Most Overrated aircraft of WWII.....? (3 Viewers)

Shortround6 · Jun 24, 2018

Navalwarrior said:
Yes, but I am talking Apr/May/Jun 1943. The Fleet Air Arm (Royal Naval Air Force) were just getting their Corsairs in 1943. And I do think that it would have been a surprise seeing them that far inland, flying cover for the bombers! The 78th surprised the Luftwaffe the day they went deeper eastward with their 'ferry' tanks. But, I get the sense that no one wants to do or look at the numbers. Shortround6 quoted numbers when he used the figure 237 against 305. Now he admits the fuel was there, but now uses the excuse that the tanks were substandard. I yielded to you in good faith. I think all who are reading would like to know the range calculations, if only to see that it was possible to fly further with an F4U than the current P-47 at that time. I think you should do the figures, since you have experience along this line, and were quick to point out that I was wrong. We can't change history, and shouldn't try. Shortround6 said it was not possible to go farther than the P-47. The numbers, please.

The numbers are not just about flying a certain distance. They are about flying that distance at a certain speed and altitude. The numbers are also about what happens after the drop tanks are gone. Standards changed, late war standards were for 5 minutes at WEP, 15 minutes at military power and an egress from the battle area at 210IAS at 25,000ft. No allowance for fuel saved in descending from 25,000ft and an allowance of 30 minutes at minimum cruise power.
Perhaps in 1943 they were different?

BTW in the original post where I mentioned the 237 gallons I did state " the F4U had 237 gallons of protected storage."

I did not change things at a later point in time.

Use of the wing tanks is a bit iffy. Not a lot, but not quite 'normal'. The Pilot's manual says:

"In general, for high power operations at high altitude, use the fuel from the main tank, which is pressurised to maintain adequate fuel flow. It is possible, on planes equipped with wing tanks in the outer panels ( prior to the installation of of center section twin pylons), to operate under the above conditions while using fuel from the wing tanks if the auxiliary fuel pump is switched "ON"; under such conditions keep a close watch on the fuel pressure and cylinder head temperature. Some attention should be paid to the fuel quantities in the wing tanks to keep the fuel consumption in the tanks approximately equal in order to to maintain the airplane in approximate lateral balance., keeping the quantity in the right tank somewhat greater than that in the left tank, since the airplane has a tendency toward left wing heaviness in the landing condition with power on. Since no quantity gages are provided for the wing tanks, the quantities of fuel consumed must be determined from the time of operation on each tank."

In another area of the manual we get this;
"The main fuel tank maintains a standpipe reserve of 50 U.S. gallons of fuel (42 Imp. gallons) after the fuel supply through the main line is exhausted. Bear in mind that the reserve fuel is made available as the quantity necessary for the final operation before landing, when the main fuel supply is exhausted and as noted below"

This is pretty standard except for the 50 gal reserve which may be taking into account having to queue up to land on a carrier which can take longer than a land runway. There is no separate tank, just a valve which accesses the tank at a lower point than the main fuel line. However, like most planes.

"Set fuel tank selector on "RESERVE" for take-off, landing, diving and maneuvers. DO NOT CRUISE ON "RESERVE."

there is a section on when to use the auxiliary electric fuel pump. No mention is made of transferring fuel from one tank to another. Iti s also there in case the engine driven fuel pump fails.

The main tank was pressurized above 12,000ft. This was automatic with a manual override.

The Co2 system is a bit interesting.

a few notes
"This system does not force fuel out of the tanks."

"WARNING"
The vapor dilution system must not be used when operating on fuel from the outer tanks. Injection of the CO2 would result in the interruption of fuel flow through the lines. However, use of the vapor dilution system does not render the gasoline in the outer tanks unfit for further use"

I will leave it the members of this forum who are pilots to decide if any of these instructions raise any warning flags.

I will also note that almost an entire squadron of Mustangs was lost when unanticipated winds blew them scores of miles off course returning from a raid, and while it was in 1944 the US lost around 80 planes during the Great Marianas turkey shoot due to running out of fuel. (more would have been lost except for measures like turning on ships lights and pointing search lights into the sky).
Cutting things too close can have very serious consequences.

drgondog · Jun 25, 2018

BiffF15 said:
Bill,

Do you have any pictures of the Allison powered Mustangs with 4 bladed props you could share? I didn't know they were even conceived let alone tested.

It's also surprising to not have shown up in post war racing. I think I remember seeing a picture of a P40 with a 4 bladed "airscrew".

