Best Pacific Fighter?

[evangilder]

Interesting analysis. That is a good point about IAS versus TAS. During dive testing with a P-47, a test pilot reached 725 MPH IAS. That is impossible, because terminal velocity on the P-47 was about 600 MPH. The TAS was estimated to be in the mid-500 MPH range. If the IAS had been accurate, the P-47 would have been the first plane to break the sound barrier. Obviously, that wasn't the case.

[wmaxt]

Originally Posted by evangilder

Interesting analysis. That is a good point about IAS versus TAS. During dive testing with a P-47, a test pilot reached 725 MPH IAS. That is impossible, because terminal velocity on the P-47 was about 600 MPH. The TAS was estimated to be in the mid-500 MPH range. If the IAS had been accurate, the P-47 would have been the first plane to break the sound barrier. Obviously, that wasn't the case.

This ia a situation that all WWII fighters went through, I've read several variations on most of the planes we talk about. It took a few years before the effects of trans sonic affects on the air speed indicator.

[wmaxt]

RG, A couple of points.

The statement comparing the P-38/P-51 was in one case for certain to be Art Heiden - certainly a P-38 fan but had over 100 missions in the P-38 and 52? in the P-51. In the C C Jordon web site he is quoting "several" pilots including Hub Zemke (who refered to the P-38 as an "icewagon").

If I came off like they, P-51/P-38, pilots All prefered the P-38 "oops" , everybodies got an opinion and they will never all be the same. If those pilots had thought the P-51 was Much worse we would have been hearing it ever since - But it remains fact that some pilots prefered the P-38 in a fight.

Note on the climb speed graph at WEP 20,000 is right at the 4.9/5.0min range and is cited at 4.91 in the C C Jordon web site. Normal power, 1,100hp, is 7 min to 20,000ft. The site also quotes climb at 20,000 is still 3,700ft/min. The P-51 is 8:20+/- in military power(1,590hp_. Art Hieden put it this way "The P-38 was at altitude before we reached the coast, the P-51 still had a long way to go.". The P-51 could not out climb a P-38 anywhere.

The Lockheed graph was a comparison with the p-51 for internal use there would be NO REASON to compare the two if they were not in the same weight and trim. Assuming they used a tricked out P-38 against a standard test loading (full ammo ballast and half fuel est from the test data as it matches the standard data) P-51 is silly esp since it was an internal test. I don't have Bodie's book so I don't have more info on the loadings. Edit: I think one of the reasons this data looks funny is that Lockheed had the Gall to test a P-38 against a P-51 at the same throttle setting WEP.

The Baugher website tells of a P-38 dive that with full control registered 740mph or so (yes we know it was under 600mph) not that this was recomended. I know that IAS redline on the P-38 is 500mph/asl or Mach .68.

The P-51 was not "hands down" the better fighter, like the P-38 it had it's strong points and bad. The F4U with a better airfoil and lighter wing loading (almost the same area as the P-38 and much lighter weight) should be better than either the P-38 or the P-51. In a dogfight there are other complications as well.

In this class of aircraft it comes down to the pilot.

Originally Posted by evangilder

Interesting analysis. That is a good point about IAS versus TAS. During dive testing with a P-47, a test pilot reached 725 MPH IAS. That is impossible, because terminal velocity on the P-47 was about 600 MPH. The TAS was estimated to be in the mid-500 MPH range. If the IAS had been accurate, the P-47 would have been the first plane to break the sound barrier. Obviously, that wasn't the case.

IAS is always lower than TAS, unless something is wrong. The air-speed indicator is supposed to measure the relative air speed of the plane. As the altitude increases, the air gets thinner, and the amount of air moving past the sensor at a given speed is lower.

However, early air-speed indicators tended to give false readings at very high speeds.

TAS measurements are usually based either on IAS speeds and a conversion function, which relies on the accuracy of the air-speed sensors, which may be incorrect, or they rely on time between two points measured from the ground, which tends to ignore wind speed. Neither method of measurement is truely accurate.

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Lunatic

wmax,

I'm in no way saying the P-51 was better than the P-38L or late J. All I'm saying it it was not totally outclassed by it. I agree the pilot made the difference. Again I go back to the point that if the conditions of the fight are equally skilled pilots engaging at high alititude, the P-51 enjoys some advantages at the start of the fight which if he can exploit should make him the victor. If the fight drags on and altitude drops much below 20K or speeds drop below 200 IAS, the P-38 gains the advantage.

