Early Mustangs-performance/experience?

[wuzak]

Depends on when the project is started. If the V-1650-1 powered Mustang is produced instead of the A-36 that would meant the USAF has a viable LR fighter for the ETO by Spring of 1943. Leaves plenty of time to escort bombers over Germany, saving 8th bombers and giving the LW bloody nose.

The discussion for installing the V-1650-1/Merlin 28 in the Mustang occurred at the same time as the discussions about installing the Merlin 61.

So, having a P-51/V-1650-1 program would have had to run concurrently with the P-51/V-1650-3 program.

The advantage is that the V-1650-1 was in production, so airframes wouldn't be waiting for engines.

The disadvantage is that there are two programs, one of which would have priority and delay the other. If the P-51/V-1650-3 had priority the P-51/V-1650-1 would be delayed such that it was available no earlier, and possibly later, which would be a waste of effort. If the P-51/V-1650-1 had priority the P-51/V-1650-3 would be delayed and wouldn't have been available when it historically was.

 

[drgondog]

Tomo - I have formed an opinion after many years of diving into the 1941 era NAA/Packard/AAF Mat'l Command web and doubt that that any action save BPC having the foresight to stipulate a Packard Merlin 28 be part of the Contract back in April 1940. A scenario that works for me is that every key agency involved peered into a crystal ball - in 1940/41 and foresaw that the "Bombers will Not always get through" and that a beer truck runs over Oliver Echols in early 1940 so that he does not persist in breathing air and hating NAA for going 'behind his back'.

Along with that branch in history, BPC funds a separate four ship build of NA-73X, devoting two to a separate Merlin XX/28 airframe/engine subset which would drive the initial lower cowl/carb design plus radiator plus even dropping the wing to clean up lines. This also probably drives a lot of complexity into Schmeud's world of driving a project completion to first flight. In my mind the completion of NA-73X prototype marks the very first possible date for engineering work on the two Merlin NA-73X to proceed in the Experimental shop. They would probably achieve completion in mid 1941 in time for flight tests, in same timeframe as NA-73.

Extrapolating the alternate reality, with Echols dead, MC may have an open mind and test the Merlin version in late 1941 and love it. At the same time news of the emerging Merlin 60 series as well as details would be exchanged with Packard to evaluate the new supercharger, as history shows us. (NOTE - the 1650-3 production with new supercharger "Wright" design change first contemplated Feb 1942 is still the Critical Milestone for the P-51B).

AAF-MC says "Wow" and NAA Mustang priority increases to "2" one year earlier and Packard gets more subcontractor resources to accelerate production of first, the 28/1650-1, then second the 61/1650-3. The changes to be made must also include dropping the wing to better fair the lower cowl.

This sets the stage for the NA-73X/Merlin to incorporate the many changes made in parallel for production NA-73/83 beginning in ~ April, 1941 (Still need funding that the A-36 got in April, 1942) to tool for a.) mass production set up of the new airframe w/1650-1 including dive brakes while finishing NA-83/-91, b.) procure funds for NA-101 due to brilliant senior level staff officer to Arnold (for clout) several months earlier as news of the high altitude performance of the Merlin 60 series emerges from RR with no knowledge of the forthcoming 8th AF loss rate escalating in another year beginning with Blitz Week July 943.

The Potential benefit is that the wing of the Army Air Force that could care less about strategic bombardment but very much cared for tactical airpower gets a production A-36/1650-1 months ahead of both the A-36 and P-51A.The Allison line is done in June, 1942. A further benefit is possible earlier discovery of yaw instability pointing to the requirement for the Dorsal Fin and reverse boost for rudder by 12 months.

The P-51B, however does NOT get delivered earlier because there is no certainty, even with new priorities that Packard receives in this perfect world, can tool fast enough for the new 1650-3. The tooling and production line preparation will be completed earlier, the first production airframe will be completed sooner if authority granted before first flight test (sans surprises due to flight tests of Radiator and Duct changes that only surfaced after XP-51B first flights - which was delayed because Packard was 30+ days late with first 1650-3).