Cheers,
Biff

Biff - I do not personally have any photos of the four blade prop - only the reference in the Chilton logbook. I think the P-40 you are referring to is the P-40Q but I will have to look

Peter Gunn · Jun 25, 2018

One of the issues I was curious about when I first started posting here was the whole F4U v. P-51 debate, could the Corsair do the Mustangs job and vice versa. This place answered that for me.

If you peruse some of the threads here, it's apparent that the short answer is "No", in it's historical configuration the Corsair could not reasonably do the job of the P-51 in the ETO. I think it could have been made to work, but for the reasons posted, it wasn't needed and really had nothing to offer the AAF in Europe that wasn't already addressed better by the P-47. By the time all the issues had been overcome, the Mustang would have been flying ops anyway.

Now to really get feathers ruffled, could the Mustang do the Corsair's job? I say "Yes". The range of the P-51 stands it in good stead over the Pacific and it's more than the equal performance wise, of any IJA/IJN fighter it see's.

Korean War loss rates clearly dictate that the F4U had no clear advantage in the ground attack role over the Mustang either.

All that said, I still like the Corsair and still think it is a premier fighter of WWII that probably could tackle any role handed to it.

drgondog · Jun 25, 2018

Navalwarrior said:
Yes, but I am talking Apr/May/Jun 1943. The Fleet Air Arm (Royal Naval Air Force) were just getting their Corsairs in 1943. And I do think that it would have been a surprise seeing them that far inland, flying cover for the bombers! The 78th surprised the Luftwaffe the day they went deeper eastward with their 'ferry' tanks. But, I get the sense that no one wants to do or look at the numbers. Shortround6 quoted numbers when he used the figure 237 against 305. Now he admits the fuel was there, but now uses the excuse that the tanks were substandard. I yielded to you in good faith. I think all who are reading would like to know the range calculations, if only to see that it was possible to fly further with an F4U than the current P-47 at that time. I think you should do the figures, since you have experience along this line, and were quick to point out that I was wrong. We can't change history, and shouldn't try. Shortround6 said it was not possible to go farther than the P-47. The numbers, please.

You have reason to raise the question "what would the operational Combat Radius for the F4U-1 have been if accepted by AAF for Long Range escort". That said, there are several practical factors that have to be addressed:
1. any F4U entering combat ops with 8th/9th AF would be required to have self sealing tanks. That is not a trivial task as the tanks would have to be ordered (short cycle but more than a month) per design specs presented from Vought to contractor (Goodyear, Firestone). The design features not only require installation of the tank during production, but also be addressable for removal and replacement due to damage. The change probably has to begin at Depots to avoid disruption of the F4U production plan. For comparison, the cycle from prototype fuselage fuel tank test of P-51B-1 to first assembled Kits delivered to Depots, was mid July 1943 to late October 1943. The actual production design release occurred in late September. NAA Field Services worked closely with Engineering to assist in the assembly of the Kits (including changes for 50% increase in O2). In addition, a 100 page Installation guide was developed to illustrate to the Depots what steps were required to modify existing Mustangs already produced before the production insertion. The insertion into the production cycle occurred in late December with the P-51B-10-NA block.
2. If the F4U O2 supply was designed to support SOP middle altitude combat ops vs 25,000 feet, then the changes to increase O2 bottles and possibly bulkhead/fuselage location - this may not be trivial. If you have the manual (I don't), look up the Oxygen supply information for both capacity and servicing requirements.
3. The actual testing for high altitude Long Range requirements (i.e greater speed than B-24 after bomb load dropped on return leg ~ 230mph TAS cruise) with drop tanks. The drag for the external drop tanks are significant. More than 40mph for Mustang (much cleaner) with 2x110 gallon tanks at 25,000 feet. I have no idea what the SFC at best cruise speed is for -8 in the F4U-1. As a rule of thumb, the best cruise settings for the P-47D achieved just under 3 miles per gallon at best cruise settings for Range. Less for Endurance. By contrast the P-51B w/85 gallon tank and 269 gallons of internal fuel was ~ 5 miles per gallon at 25K - more than 60% over the P-47D.

IF the R-2800-8 in the F4U was equal to the P-47D series with respect to cruise efficiency at 25K, the F4U-1 was indeed capable of performing long range escort to possible Berlin-Leipzig-Munich radius as the P-47D-25, introduced into ETO ops in June/July 1944.

