Supose the Corsair went to the 8th AF !

[renrich]

Thanks, Bill. In my research I stumbled on another table which shed some light on this discussion. This table was a dive capability comparison and it compared in two ways. First in initial diving acceleration from high altitude. The second in limit dive speeds imposed at 10000 feet. In the first which was a ranking showing only the first part of a dive from about 25000 feet at both 30 degrees and 90 degrees, the ranking from first to last was P38G, tie between P51D and F4U1D, P47D, F6F5, P39D, F4F4, P40E. The second table listed the one G limit dive speeds for the altitude of 10000 feet. P47D, P51D, P63A, all at 500MPH IAS. The F4U1D was further down the list with 443 MPH IAS, 516 TAS, Mach 0.63 which resulted in a 6.5 G pullout. This ranking indicates, I think, the speed at which a fighter must not go beyond at 10000 feet if he begins to pull out from a dive. If that speed at that altitude was exceeded, compressibility problems began to become severe. At 20000 feet the F4U1D was restricted to a dive speed of 504MPH TAS which was about .72 Mach.

 

[drgondog]

Thanks, Bill. In my research I stumbled on another table which shed some light on this discussion. This table was a dive capability comparison and it compared in two ways. First in initial diving acceleration from high altitude. The second in limit dive speeds imposed at 10000 feet. In the first which was a ranking showing only the first part of a dive from about 25000 feet at both 30 degrees and 90 degrees, the ranking from first to last was P38G, tie between P51D and F4U1D, P47D, F6F5, P39D, F4F4, P40E. The second table listed the one G limit dive speeds for the altitude of 10000 feet. P47D, P51D, P63A, all at 500MPH IAS. The F4U1D was further down the list with 443 MPH IAS, 516 TAS, Mach 0.63 which resulted in a 6.5 G pullout. This ranking indicates, I think, the speed at which a fighter must not go beyond at 10000 feet if he begins to pull out from a dive. If that speed at that altitude was exceeded, compressibility problems began to become severe. At 20000 feet the F4U1D was restricted to a dive speed of 504MPH TAS which was about .72 Mach.

That clarifies it and makes sense - I could not figure out why the F4U would be limited to a true 440+ mph dive at high altitude.. simply stated is there is no real difference where it counts in this debate - namely the push over and chase from 25,000 to the deck.

The 51 red line, often exceeded in combat was .75M.

Ren - 516 mph TAS at 10k would be closer to .7M and logically should be the same limit (~ .7M) as in high altitude. What that (I think) the report is saying is 'don't do a design limit pullout of 8 g's' - keep it below that - rather than 'this is where compressibility affects you'. I haven't seen the data but I wouldn't be suprised if the number for Mcr was close to .72M for all altitude regimes for the F4U.

I suspect it would be slower in dive than both the 109 and 190 but doubt that would be serious drawback.

 

[MikeGazdik]

I suspect it would be slower in dive than both the 109 and 190 but doubt that would be serious drawback.[/QUOTE]
The only time I can recall a Bf 109 using a dive as an effective means of escape was against the RAF during the B.o.B. I suspect it may have worked against the Russians. But unless they had an early P-38 on thier tail, the P-47 and obviously P-51 overhauled them in a hurry. I don't see why the Corsair would be any different, even if it was a bit slower than the other 2 USAF fighters. Were not the wings of the 109 comparatively fragile as compared to other fighters? I think it would take an extremely skilled (or scared) Bf 109 pilot to outdive a 47 / 51/ F4U.

 

[renrich]

Some of the dive data from Dean on the P47. " 500 MPH IAS was the dive limit speed(400 MPH above 25000 feet), and it was recommended dive recovery be made no lower than 12000 feet. At this altitude the limit dive speed corresponded to 601 MPH TAS and Mach .82. At this speed the P47 was well into compressibility with a drag coefficient of at least two and one half times the value at moderate speeds."

