Spitfire V Versus P-40E

PAT303 · Jul 24, 2020

Mike Williams said:
What sources did you guys use that support your statements related to dates and amount of boost? Thanks.

I think it was originally posted by Edger Brooks?.

29.04.1941 - Spitfire V X.4922: Merlin 45 @ 3000 rpm/+9 lbs all-out level, 2850 rpm/+9 lbs climb, increased to 3000 rpm above ca. 25000 ft
18.06.1941 - Spitfire VB W.3134: Merlin 45 @ 3000 rpm/+9 lbs all-out level, 2850 rpm/+9 lbs climb, increased to 3000 rpm above ca. 25000 ft
xx.01.1942 Merlin 45 type test +16lbs boost. (The Merlin 100 series. RR Heritage Trust).
03.01.1942 - Ministry of Aircraft Production mentions +12 lbs and +15 lbs boosts
08.03.1942 - Spitfire Vc AA.873: Merlin 45 @ 3000 rpm/+9 lbs all-out level, 2850 rpm/+9 lbs climb, increased to 3000 rpm above ca. 20000 ft
30.06.1942 - No. 129 sqn ORB, speed tests at +16lbs boost.
29.07.1942 - R.D.T.3. R.D.E.2. R.T.P.7 Increased Rating for Merlin Engines. Approval 3,000rpm +16lbs boost Merlin 45,46 and 47 engines, operational units of Fighter Command. Previously only applicable to Seafire aircraft and for special applications. 3 minutes duration.
xx.08.1942 - Air Ministry issues memorandum declaring conversion to +16 lbs is currently done
25.11.1942 - Spitfire VC AA.878: Merlin 45 @ 3000 rpm/+16 lbs climb and level
27.01.1943 - Spitfire VB W.3322: Merlin 45 @ 3000 rpm/+9 lbs all-out level, 2850 rpm/+9 lbs climb, increased to 3000 rpm above ca. 20000 ft, 3000 rpm/+12 lbs take-off
03.02.1943 - 1 Sqn (Spitfire V tropicalized and Aboukir filter) clipped wings and +18lbs boost. SB.45457 Performance improvements on Spitfire F Mark V.
12.02.1943 - RAAF clears Merlin 46 and 47 for use of +12 lbs
25.05.1943 - Spitfire VB W.3228: cropped Merlin 50 @ 3000 rpm/+18 lbs climb and level

Shortround6 · Jul 24, 2020

Mike Williams said:
The Merlin 46 & 47 chart shows max all-out level conditions, etc.

While some of the Merlin charts do say "max all-out level conditions" this one
http://www.wwiiaircraftperformance.org/Merlin_46_47_Power_Chart.jpg
does not. It does say "provisional"

It also differs only a little bit from the figures in "the Merlin in Perspective"

which gives 1415hp at 14,000 ft vs the 1440hp at 14,500ft in the chart.

perhaps the chart, being provisional is a bit optimistic. But gains of only 500ft-1000ft in altitude for the effects of ram at full level speed seem awfully low.

the last chart on your page for the Spitfire MK V compares 10 different planes (including Spitfire VI) using Merlin 46 and 47 engines. FTH for 9lbs and 3000rpm varies from 20,200ft to 22,600ft.
FTH in climb (9lbs and 2850rpm) varies from 15,200ft to 18,000ft. the lowest performing engine is noted as below average.

This may just add confusion

Schweik · Jul 24, 2020

Mike Williams said:
+9 lbs boost for the Spitfire and +44" Hg. for the P-40E may be what the authorities at the Australian testing establishments thought those aircraft should be operating at during 1942-43 period. I've no idea what powers the operational units used in the field.

Looking at a couple of reports from Australia gives some context to the Comparitive Tests:
Kittyhawk Trials, Report No. F.8
Performance of Spitfire Vc - Tropicalized Version, C.S.I.R. Report F.12/1
Report on Comparitive Tests Capstan v. Kittyhawk (P40E)

Charts out about like so:

View attachment 589479 View attachment 589480

If you are up for a challenge, how about adding a couple of other things that chart.

