Fw 190A vs P-47D diving from 25,000 ft to deck.

[Viking]

Originally posted by Knegel
I already wrote that i had the impression its a RAE statement, not only Browns opinion, i got this impression cause it was offered by Viking in one contex with the RAE testresults. I so sorry that i got this impression, realy iam so sorry.

You seem to have a problem understanding my posts or you simply remember wrong and don’t take the time to re-read my post before referring to them.

Here are my posts pertaining to Brown or RAE from page one:

Originally posted by Viking
Interestingly the Fw 190 has a higher critical Mach number than the P-47, so if both aircraft dived steeply enough to reach such speed the Fw 190 would pull away from the P-47. I don’t know what angle the dive would be however.

Originally posted by Viking
According to Eric Brown they actually did. See the videos I posted.

Originally posted by Viking
He said that when Doolittle found that his fighters didn't engage the enemy, but simply dived past them into oblivion never to be heard from again, he contacted the British at RAE Farnborough to find out what was going on. The British being the leading authority on high speed testing at that time. RAE found that the 109 and 190 had a tactical Mach limit of 0.75, the P-38 had a tactical limit of 0.68 or 0.69 (I don’t recall which) and the P-47 had 0.71. Brown said they were useless as high altitude escorts and that only the P-51 with a tactical Mach limit of 0.78 could deal with the Germans at 30k.

Nowhere do I mention RAE reports or findings except what Brown told me at the lecture.

Originally posted by gripen
Perhaps you should stop shouting and instead actually read the RAE reports and also the article on the Republic tests. The phenomena is described exactly same in the both cases; heavy and uneffective elevaror control, uneffective trim, buffeting etc. The only (minor) difference between the results is about 0,03-0,05 unit difference in the measured Mach numbers which is probably caused by measurement errors. The RAE results are probably more accurate because they were doing quite a lot high speed research that time.

Originally posted by gripen
I don't think that there is somekind of accurate/exact/final truth on this kind of issue. It can be said that at least in the tested configuration (both tests, RAE and Republic) the P-47 had some undesirable characters at high mach numbers. Anyway, they certainly had a good reason to add the dive recovery flaps.

A voice of reason, how refreshing. Of all the fighters of WWII to my knowledge only two had to have dive flaps mounted to alleviate dangerous dive characteristics: P-38 and P-47.

As always people will have to draw their own conclusion, but I think this thread is done.

[BlauK]

Gripen,
I think your Brown quotes don't deal with diving tests, right?

The same man writes in his book 'Wings On My Sleeve' (pp.70-72):

"The big job in Aerodynamics Department when I arrived was the exploration of high-speed flight problems. It was te first full-scale research in the country on the compressibility of airflow causing loss of control at transonic speeds - the first probing of the sound barrier. Chasing higher and higher Mach number decimals we dived our machines from high altitude until they began to go out of control.

This transonic flight testing took a new emphasis after a visit to RAE early in 1944 by Lt.Gen. Jimmy Doolittle, who had just taken over command of the 8th USAAF. This American air force had started worrying fighter losses when the fighters on high cover over Flying Fortresses dived down to intercept German fighters attacking the bombers and lost contreol before they could engage the enemy in combat.

Americans needed urgent help, and RAE was the world leader in transonic flight testing. There was no time to set up normal instrumented research programme, but what was wanted was a hands-on series of tests on three USAAF escort fighters - the P-38H Lightning, P-47C Thunderbolt and P-51B Mustang. The requirement was for detailed description of the handling behaviour of these aircraft at high speeds up to their tactical (manoeuvring) and critical (loss of control) Mach number, so that the operational pilots could recognize they were near these limits without reference to instruments in the cockpit."


"We knew from tests at RAE on captured German fighters that the Me109 and Fw190 both had tactical Mach number of 0.75, so that figure was the name of combat game at 30,000 feet. The tests we conducted on the American fighters revealed that the Lightning and Thunderbolt fell well short of that figure, with tactical Mach numbers of 0.68 and 0.71 respectively. However, the Mustang with its laminar-flow wing achieved 0.78 tactically, and soon after receiving these results Doolittle asked that his Force be supplied with only P-51Bs."

I suppose this might not have been the only reason for requesting Mustangs, but Brown does not discuss any other reasons (e.g. range) in this text. I think he might be jumping into a conclusion or at least making a pretty big shortcut.

[gripen]

Here is the diving part from the "Testing for Combat" (p.145-146):

"Before next flight a Machmeter was fitted to the aircraft, and as intructed I climbed to 35,000 ft, carried out a 2 min level run at full power and trimmed the aircraft before pushing over into a 30 degree dive. At Mach=0.72 the aircraft began to buffet slightly and pitch nose down, requiring a strong pull force to maintain the dive angle. At Mach=0.73 the buffeting increased severely and the nose-down pitch was so strong that I needed a full-blooded two-handed pull to keep the dive angle constant. I had to hang on grimly in this situation, unable to throttle back until Mach number decreased as altitude was lost. The pull-out was not effected until 8,000 ft. Analysis showed that a dive to M=0.74 would almost certainly be a 'graveyard dive'.

I have only subsequently experienced such severe compressibility nose-down pitch effects in two other aircraft, the Messerschmitt 163B and the Grumman F8F Bearcat. Anyway, the RAE recommendation was to fit a dive recovery flap on the underside of the wing which when activated would give a nose-up pitch to counter the compressibility nose-down pitch. This was eventually fitted to all Thuderbolt models."

[Knegel]

Hi Viking,

this made me believe it was also a RAE conclusion:
Originally posted by Viking
He said that when Doolittle found that his fighters didn't engage the enemy, but simply dived past them into oblivion never to be heard from again, he contacted the British at RAE Farnborough to find out what was going on. The British being the leading authority on high speed testing at that time. RAE found that the 109 and 190 had a tactical Mach limit of 0.75, the P-38 had a tactical limit of 0.68 or 0.69 (I don’t recall which) and the P-47 had 0.71. Brown said they were useless as high altitude escorts and that only the P-51 with a tactical Mach limit of 0.78 could deal with the Germans at 30k.
As i wrote before, i got this impression and obvious it was a mistake, but it have nothing to do with the fakt that history did proof the P47 to be a very good high alt fighter also without the flaps.
And it looks like even Brown wasnt the opinion the P47 was useless as high alt fighter, therefor it dont matter even more who made this statement.  
The low critical mach was a disadvantage, nothing to argue, but the P47 had otherwise huge advantages in 30k alt. And actually the critical mach problems in 30k isnt that a problem for the headline question of this theatre anyway.
In a dive from 25k downward, we get a absolut different picture.  

Greetings,

Knegel