 

[drgondog]

I suspect it would be slower in dive than both the 109 and 190 but doubt that would be serious drawback.

The only time I can recall a Bf 109 using a dive as an effective means of escape was against the RAF during the B.o.B. I suspect it may have worked against the Russians. But unless they had an early P-38 on thier tail, the P-47 and obviously P-51 overhauled them in a hurry. I don't see why the Corsair would be any different, even if it was a bit slower than the other 2 USAF fighters. Were not the wings of the 109 comparatively fragile as compared to other fighters? I think it would take an extremely skilled (or scared) Bf 109 pilot to outdive a 47 / 51/ F4U.[/QUOTE]

Not exactly true. The difference in dive speeds was not much. If a 109 split S 200 yards in front of a Mustang it would be caught. If he was 800-1000 yards out the 51 would be in for a long chase - ditto P-47.

I haven't seen evidence that a 109 wasn't designed to 8 G limit/12 Ultimate so theoretically its wings were just as strong a 51. I have seen evidence of both 109 and 51 losing wings in a dive and the 51 was mostly (not all) attributed to a dropping main gear on pullout before the uplocks were installed in late B's and all D's.

 

[davparlr]

To answer the question of how the Air Force missions would have been affected we need to look at two time periods, 1943, when AF bombers were taking a pounding, and 1944, January through June, when the build up for D Day was critical.

In 1943, the primary mission was escort and some interdiction. The US players were the P-47B/C/D and P-38F/G. The F4U-1, without water injection, would be the player here. Water injection did not come in play for the F4U until the end of 43. The P-47C had water injection early in 1943 and the D, with water injection also showed up early in the year, also. Here are some comparison data.

Note: F4U data seems all over the map. For instance, I had three sources for F4U-1D data, all different so I chose the middle, which also compared favorably with the P-47 with the same HP.

SL airspeed, climb
P-38 330 mph, 3500 ft/min
P-47 333, 2870
F4U 350, 2800

5k
P-38 343, 3000
P-47 353, 2810
F4U 348, 2300

10k
P-38 363, 2500
P-47 372, 2680
F4U 363, 2300

15k
P-38 380, 2200
P-47 390, 2460
F4U 379, 2300

20k
P-38 395, 2000
P-47 406, 1800
F4U 382, 1800

25k
P-38 412, 1800
P-47 421, 1860
F4U 392, 1500

30k
P-38 372, 1600
P-47 433, 1400
F4U 360, 900

Just reviewing this data, it is apparent that the non-water injected F4U-1 is not up to the performance standards of the AF contemporaries in 1943, the P-38G, or the water injected P-47, coming in last place in climb at every altitude and falling behind in airspeed above 10k. Now if the F4U was being flown by the AF, it is reasonable to assume that they would have upgraded to the water-injected -1D very early to handle the higher performing enemy in the ETO. Therefore the F4U comparison would significantly improve (see -1D performance below). As for escort duty, the P-47 does not have the endurance to escort bombers to Germany, the P-38 and F4U do, but the F4U has better in-combat time. As for high altitude combat capability, none of these aircraft have any significant advantage, if any, over the German opposition, with the F4U the least capable.

For interdiction, the F4U would have been very good, with superior range and legendary ruggedness.

For the period of January through June, 1944, the mission is escort, fighter sweeps and interdiction. US aircraft players are P-47D-25 and P-51B/D. The F4U version available is the much improved -1D, with water injection. Here is some comparison data.