Only a steady supply of Merlin 61s diverted from RR and shipped to US (at sacrifice of Spit IX - fat chance) could accelerate the delivery of complete P-51B-1-NA airframes.

With that scenario, the engineering hours devoted to A-36/P-51A after April 1942 (miraculously available to NAA in 1941 under this scenario) may be available to contract and develop NA-105/XP-51F six to seven months earlier.

 

[EKB]

You are correct, type of wing guns has little to with engine performance
however weight of the guns (and ammo) has a very noticeable and measurable affect on performance of the aircraft.

Ceiling is a measure of aircraft performance not engine performance.

Strip enough weight out of an aircraft and you can increase the ceiling by thousands of feet with no change to the engine.
And that is what your examples of the P-39 and P-40 are doing, running hundreds hundreds of pounds lighter than the normal combat versions.
They only built about 200 of the light weight P-40Ns and after they were in service the units operating them often installed the electric starters and bigger batteries, they often added the forward fuel tank back in too, finding the 120 gallons of internal fuel too limiting. Likewise the lightweight P-39s with only 87 US gallons were found to be to limited in service and retrofit kits were issued to bring them back up to the standard 120 gallons.

I happen to like facts but I Like my facts applied equally and not cherry picked. The P-40F did deliver some thrills. at altitudes over 20,000ft it was 30-40mph faster than a P-40E. The P-40N prototype you quote figures for is not only 1000lbs lighter than a standard P-40F with Merlin it it is almost 800-900lbs lighter than vast majority of P-40Ns.

I was talking about engine performance vs. a given loaded weight. I'm not here to argue about shortcomings of using four vs. six guns on the P-40N. And besides, the P-51B went into battle with four guns.

If you don't want to cherry pick, then show us some proof that a P-40F out-climbed a P-40N with the same loaded weight and surface attachments. Otherwise you don't practice what you preach.

It should be obvious by now that a Merlin 45 Spitfire ballasted to 7,400 lbs. would not have a service ceiling anywhere near 38,200 feet but P-40N - 42-9987 did, according to Wright Field tests. The Merlin XX gave essentially the same high flying performance as a Merlin 45, and that was the point in case you didn't get it the first time.

I actually think that the Merlin XX in the Mustang was not that great an Idea as the amount of time and effort to get it to work is not worth the result

We agree.

 

[EKB]

The high altitude performance of a FB Mosquito is about as relevant as a Stukas. The first Mosquitos in service were PR types which were quite obviously high altitude planes.

Mosquito I - W4050, the first hand-built prototype, was a feather weight at 16,770 lbs. when tested at the A&AEE. At that time the service ceiling was 33,900 feet with Merlin 21 engines. No data about time to climb, up to specific heights. Apparently the climbing test of serial W4050 was not finished, possibly for the same reason as serial W4052.

At any rate the results would have been immaterial because the operational load ballooned considerably. Typical all-up weights for the nine Mosquito PR 1s were 18,050 lbs. as normal, and 19,310 lbs. for two aircraft in the long-range configuration. This is according to Martin Sharp who worked at de Havillands.

He cited Victor Ricketts of the PRU, who said that 24,000 feet was the common transit height for a Mosquito PR 1 on those early missions. Pictures were usually taken from 22,000 feet or below, depending on cloud cover.

 

[Shortround6]

You are cherry picking which P-40N. Strange how later tests at higher weights (8300lbs take off) show a service ceiling of 31,000ft even though the plane burned off enough fuel to get under 8100lbs. Climb at 31,000ft being 100ft per minute and at 25,000ft it was 760fpm, both at 3000rpm and full throttle.

test of a P-40F with a take-off weight of 8450lbs has a climb of 1000fpm at 25,000ft, 530fpm at 30,000ft and 100fm at 34,000ft.
All done at 2850rpm, not 3000 rpm (max continuous Or 30 minute rating and not military)
Yes the P-40F had probably burned off several hundred pounds of fuel also.

