F4U Corsair vs P-51 Mustang

[don4331]

But on top of all these numbers comes another caveat: These are the power off (with power on the Clmax is much higher) stall and turn Clmax numbers at low altitudes, and if you throw the effects of Mach into the mix as well (which comes into play at higher altitudes because you're going faster in turns), or look at instantaneous turns starting at higher speeds, then the Clmax numbers will be even lower due to buffeting effects.

Are you really increasing CLmax with power on? Or are you accelerating the air over the wing, so while the CLmax would be constant but the lift is greater due to the faster moving air (possibly at lower AoA)??

Another cavaet would be, you need control of the aircraft as it approached CLmax to determine the "in service" value. Planes with nasty stall characteristics make testing...challenging.

 

[Holtzauge]

Are you really increasing CLmax with power on? Or are you accelerating the air over the wing, so while the CLmax would be constant but the lift is greater due to the faster moving air (possibly at lower AoA)??

Another cavaet would be, you need control of the aircraft as it approached CLmax to determine the "in service" value. Planes with nasty stall characteristics make testing...challenging.

Yes, it's a documented fact that the Clmax does increase with power on for tractor propeller powered aircraft: As an example, for the Spitfire, there is a British report by the RAE (RM 2349) which list the Spitfire MkI's Clmax as 1.36 power off, and 1.89 power on.

I think you can see this effect as a combination of the slipstream adding momentum to the flow close to the root of the wing thus delaying the stall, and that the thrust vector is pointing upwards, thus lowering the load on the wing somewhat.

Then about the stall characteristics as such: Sure: A benign stall most likely makes the average pilot feel comfortable flying close to the edge, while the opposite of course would make him hesitant to do so.

 

[Shortround6]

I would also note that flying anywhere near the max coefficient of lift means the plane is flying at an angle 15-20 degrees from the direction of travel. Basically the wing is acting like a giant airbrake (fuselage lesser) and you are not going to be flying at that speed for very long or you are going to be flying very, very slowly.

Each airfoil is going to have it's own set of curves but a lot of them are going to be close.
It this example the best lift to drag is about 6 degrees angle of attack and the CL is 0.5 and the CD is about .0400.

At the CL of 1.5 with the airfoil tilted 20 degrees higher than the line of flight the the plane has stalled and the CD is off the chart.
Backing off to 18 degree angle of attack the CL is around 1.43 (?) the plane is flying (barely) and the CD is about 10 times higher than high speed level flight.

Figure out for your favored airfoil but extreme CLs are going to only apply at a tiny fraction of the flight envelope and if the pilot is using them he has either successful shot down his opponent and/or he is about to be shot down by another aircraft in a better energy state (flying faster).

 

[Holtzauge]

I would also note that flying anywhere near the max coefficient of lift means the plane is flying at an angle 15-20 degrees from the direction of travel. Basically the wing is acting like a giant airbrake (fuselage lesser) and you are not going to be flying at that speed for very long or you are going to be flying very, very slowly.

View attachment 796015
Each airfoil is going to have it's own set of curves but a lot of them are going to be close.
It this example the best lift to drag is about 6 degrees angle of attack and the CL is 0.5 and the CD is about .0400.

At the CL of 1.5 with the airfoil tilted 20 degrees higher than the line of flight the the plane has stalled and the CD is off the chart.
Backing off to 18 degree angle of attack the CL is around 1.43 (?) the plane is flying (barely) and the CD is about 10 times higher than high speed level flight.

Figure out for your favored airfoil but extreme CLs are going to only apply at a tiny fraction of the flight envelope and if the pilot is using them he has either successful shot down his opponent and/or he is about to be shot down by another aircraft in a better energy state (flying faster).

Absolutely, the wing profile drag rises a lot when you approach stall. However, I think the figure you posted is more schematic when it comes to drag close to stall and attempts to show that it increases a lot (which it certainly does) only perhaps not as dramatically as that figure suggests.

Below is the profile lift/drag for the NACA 230 (Figure from airfoiltools.com) which is used on a lot of WW2 aircraft, and as can be seen, the drag does rise quite a lot close to stall, but as long as you stay close to the Clmax but don't actually stall it, it's not "inifinite". (Note that this is at Re=1M and that at higher full-scale Re the Clmax is closer to 1.7)

Added to this is the fact that the major part of the drag in tight turns close to stall is not from the rise of the profile drag, but rather from the so-called induced drag which is much larger and is the major determinant for the drag in tight turns.

Finally, as long as we are talking about sea-level up to medium altitudes, the best turn rate is actually attained at the intersection of the stall boundary with the power limited turn rate (enigmatically called angle of straight climb in figure below) as shown in the figure below for the Spitfire MkI and Bf 109E at an altitude of 12,000 ft (Figure is from the British RAE report RM 2361).

 

[henshao]

WI means "water injection" (MW 50 to the Germans). Not all planes had WI even if they used the same basic engine, you do have to fit the water tank and the associated plumbing fittings.