So, we have arrived at my stopping point. I do not possess any flight test data that USN flew above 15000 feet but I do know that comparing maximum range (estimate) for Ferry purposes between a P-47D (305 gallons internal) and a F4U-1D (237 internal) using same SFC of 0.50 lb/HP/Hr for the R-2800 is 1135 vs 811 per the tables reproduced by Dean. I do know that AAF test flights for the P-47C/early D used the same SFC. I presume that they applied to F4U R-2800 also.

These data below are for 10,000 feet. Using this set for calcs, the cruise efficiency extrapolated indicates that the Ferry Range advantage of 40% for 2% more P-47D-25 fuel (370gal) than F4U-1A (361gal). -----------------> points to about 9% less range for F4U-1A on same fuel. With 18% more internal fuel of F4U-1A than P-47D through the -22, then we project that the F4U-1A will have a Ferry Range close to the later P-47D-25. but 150 miles less than P-51B and about the same as the P-38J with LE tanks.

So the F4U-1 with 361 gallons by the rule of thumb math above in terms of Combat Radius as defined by AAF, fits with P-47D-25 in July 1944. The Combat Radius reproduced by Dean on pg 599 is P-38J=275 miles with 410 gallons; P-47D-25 =225 miles w/370 gallons; P-51B= 375 miles w/269 gallons of internal fuel. The earlier P-47C and D's had only 125mi CR.

These Ferry Ranges are calculated based on Breguet theoretical optimal cruise capability - not actual.

F4U-1A Combat Radius --------->225 miles without external tanks, after 20 minutes of Combat (15 minutes at MP, 5 min WEP)
All data for 25,000 feet.

The problem for practical extrapolation is that AAF would have had to intercept and over ride all delivery of the modified F4U-1 (combat tanks-wing, O2, remove arresting gear) by the time the P-47C was being delivered in late 1942 for combat ops in ETO in April/May 1943 That would speculatively require that Vought complete design changes in early 1942 for insertion into the production sequence.

USN up to that? No. AAF up to that? No. Any awareness that Fighter escort to Berlin was necessary in late 1941 to initiate the transfer the prized USN asset based on Executive Order by Roosevelt?. No. Would the F4U-1A be better in air to air combat than P-4&C/D at 25000 feet? Probably but much less speed and dive capability. Below 20,000 feet? F4U-1A moderately superior maneuverability but slower.

Navalwarrior · Jun 25, 2018

Shortround6 said:
The numbers are not just about flying a certain distance. They are about flying that distance at a certain speed and altitude. The numbers are also about what happens after the drop tanks are gone. Standards changed, late war standards were for 5 minutes at WEP, 15 minutes at military power and an egress from the battle area at 210IAS at 25,000ft. No allowance for fuel saved in descending from 25,000ft and an allowance of 30 minutes at minimum cruise power.
Perhaps in 1943 they were different?

BTW in the original post where I mentioned the 237 gallons I did state " the F4U had 237 gallons of protected storage."

I did not change things at a later point in time.

Use of the wing tanks is a bit iffy. Not a lot, but not quite 'normal'. The Pilot's manual says:

"In general, for high power operations at high altitude, use the fuel from the main tank, which is pressurised to maintain adequate fuel flow. It is possible, on planes equipped with wing tanks in the outer panels ( prior to the installation of of center section twin pylons), to operate under the above conditions while using fuel from the wing tanks if the auxiliary fuel pump is switched "ON"; under such conditions keep a close watch on the fuel pressure and cylinder head temperature. Some attention should be paid to the fuel quantities in the wing tanks to keep the fuel consumption in the tanks approximately equal in order to to maintain the airplane in approximate lateral balance., keeping the quantity in the right tank somewhat greater than that in the left tank, since the airplane has a tendency toward left wing heaviness in the landing condition with power on. Since no quantity gages are provided for the wing tanks, the quantities of fuel consumed must be determined from the time of operation on each tank."

In another area of the manual we get this;
"The main fuel tank maintains a standpipe reserve of 50 U.S. gallons of fuel (42 Imp. gallons) after the fuel supply through the main line is exhausted. Bear in mind that the reserve fuel is made available as the quantity necessary for the final operation before landing, when the main fuel supply is exhausted and as noted below"

This is pretty standard except for the 50 gal reserve which may be taking into account having to queue up to land on a carrier which can take longer than a land runway. There is no separate tank, just a valve which accesses the tank at a lower point than the main fuel line. However, like most planes.