As you can see below, the P-51 climb was not that much worse than the P-38 climb. However, I suspect the P-38 climb in cruise condition was much better which is what was being refered to by the pilot you referenced.

As for the P-38 being in "full control" at such a high speed, I just don't see how. The dive recovery flaps do not change the laws of physics. Once the airflow over the wings goes into the transonic region the ailerons are nearly useless and the plane is going to suffer buffeting. I really suspect what they mean is that it was fully able to recover from the dive, not that it was in sufficient control for the pilot to aim the guns or do much manuvering.

I've made another post for purposes of displaying I chart I found comparing US plane performance. As you will see the image is so large it would disrupt this chat, so i've put it in it's own thread called US Plane Performance Chart for easy and perminant reference on this forum.

As you can see in the chart, climb to 20k times and radius of action figures (in parans) are given as follows:

F4U-4: 5.0 mins (615 mi) -- F4U-1: 7.4 mins (500 mi) -- F6F-5: 7.0 mins (500 mi)

P-47D: 7.6 mins (650 mi) -- P-38J: 5.9 mins (450 mi) -- P-51B: 6.6 mins (550 mi)

F2G-1: 5.5 mins (525 mi) -- F7F: 5.2 mins (403 mi) -- F8F: 4.7 mins (208 mi)

Note that the P-51B climb is at MP, all the rest are at WEP. Given that the P-51 is at 67 hg manifold pressure, perhaps they just didn't consider the Merlin had WEP?

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Lunatic

[Lightning Guy]

I am immediately skeptical of those numbered. There is no was that the F4U could match the P-38J in radius of action. And the P-47D certainly didn't better any of the fighter in the list (except the F8F).

Originally Posted by Lightning Guy

I am immediately skeptical of those numbered. There is no was that the F4U could match the P-38J in radius of action. And the P-47D certainly didn't better any of the fighter in the list (except the F8F).

Read the definition of "Range":

Radius of action is based upon Navy requirements for a combat mission. This includes fuel allowances for 20-minute warm-up and idling; 1-minute takeoff; 10-minute rendezvous at 60% normal power at sea level; climb to 15,000 feet , 60% normal power; cruising to objective at 15,000 feet at optimal cruising. 20-minute combat (15,000 ft.) at full power; return to base at 1,500 feet at optimum cruising; and reserve 60 minutes at optimum cruising; An auxillary tank is used for rendevous, climb, and cruising to object and is dropped upon reaching the objective. All other fuel comes from the main protected tank. Radius includes distance covered in climb but not in descent.

Well, this is not terribly clear but by looking at the fuel loading (right under the weights) we can see that on the P-38 the leading edge tanks are empty, the main and reserve tanks (90 gallons and 60 gallons respectively) are filled, giving 300 gallons. For the P-47 however, both the 205 gallon main and 100 gallon aux. tanks are filled, giving it 305 gallons. It is pretty obvious that even though the allisons are more efficient than the R-2800, they are not twice as efficent.

Furthermore the P-38 gains no range advantage from its ability to carry those huge 250 gallon drop tanks because these are dropped upon reaching the objective with the plane needing to meet the remainder of the mission spec, which requires 20 minutes of combat, cruise home, and still have 60 mins cruising time in reserve. So the advantage gained by being able to carry up to 500 gallons in the drop tanks is totally lost.

If the two 55 gallon leading edge tanks were filled, the P-38J would do much better in this chart, as this would apply entirely to the cruise back range and thus allow more time on the drop tanks as well. Given that all of this fuel would be applied to the optimal cruise back, I'm guessing it would increase the overall range by 50% or more - to at least 675 miles. But still a fair amount of the drop tank range would be lost.

So I agree the P-38 is a little short-changed in terms of range in this chart. The P-51B gets short-changed 65 gallons as well, but that does not invalidate the rest of the chart.

Another consideration is that lacking that fuel probably benifited the relative climb rates attributed to the P-51B and the P-38J.

As for the F4U-4, the cruise is done closer to the engines rated altitude than the others, which may contribute some. Also, it could carry two large 150 gallon drop tanks where the F4U-1 and Hellcat could only carry one, so that may also be a factor. Also the R-2800(C) had much better cooling than the R-2800(B) so it may have cruised at a leaner fuel mixture setting which could noticably improve its range.

Finally, I would say that range figures are much more abitrary than climb figures. The Navy probably had to estimate the range capabilities of the USAAF planes in the list based upon USAAF supplied data to some degree, to fit them to their mission profile. But climb to altitude data is very strait-forward and so probably much more accurate.

