P-47N/M vs P-51H

[mig-31bm]

How does the last massed production P-51 version compared to the last mass production P-47?
In term of acceleration?
Top speed?
Turn rate?
Climb rate?
Overall which is the better fighter? and more suited to deal with FW-190D-9 and TA-152C/H?
P/s: how come the p-47 so insanely fast? it look so draggy. And what is the benefit of curvy elliptical wing and tail on P-47, Splitfire compared to square/trapezoid wind like on P-51, FW-190?

 

[pbehn]

The P-47N doesnt look draggy to me, even if you can discern drag with your eyes, I believe it did have a lot of horses though. The eliptical wings on a Spitfire were mainly to have the space for the U/C and weapons, not the same as the P-47 at all.

 

[wuzak]

P/s: how come the p-47 so insanely fast? it look so draggy. And what is the benefit of curvy elliptical wing and tail on P-47, Splitfire compared to square/trapezoid wind like on P-51, FW-190?

Brute force.

Maximum power (2,800hp) from the engine is still available at 30,000ft+.

Aerodynamics were improved too. The wing was different, with squared off wing tips and more trapezoidal, rather than the earlier elliptical trailing edge.

And what is the benefit of curvy elliptical wing and tail on P-47, Splitfire compared to square/trapezoid wind like on P-51, FW-190?

Brand identity.

https://upload.wikimedia.org/wikipedia/commons/a/a9/Seversky_P-35A_USAF.jpg

 

[pbehn]

Brand identity.

Was the P-47 sponsored by the milk industry?

 

[mig-31bm]

The P-47N doesnt look draggy to me, even if you can discern drag with your eyes, I believe it did have a lot of horses though.

It is fat with very wide sectional area, it should be more draggy than slender and long airframe like FW-190D9 or P-51H

The eliptical wings on a Spitfire were mainly to have the space for the U/C and weapons, not the same as the P-47 at all.

I mean, what is the advantage of eliptical wing and tail like on P-47 and Splitfire in general compared to the more square wing and tail like on P-51 and FW190, from aerodynamic point of view.

 

[mig-31bm]

Brute force.

Maximum power (2,800hp) from the engine is still available at 30,000ft+.

Didn't the F8F and F7F, TA-152 also have a lot off brute force? They don't seem to be as fast as P-47, how come?

 

[SaparotRob]

Before the knowledgeable answer I'd like to try.
The F8F was a carrier borne interceptor maximized for lower, denser altitudes than the P-47. The 'Bolt was getting its second wind at higher, thinner altitudes with more power.
The TA-152 was a rush job and sent into action (armed) too soon, but not soon enough.
Republic had been tinkering with the P-47 for years. The super duper fast P-47s were prototypes and weren't for use in combat operational theaters.
The F7F is really cool and I know less about it than I do the TA-152 even though it's Grumman. Don't let Capt. Vick find out.

 

[wuzak]

Didn't the F8F and F7F, TA-152 also have a lot off brute force? They don't seem to be as fast as P-47, how come?

The F8F and F7F used single stage R-2800s. Their peak performance was at lower altitudes. The F8F-1 at around 20,000ft, the F8F-2 (with variable speed supercharger) at around 28,000ft and the F7F at around 21,000-22,000ft. Though the F8Fs and F7F also used the R-2800, they were altitude rated rather than low altitude/sea level rated R-2800 that the P-47 could use because of the turbocharger. That meant more power was used to drive the supercharger and less was available for the prop.

The P-47N's critical altitude was 32,500ft at 2,800hp.

The Ta-152H used a 2 stage, 3 speed supercharged Jumo 213E. It's maximum power at rated altitude was 1,750hp @ 31,500ft, according to Wiki. The Ta-152H was also equipped with nitrous oxide, but I believe that was only activated above critical altitude. So the Ta 152H didn't use nearly as much brute force as the P-47N did, being about 1,100hp down at a similar altitude.

 

[pbehn]

I mean, what is the advantage of eliptical wing and tail like on P-47 and Splitfire in general compared to the more square wing and tail like on P-51 and FW190, from aerodynamic point of view.

The Spitfire and Bf 109 were a generation before the other types mentioned. As designed they had much less power and even less for take off until variable pitch/ CS propellers were fitted.