"Set fuel tank selector on "RESERVE" for take-off, landing, diving and maneuvers. DO NOT CRUISE ON "RESERVE."

there is a section on when to use the auxiliary electric fuel pump. No mention is made of transferring fuel from one tank to another. Iti s also there in case the engine driven fuel pump fails.

The main tank was pressurized above 12,000ft. This was automatic with a manual override.

The Co2 system is a bit interesting.

a few notes
"This system does not force fuel out of the tanks."

"WARNING"
The vapor dilution system must not be used when operating on fuel from the outer tanks. Injection of the CO2 would result in the interruption of fuel flow through the lines. However, use of the vapor dilution system does not render the gasoline in the outer tanks unfit for further use"

I will leave it the members of this forum who are pilots to decide if any of these instructions raise any warning flags.

I will also note that almost an entire squadron of Mustangs was lost when unanticipated winds blew them scores of miles off course returning from a raid, and while it was in 1944 the US lost around 80 planes during the Great Marianas turkey shoot due to running out of fuel. (more would have been lost except for measures like turning on ships lights and pointing search lights into the sky).
Cutting things too close can have very serious consequences.

davparlr · Jun 25, 2018

At the start of the war, the Japanese used unprotected fuel tanks and were noted for burning easily, not a configuration one would like to fight with.

Navalwarrior said:
In early 1943 (I want to say Mar) the USAAF sponsored a Joint Fighter Meet at Elgin Field, FL where all services were allowed to fly the other service's aircraft. The USAAF pilots who flew the F4U and raved about its ability. It easily out manuvered the P-38, Allison P-51 and their P-47. The F4U was the champion fighter there, as per USAAF pilots who flew it.

In early '43, the F4U would be the -1 version without water injection and the P-51 would be the baseline version with the -39 engine. The P-51A with the -81 engine, which was coming out at this time was a great performer even in the ETO where it was equal to or was out performing most Allied and Axis fighters up to 15K, maybe a bit higher. The data I have, mostly from Spitfireperformance shows the P-51A outperforming the F4U-1, often significantly, in both airspeed and climb up to about 23k ft, where the F4U-1 catches up. Unfortunately, the P-51A performance at these altitudes, was NOT deemed acceptable for combating the latest German fighters as power was dropping off quickly, AND, since the the F4U-1 had less than or similar performance of the P-51A, and, power was also dropping off quickly at altitude, neither would be acceptable as a high altitude bomber escort. Why would the AAF select a completely different aircraft when a better performing P-51A was coming off the assembly line, and the clearly superior P-51B was being built and was in flight test. In August, 1943, the water injected F4U-1(A) became operational and was a significant improvement over the F4U-1, mission operations began later in October. However, on December 1, 1943, about a month later, the P-51B flew its first sweep over France. It is apparent that the F4U would not have provided an acceptable bomber escort before the P-51B Mustang became available.

Clayton Magnet · Jun 25, 2018

davparlr said:
At the start of the war, the Japanese used unprotected fuel tanks

It is worthy of note, and often overlooked, but so did the US.

Navalwarrior · Jun 25, 2018

drgondog said:
You have reason to raise the question "what would the operational Combat Radius for the F4U-1 have been if accepted by AAF for Long Range escort". That said, there are several practical factors that have to be addressed:
1. any F4U entering combat ops with 8th/9th AF would be required to have self sealing tanks. That is not a trivial task as the tanks would have to be ordered (short cycle but more than a month) per design specs presented from Vought to contractor (Goodyear, Firestone). The design features not only require installation of the tank during production, but also be addressable for removal and replacement due to damage. The change probably has to begin at Depots to avoid disruption of the F4U production plan. For comparison, the cycle from prototype fuselage fuel tank test of P-51B-1 to first assembled Kits delivered to Depots, was mid July 1943 to late October 1943. The actual production design release occurred in late September. NAA Field Services worked closely with Engineering to assist in the assembly of the Kits (including changes for 50% increase in O2). In addition, a 100 page Installation guide was developed to illustrate to the Depots what steps were required to modify existing Mustangs already produced before the production insertion. The insertion into the production cycle occurred in late December with the P-51B-10-NA block.
2. If the F4U O2 supply was designed to support SOP middle altitude combat ops vs 25,000 feet, then the changes to increase O2 bottles and possibly bulkhead/fuselage location - this may not be trivial. If you have the manual (I don't), look up the Oxygen supply information for both capacity and servicing requirements.
3. The actual testing for high altitude Long Range requirements (i.e greater speed than B-24 after bomb load dropped on return leg ~ 230mph TAS cruise) with drop tanks. The drag for the external drop tanks are significant. More than 40mph for Mustang (much cleaner) with 2x110 gallon tanks at 25,000 feet. I have no idea what the SFC at best cruise speed is for -8 in the F4U-1. As a rule of thumb, the best cruise settings for the P-47D achieved just under 3 miles per gallon at best cruise settings for Range. Less for Endurance. By contrast the P-51B w/85 gallon tank and 269 gallons of internal fuel was ~ 5 miles per gallon at 25K - more than 60% over the P-47D.