SL airspeed and climb
P-47 345 mph, 3250 ft/min
P-51 373, 3780
F4U 365, 3750

5k
P-47 368, 3200
P-51 394, 3700
F4U 377, 3710

10k
P-47 385, 3100
P-51 418, 3310
F4U 397, 3550

15k
P-47 405, 3000
P-51 417, 3100
F4U 408, 3150

20k
P-47 415, 2800
P-51 427, 3080
F4U 421, 2500

25k
P-47 425, 2600
P-51 427, 2350
F4U 413, 1850

30k
P-47 425, 2300
P-51 429, 1600
F4U 380, 1200

Now the data shows that the F4U-1D, with water injection, performs much better and these three aircraft fly pretty well nose-to-nose up to 20k. Above that, the F4U runs out of air and rapidly drops off. For escort, the F4U-1D, as built, could not perform as needed. Also, the wing tanks had been removed and the range would be insufficient. However, if the F4U was an AF bird, the nice range of the F4U-1 would have been maintained and the -1D could easily have performed the escort mission. The P-47D-25, which had increased internal fuel, was now capable of performing the escort mission. With the wing tanks installed, the F4U-1D, with the range of the P-51 and the ruggedness of the P-47, would have made an outstanding deep interdiction fighter. Unfortunately, the F4U-1D engine was not configured for high altitude performance. A high altitude, non-turbo-supercharged, PW2800 would not be available until mid 1944. In addition, turbo-supercharging the F4U would have been problematic. The fuselage fuel tank would certainly be impacted significantly even if the turbo was mounted aft of the pilot. This turbo mounting would have affected the CG thus probably requiring quite a redesign.

The F4U and the P-47 were designed for different missions. The F4U-1 and -1D were optimized for combat from SL to 20k ft., where Japanese aircraft normally fought, and the P-47 was optimized for combat between 20k and 35k ft., where bomber protection was required. It was probably too difficult to update the F4U for high altitude combat until mid '44. The F4U-1 could not have performed up to the P-47 level in low altitude combat due to its lack of water injection; however, this could easily have been corrected. The F4U-1D would have out performed the P-47 up to 20k ft, but still would not be as capable of performing the high altitude escort mission.

In my opinion, the F4U-1, as delivered, was unacceptable to place the P-47C/D, certainly not in the high altitude escort mission. In 1943, this was a pretty critical capability. The F4U-1D was easily capable of replacing the P-47C/D for mission below 20k ft, but not acceptable for high altitude escort. However, from '44 on, the high altitude mission was not a priority for the P-47, as the P-51 was taking over this job. So, to answer the question, because of the critical high altitude missions in 1943, it would have been unwise for the AF to use the F4U instead of the P-47.

 

[MikeGazdik]

An excellent and well argued post!!! You post fact and opinion neatly woven together. Like I stated a bit earlier, the only "thing" the P-47 really lacked was range. Once the groups / pilots got thier time in and learned the lessons they needed to learn, the P-47 became an extremely effective escort aircraft, again only lacking the long legs to go all the way into Germany.

It is sometimes hard for me to pick a singular WWII aircraft to say "this is my favorite", but in discussion I always fall back on the sturdiness and capability of the P-47. And I know for a fact if I had to go to war back then, in a fighter, I would hope it was in a P-47.

That being said, you cannot argue the merits of how great an airplane the F4U was, I think right up there with the P-51, and in some aspects better than the P-51. I do really wish I could read some first hand accounts of how the F4U fought against the great German fighters!

 

[drgondog]

In my opinion, the F4U-1, as delivered, was unacceptable to place the P-47C/D, certainly not in the high altitude escort mission. In 1943, this was a pretty critical capability. The F4U-1D was easily capable of replacing the P-47C/D for mission below 20k ft, but not acceptable for high altitude escort. However, from '44 on, the high altitude mission was not a priority for the P-47, as the P-51 was taking over this job. So, to answer the question, because of the critical high altitude missions in 1943, it would have been unwise for the AF to use the F4U instead of the P-47.

Dave - two things occur to me,

First a USAAF Corsair would be spec'd for a Pratt config to yield high altitude (better) performance as part of the Corsair/Army design process.

Second the Army version would have carved at least 600-1200 pounds out of the carrier qual Navy version. Absent the engine change, this F4U-1 should climb ~ 10% better and dash 2-3% better than the USN version.