Spitfire V at +12 lb of boost Merlin 45 or 46
A6M2
BF 109E (any subvariant)
BF 109F2 or F4
F4F-3
Hurricane Mk I or II

Mike Williams · Jul 24, 2020

Schweik said:
If you are up for a challenge, how about adding a couple of other things that chart.

Spitfire V at +12 lb of boost Merlin 45 or 46
A6M2
BF 109E (any subvariant)
BF 109F2 or F4
F4F-3
Hurricane Mk I or II

Interesting challenge Maybe, we'll see. I thought I'd finish up that P-40E comparison exercise with a climb chart if I can get to it today.

Mike Williams · Jul 24, 2020

Shortround6 said:
While some of the Merlin charts do say "max all-out level conditions" this one
http://www.wwiiaircraftperformance.org/Merlin_46_47_Power_Chart.jpg
does not. It does say "provisional"

It also differs only a little bit from the figures in "the Merlin in Perspective"

which gives 1415hp at 14,000 ft vs the 1440hp at 14,500ft in the chart.

perhaps the chart, being provisional is a bit optimistic. But gains of only 500ft-1000ft in altitude for the effects of ram at full level speed seem awfully low.

the last chart on your page for the Spitfire MK V compares 10 different planes (including Spitfire VI) using Merlin 46 and 47 engines. FTH for 9lbs and 3000rpm varies from 20,200ft to 22,600ft.
FTH in climb (9lbs and 2850rpm) varies from 15,200ft to 18,000ft. the lowest performing engine is noted as below average.

This may just add confusion

I checked it out using the same sources you did and wasn't entirely satisfied. The Merlin 46 & 47 chart does, however, state "Emergency Max All Out Level Condition" and "Max All Out Level Power". It can be a tad confusing.

Shortround6 · Jul 24, 2020

On second look you may be correct. The charts for the later engines don't have as many lines and the chart is labeled at the bottom that it is for 400mph in level flight or some like condition. This chart labels individual lines with different conditions.

Schweik · Jul 24, 2020

I don't understand why the Spit is so slow at low altitude? Is that the Vokes filter? The wing is slightly shorter span than the P-40s wing and I think it's thinner. The Spit seems to be very streamlined, though it does have a few protrusions like the external tail wheel, so does the P-40 (gun camera and wheels not fully covered).

Where is all the drag coming from?

Shortround6 · Jul 24, 2020

Schweik said:
Spitfire V at +12 lb of boost Merlin 45 or 46
A6M2
BF 109E (any subvariant)
BF 109F2 or F4
F4F-3
Hurricane Mk I or II

Quite a challenge.

The Merlin 45 and 46 are going to be different.
109Es came with a variety of engines.
the 109F2 used a different engine than the F4

The F4F-3 should simply be a bit lighter than an F4F-4 (same engine)

Hurricanes used different engines.

nine or more different aircraft?

Schweik · Jul 24, 2020

Shortround6 said:
Quite a challenge.

The Merlin 45 and 46 are going to be different.
109Es came with a variety of engines.
the 109F2 used a different engine than the F4

The F4F-3 should simply be a bit lighter than an F4F-4 (same engine)

Hurricanes used different engines.

nine or more different aircraft?

I wouldn't suggest trying to be completely comprehensive, I think the realistic approach would be to utilize what is available (like on WW2aircraftperformance.org, which he is already using I think), and try to shoot for what is typical rather than an outlier (if possible)

Mike Williams · Jul 24, 2020

PAT303 said:
I think it was originally posted by Edger Brooks?.