IF the R-2800-8 in the F4U was equal to the P-47D series with respect to cruise efficiency at 25K, the F4U-1 was indeed capable of performing long range escort to possible Berlin-Leipzig-Munich radius as the P-47D-25, introduced into ETO ops in June/July 1944.

So, we have arrived at my stopping point. I do not possess any flight test data that USN flew above 15000 feet but I do know that comparing maximum range (estimate) for Ferry purposes between a P-47D (305 gallons internal) and a F4U-1D (237 internal) using same SFC of 0.50 lb/HP/Hr for the R-2800 is 1135 vs 811 per the tables reproduced by Dean. I do know that AAF test flights for the P-47C/early D used the same SFC. I presume that they applied to F4U R-2800 also.

These data below are for 10,000 feet. Using this set for calcs, the cruise efficiency extrapolated indicates that the Ferry Range advantage of 40% for 2% more P-47D-25 fuel (370gal) than F4U-1A (361gal). -----------------> points to about 9% less range for F4U-1A on same fuel. With 18% more internal fuel of F4U-1A than P-47D through the -22, then we project that the F4U-1A will have a Ferry Range close to the later P-47D-25. but 150 miles less than P-51B and about the same as the P-38J with LE tanks.

So the F4U-1 with 361 gallons by the rule of thumb math above in terms of Combat Radius as defined by AAF, fits with P-47D-25 in July 1944. The Combat Radius reproduced by Dean on pg 599 is P-38J=275 miles with 410 gallons; P-47D-25 =225 miles w/370 gallons; P-51B= 375 miles w/269 gallons of internal fuel. The earlier P-47C and D's had only 125mi CR.

These Ferry Ranges are calculated based on Breguet theoretical optimal cruise capability - not actual.

F4U-1A Combat Radius --------->225 miles without external tanks, after 20 minutes of Combat (15 minutes at MP, 5 min WEP)
All data for 25,000 feet.

The problem for practical extrapolation is that AAF would have had to intercept and over ride all delivery of the modified F4U-1 (combat tanks-wing, O2, remove arresting gear) by the time the P-47C was being delivered in late 1942 for combat ops in ETO in April/May 1943 That would speculatively require that Vought complete design changes in early 1942 for insertion into the production sequence.

USN up to that? No. AAF up to that? No. Any awareness that Fighter escort to Berlin was necessary in late 1941 to initiate the transfer the prized USN asset based on Executive Order by Roosevelt?. No. Would the F4U-1A be better in air to air combat than P-4&C/D at 25000 feet? Probably but much less speed and dive capability. Below 20,000 feet? F4U-1A moderately superior maneuverability but slower.

davparlr said:
At the start of the war, the Japanese used unprotected fuel tanks and were noted for burning easily, not a configuration one would like to fight with.

In early '43, the F4U would be the -1 version without water injection and the P-51 would be the baseline version with the -39 engine. The P-51A with the -81 engine, which was coming out at this time was a great performer even in the ETO where it was equal to or was out performing most Allied and Axis fighters up to 15K, maybe a bit higher. The data I have, mostly from Spitfireperformance shows the P-51A outperforming the F4U-1, often significantly, in both airspeed and climb up to about 23k ft, where the F4U-1 catches up. Unfortunately, the P-51A performance at these altitudes, was NOT deemed acceptable for combating the latest German fighters as power was dropping off quickly, AND, since the the F4U-1 had less than or similar performance of the P-51A, and, power was also dropping off quickly at altitude, neither would be acceptable as a high altitude bomber escort. Why would the AAF select a completely different aircraft when a better performing P-51A was coming off the assembly line, and the clearly superior P-51B was being built and was in flight test. In August, 1943, the water injected F4U-1(A) became operational and was a significant improvement over the F4U-1, mission operations began later in October. However, on December 1, 1943, about a month later, the P-51B flew its first sweep over France. It is apparent that the F4U would not have provided an acceptable bomber escort before the P-51B Mustang became available.

