a handshake agreement with the Brits to produce the NA-73 prototype 120 days after the design was approved. Moreover, if performance was not measurably superior to the P-40, NA would be in default on the contract and not get paid for their cash outlay. Lee Atwood was present at all meetings with the Brits and stated that this was the understanding.
Now, as to the USAAC's interest in the P-51. There wasn't any interest. You refer to 150 aircraft being ordered. Not until the Lend Lease act was passed, did the Air Corps order the fighter. All were purchased for transfer to the RAF, and only two (the 2nd and 10th off the line) were to be retained for testing. After Dec. 7th, the Air Corps decided to retain an additional 56 of the fighters. Yet, no orders were placed by the Air Corps until well into 1942.
It was standard procedure to request that one or more aircraft be provided to the Langley test center for evaluation. The fact remains that the USAAC did not order the P-51 for their use despite glowing flight test reports from Langley. It is now accepted that Curtiss did a lot of arm twisting in an effort to delay P-51 procurement. Evidently, they were successful to a degree.
Escorting Bombers: Despite what many perceive, American heavy bombers were escorted whenever possible. Indeed, the first B-17 raid into France was escorted by British and American piloted Spitfires. Likewise, Eaker used the P-47s to escort the heavies to the limit of their range (the escorts). Those P-38s that deployed to Britain in 1942/43 had flown only a handful of sweeps before being transferred to North Africa. After the debacles of the two Schweinfurt missions, two P-38 Groups (20th and 55th) were rushed to England to provide escort for deep penetrations. However, virtually no theater training was provided, and the two Groups went active long before they should have, due to the political pressure being applied to 8th Air Force. Doolittle did not replace Eaker until January of 1944. By then, the P-51 and P-38 had already been flying escort for some three months. What Doolittle did was allow the escort to range out ahead of the bombers, discontinuing Eaker's policy of "close escort".
My regards,
Widewing
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Bring it on...
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Fantastic thread, guys!
I wasn't sure the AH community had this in it. Thanks for restoring my confidence!
:D
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An additional note:
the Ford of England Merlins were better than the Merlins produced by Rolls-Royce.
It is my understanding that the XP-51 (41-038, -039) sat around at Wright(-Patterson) Field for several months before being tested (gun trials) in late 1941 and that was for the USN/RAF not the USAAF.
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IMO I can only echo others (Mr. Brody as well as Widewings comments in the past) have said in that what the Curtis co. and the WPB head (forget his name at moment. Big 'GM' guy) did to promote thier "pet" products at the expense of other proven, war winning developments was almost (was!) criminal.
Westy
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according to AHT.. the early allison Mustangs would do about 390 at altitude and 335 on the deck. The allison mustangs were lighter and so.. rturned better. they would make great arena planes.
lazs
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An interesting technical thread on the Allison engined mustangs can be found at: http://agw.warbirdsiii.com/agw//Forum3/HTML/026455.html
Hooligan
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the allison mustangs were single speed single stage superchargers. they worked very well at low to medium alts with some models doing as high as 360-380 on the deck and about 400 at alt. They would be very fomidable arena planes. Much lighter and more nimble than merlin mustangs. They had a fantastic K/D ratio against LW planes but then... who didn't?
Glad to se WB finally seen the light and put em in the game. Real cure for the "allied vs axis" dead zone that is '42 FW days.
lazs
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Hurry up and get to the F4U stuff!!
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Niklas, I don't have the report but here are the particulars:
Report: NA-5798
Title: "Flight Test Performance for the P-51B-1
Date: January, 1944
Test Weight: 8,460 lbs
High Speed: 453 mph true airspeed at 28,800 feet at 67" HG and 1298 HP,
war emergency power, high blower, critical altitude.
I think America's Hundred Thousand has references to the tests in the 440 mph range for P-51B and P-51D. I'll try to get my copy out of storage and find the report numbers.
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Question for Bohdi:
1st are you Bodi from AW? if so, hey this is .
2nd I read somewhere and I'm too lazy to dig it up again, that there were a relatively small number of P-51's manufactured in Australia. Additionally these seemed to be a large percentage of the surviving planes after the war and are sought after by restorers and collectors due to their craftsmanship. Not because the Aussies were better manufacturers, but because they took more time to build them and had less pressure on production rates. Have you heard the same?