The P-40F was supposed to climb from sea level to 30,000ft in 21 minutes. Chart for the P-40N-5 shows 27.5 minutes.

That is how to compare different engines, try to use the same airframe at as close a weight as you can find.
The British in a seperate test of the P-40F got about 300ft more service ceiling but took 21.8 minutes to get to 30,000ft which is certainly close enough.

A few British tests show better numbers for the P-40N but then they were testing lighter versions, 7900lbs or under.
You may not care about the reduction in guns but one test of the light weight P-40N had it weighing 900lbs less than a P-40E, due in part to the elimination of fo the forward fuel tank 100imp gallons instead of 125 imp gallons. change in type of fuel tank (non-metallic), 33% reduction in oil capacity. Elimination of vacuum system, only blind flying instrument left was an electric bank and turn indicator. Electric starter taken out, electric trim tab motor removed. much simplified radio installation. The change in wheel size and material (magnesium ) and the change to aluminum radiators and oil coolers helped and did not degrade operational capabilities like many of the other changes.

 

[drgondog]

I was talking about engine performance vs. a given loaded weight. I'm not here to argue about shortcomings of using four vs. six guns on the P-40N. And besides, the P-51B went into battle with four guns.

If you don't want to cherry pick, then show us some proof that a P-40F out-climbed a P-40N with the same loaded weight and surface attachments. Otherwise you don't practice what you preach.

On Shortround's behalf, I think this is what he had in mind about matching flight test conditions

Here are a couple of relevant P-40F (at 8450 GW at T.O.) vs P-40N-5 (at 8300 GW at T.O.). Time to 20K for P-40F=10.2 min, Time to 20K for P-40N=11.2. A/C ceilings are 35.5K for P-40F and 32K for P-40N. Both fully loaded internally, with 6x50 plus fuel, 157 gal fuel for F/161Gal fuel for N-5 - But P-40F on this comparison has a 330 # advantage by virtue of not having a full ammo load.

P-40 Performance Tests
http://www.wwiiaircraftperformance.org/P-40/P-40N-5_42-105241_Eng-47-1685-A.pdf

It should be obvious by now that a Merlin 45 Spitfire ballasted to 7,400 lbs. would not have a service ceiling anywhere near 38,200 feet but P-40N - 42-9987 did, according to Wright Field tests. The Merlin XX gave essentially the same high flying performance as a Merlin 45, and that was the point in case you didn't get it the first time.

The P-40F out performs the P-40N-5 in just about every category.

 

[EKB]

You are cherry picking which P-40N. Strange how later tests at higher weights (8300lbs take off) show a service ceiling of 31,000ft even though the plane burned off enough fuel to get under 8100lbs. Climb at 31,000ft being 100ft per minute and at 25,000ft it was 760fpm, both at 3000rpm and full throttle.

test of a P-40F with a take-off weight of 8450lbs has a climb of 1000fpm at 25,000ft, 530fpm at 30,000ft and 100fm at 34,000ft.
All done at 2850rpm, not 3000 rpm (max continuous Or 30 minute rating and not military)
Yes the P-40F had probably burned off several hundred pounds of fuel also.

The P-40F was supposed to climb from sea level to 30,000ft in 21 minutes. Chart for the P-40N-5 shows 27.5 minutes.

Well I figured you might pick this low hanging fruit, but you have missed a few cherries:

P-51A-1 No. 43-6007 also had a V-1710-81 engine, yet the service ceiling was 35,100 feet on 8,000 lb.

Clearly, something was amiss with P-40N-5 No. 42-105241 at 8,300 lb. because the service ceiling was 4,000 feet lower.

The B-7 wing racks and center line rack with braces put on the P-40N-5 caused some drag, but not that much!