Last and most important the Army probably would have taken slighly less performance than the P-38 and P-47 simply because it could escort the bombers to their targets (reliably) and 8th AF HQ would have easily accepted higher losses in fighter crews to dramatically reduce the bomber losses.

Just opinion,

 

[DBII]

Great thread guys.

DBII

 

[davparlr]

Dave - two things occur to me,

First a USAAF Corsair would be spec'd for a Pratt config to yield high altitude (better) performance as part of the Corsair/Army design process.

I don't know much about PW engine development. I do know that a high altitude engine for the F4U was not available until mid '44. I do not know if this was because of techincal issues or just no requirements. However, it does appear that a new engine would be required for sucessful high altitude performance for the F4U and that this would be more complex than adding more internal fuel to the already high altitude capable P-47.

Second the Army version would have carved at least 600-1200 pounds out of the carrier qual Navy version. Absent the engine change, this F4U-1 should climb ~ 10% better and dash 2-3% better than the USN version.

I was lazy with my response and didn't bother with normalizing the weight. This is certainly true and would have helped climb but would probably been minor impact on AS

Last and most important the Army probably would have taken slighly less performance than the P-38 and P-47 simply because it could escort the bombers to their targets (reliably) and 8th AF HQ would have easily accepted higher losses in fighter crews to dramatically reduce the bomber losses.

I buy this argument, but, if the AF was really interested in long range escort, why wouldn't they just increase the internal fuel of the P-38 and P-47. Tis a puzzlement. Maybe the comment regarding wanting to demonstrate the self-protecting of the bombers was true.

 

[kool kitty89]

Range wasn't the problems so mouch for the P-38, I beleive Bill was taliking about the other problems the early (pre-J) P-38's had.

On the Corsair's engine, it may not have gotten the more powerful engine of the F4U-4 too much earlier (though greater concentration on such development rather than the P-47's turbocharged engine should help). However I think water injection woud be available sooner given te timeline for the P-47 and that it was the same engine just with a new accessory. (Renrich also mentioned that the -8W engine was being equipped on late production F4U-1A's prior to the -1D as well as being retrofitted to earlier Corsairs)

There also may have been a change in the propeller for better climb and high altitude performance. (4-blade, eventually paddle-prop similar to the P-47's)

 

[davparlr]

However I think water injection woud be available sooner given te timeline for the P-47 and that it was the same engine just with a new accessory. (Renrich also mentioned that the -8W engine was being equipped on late production F4U-1A's prior to the -1D as well as being retrofitted to earlier Corsairs)
There also may have been a change in the propeller for better climb and high altitude performance. (4-blade, eventually paddle-prop similar to the P-47's)

Earlier water injection should have easily have been implemented. I don't know about the propeller issue, except it should be similar to the P-47 update. I think the point is that the F4U could be modified to perform the P-47 mission, but the P-47 was already designed to do the job.

 

[drgondog]

Earlier water injection should have easily have been implemented. I don't know about the propeller issue, except it should be similar to the P-47 update. I think the point is that the F4U could be modified to perform the P-47 mission, but the P-47 was already designed to do the job.

Dave - I agree your points. I assume the above is about the emphasis and possible development of a high altitude engine by mid 1943 if the Corsair had been not been purchased by the USAAF.

Had it been purchased at the same time as the Navy version but modified to achieve P-38/P-47 specs I believe the high altitude engine development may have proceeded earlier than it did for the F4U-4.

The issue for me is that until the M and the N, the Jug never truly had the ability to defeat the Luftwaffe over Germany from bases in Italy and England, whereas even the F4U-1A as designed (heavy) could have fought over Germany at bomber altitudes and below (probably with higher losses than Mustangs) and dramatically reduced bomber losses.

Remember - given the high altitude spec capabilities of the P-38F and G, it had huge reliability problems at 25000 feet and combined with compressibility issues in dive - wasn't a great solution in the ETO. I would pose a thought that as diminished as the F4U-1 was at 25,000 feet, it could still compete.