Res

Navalwarrior · Jun 25, 2018

Navalwarrior said:
Res

Resp: Well said, boys! Thank you for taking the time to outline it for me.
Why we waited for drop tanks, bomber crews of the 8th AF were getting slaughtered; on two separate missions we lost 60 4 engined bombers, for a total of 1200 lost in the last quarter of 1943. General Arnold was a very perceptive man; in 1940 he read the reports of the F4U when it broke 400 mph in level flight using the P&W R-2800. He immediately cancelled a request for P&W to build an inline engine, telling them to concentrate on refining the 2800, which went into the P-47 and F4U. Just think how things would have been different if the USAAC hadn't forbid building fighters capable of carrying external fuel stores in 1939. The P-47 would have been capable of flying deep penetration of Germany at the outset. But we cannot change history.

Kevin J · Jun 25, 2018

Navalwarrior said:
Resp: Well said, boys! Thank you for taking the time to outline it for me.
Why we waited for drop tanks, bomber crews of the 8th AF were getting slaughtered; on two separate missions we lost 60 4 engined bombers, for a total of 1200 lost in the last quarter of 1943. General Arnold was a very perceptive man; in 1940 he read the reports of the F4U when it broke 400 mph in level flight using the P&W R-2800. He immediately cancelled a request for P&W to build an inline engine, telling them to concentrate on refining the 2800, which went into the P-47 and F4U. Just think how things would have been different if the USAAC hadn't forbid building fighters capable of carrying external fuel stores in 1939. The P-47 would have been capable of flying deep penetration of Germany at the outset. But we cannot change history.

It seems to me that in 1939/40 no air forces had drop tanks, so was there a problem with the fuel transfer technology that prevented their use?

Navalwarrior · Jun 25, 2018

Kevin J said:
It seems to me that in 1939/40 no air forces had drop tanks, so was there a problem with the fuel transfer technology that prevented their use?

Resp:
The A6M Zero was outfitted with one drop tank. In fact, Gen Chennault sent a full report to Gen Marshall on the capabilites, to include range. In April 1941, Chennault went to Hawaii to brief AAF (and possibley Navy) pilots on the attributes of the Zero. Drop tanks not only increase range, they give defenders longer loitering times (as in air patrols).

eagledad · Jun 25, 2018

Drgondog

Would these SAC's help with range calculations of the F4U at 25.000 feet?

Also, weren't F4Us used as escorts for B-24s over Truk and Rabaul?

Just trying to be helpful.

Eagledad

Kevin J · Jun 25, 2018

Navalwarrior said:
Resp:
The A6M Zero was outfitted with one drop tank. In fact, Gen Chennault sent a full report to Gen Marshall on the capabilites, to include range. In April 1941, Chennault went to Hawaii to brief AAF (and possibley Navy) pilots on the attributes of the Zero. Drop tanks not only increase range, they give defenders longer loitering times (as in air patrols).

The Zero was first deployed in small numbers in 1940/41. This was the time that the Luftwaffe was building and operating the Bf 109E-7 with drop tank capability and when the RAF was experimenting with fixed tanks on the Hurricane I/II and Spitfire II so what the Japs were doing was in line with their European opponents. Drop tank capability appeared in 1941 on the P-40C after a change in the P-40's internal fuel capacity. Drop (slipper) tanks were fitted to the Spitfire Vb in 1941. Might I suggest that drop tanks appeared in the P-47 and P-51 later because both planes development had been rushed in order to get them into service fast so is that the same issue with the F4U-1/1A that the outer wing unprotected fuel tanks were there initially as a substitute for drop tanks.