I am no doctor of physics, but I know that 300 lbs. and a different wing shape will not cause a 4,000 ft. drop in ceiling, but a motor down on power would.

Another hint is the lack of War Emergency Power readings for speed and climb on P-40N-5 No. 42-105241. Odd because the P-40N-1 was tested at WEP one year earlier.

There is no explanation for that in the report, but if the engine in the P-40N-5 worked properly then why was it not tested at full power?

 

[wuzak]

Well I figured you might pick this low hanging fruit, but you have missed a few cherries:

P-51A-1 No. 43-6007 also had a V-1710-81 engine, yet the service ceiling was 35,100 feet on 8,000 lb.

Clearly, something was amiss with P-40N-5 No. 42-105241 at 8,300 lb. because the service ceiling was 4,000 feet lower.

The B-7 bomb racks put on the P-40N-5 caused some drag, but not that much!

I am no doctor of physics, but I do know that 300 lbs. and a different wing shape will not cause a 4,000 ft. drop in ceiling, but a motor down on power would.

Another hint is the lack of War Emergency Power readings for speed and climb on P-40N-5 No. 42-105241. Odd because the P-40N-1 was tested at WEP one year earlier.

There is no explanation for that in the report, but if the engine in the P-40N-5 worked properly then why was it not tested at full power?

P-51A-1 No. 43-6007 had a high speed of 408mph at 17,500ft at military rated power - 1,125hp (415mph @ 10,400ft @ 1,480hp).

P-40N-5 No. 42-105241 had a high speed of 350mph @ 16,400ft at 1,110hp.
P-40N. No. 42-9987 had a high speed of 378mph @ 10,550ft @ 1,480hp and 371mph @ 17,300ft @ 1,125hp at a weight of 7,413lb.

At 7,413lb 42-9987 had a service ceiling of 38,200ft. The advantage of nearly 1,000lb less weight (~11%).

Which suggests that the P-51 had much lower drag than the P-40. Which would account for the difference in ceiling and general performance.

 

[EKB]

P-51A-1 No. 43-6007 had a high speed of 408mph at 17,500ft at military rated power - 1,125hp (415mph @ 10,400ft @ 1,480hp).

P-40N-5 No. 42-105241 had a high speed of 350mph @ 16,400ft at 1,110hp.
P-40N. No. 42-9987 had a high speed of 378mph @ 10,550ft @ 1,480hp and 371mph @ 17,300ft @ 1,125hp at a weight of 7,413lb.

At 7,413lb 42-9987 had a service ceiling of 38,200ft. The advantage of nearly 1,000lb less weight (~11%).

Which suggests that the P-51 had much lower drag than the P-40. Which would account for the difference in ceiling and general performance.

That doesn't track because of a similar difference in drag with the Spitfire and Hurricane.
The variation in ceiling was less than 1,000 feet, not 4,000 feet.


Spitfire I - N3171
Merlin III
auw 6,050 lb.
h/s 354 mph
s/c 34,700 ft.

Hurricane I - L2026
Merlin III
auw 6,316 lb.
h/s 316 mph
s/c 33,750 ft.

 

[tomo pauk]

That doesn't track because of a similar difference in drag with the Spitfire and Hurricane.
The variation in ceiling was less than 1,000 feet, not 4,000 feet.


Spitfire I - N3171
Merlin III
auw 6,050 lb.
h/s 354 mph
s/c 34,700 ft.

Hurricane I - L2026
Merlin III
auw 6,316 lb.
h/s 316 mph
s/c 33,750 ft.

Hurricane is draggier by a large margin, and almost 300 lbs heavier.

 

[Shortround6]

The faster plane (with the same engine) will have a higher ceiling for several reason.
One, as already mentioned is the lower drag. At the same or similar speed the aircraft will have more power left to climb with.
Two. the faster plane will have more ram effect going to the carburetor, meaning it is making more power at a given altitude above FTH than the slower plane.
Three, for planes using ejector exhausts the higher speed plane gets more benefit from the same thrust because the exhaust gas velocity is a closer match to the planes exhaust (and actually there is more thrust due to the higher ram increasing the actual charge weight).