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Lunatic

[wmaxt]

Originally Posted by RG_Lunatic

wmax,

I'm in no way saying the P-51 was better than the P-38L or late J. All I'm saying it it was not totally outclassed by it. I agree the pilot made the difference. Again I go back to the point that if the conditions of the fight are equally skilled pilots engaging at high alititude, the P-51 enjoys some advantages at the start of the fight which if he can exploit should make him the victor. If the fight drags on and altitude drops much below 20K or speeds drop below 200 IAS, the P-38 gains the advantage.

As you can see below, the P-51 climb was not that much worse than the P-38 climb. However, I suspect the P-38 climb in cruise condition was much better which is what was being refered to by the pilot you referenced.

As for the P-38 being in "full control" at such a high speed, I just don't see how. The dive recovery flaps do not change the laws of physics. Once the airflow over the wings goes into the transonic region the ailerons are nearly useless and the plane is going to suffer buffeting. I really suspect what they mean is that it was fully able to recover from the dive, not that it was in sufficient control for the pilot to aim the guns or do much manuvering.

I've made another post for purposes of displaying I chart I found comparing US plane performance. As you will see the image is so large it would disrupt this chat, so i've put it in it's own thread called US Plane Performance Chart for easy and perminant reference on this forum.

As you can see in the chart, climb to 20k times and radius of action figures (in parans) are given as follows:

F4U-4: 5.0 mins (615 mi) -- F4U-1: 7.4 mins (500 mi) -- F6F-5: 7.0 mins (500 mi)

P-47D: 7.6 mins (650 mi) -- P-38J: 5.9 mins (450 mi) -- P-51B: 6.6 mins (550 mi)

F2G-1: 5.5 mins (525 mi) -- F7F: 5.2 mins (403 mi) -- F8F: 4.7 mins (208 mi)

Note that the P-51B climb is at MP, all the rest are at WEP. Given that the P-51 is at 67 hg manifold pressure, perhaps they just didn't consider the Merlin had WEP?

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Lunatic

I can go there.

Actually as I understand it the slat both pitched up the angle of attack but also broke up the super/trans sonic airflow that locked the stabilizer/elevator and restored lift. Even in the earlier models of the P-38 the aileron is not affected, in fact the use of aileron/barrel rolls was part of the technique used to control speeds in a dive.

The P-51D was not supposed to go over 505mph. Above that all bets are off. I've read the P-51 was good for a while after that and Heiden says it's not a problem in the P-38L at least at the speeds needed in a chase of a bf-109/fw-190. Heiden's comment may also have been follow to an altitude/speed suitable for engagement too. Beyond that I just don't know.

Flight manual data: P-51D climb normal power to 25,000ft (the P-38 listing does not show 20,000ft) in a loaded condition 11,200lbs - 24min. P-38L same conditions, 21,000lbs with pylons 14min. The laminar flow wing was good for range and speed but climb and manuvering are hurt. The P-38 was originaly an intercepter - optimized for climb. That being so it's pretty suprising it did as well as it did in other areas.

FYI, The P-38L is given a 1,210 mi range (internal) with a 50 gal reserve and pylons @ 30,000ft/285tas for max range.

As you can see that is 505 IAS.

This compares with the following for the P-38:



Breaking up the tubulence did help to achieve some proper airflow over the tail, but it also increased the turbulence and thus there had to be buffeting. Remember, air goes from acting like a liquid to acting like a solid when you hit mach speed.

Interestingly, the USAAF P-38L combat range is 450 mph (at 290 mph @ 10,000 feet). I suspect this is where the USN got that figure for the J from.

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Lunatic

[Lightning Guy]

I assume you mean 450 miles and not miles per hour. That figure is often posted but is actually the range at maximum power.

It is interesting that the P-38's stats were given for less that optimal conditions, at least in range . . . what else might be wrong on the chart? Maybe nothing, but it does make everything else suspect does it not?

Interestingly, Milo Burcham tested a P-38F (no leading edge tanks) and found that the P-38 had a ferry range without external tanks of 1,300 miles. Granted combat range would be less, but could a P-47 or F4U match that figure? By the end of the war, P-38Ls in the Pacific were flying missions to a RADIUS of 950 miles.

The P-38 never carried 250 gallon tanks so far as I know. They did, however carry 165 gallon tanks (usually referred to as 150 gallon) and 310 gallon tanks (usually referred to as 300 gallon). Correct internal fuel for a P-38L was 430 gallons (2 x 90 gallon mains, 2 x 63 gallon reserves, 2 x 62 gallon leading edge). This is more fuel than two 165 gallon tanks (330 gallons) and this mission load was regularly flown in the ETO. In the PTO, P-38s regularly carried 1 310 and 1 165 gallon tanks (475 gallons) without undue difficulty. No other WWII fighter could match the P-38 for range, ferry or combat.