29.04.1941 - Spitfire V X.4922: Merlin 45 @ 3000 rpm/+9 lbs all-out level, 2850 rpm/+9 lbs climb, increased to 3000 rpm above ca. 25000 ft
18.06.1941 - Spitfire VB W.3134: Merlin 45 @ 3000 rpm/+9 lbs all-out level, 2850 rpm/+9 lbs climb, increased to 3000 rpm above ca. 25000 ft
xx.01.1942 Merlin 45 type test +16lbs boost. (The Merlin 100 series. RR Heritage Trust).
03.01.1942 - Ministry of Aircraft Production mentions +12 lbs and +15 lbs boosts
08.03.1942 - Spitfire Vc AA.873: Merlin 45 @ 3000 rpm/+9 lbs all-out level, 2850 rpm/+9 lbs climb, increased to 3000 rpm above ca. 20000 ft
30.06.1942 - No. 129 sqn ORB, speed tests at +16lbs boost.
29.07.1942 - R.D.T.3. R.D.E.2. R.T.P.7 Increased Rating for Merlin Engines. Approval 3,000rpm +16lbs boost Merlin 45,46 and 47 engines, operational units of Fighter Command. Previously only applicable to Seafire aircraft and for special applications. 3 minutes duration.
xx.08.1942 - Air Ministry issues memorandum declaring conversion to +16 lbs is currently done
25.11.1942 - Spitfire VC AA.878: Merlin 45 @ 3000 rpm/+16 lbs climb and level
27.01.1943 - Spitfire VB W.3322: Merlin 45 @ 3000 rpm/+9 lbs all-out level, 2850 rpm/+9 lbs climb, increased to 3000 rpm above ca. 20000 ft, 3000 rpm/+12 lbs take-off
03.02.1943 - 1 Sqn (Spitfire V tropicalized and Aboukir filter) clipped wings and +18lbs boost. SB.45457 Performance improvements on Spitfire F Mark V.
12.02.1943 - RAAF clears Merlin 46 and 47 for use of +12 lbs
25.05.1943 - Spitfire VB W.3228: cropped Merlin 50 @ 3000 rpm/+18 lbs climb and level

Thanks, that's helpful. There is this then:

Shortround6 · Jul 24, 2020

Schweik said:
I don't understand why the Spit is so slow at low altitude? Is that the Vokes filter? The wing is slightly shorter span than the P-40s wing and I think it's thinner. The Spit seems to be very streamlined, though it does have a few protrusions like the external tail wheel, so does the P-40 (gun camera and wheels not fully covered).

Where is all the drag coming from?

It is an interesting question.

The P-40 was actually a pretty streamline airplane, not a P-51 but compared to the Spitfire, the 109, ealy Yaks and even the Ki-61 it is a fast plane for the installed power.

Compare to any other 1100-1200hp V-12 powered plane of your choice.

What screwed it up was the weight, It was much heavier than any of the other planes in that catagory (except Mustang I) which meant climb sucked, and altitude performance sucked, high wing loading (despite larger wing than some) and low power to weight at altitude.

I would note that the wheel covers came off during the time that Curtiss was trying to get the XP-40 to go from a first tested 299mph (with rear radiator) up to about 340mph so I would guess that Curtiss knew exactly what those wheel covers were worth in terms of drag.

overbeck · Jul 24, 2020

Schweik said:
I don't understand why the Spit is so slow at low altitude?

Single speed supercharger. With a 20 series Merlin it would be faster low down than a P-40.

Schweik · Jul 24, 2020

Shortround6 said:
It is an interesting question.

The P-40 was actually a pretty streamline airplane, not a P-51 but compared to the Spitfire, the 109, ealy Yaks and even the Ki-61 it is a fast plane for the installed power.

Compare to any other 1100-1200hp V-12 powered plane of your choice.

What screwed it up was the weight, It was much heavier than any of the other planes in that catagory (except Mustang I) which meant climb sucked, and altitude performance sucked, high wing loading (despite larger wing than some) and low power to weight at altitude.