For the Hurricane vs SPitfire comparison look a little deeper. The engine had a nominal rating of 1030hp at 16,250 at 6 1/4lbs without RAM yet due to RAM effect it could hold the needed manifold pressure to 17,750ft in a 6,316lb Hurricane and 17,200ft in a 6,750lb Hurricane Please note that the extra weight knocked about 1000ft off the estimated ceiling.

On the Spitfire the engine could hold 6+ pounds to 18,900 feet in one example. And there is part of the answer, The Spitfire, with it's higher speed, is always going to have more RAM effect (more power in the cylinders) and more exhaust thrust an any altitude over these FTH unless it slows down to the Hurricanes speed.

Likewise the nominal altitude for the V-1710-81 was 14,600-15,500ft(?, sources differ) yet the critical altitude in level flight for the P-51A with that engine was 17,500ft. In the stripped P-40N it was 17,200ft and in more normally equipped P-40 it was 16,200ft in one test. Something seems just a little too good about that stripper P-40N? When the British tested one it was 27mph slower at 17,000ft???? bad engine???

By the time you get the Allison powered planes to 30,000ft you are down to a bit over 600hp and individual aircraft and engines can show significant differences which is why. even in 1940, The British figured that a 500fpm climb rate ceiling was needed for even small formation flying and 1000fpm was about the minimum for combat.

 

[Peter Gunn]

Tomo - I have formed an opinion after many years of diving into the 1941 era NAA/Packard/AAF Mat'l Command web and doubt that that any action save BPC having the foresight to stipulate a Packard Merlin 28 be part of the Contract back in April 1940. A scenario that works for me is that every key agency involved peered into a crystal ball - in 1940/41 and foresaw that the "Bombers will Not always get through" and that a beer truck runs over Oliver Echols in early 1940 so that he does not persist in breathing air and hating NAA for going 'behind his back'.

Along with that branch in history, BPC funds a separate four ship build of NA-73X, devoting two to a separate Merlin XX/28 airframe/engine subset which would drive the initial lower cowl/carb design plus radiator plus even dropping the wing to clean up lines. This also probably drives a lot of complexity into Schmeud's world of driving a project completion to first flight. In my mind the completion of NA-73X prototype marks the very first possible date for engineering work on the two Merlin NA-73X to proceed in the Experimental shop. They would probably achieve completion in mid 1941 in time for flight tests, in same timeframe as NA-73.

Extrapolating the alternate reality, with Echols dead, MC may have an open mind and test the Merlin version in late 1941 and love it. At the same time news of the emerging Merlin 60 series as well as details would be exchanged with Packard to evaluate the new supercharger, as history shows us. (NOTE - the 1650-3 production with new supercharger "Wright" design change first contemplated Feb 1942 is still the Critical Milestone for the P-51B).

AAF-MC says "Wow" and NAA Mustang priority increases to "2" one year earlier and Packard gets more subcontractor resources to accelerate production of first, the 28/1650-1, then second the 61/1650-3. The changes to be made must also include dropping the wing to better fair the lower cowl.

This sets the stage for the NA-73X/Merlin to incorporate the many changes made in parallel for production NA-73/83 beginning in ~ April, 1941 (Still need funding that the A-36 got in April, 1942) to tool for a.) mass production set up of the new airframe w/1650-1 including dive brakes while finishing NA-83/-91, b.) procure funds for NA-101 due to brilliant senior level staff officer to Arnold (for clout) several months earlier as news of the high altitude performance of the Merlin 60 series emerges from RR with no knowledge of the forthcoming 8th AF loss rate escalating in another year beginning with Blitz Week July 943.