The P-38 never carried 250gallon tanks. I'm not sure where you got that figure.

[wmaxt]

Originally Posted by Lightning Guy

I assume you mean 450 miles and not miles per hour. That figure is often posted but is actually the range at maximum power.

It is interesting that the P-38's stats were given for less that optimal conditions, at least in range . . . what else might be wrong on the chart? Maybe nothing, but it does make everything else suspect does it not?

Interestingly, Milo Burcham tested a P-38F (no leading edge tanks) and found that the P-38 had a ferry range without external tanks of 1,300 miles. Granted combat range would be less, but could a P-47 or F4U match that figure? By the end of the war, P-38Ls in the Pacific were flying missions to a RADIUS of 950 miles.

The P-38 never carried 250 gallon tanks so far as I know. They did, however carry 165 gallon tanks (usually referred to as 150 gallon) and 310 gallon tanks (usually referred to as 300 gallon). Correct internal fuel for a P-38L was 430 gallons (2 x 90 gallon mains, 2 x 63 gallon reserves, 2 x 62 gallon leading edge). This is more fuel than two 165 gallon tanks (330 gallons) and this mission load was regularly flown in the ETO. In the PTO, P-38s regularly carried 1 310 and 1 165 gallon tanks (475 gallons) without undue difficulty. No other WWII fighter could match the P-38 for range, ferry or combat.

The P-38 never carried 250gallon tanks. I'm not sure where you got that figure.

Range is an interesting thing The 1,210miles I noted above was internal fuel only, as listed in the "Flight Operation Instructing Manual" for the P-38L with full internal fuel listed at 410gal-50 gal reserve or 360gal usable. My understanding is that basic range numbers are the radius on internal fuel. So for the P-38L warm-up, takeoff, form-up, mission, combat @WEP, return, landing, and reserve gives 450mi/nominal. The P-51 had more fuel internal so it actually does a little better. All range numbers are theroretical due to all the variables involved, P-38s flew many missions over 2,000 miles R/T with combat. The last combat mission was reported to have been 2,800mi with combat over Borneo on 15, Aug. '45, can you imagine more than 13hrs in a P-38 cocpit?

An interesting point on the P-51 - the last 20 gallons in the Fusalage tank was not recomended for use except in extreme emergancies because of severe CG problems.

[wmaxt]

Originally Posted by RG_Lunatic

Breaking up the tubulence did help to achieve some proper airflow over the tail, but it also increased the turbulence and thus there had to be buffeting. Remember, air goes from acting like a liquid to acting like a solid when you hit mach speed.

Interestingly, the USAAF P-38L combat range is 450 mph (at 290 mph @ 10,000 feet). I suspect this is where the USN got that figure for the J from.

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Lunatic

I understand your reasoning, however signifcant buffeting is not reported and with correct usage critical speed was not exceeded possibly accounting for that fact.

The range I quoted does not include combat activities possibly accounting for the difference. It also stated 360gal useable fuel to. The USAAF seemed to have a different set of performance rules/specs with the P-38. Then there is the P-51B with Mil power rated at full engine power. The numbers don't always make sense.

One thing about your report by George, I've read about techniques like differential throttle in many places - it was done and it was effective both in rolling and in turning (check out Jeff Ethels article in the "Flight Journal Magazine"). I've also read that there was more training and ues of such techniques in the pacific. A number of P-38 pilots felt the Aircrews/aircraft was handled very poorly in the ETO, from support to training, where it was always the "Red headed stepchild". George doesn't sound like he ever felt comfortable in a P-38.

Originally Posted by Lightning Guy

I assume you mean 450 miles and not miles per hour. That figure is often posted but is actually the range at maximum power.

It is interesting that the P-38's stats were given for less that optimal conditions, at least in range . . . what else might be wrong on the chart? Maybe nothing, but it does make everything else suspect does it not?

Interestingly, Milo Burcham tested a P-38F (no leading edge tanks) and found that the P-38 had a ferry range without external tanks of 1,300 miles. Granted combat range would be less, but could a P-47 or F4U match that figure? By the end of the war, P-38Ls in the Pacific were flying missions to a RADIUS of 950 miles.