Navalwarrior · Jun 25, 2018

Resp
Attached is an EOV Range Map of allied fighter ranges. Let's look at the escort issue as if we were tasked to use the F4U-1A in the May 1943 time frame. Personal points asside, we have been ordered to incorporate the Corsair to support 8th AF in Long Range Escort. It is late May/early June 1943, and a Fleet Air Arm carrier just anchored in England, with 48 Corsairs on board. Gen Hap Arnold has ordered a plan for their use in LRE. We, the blog members are charged with coming up with a workable plan.
As you can see on the EOV chart, the P-47 w/o drop tank can go 230 miles before it must turn from home. The Spitfire can go 175 miles before turning for home.

drgondog said:
You have reason to raise the question "what would the operational Combat Radius for the F4U-1 have been if accepted by AAF for Long Range escort". That said, there are several practical factors that have to be addressed:
1. any F4U entering combat ops with 8th/9th AF would be required to have self sealing tanks. That is not a trivial task as the tanks would have to be ordered (short cycle but more than a month) per design specs presented from Vought to contractor (Goodyear, Firestone). The design features not only require installation of the tank during production, but also be addressable for removal and replacement due to damage. The change probably has to begin at Depots to avoid disruption of the F4U production plan. For comparison, the cycle from prototype fuselage fuel tank test of P-51B-1 to first assembled Kits delivered to Depots, was mid July 1943 to late October 1943. The actual production design release occurred in late September. NAA Field Services worked closely with Engineering to assist in the assembly of the Kits (including changes for 50% increase in O2). In addition, a 100 page Installation guide was developed to illustrate to the Depots what steps were required to modify existing Mustangs already produced before the production insertion. The insertion into the production cycle occurred in late December with the P-51B-10-NA block.
2. If the F4U O2 supply was designed to support SOP middle altitude combat ops vs 25,000 feet, then the changes to increase O2 bottles and possibly bulkhead/fuselage location - this may not be trivial. If you have the manual (I don't), look up the Oxygen supply information for both capacity and servicing requirements.
3. The actual testing for high altitude Long Range requirements (i.e greater speed than B-24 after bomb load dropped on return leg ~ 230mph TAS cruise) with drop tanks. The drag for the external drop tanks are significant. More than 40mph for Mustang (much cleaner) with 2x110 gallon tanks at 25,000 feet. I have no idea what the SFC at best cruise speed is for -8 in the F4U-1. As a rule of thumb, the best cruise settings for the P-47D achieved just under 3 miles per gallon at best cruise settings for Range. Less for Endurance. By contrast the P-51B w/85 gallon tank and 269 gallons of internal fuel was ~ 5 miles per gallon at 25K - more than 60% over the P-47D.

IF the R-2800-8 in the F4U was equal to the P-47D series with respect to cruise efficiency at 25K, the F4U-1 was indeed capable of performing long range escort to possible Berlin-Leipzig-Munich radius as the P-47D-25, introduced into ETO ops in June/July 1944.

So, we have arrived at my stopping point. I do not possess any flight test data that USN flew above 15000 feet but I do know that comparing maximum range (estimate) for Ferry purposes between a P-47D (305 gallons internal) and a F4U-1D (237 internal) using same SFC of 0.50 lb/HP/Hr for the R-2800 is 1135 vs 811 per the tables reproduced by Dean. I do know that AAF test flights for the P-47C/early D used the same SFC. I presume that they applied to F4U R-2800 also.

These data below are for 10,000 feet. Using this set for calcs, the cruise efficiency extrapolated indicates that the Ferry Range advantage of 40% for 2% more P-47D-25 fuel (370gal) than F4U-1A (361gal). -----------------> points to about 9% less range for F4U-1A on same fuel. With 18% more internal fuel of F4U-1A than P-47D through the -22, then we project that the F4U-1A will have a Ferry Range close to the later P-47D-25. but 150 miles less than P-51B and about the same as the P-38J with LE tanks.

So the F4U-1 with 361 gallons by the rule of thumb math above in terms of Combat Radius as defined by AAF, fits with P-47D-25 in July 1944. The Combat Radius reproduced by Dean on pg 599 is P-38J=275 miles with 410 gallons; P-47D-25 =225 miles w/370 gallons; P-51B= 375 miles w/269 gallons of internal fuel. The earlier P-47C and D's had only 125mi CR.

These Ferry Ranges are calculated based on Breguet theoretical optimal cruise capability - not actual.

F4U-1A Combat Radius --------->225 miles without external tanks, after 20 minutes of Combat (15 minutes at MP, 5 min WEP)
All data for 25,000 feet.

The problem for practical extrapolation is that AAF would have had to intercept and over ride all delivery of the modified F4U-1 (combat tanks-wing, O2, remove arresting gear) by the time the P-47C was being delivered in late 1942 for combat ops in ETO in April/May 1943 That would speculatively require that Vought complete design changes in early 1942 for insertion into the production sequence.