What is fair is to use the max boost used in service (or soon to be) for the different airplanes.
Air cooled radial engines never operated at the same max boost as allied liquid cooled engines using the same fuel.

War Time R-2800 Bs never operated at over 54in with any supercharger unless they had water injection.

This is mostly true except if they were fortunate enough to get 150 octane fuel, in which case they could see up to 65" of manifold pressure before the water had to come in

Then there is the shifting of the rations. Its not like your car where you can let off the gas to ease the shift, the shifts are happening at full power (what I would call powershifting, you push in the clutch, while pulling the shifter into next gear, never lifting off on the throttle). And that was a problem for the F4U-5 side winder - the load was so high, it broke things. So, rather than use clutches, P&W used more/less torque convertors. And "hydraulic connection" of torque convertor smoothed the acceleration of the auxiliary stage from neutral to low and from low to high (and back down again). Once the supercharger impeller had been accelerated, the connection speed was more/less constant. So, the R-2800-32W has a geared drive supercharger, it just has a fluid coupler for shifting, so it have the same jagged profile as the Merlin would.

Perhaps it would be more detail than necessary to get into the smoothing effects of stall and torque multiplication of torque converters

 

[drgondog]

Absolutely, the wing profile drag rises a lot when you approach stall. However, I think the figure you posted is more schematic when it comes to drag close to stall and attempts to show that it increases a lot (which it certainly does) only perhaps not as dramatically as that figure suggests.

Below is the profile lift/drag for the NACA 230 (Figure from airfoiltools.com) which is used on a lot of WW2 aircraft, and as can be seen, the drag does rise quite a lot close to stall, but as long as you stay close to the Clmax but don't actually stall it, it's not "inifinite". (Note that this is at Re=1M and that at higher full-scale Re the Clmax is closer to 1.7)

View attachment 796079

Added to this is the fact that the major part of the drag in tight turns close to stall is not from the rise of the profile drag, but rather from the so-called induced drag which is much larger and is the major determinant for the drag in tight turns.

Finally, as long as we are talking about sea-level up to medium altitudes, the best turn rate is actually attained at the intersection of the stall boundary with the power limited turn rate (enigmatically called angle of straight climb in figure below) as shown in the figure below for the Spitfire MkI and Bf 109E at an altitude of 12,000 ft (Figure is from the British RAE report RM 2361).

View attachment 796080

Good post. I would add that while Induced drag is high in a constant altitude high G turn, that Pressure Drag as a function of CL (different from Induced Drag) is very high also.

Also notable is that wind tunnel testing on the P-51B showed much higher CLmax for dive pullout (circa 1.8) which leads us to all question 'aircraft vs Wing' in CLmax discussions for accelerated flight.

 

[Holtzauge]

Good post. I would add that while Induced drag is high in a constant altitude high G turn, that Pressure Drag as a function of CL (different from Induced Drag) is very high also.

Also notable is that wind tunnel testing on the P-51B showed much higher CLmax for dive pullout (circa 1.8) which leads us to all question 'aircraft vs Wing' in CLmax discussions for accelerated flight.

Yes, the pressure drag also goes up so that certainly contributes to the drag rise as well.

And as you say, in transient maneuvers the Clmax can also go up momentarily to a higher value. This is caused by a so-called leading edge vortex (LEV) that temporarily fills the "void" behind a profile at a sudden increase in angle of attack. I remember seeing a NACA report about the phenomena on the P-47 as well. So while the LEV cannot be used to maintain lift a turn, it can certainly pull the wings off if a pilot makes a too rapid pullout. And as I recall it, the LEV is "active" only for a second or so, so does not have much of an impact even on an instantaneous turn.

 

[N4521U]

But they were on the same side????

 

[Terry Baird]

If the US had to make do without one of the aircraft, I would say dispense with the P-51 and keep the F4U. We could have won the war with the P-47 in Europe, but the same could be said about the F6F in the Pacific. But what about 1951 in Korea? I know that I would rather be flying an F4U than a P-51. This is not meant to be a slight to the P-51 in any manner.

 

[drgondog]

If the US had to make do without one of the aircraft, I would say dispense with the P-51 and keep the F4U. We could have won the war with the P-47 in Europe, but the same could be said about the F6F in the Pacific. But what about 1951 in Korea? I know that I would rather be flying an F4U than a P-51. This is not meant to be a slight to the P-51 in any manner.

The F4U and P-47 didn't have the range to prevent catastrophic losses to 8th and 15th AF over key strategic targets (Schweinfurt and deeper) pre D-Day. Summer/fall 1943 was nearly catastrophic for post war USAF ambitions.

If the P-47D-25 had been in combat ops Dec/Jan 1944 I would agree with you - but air to air losses would have been higher. Of all the P-47 FGs, Only the 56FG excelled/compared to 4th, 31st, 52nd, 325th, 352nd, 354th & 357th FGs vs LW air to air and far behind in strafing destruction over airfields.