The P-38 never carried 250 gallon tanks so far as I know. They did, however carry 165 gallon tanks (usually referred to as 150 gallon) and 310 gallon tanks (usually referred to as 300 gallon). Correct internal fuel for a P-38L was 430 gallons (2 x 90 gallon mains, 2 x 63 gallon reserves, 2 x 62 gallon leading edge). This is more fuel than two 165 gallon tanks (330 gallons) and this mission load was regularly flown in the ETO. In the PTO, P-38s regularly carried 1 310 and 1 165 gallon tanks (475 gallons) without undue difficulty. No other WWII fighter could match the P-38 for range, ferry or combat.

The P-38 never carried 250gallon tanks. I'm not sure where you got that figure.

http://www.acepilots.com/planes/p38_lightning.html <--- 250 gal drop tank

Cruise and Range
Typical combat radius for the J/L variants was 275 miles for 410 US gallons of fuel (no external tanks) and 650 miles with 740 US gallons (w/ 165 gal external tanks). These ranges allowed for 20 minutes combat at target and 30 minutes of reserves. With 300 gal tanks, missions were made over ranges in excess of 1000 miles and durations of nine hours or more.
http://www.kazoku.org/xp-38n/articles/p38info.htm

Again, I don't see anything wrong with the chart. It specifies 300 gallons of internal fuel equals a 450 mile combat range. This fits the above info almost exactly, showing a 575 mile range listed above using the full ~410 gallons of internal fuel and only a 30 min reserve. The rest of the data, including the climb rates, are backed up by numerous other sources.

Why did the USN not consider fuel in the wing tanks? Why didn't they consider fuel in the rear tank of the P-51? That's hard to answer, but perhaps they felt that entering combat with fuel in these tanks made the plane too vulernable or hurt manuverability too much. If the tank has had fuel in it at all, it is subject to fire even if the fuel has been expended - in fact, a tank with 25% fuel is much more vulnerable than a full one. If a tank been purged before flight, it's not subject to fire. The weight in the outer wing panels of the P-38 would have detracted from its combat capability which it was assumed would be needed the moment the drop tanks were released, and would make it more vulnerable to fire. Perhaps that is the reasoning?

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Lunatic

Originally Posted by wmaxt

An interesting point on the P-51 - the last 20 gallons in the Fusalage tank was not recomended for use except in extreme emergancies because of severe CG problems.

I accounted only 65 gallons to the P-51B's rear tank for just this reason, it could in fact hold 85 gallons. A skilled pilot could handle a full rear tank, but it was tricky and takeoff with any crosswind whatsoever was very dangerous.

As for the P-38J figures, all I'm saying is the 450 mile return distance is very reasonable given the 300 gallons of fuel stated and the other conditions listed. I agree the P-38J/L could fly a lot further than that, especially if it had full internal fuel and the large (300 gallon?) drop tanks. However, a 1000 mile return flight after combat is doubtful. It might be possible if combat were minimal and altitude was retained (fuel economy is better at rated altitude).

Many PTO sorties were flown such that they landed at a base much closer to the target than they took off from. You cannot look at total distance flown and simply divide by two to get the effective combat radius.

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Lunatic

[wmaxt]

Originally Posted by RG_Lunatic

I accounted only 65 gallons to the P-51B's rear tank for just this reason, it could in fact hold 85 gallons. A skilled pilot could handle a full rear tank, but it was tricky and takeoff with any crosswind whatsoever was very dangerous.

As for the P-38J figures, all I'm saying is the 450 mile return distance is very reasonable given the 300 gallons of fuel stated and the other conditions listed. I agree the P-38J/L could fly a lot further than that, especially if it had full internal fuel and the large (300 gallon?) drop tanks. However, a 1000 mile return flight after combat is doubtful. It might be possible if combat were minimal and altitude was retained (fuel economy is better at rated altitude).

Many PTO sorties were flown such that they landed at a base much closer to the target than they took off from. You cannot look at total distance flown and simply divide by two to get the effective combat radius.

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Lunatic

I was primarily clarifing the earlier post, not trying to make a point. As I said earlier the numbers don't allways add up either.

A skilled P-51 pilot could handle it if NO maneuvering took place. Climbout was always on the fusalage tank to get it down to 50gals before combat. The P-51H had the tank reduced to 50/55gal. It should also be remembered the H model was Escort Only and deemed to light to do ground attack in Korea.

I agree, at least to a point, figuring from drop tank release, combat and return through unknown conditions with 400/360gals total fuel and 1,000 miles home was probably not wise. Tom McGuire, made that "keep the Tanks" in combat error himself and we all know the result of that.