P40E vs Bf109E4

[GRUNHERZ]

Why does the AH P40E climb so well against the the AH Bf109E4 and even manages to slightly outclimb it?

P40E:  8400lbs 1150hp Allison V1710-39

Bf109E4:  5875lbs 1175hp DB601A

Or for that matter why does it outclimb the 5300lb  1000hp A6M2, 150 less HP but 3100lbs lighter.....

[GRUNHERZ]

P40E:  8400lbs  1150hp

[GRUNHERZ]

Bf109E4: 5875lbs 1175hp

[gofaster]

Its not just weight and horsepower, its also the amount of lift that the wing can generate.  My understanding is that the P40E has a thicker wing and lighter wing load (meaning it produces more lift per wing space) than the 109E.

[GRUNHERZ]

Ok then explain why the P40E outclimbs the Zero so drastically....  Or do you think 150hp overcomes the Zeros advantage in light wing loading and lift, not to mention the 3100lbs weight difference....

[ra]

The Hurricane climbs pretty damn well, too.

ra

[oboe]

HOLY CRAP!  Look at the WEP on the P-40!    I don't think I've ever seen WEP make such a drastic difference in performance before.

Can that be correct?

[HoHun]

Hi Günherz,

Neil Stirling posted the following numbers which he noted down in the British public records office:

>Kittyhawk Ia. 42"hg - Time to 20000ft 14.25 mins - Initial climb 1570ft/min

The 42" Hg, 3000 rpm power setting was the British Emergency Power setting, limited to 5 min of use. Since the Allison's take-off rating was 1150 hp, 3000 rpm at 45.5 in Hg, the power used in the British test probably was a bit less than that.

(The Me 109E-4 probably only gets 1000 HP in Aces High, too.)

From the Aces High graph, the AH P-40E should get to 20000 ft in about 8.3 min using WEP and in 9.9 min at MIL, which looks a bit optimistic compared to the 14.25 mins measured by the British.

On the other hand, it seems to have been possible to boost the Allison engine to 56" Hg at 3000 rpm, yielding 1490 HP at 4300 ft. Of course, this would have improved the climb considerably, but the Aces High critical altitude seems to be about 9000 ft and not 4300 ft, so they apparently used a lower power setting.

Since the Americans didn't provide any WEP ratings early on, the British apparently re-rated the engines to conform with their practice, and that they didn't employ the higher power setting but one actually lower than the American 5 min MIL power of 45.5" at 3000 rpm seems somewhat confusing.

In short, I believe the Aces High P-40E uses more power than the rated 1150 HP.

Regards,

Henning (HoHun)

[GRUNHERZ]

So you assume the AH Bf109E4 gets less power than its 1175hp while the P40 gets more than its 1150hp?

[Hristo]

It's the shark teeth, ya know

[funkedup]

Just making a rough estimate off of those charts and weights and powers, I get about 900 hp for the 109 and 1300 hp for the P-40.

[funkedup]

PS There is documentation (I'll do some digging) for a P-39D having emergency power of 1325 hp from a V-1710 version which was very similar to the one used in the P-40.  So maybe we can explain that part of it.

[GRUNHERZ]

I think P39D used a different V1710, but then again there were 300 variants variants of that Allison .

Your guess for the 1300/900hp is astounding if true. It may be possible HTC is using some uprated V1710 model for our P40E, but a 900hp DB601A in a Bf109E4 is simply atrocious.
Even the earliest DB601 model put out over 1000hp.

[funkedup]

My estimate is just a rough one.  Power = hp * lbs / 19800

A 60% efficiency is assumed (i.e. 40% of crankshaft power lost to prop inefficiency and drag).  It's a fudge factor, but it will get you within 5% of actual figures on most WW2 fighters.

I can buy the 1300 hp P-40 but the 900 hp Me 109, that I don't know about.  I don't know enough about DB engines to make any kind of judgement.

[GRUNHERZ]

The 900hp DB601A is not possible for a Bf109E4. The Bf109E3 started using the 1175hp version and some E4 even had a 1270hp version on WEP.  So 900hp in the E4 is out of the question....