Who would get to 40,000 feet first?

[davparlr]

Maybe go with the P-47M? Though I guess that Griffon Spitfires would've been 1st pick here.

You could be right. I picked the N due to its larger wing and better aspect ratio. It is only 500 lbs heavier than an equally loaded out M. Not sure if 5% increase in wing area and better aspect ratio would provide a noticeable advantage though. I don't know the power curve of the Griffon but I suspect its power is significantly less than the N/M engine at higher altitudes (less than half?). However the Spit XIV weight is also significantly less. Also, the Spit is much cleaner than the P-47 which is an advantage in climb, but this difference decreases with altitude.

davparlr
The P47N/M certainly have the benefit of an engine having impressive altitude performance. On the other hand, the low aspect ratio wing would be a disadvantage at extreme altitudes.

I think the aspect ratio of the P-47M and N (which is higher) is higher (better at high altitude) than the Spit XIV. Weight is a big difference though.

 

[tomo pauk]

Here is the data table for the Spit XIV:

http://www.spitfireperformance.com/spitfire-XIV-ads.jpg

 

[wuzak]

You could be right. I picked the N due to its larger wing and better aspect ratio.

Only slightly better aspect ratio to the M. It's not as if it is a Ta 152H type wing developed specifically for high altitudes.

You could be right. I picked the N due to its larger wing and better aspect ratio. It is only 500 lbs heavier than an equally loaded out M. Not sure if 5% increase in wing area and better aspect ratio would provide a noticeable advantage though. I don't know the power curve of the Griffon but I suspect its power is significantly less than the N/M engine at higher altitudes (less than half?).

At 39,000ft the Spitfire XIV is able to do ~420mph TAS with the engine developing +3.8psi boost. So not much power. At that altitude, however, I suspect that the exhaust thrust plays a significant role in the Spitfire's performance.

The Griffon chart shows 1600hp @ 27,500ft. I estimate around 700hp @ 40,000ft.

I think the aspect ratio of the P-47M and N (which is higher) is higher (better at high altitude) than the Spit XIV. Weight is a big difference though.

The M has superior straight line performance at 40,000ft than the N does.

http://www.wwiiaircraftperformance.org/p-47/p47m-n-speed.jpg

But the N has ever so slightly better climb rate.

http://www.wwiiaircraftperformance.org/p-47/p47m-n-climb.jpg

The chart has 500ft/min at around 36,000ft for the M and 37,000ft for the N. So they are going to be less than the Spitfire XIV's 810ft/min at 40,000ft.

As to the aspect ratio, if the XIVs were expected to be fighting regularly at over 35,000ft I'm sure that the extended wing tips of the VII could be bolted up in a few hours.

 

[GregP]

I'm seeing exactly wqhat I thought I would in this thread. People posting rate of climb times at some arbitrary weight.

That's wrong.

We usually have a basic fighter weight, a basic gross weight and a basic overload weight, If you want to compare things equally, load up the plane, the pilot, full ammunition, the same amount of fuel in pounds, gallons, liters, or kilograms, and go for it. The P-51D had some extra tankage, but if you take a standard P-51D and load it with the same fuel as a Spitfire (with full ammo and pilot) ... then what are the climb rates?

If we're going to decide, let's at LEAST have a level playing field. No drop tanks, full ammo, and the same amount of fuel.

The real issue is finding those data.

 

[GrauGeist]

Greg, that's why I posted to two figures in my post #35 regarding the KI-84.

The testing done was both "clean" and "overload".

Because very rarely would a fighter go off to battle in "clean" condition

 

[Dupplin Muir]

GregP wrote:

The P-51D had some extra tankage, but if you take a standard P-51D and load it with the same fuel as a Spitfire (with full ammo and pilot) ... then what are the climb rates?

But surely if you're going to do this you'd need to do the same for firepower? Given that one 20mm cannon equals 3 Brownings, you could take out the 4 x 0.303" which would reduce the Spitfire's weight by about 200 lbs.

Additionally, Spitfire climb-tests were carried out with the radiator flaps forced open to simulate a 'worst-case scenario'. Given that the Merlin didn't often overheat, I suspect one should reduce the Spitfire's time to 40,000' by at least a minute and probably more.

 

[GrauGeist]

But surely if you're going to do this you'd need to do the same for firepower? Given that one 20mm cannon equals 3 Brownings, you could take out the 4 x 0.303" which would reduce the Spitfire's weight by about 200 lbs.

Hispano Mk.II weighed up to 110 pounds (50kg) versus the Browning AN/M2 at 61 pounds (28kg)

 

[BiffF15]

There's a little bit of apples and oranges comparisons going on here. Greg alluded to it with his adjusting of fuel loads. Comparing a Mustang to a Spit's climb rate is a bit of the apples to oranges, as the planes were designed or built to different missions (yes both were made to shoot down enemy aircraft but the difference was where). The Mustang B/C/D had the legs and ability to go much deeper than most of the Spit models and carried the weight / perf hit for that (larger fuel tanks and the structure to support them, drop tank racks, heavier long range radios, larger oxygen tanks). The US equipment was built for the deeper fight, while the Brit and German equipment, was for the most part, built for shorter sorties (resulting in much lighter / better performing airframes).
The US stuff will most likely be the lessor performing equipment even if fuel loads are "evened" out.
Cheers,
Biff

 

[parsifal]

Spit fuel loads varied a lot.....A variety of external fuel tanks were fitted to the Spitfire over its wartime career -

30 gal c/l slipper tank

90 gal c/l tank (used by Malta Spitfires: one-way transit range approx 800 miles)

170 gal c/l tank

45 gal streamlined c/l tank

90 gal streamlined c/l tank

The absolute maximum operating range of a Spitfire occurred in the case of the unarmed photo-recon types, which had a range of "well over 2,000 miles and a consumption ... of nine miles per gallon". Fuel stowage would have included 297 gals of internal fuel + 170 gal drop tank (by my arithmetic).

