Hawker Tempest V vs. P-47D-27

[Sal Monella]

I used to think that would prefer to be in a Tempest if in aerial combat. I think I would if I were at low altitude. This data surprised me though.

From Jabberwocky -

Tempest V (ADFU and Hawker Trials)


5,000 ft - 3,640 ft/ min and 405-412 mph

15,000 ft - 2,750 ft/min and 420-430 mph

28,000 ft - 850 ft/min and 405 mph


From Jank -

P-47D


5,000 ft - 3,150 ft/min and 365mph

15,000 ft - 2,950 ft/min and 405 mph

28,000 ft - 1,800 ft/min and 435 mph

I have the following chart for the P-47

[Soren]

The Tempest will definitely climb better than that, at something like 4,000 ft/min atleast.

[Sal Monella]

Tempest V Performance Data

At Combat Power Rating

S/L 4,380 ft/min and 376 mph

4,000 ft - 3,740 ft/min and 397 mph

15,000 ft - 2,785 ft/min and 421 mph @ 16,000ft

28,000 ft - 1,020 ft/min and 405 mph

[Soren]

Thats with the radiator flap open..

[red admiral]

Closterman gives top speed of Tempest as 485mph with 2850hp (max rated) and 510mph with 3040hp (emergency), presumably at 16000ft.

Major difference in wing loading as well,

45lb/sq ft for the Tempest MTO

58lb/ sq ft for the P-47 MTO

[Sal Monella]

Wing loading for P-47 was 48.33 (14,500lbs / 300 sq. ft.)

Is that 485 mph and 510 mph data post war or non-production variants? Sounds awfully high like in 60-80 mph too high.

[red admiral]

With max take off the wing loading is 58 lb/sq ft, going for combat weight as above then the Tempest V is about 36-37lb/sq ft

Those figures are for wartime Mk V aircraft that Closterman (33 victories) flew with 274 and 3 squadron.

Closterman's Book

[Sal Monella]

Call me unreasonable but I'm afraid I just don't believe there were production Tempests that saw combat that flew 485-510mph.

I'm seeing 2,420hp at 11lbs of boost (Sabre IIb - final production version). This spec sheet supercedes all priors and is dated February 2, 1945. Can you provide any further information?

[Sal Monella]

I think Closterman was playing rather loosely with his words. I frankly don't believe the account you stated above, nor his as stated below. The fourth, final and most powerful production of the Tempest was with the Sabre IIb which generated a maximum of 2,420hp with 11lbs of boost.

Closterman says "In emergencies, you could over-boost it up to nearly 3,000hp and 4,000 revs; and the speed went up to 460 mph. In a dive the Tempest was the only aircraft to reach, without interfering with its handling qualities to any marked extent, subsonic speeds, ie. 550-600mph"

He goes on to say, "The 109's, knowing that we dived faster than they did, tried to get us up to 16,000 feet where our Tempests were heavy and our engines sluggish."

Scroll down to read his account at:

Tempest V Performance Data

[red admiral]

Maybe the speeds he quoted are exaggerations, but being 50mph off seems unlikely. 10-20mph more likely. What I can only surmise is that Closterman's Tempest had a Sabre V revving to 4000rpm and 3040hp. Maybe an in-field modification.

[Jank]

On the subject of in field modifications, I understand that mechanics used to tweak the late war P-47D and raised the HP from 2,530 to something closer to the "M" which had 2,800.

Overboosting from max of 2,420 to 3,040? I'd like to see that!

[Twitch]

Here's exactly what Clostermann said from his book-

"It was heavy, all of 7 tons. Thanks to its 2,400 HP engine it had a considerable margin of excess power and its acceleration was phenomenal. It was tricky to fly but its performance made up for it; at 3,000 feet, at economical cruising speed on 1/3rd power (950HP) with 2 45-gallon auxillary tanks, 310MPH on the clock ie., a true airspeed of 320MPH; at fast cruising speed, at 1/2 power (1,425HP) without auxillary tanks, 350MPH on the clock ie, a true airspeed of nearly 400MPH; maximum speed straight and level with +13 boost and 3,850 revs: 430MPH on the clock ie., a true air speed of 440MPH.

In emergencies you could over-boost it up to nearly 3,000HP and 4,000 revs, and the speed went up to 460MPH" and so on as you all have noted.

He never mentions 485 or 510 MPH as a maximum anywhere. He says he did 490 IAS once but at what altitude is unknown and it is unclear if he was in a shallow dive or not. What could be the blurry are is the difference in conversion of knots, IAS and TAS relative to the altitude. Clostermann being French thought in KPH too so did the editor assisting with "The Big Show" get any of the conversions right? Good question!

Clostermann is talking about speeds at 3,000 feet here and in one case with the drag of external tanks. We don't know the OAT -outside air temperature either, which affects things. Today we use a 2% factor as an average. Mathematically increase your indicated airspeed (IAS) by 2% per thousand feet of altitude to obtain the true airspeed (TAS).

Clostermann's conversions of IAS and TAS calculated at the 2% OAT factor come out a bit differently 310MPH IAS is 328MPH TAS, 350MPH IAS is 371 MPH TAS and 430MPH IAS is 456MPH TAS. A 1 % OAT factor would be 320, 360 and 443MPH TAS.

My P-51 manual shows a chart of the comparisons of IAS and TAS
at 40,000 ft.
IAS 260 MPH is 495 TAS
35,000 ft
290/500
30,000 ft
330/510
25,000 ft
360/520
20,000 ft
400/530
15,000 ft
440/540
10,000 ft
480/550
5,000 ft
IAS 505 MPH is 560 TAS

Since Clostermann is probably talking about the 1st Tempests in service we can assume it was the Tempest V (Tempest Is production plans were abandoned & Tempest IIs entered service after the V) which had a top end of 435 MPH @ 17,000 ft.

The only 485 MPH airplane Hawker made was the Fury prototype with the 3,055 HP Napier Sabre VII 24-cyl flat H engine. This and the less powerfull 18 cylinder radial production aircraft were post war anyhow.

The V was the only legitimate Tempest in service in numbers. It was officially a low and medium interceptor fighter and fighter bomber hence the lower performance at altitude. This was the ship used to combat V-1s. Only 800 Tempest Vs ever existed with the total including post-war delivered VIs being 1,149.

[Glider]

Originally Posted by Jank

.

Overboosting from max of 2,420 to 3,040? I'd like to see that!

Wouldn't like to fly it though. I would be waiting for the big bang and seeing expensive pieces of metal flying around my ears

[Sal Monella]

Kids, don't try this at home with your Sabre IIb.

7-1/2 hour WEP test on Thunderbolt engine

[pbfoot]

Originally Posted by Sal Monella

Kids, don't try this at home with your Sabre IIb.

7-1/2 hour WEP test on Thunderbolt engine

I agree its pretty hard to rebuild a previously failed block