The Potential benefit is that the wing of the Army Air Force that could care less about strategic bombardment but very much cared for tactical airpower gets a production A-36/1650-1 months ahead of both the A-36 and P-51A.The Allison line is done in June, 1942. A further benefit is possible earlier discovery of yaw instability pointing to the requirement for the Dorsal Fin and reverse boost for rudder by 12 months.

The P-51B, however does NOT get delivered earlier because there is no certainty, even with new priorities that Packard receives in this perfect world, can tool fast enough for the new 1650-3. The tooling and production line preparation will be completed earlier, the first production airframe will be completed sooner if authority granted before first flight test (sans surprises due to flight tests of Radiator and Duct changes that only surfaced after XP-51B first flights - which was delayed because Packard was 30+ days late with first 1650-3).

Only a steady supply of Merlin 61s diverted from RR and shipped to US (at sacrifice of Spit IX - fat chance) could accelerate the delivery of complete P-51B-1-NA airframes.

With that scenario, the engineering hours devoted to A-36/P-51A after April 1942 (miraculously available to NAA in 1941 under this scenario) may be available to contract and develop NA-105/XP-51F six to seven months earlier.

So what you're saying in this incredibly simple scenario ( which by the way, I fail to comprehend why it didn't go down this way in reality ) is that the we will not get a Mustang with -B performance into action any sooner but the possibility of getting a scorcher type P-51F about the time the -D was coming on line instead? Or is the headache I'm battling today totally muddling up what I'm reading? ( Which is entirely possible. )

 

[EKB]

The faster plane (with the same engine) will have a higher ceiling for several reason.
One, as already mentioned is the lower drag. At the same or similar speed the aircraft will have more power left to climb with.
Two. the faster plane will have more ram effect going to the carburetor, meaning it is making more power at a given altitude above FTH than the slower plane.
Three, for planes using ejector exhausts the higher speed plane gets more benefit from the same thrust because the exhaust gas velocity is a closer match to the planes exhaust (and actually there is more thrust due to the higher ram increasing the actual charge weight).

For the Hurricane vs SPitfire comparison look a little deeper. The engine had a nominal rating of 1030hp at 16,250 at 6 1/4lbs without RAM yet due to RAM effect it could hold the needed manifold pressure to 17,750ft in a 6,316lb Hurricane and 17,200ft in a 6,750lb Hurricane Please note that the extra weight knocked about 1000ft off the estimated ceiling.

On the Spitfire the engine could hold 6+ pounds to 18,900 feet in one example. And there is part of the answer, The Spitfire, with it's higher speed, is always going to have more RAM effect (more power in the cylinders) and more exhaust thrust an any altitude over these FTH unless it slows down to the Hurricanes speed.

Likewise the nominal altitude for the V-1710-81 was 14,600-15,500ft(?, sources differ) yet the critical altitude in level flight for the P-51A with that engine was 17,500ft. In the stripped P-40N it was 17,200ft and in more normally equipped P-40 it was 16,200ft in one test. Something seems just a little too good about that stripper P-40N? When the British tested one it was 27mph slower at 17,000ft???? bad engine??? .

This overlooks other Wright Field trials that stated a P-40 lost just 600 feet of service ceiling from adding 271 lbs.
(Re: P-40D - 40-362 and P-40E - 40-384 with V-1710-39 engines).

It does not make sense that a P-40 in good condition would lose 7,200 feet of service ceiling from adding
887 lbs. (Re: P-40N - 42-9987 and P-40N - 42-105241 with V-1710-81 engines).

Add to that, No. 42-105241 was a fighter but it wasn't tested at max power. Clearly the engine was not tip-top,
or some other important piece of information was omitted from the return.

 

[EKB]

The faster plane (with the same engine) will have a higher ceiling for several reason. One, as already mentioned is the lower drag.

I understand, but you have to accept that some airplanes were simply down on performance.