The P-51 had just over the loss rate per 1000 sortie as the F4U in Korea. The F6F probably would have been a better air to ground based on WWII loss statistics.

Post Jan 1 1944, you could dispense with the P-47 vs P-51 if you had to choose as Combat Radius became the differentiator in Europe, CBI and Pacific. The P-51 would perhaps suffer more losses in CAS but experience in Korea demonstrated common equivalency of in-line vs radial in a AAA environment that rivaled ETO.

 

[Peter Gunn]

If the US had to make do without one of the aircraft, I would say dispense with the P-51 and keep the F4U. We could have won the war with the P-47 in Europe, but the same could be said about the F6F in the Pacific. But what about 1951 in Korea? I know that I would rather be flying an F4U than a P-51. This is not meant to be a slight to the P-51 in any manner.

I would say dispense with the F4U, as drgondog stated, neither the F4U or the P-47 had the legs for deep penetration, not to mention combat was mostly 15,000 - 25,000 ft band, RIGHT in the Mustangs wheelhouse. Performance wise it was a perfect fit and as for broad statements, well, the Mustang could (and did) do the Corsair's job, the reverse was NOT true.

Besides, I think drgondog can produce accurate numbers but the Mustang scored something along the lines of double the kills of the P-47 and P-38 combined, but don't quote me on that. And that was against some of the best the Luftwaffe had to offer.

As for Korea, from a quick memory check (flying very similar mission profiles in the same environment):

F-51 Losses = 341 combat related and 474 overall

F4U losses = 325 combat related (Navy & Marines combined) and 495 overall

Kinda' dispenses the myth that the F4U was tougher for ground attack work.

 

[GrauGeist]

As for Korea, from a quick memory check (flying very similar mission profiles in the same environment):

F-51 Losses = 341 combat related and 474 overall

F4U losses = 325 combat related (Navy & Marines combined) and 495 overall

Out of curiosity, of both types listed, what were the numbers for losses against enemy aircraft versus enemy ground fire for each type?

 

[Shortround6]

also interesting would be the losses per 1000 sorties and perhaps distance from bases?

 

[henshao]

Among the R-2800 fighters, the Corsair was not as resilient against enemy fire as the Jug and Hellcat due in part to the oil coolers in the wings. It probably didn't help that it was a handful to land on a carrier under ideal circumstances, let alone battle-damaged (more likely to be ditched when the others could have been saved)

 

[PAT303]

If the US had to make do without one of the aircraft, I would say dispense with the P-51 and keep the F4U. We could have won the war with the P-47 in Europe, but the same could be said about the F6F in the Pacific. But what about 1951 in Korea? I know that I would rather be flying an F4U than a P-51. This is not meant to be a slight to the P-51 in any manner.

Without the Hurricane Spitfire P40 and Wildcat you don't have an island base or aircraft carriers so you've lost the war before the F4U P47 F6F and P51 have even entered production. All those aircraft entered production and were used in all theatres, because all of them were needed.

 

[mig-31bm]

Among the R-2800 fighters, the Corsair was not as resilient against enemy fire as the Jug and Hellcat due in part to the oil coolers in the wings. It probably didn't help that it was a handful to land on a carrier under ideal circumstances, let alone battle-damaged (more likely to be ditched when the others could have been saved)

that interesting, I always thought that Corsair is more durable given that it is armored against 0.5 caliber machine gun while P-47 is not

 

[henshao]

that interesting, I always thought that Corsair is more durable given that it is armored against 0.5 caliber machine gun while P-47 is not

it has been discussed in great detail over the years on this site, there are some good tidbits here P-47N Thunderbolt vs. F4U-4 Corsair - Which was superior?

 

[GrauGeist]

Among the R-2800 fighters, the Corsair was not as resilient against enemy fire as the Jug and Hellcat due in part to the oil coolers in the wings. It probably didn't help that it was a handful to land on a carrier under ideal circumstances, let alone battle-damaged (more likely to be ditched when the others could have been saved)

The P-47's turbo system was more vulnerable, being in the belly of the fuselage and unlike the F4U and F6F, never had to ditch due to battle damage...

 

[Thumpalumpacus]

Get a P-51 on a deck. I bet the folding wings, reinforced gear, and extra metal all around drops performance. Whether it's enough to make it close, I don't know, but I do know that comparing carrier F4Us -- and of course most weren't -- to land-based P-51s isn't full apples on apples.

 

[Peter Gunn]

Out of curiosity, of both types listed, what were the numbers for losses against enemy aircraft versus enemy ground fire for each type?

I'll dig out the book this weekend, the numbers I posted I copied out real quick for another post quite some time back and they were still sitting in that pile of papers on my desk. Going from memory however (DO NOT quote me on this but...) I believe for the mustang it was only 10 lost in air to air vs MiG-15s and about a like number for the F4U, all other combat losses were to GF.