USN up to that? No. AAF up to that? No. Any awareness that Fighter escort to Berlin was necessary in late 1941 to initiate the transfer the prized USN asset based on Executive Order by Roosevelt?. No. Would the F4U-1A be better in air to air combat than P-4&C/D at 25000 feet? Probably but much less speed and dive capability. Below 20,000 feet? F4U-1A moderately superior maneuverability but slower.

Resp:
The F4U-1A still had the two 62 gallon wing tanks. From the 863rd aircraft, the P&W R-2800-8W had a water injected engine, giving it 2250 HP. Would the water injection help at altitude?

Navalwarrior · Jun 25, 2018

Kevin J said:
It seems to me that in 1939/40 no air forces had drop tanks, so was there a problem with the fuel transfer technology that prevented their use?

Resp:
Captain Claire Chennault, USAAF, while flight operations officer at Barksdale Field, LA argued for figher drop tank capability in 1936. He was force to resign/retire, which was granted Jan 1937.

GrauGeist · Jun 25, 2018

Kevin J said:
It seems to me that in 1939/40 no air forces had drop tanks, so was there a problem with the fuel transfer technology that prevented their use?

There was several philsophies in play by all the major militaries that delayed the use of droptanks.

In the case of Japan, particularly the IJN, their aircraft were desigend with long range in mind, so droptanks were not a primary concern.
However, they did use them. Case in point: Mitsubishi's A5M4 variant, which was in use in the later part of the 1930's, did have provisions for drop tanks and did use them to give them the range needed to escort the G3M bombers.

Here's an A5M4 of the Akagi in flight, 1938.

Navalwarrior · Jun 25, 2018

Kevin J said:
The Zero was first deployed in small numbers in 1940/41. This was the time that the Luftwaffe was building and operating the Bf 109E-7 with drop tank capability and when the RAF was experimenting with fixed tanks on the Hurricane I/II and Spitfire II so what the Japs were doing was in line with their European opponents. Drop tank capability appeared in 1941 on the P-40C after a change in the P-40's internal fuel capacity. Drop (slipper) tanks were fitted to the Spitfire Vb in 1941. Might I suggest that drop tanks appeared in the P-47 and P-51 later because both planes development had been rushed in order to get them into service fast so is that the same issue with the F4U-1/1A that the outer wing unprotected fuel tanks were there initially as a substitute for drop tanks.

Resp:
Possibly, but in April 1943 the F4U-1 (-1A) got its second drop tank. But as has been posted, the 'main' issue to long range flying was 'protected internal fuel.'

XBe02Drvr · Jun 25, 2018

Navalwarrior said:
Captain Claire Chennault, USAAF, while flight operations officer at Barksdale Field, LA argued for figher drop tank capability in 1936. He was force to resign/retire, which was granted Jan 1937.

He was an unconventional, loudmouth, insubordinate, PITA who couldn't keep his mouth shut, even when ordered to, as people who have truer vision than their superiors so often are. I remember reading somewhere that the final straw was that he was discovered surreptitiously teaching pilots in his squadron "boom and zoom" tactics to keep them alive in combat, whereas AAC doctrine called for a Lufberry style turning fight. This, of course, was long before P-40 vs KI-43.
Cheers,
Wes

drgondog · Jun 25, 2018

eagledad said:
Drgondog

Would these SAC's help with range calculations of the F4U at 25.000 feet?

Also, weren't F4Us used as escorts for B-24s over Truk and Rabaul?

Just trying to be helpful.

Eagledad

The striking thing is that best cruise speed is 186 mph for 1550 mi ferry range w/361 gallons. Didn't see altitude but guessing 10K.

186mph TAS cruise in ETO means that F4U-1A can't keep pace with B-17. Also suggests that Bf 109s and FW 190s enter combat with 2X speed advantage.

Navalwarrior · Jun 25, 2018

eagledad said:
Drgondog

Would these SAC's help with range calculations of the F4U at 25.000 feet?

Also, weren't F4Us used as escorts for B-24s over Truk and Rabaul?

Just trying to be helpful.

Eagledad

Resp:
When I reviewed individual AAR by 8th AF pilots for the year 1943, I was surprised that most bomber formations were @ 12,000 to 14,000 ft. Also noted that weather (pilot mentioned cloud ceiling) brought flying altitudes much lower than what was preached. If I remember correctly, P-47s flew 2 to 3 thou ft above the bombers. However, this all depended on 'ceiling' visibility.

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