For example Spitfire IX - JL165 on +25 psi boost and 2000 hp could not reach 390 mph going straight and level (Ref: A&AEE trials).

 

[tomo pauk]

I understand, but you have to accept that some airplanes were simply down on performance.

For example Spitfire IX - JL165 on +25 psi boost and 2000 hp could not reach 390 mph going straight and level (Ref: A&AEE trials).

Yay, crusade is on - it is not just that Merlin is crap (never mind the 2000 HP figure), but Spitfire is, too.
It does not matter that Fw 190 with 1.56 ata boost (= 1950 PS) was good for 370 mph, nor it does not matter that oh so good Fw 190D-9 was about as good as Spit with 2000 HP, but while using 2100 HP provided by series engine that used MW 50. The another oh so good fighter, Bf 109K-4, also can't do it with either 1800 or 2000 HP.

 

[pbehn]

Why did the allies persist with the Spitfire and P51 when the P 40 was obviously the way ahead? Or did I read things wrong again?

 

[Shortround6]

Add to that, No. 42-105241 was a fighter but it wasn't tested at max power. Clearly the engine was not tip-top,
or some other important piece of information was omitted from the return.

It was tested at full military power.

If you are running an Allison at 3000rpm and 44.5in MAP (or anything close depending on model) you are running at full Military power.

WEP or WER was only available below FTH and have nothing to do with service ceiling or speed or climb at altitudes above FTH.

Purpose of the test was to get data for range charts. Stressing the engine and possibly having to delay tests while waiting for replacement engine or aircraft wouldn't have been smart.

Please note that any flight that used WEP/WER required notation in the log books and this could result in more frequent spark plug changes and extra checks for metal in the oil and depending on number of times and length of time at WEP it could shorten time before overhaul.

 

[drgondog]

So what you're saying in this incredibly simple scenario ( which by the way, I fail to comprehend why it didn't go down this way in reality ) is that the we will not get a Mustang with -B performance into action any sooner but the possibility of getting a scorcher type P-51F about the time the -D was coming on line instead? Or is the headache I'm battling today totally muddling up what I'm reading? ( Which is entirely possible. )

The problem with the F was that there was no 'Interceptor' buy and the F/G had no internal fuselage tank. To add it and extend the range, while maintaining the stress allowables, the airframe needed a complete 'structural re-do' ------------> which led to P-51H

 

[pbehn]

I understand, but you have to accept that some airplanes were simply down on performance.

For example Spitfire IX - JL165 on +25 psi boost and 2000 hp could not reach 390 mph going straight and level (Ref: A&AEE trials).

EKB, you are obviously well informed but you are not as well informed as the people making the decisions in WW2. It is an historical fact that the Hurricane was inferior to the P 40 which were inferior to the Spitfire. That is why they were used how they were used. The limitations of Allison engine aircraft be they P40s or Mustang Mk 1s at altitudes over 15,000ft were known when they were ordered by the purchasing commission. Those Mustang Mk Is were optimised for performance below 15,000ft and served well until the end of the war. In 1944 The P51 was without peer as a long range escort, although the P47N was arriving. The Tempest was the dogs dangly bits as a low level air superiority fighter and the Spitfire retained its role as the interceptor of choice to defend the UK at any altitude. Pilots have an historical preference for the planes they flew for natural reasons, they had lived to tell the tale flying those planes so they may be more than a little biased. In 1944 the Spitfire was for air superiority at all altitudes the P 51 for bomber escort, the Tempest for air superiority over the battle fields after D Day, the P 40 didn't figure in anyones calculations for front line combat after the early days in North Africa.

That is not at all to disparage what the P 40 did historically, like the Hurricane it achieved a lot when there were no other alternatives.

 

[Greyman]

Yay, crusade is on - it is not just that Merlin is crap (never mind the 2000 HP figure), but Spitfire is, too.

I think he was pointing out that JL165 was down on performance (compared to other Mk.IX examples tested), not the Spitfire as a whole.