The Spitfire had to be light because it didnt have much power. Mitchell wanted a thin wing as he believed that was the best route to low drag. To have a thin wing meant a quirky landing gear arrangement and the double ellipse allowed space at the root for the landing gear and weapons. AFAIK it has a small advantage over a trapezoidal wing in the distribution of lift along the wing, but not worth the difficulty of building elliptical wings with washout. The Bf 109 took a different route to a lightweight design basically the landing gear was attached to the back of the engine resulting in an even more quirky set up but it was a small light design.

By the time the P-51 was designed knowledge had moved on. Whereas the first Spitfires had about 660BHP for take off with a wooden two blade prop (any more revs and the prop stalls) the P-51 had 1,200-1,400 with its variable pitch prop. Plus knowledge of aerofoils had moved on, the P-51 had much thicker wings than the Spitfire but due to a better profile it had less drag and much more space to put fuel undercarriage guns etc and it was more rigid.


I have never considered the P-47 to be elliptical. the leading edge is straight as is much of the trailing edge.

 

[mig-31bm]

I have never considered the P-47 to be elliptical. the leading edge is straight as is much of the trailing edge.

There is quite a distinct different between P-47 and Splitfire wing style compared to P-51. And even the prototype XP-72 use the curvy wing style. By contrast, Spiteful and P-51H both use short of trapezoid wing

 

[mig-31bm]

The F8F and F7F used single stage R-2800s. Their peak performance was at lower altitudes. The F8F-1 at around 20,000ft, the F8F-2 (with variable speed supercharger) at around 28,000ft and the F7F at around 21,000-22,000ft. Though the F8Fs and F7F also used the R-2800, they were altitude rated rather than low altitude/sea level rated R-2800 that the P-47 could use because of the turbocharger. That meant more power was used to drive the supercharger and less was available for the prop.

The P-47N's critical altitude was 32,500ft at 2,800hp.

The Ta-152H used a 2 stage, 3 speed supercharged Jumo 213E. It's maximum power at rated altitude was 1,750hp @ 31,500ft, according to Wiki. The Ta-152H was also equipped with nitrous oxide, but I believe that was only activated above critical altitude. So the Ta 152H didn't use nearly as much brute force as the P-47N did, being about 1,100hp down at a similar altitude.

So if i understand you correctly. All thing equal then
A supercharger and turbocharger will allow the aircraft to keep high power at high altitude but reduce power at low altitude compared to aircraft without it?.
So how come P-51H still faster in both top speed and climb rate than F8F-2 at all altitude but slower than P-47 at high altitude?

 

[pbehn]

 

[mig-31bm]

View attachment 650482

But you can see from actual photo of P-47 that its wing is extremely curvy compared to P-51 right?

 

[pbehn]

But you can see from actual photo of P-47 that its wing is extremely curvy compared to P-51 right?

The leading edge is straight. The trailing edge is curved maybe even elliptical in parts but I think that is just for smooth transition and to get as much aileron as possible in the set up.

 

[mig-31bm]

The F8F and F7F used single stage R-2800s. Their peak performance was at lower altitudes. The F8F-1 at around 20,000ft, the F8F-2 (with variable speed supercharger) at around 28,000ft and the F7F at around 21,000-22,000ft. Though the F8Fs and F7F also used the R-2800, they were altitude rated rather than low altitude/sea level rated R-2800 that the P-47 could use because of the turbocharger. That meant more power was used to drive the supercharger and less was available for the pro

Another question, why didn't they add a supercharger to the F7F ? Seem like very simple for a massive gain.
Also, what make the turbo charger on P-47 better than the supercharger on F8F-2 or P-51 at high altitude?

 

[swampyankee]

It is fat with very wide sectional area, it should be more draggy than slender and long airframe like FW-190D9 or P-51H


I mean, what is the advantage of eliptical wing and tail like on P-47 and Splitfire in general compared to the more square wing and tail like on P-51 and FW190, from aerodynamic point of view.

Piston-engined aircraft were too slow -- even the fastest fighters of the era -- for cross sectional area, nose shape, or volume distribution to dictate drag coefficient. What counts are wetted area and avoidance of separation. While the P-51 was the lowest drag piston-engined fighter of the era, largely due to superlative cooling system design, virtually all other single-engined, piston-powered fighters clustered, indistinguishable by engine type in a narrow range of zero-lift drag coefficients.