I would note that the wheel covers came off during the time that Curtiss was trying to get the XP-40 to go from a first tested 299mph (with rear radiator) up to about 340mph so I would guess that Curtiss knew exactly what those wheel covers were worth in terms of drag.

I don't think the wing loading was actually that high - at 31- 35 lb / sq ft (depending on the variant) it's lower than most other monoplane fighters outside of Japan. We have touched on that before.

My numbers:

P-40B at 6,835 loaded - 31 lb
P-40E-1 at 8,280 loaded - 35.1
P-40K-15 at 8,400 loaded - 35.6
P-40F-5 at 8,480 loaded - 35.9 (6 guns)
P-40L-10 at 8,020 loaded - 33.9 (4 guns)
P-40N-1 at 7,730 loaded - 31.36 (4 guns)

As we know, the Soviet turn-time tests also showed the P-40 as out-turning most other aircraft except the Spitfire & the Hurricane

Schweik · Jul 24, 2020

overbeck said:
Single speed supercharger. With a 20 series Merlin it would be faster low down than a P-40.

I was trying to look up speed tests for Spit V's but most of them seem to start at 8,000 ft

Mike Williams · Jul 24, 2020

Schweik said:
I was trying to look up speed tests for Spit V's but most of them seem to start at 8,000 ft

The lower altitude speeds can be extrapolated:

Schweik · Jul 24, 2020

Sadly I've never found original performance test data for a P-40K

How about adding a P-40F

http://www.wwiiaircraftperformance.org/P-39/P-39D-PHQ-M-19-1325-A.jpg

Schweik · Jul 24, 2020

From this and a couple of others I looked at, it appears that the 109E would also be slower than P-40E below 12,000 ft

Shortround6 · Jul 24, 2020

For the P-40K (and any P-40 using the 8.80 supercharger gear) the speeds above the sharp break/angle in the line are going to be the same, subject to minor changes in drag (racks,fittings) it is how far down (lower altitude) the upper curve will go before you get the sharp break and the straight line going down to sea level.

Some numbers from "Curtiss Fighter AIrcraft 1917-1948" by Dean and Hagedorn give 320mph at 5,000ft, 343mph at 10,000ft and 362mph at 15,000.
No comment on what power levels were used. However unless over boosted the engine would give the same power as the engine in the P-40E, the 1325hp at take-off being a special condition?

slaterat · Jul 24, 2020

Schweik said:
If you are up for a challenge, how about adding a couple of other things that chart.

Spitfire V at +12 lb of boost Merlin 45 or 46
A6M2
BF 109E (any subvariant)
BF 109F2 or F4
F4F-3
Hurricane Mk I or II

Here some comparative charts that might be of interest to you.

Schweik · Jul 24, 2020

Shortround6 said:
For the P-40K (and any P-40 using the 8.80 supercharger gear) the speeds above the sharp break/angle in the line are going to be the same, subject to minor changes in drag (racks,fittings) it is how far down (lower altitude) the upper curve will go before you get the sharp break and the straight line going down to sea level.

Some numbers from "Curtiss Fighter AIrcraft 1917-1948" by Dean and Hagedorn give 320mph at 5,000ft, 343mph at 10,000ft and 362mph at 15,000.
No comment on what power levels were used. However unless over boosted the engine would give the same power as the engine in the P-40E, the 1325hp at take-off being a special condition?

Three comments on that -

That would 14 mph faster than the P-40E in the Australian test we've been looking at.
I would agree with you that what you mentioned there probbaly represents takeoff power of 1,325 Hp, which is achieved at 51" Hg
However the normal WEP rating (not overboost) for the P-40K-15 was 60" Hg for 1,550 hp. So that would be 15% more power.

My source for that is Shamburger, Page & Christy, Joe. The Curtiss Hawks. Wolverine Press, 1972. Library of Congress No. 79-173429 , page 231

Spitfire V Versus P-40E

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