Typically, for long range work, the late war spits like the mkXIV had a fuel load of around 250 Imp gals. This gave it a range (radius) of around 860 miles.

A more typical fuel load was a 90 gal tank, compared to 2 x 62.5 gal tanks carried by the P-51

 

[Geisel_der_Lufte]

Ta 152 H-1 hands down, it may not be the best at low altitudes, but it will maintain that climb rate at high altitudes because of the special modifications to the engine and airframe.

 

[wuzak]

Ta 152 H-1 hands down, it may not be the best at low altitudes, but it will maintain that climb rate at high altitudes because of the special modifications to the engine and airframe.

I seriously doubt it.

The Ta 152 was reckoned, by Eric Brown, to match the Spitfire XIV in performance from 30-35,000ft and be superior above that height. By the time the Ta 152 gets into that good band the Spitfire XIV is already up to 40,000ft.

 

[Milosh]

I seriously doubt it.

The Ta 152 was reckoned, by Eric Brown, to match the Spitfire XIV in performance from 30-35,000ft and be superior above that height. By the time the Ta 152 gets into that good band the Spitfire XXIV is already up to 40,000ft.

Was that with/without MW50 and GM1?

 

[wuzak]

Was that with/without MW50 and GM1?

Probably without, but I'm not sure.

 

[Milosh]

After a little searching, found the Ta152H never flew in the UK with MW50 or GM1.

 

[GregP]

The Ta-152H could not achieve even 4,000 feet per minute at sea level. It might maintain a good climb rate at altitude, but would surely lose out to a plane with a lower altitude advantage of almost half and that is still a strong climber at 30,000 feet.

Hi Dupplin and welcome to the forum. I don;t agree with you here. The armament was chosen by the designer, not the field personnel. The ful carried was elective. No self-respecting fighter pilot would fly off into combat with less ammunition than he could carry, but would happily fly off with less fuel if he had enough for the mission and reserves. It is a matter of real-world missions.

However, if you want to make everything REALLY equal, you could take the empty aircraft, the fraction of ammunition weight for yiour baseline and apply it to the others, the fractiopn of fuel for the baseling and apply it to the others, etc. The peoblem becomes choosing the baslkeing aircraft. Once you do that, the REAL problem is getting the data for all the types you want to consider at that loading.

Most WWII aircraft have performance data for normal loadout and overload loadout and not much else ... so we're stuck with using data we HAVE but really don't want.

I have no good answer and climbing to 40,000 feet the fastest was never the mission of ANY of these planes.

If you see a resolution to this, please post it. I'll bite and be intersted.

Drgondog has a lot of data for the P-51 models (and others) and is good at aerodynamics, but he probably doesn't have data at arbitrary loadings that make things "equal," whatever THAT means. Maybe load them all until the increase in wing loading from empty weight due to crew, fuel, and ammunition is the same percentage? Good luck finding THAT data! You might find it for ONE aircraft, but what about all the other candidates.

I think we have to use the data and loadings for which we HAVE data ... but maybe not. There is a LOT of information floating about. The problem is finding it.

 

[parsifal]

Funny thing is greg, id be more interested in what an aircraft does at full combat load out, rather than trying to create a level playing field weight wise. I have more interest in seeing what an aircraft with full fuel and full ammo will do compared another aircraft also at full load out. if that means one aircraft is "unfairly penalised, then so be it. Its how they were configured for battle that is of most interest to me...

 

[GrauGeist]

I will admit I get irritated when everyone is posting specs for stripped down aircraft for maximum possible performance and then making comparisons under ideal conditions.

Those were not the machines that climbed into the sky to do battle. They were war-weary, patched together, loaded down with ammunition and fuel...sometimes they had field mods to give them an advantage over the enemy and so on, but those are the machines that made a difference...not some hangar queen sitting somewhere on an evaluation field way to the rear.

 

[Shortround6]

While climbing to 40,000ft at "FULL" or WEP power might have been done in testing ( or not, sometimes such a climb was calculated and the results charted) it would rarely be done in practice.

I don't believe ANY of the engines were rated to run at these high power levels for the time it would take to make the climb. In combat you might have to do what you had to do and the time limit ignored or pushed for several minutes past book figure/limit.

Beating the snot out of the engine for the first 15-30 minutes of a combat mission, even if it is an intercept mission near the home field may not be the best idea.

and then you have the consumables problem.

http://www.wwiiaircraftperformance.org/p-47/p-47n-republic-wep.jpg

IF you are using water injection/MW 50 or some other additive system how much are using per minute and how much will you have left (if any) when you reach 40,000ft to actually fight with?

An early P-47 with 12,500lb take-off weight could burn 91 gallons of fuel just reaching 25,000ft using 2000hp for the first 5 minutes and 1625hp for the remaining 9.5 minutes it took to get to 25,000ft. Another 15 minutes of climb could burn another 40-50 gallons?