The idea that US fighters, except the P-51, succeeded because of sheer brute engine power is a blatant falsehood.

 

[pbehn]

Another question, why didn't they add a supercharger to the F7F ? Seem like very simple for a massive gain.
Also, what make the turbo charger on P-47 better than the supercharger on F8F-2 or P-51 at high altitude?
View attachment 650487
View attachment 650488

All military aircraft had a supercharger in that era. The P-47 had a turbo which fed the supercharger. The P-51A had an Allisson engine with a supercharger as per your diagram, the P-51B/C and later had a RR engine which had a two stage supercharger, so the first stage fed the second.

 

[tomo pauk]

Another question, why didn't they add a supercharger to the F7F ? Seem like very simple for a massive gain.
Also, what make the turbo charger on P-47 better than the supercharger on F8F-2 or P-51 at high altitude?

F7F and F8U have had a supercharger on each of their engines = one stage of supercharging on the F7F and on F8.
(their superchargers were powered by engine itself).

There was no ww2 aero engines without a supercharger.

P-47 have had also a turbo-supercharger, that fed compressed air to the supercharger on the engine itself. Two stages or supercharging.

The F4U, F6F, P-51B to H were also outfitted with engine that had two stages of supercharging, in short '2-stage supercharger': both stages were on the engine itself and were powered by engine. Same for Spiteful and many mid- and late marks of Spitfires.

Engines with more compressor stages were making better power at altitude than the engines with just one compressor stage, provided there is not a huge difference in engines displacement and/or RPM.

 

[wuzak]

Another question, why didn't they add a supercharger to the F7F ? Seem like very simple for a massive gain.
Also, what make the turbo charger on P-47 better than the supercharger on F8F-2 or P-51 at high altitude?

The F7F and F8F had single stage supercharged engines. Which means they had one stage of compression.

The engine on the P-47 had a similar supercharger connected to the engine, but with different gearing and only 1 ratio (F7F and F8F-1 had 2 ratios + neutral, F8F-2 had variable speed drive). The P-47 also had a turbocharger, which used exhaust gases to drive a compressor. So the P-47 had two stages of compression - the engine stage and the turbocharger.

As the air gets thinner at high altitudes, higher compression ratios in the supercharger are required. There is a point of compression ratios where the efficiency of a single stage falls away, which means eve more power is required to give the desired air flow and pressure to the engine. Adding a second stage means that each stage needs a lower compression ratio to achieve the desired overall compression ratio.

(Compression ratio = output air pressure/input air pressure)

In the P-51, from the B onward, this was achieved with a two stage supercharger driven by the engine. The 2 stage Merlin had the compressors on the same shaft, spinning at the same speed. The first compressor fed the second compressor, which fed the engine.

The engine has to drive the compressors, which costs power - up to a few hundred horsepower. The bigger the compression ratio required, the more power to drive the supercharger.

In the P-47 the turbocharger is that second compressor. The exhaust gases drive the turbine which drives the compressor. This doesn't cost much, if any, power at the crankshaft.

The turbocharger automatically compensates for altitude. It will allow the engine to maintain constant power up until the the critical altitude of the engine/turbocharger combination. One of the limiting factors there is the turbocharger's rpm.

The downsides of the turbocharger include the extra weight, extra space required, loss of exhaust thrust and complexity. For much of the war controlling the turbocharger was a problem.

 

[wuzak]

So if i understand you correctly. All thing equal then
A supercharger and turbocharger will allow the aircraft to keep high power at high altitude but reduce power at low altitude compared to aircraft without it?.

An aircraft with a supercharger and turbocharger will have the same power from sea level until its critical altitude. For the P-47N that was 32,500ft at 2,800hp (it would be higher for lower power/boost).

So how come P-51H still faster in both top speed and climb rate than F8F-2 at all altitude but slower than P-47 at high altitude?

P-51H vs F8F-2: Aerodynamics. Power-to-weight. Though the F8F-2 did hold the time to climb record to 10,000ft for a while.

P-47N vs P51H - power at altitude.