Corsair and Hellcat in Europe

[BiffF15]

Since they couldn't compute exact strength, they usually erred on the side of caution. That's why a modern plane rated to a given amount seems flimsy to an older design. It actually is, in a way, since people can better compute what the exact limit is, they can build right onto that limit.

If you really wanted to evaluate strength, you'd want to evaluate an old plane's strength with modern technology; then use the figures you got out of that as a baseline figure, and you'd be building as tough as the past.
That had to also do with older-fashioned ideas about how a design should last as long as the customer wants it to. If you want to keep it a long time, we'll keep repairing it. Boeing, from what it appeared, seemed to subscribe less to the idea: The 707 for example was expected to last 40,000 hours. While the plane could probably be repaired and maintained past that point, there was the presumption that people would probably just buy the newer model.

This idea, when carried to conclusion, results in what's called planned obsolescence: You design a product to fail after a certain amount of time, so people would have to buy a newer model. I'm not a big fan of this practice.

An interesting thing was MacD / Boeing had gone to the USAF asking for money plus an old Eagle so they could test it to destruction to determine its actual failure point in hours. The USAF said nope, so the engineers did some calculations to determine best guess when the average jet would fail. They had a formula that included hours, over Gs plus who knows what else. They came up with 12000 hours. The MOGUARD Eagle that broke up in mid air was put thru the formula and was determined to have about 11700 hours ish on it when it failed with a defective structural part.

Not bad hypothesizing on the engineers part, that includes the guys who designed and built as well as their protégés who figured out the failure formula.

Cheers,
Biff

 

[jetcal1]

Since they couldn't compute exact strength, they usually erred on the side of caution. That's why a modern plane rated to a given amount seems flimsy to an older design. It actually is, in a way, since people can better compute what the exact limit is, they can build right onto that limit.

If you really wanted to evaluate strength, you'd want to evaluate an old plane's strength with modern technology; then use the figures you got out of that as a baseline figure, and you'd be building as tough as the past.
That had to also do with older-fashioned ideas about how a design should last as long as the customer wants it to. If you want to keep it a long time, we'll keep repairing it. Boeing, from what it appeared, seemed to subscribe less to the idea: The 707 for example was expected to last 40,000 hours. While the plane could probably be repaired and maintained past that point, there was the presumption that people would probably just buy the newer model.

This idea, when carried to conclusion, results in what's called planned obsolescence: You design a product to fail after a certain amount of time, so people would have to buy a newer model. I'm not a big fan of this practice.

Please don't forget that systems wear out long before the airframe. We've pulled a few corporate jets through the hangar to part out with less than 12,000 hours TT time because the engines were at TBO. And the overhaul costs were close to, or in some cases exceeded the value of the jet.

 

[XBe02Drvr]

We've pulled a few corporate jets through the hangar to part out with less than 12,000 hours TT time because the engines were at TBO.

Just curious, were those engines in an "on condition" maintenance program? Our turboprops at the commuter came from the factory with 5300 hour TBOs, but went "on condition" immediately, and most were still on their original airframes when the company went T.U., some with 20K+ hours/cycles. Our average leg was 50-55 min, so time and cycles tracked pretty close. We did a lot of single engine turns in the Podunk airports, so you could usually tell which side of the plane an engine came from by its hours/cycles ratio. We were the only operator in our neck of the woods whose Ops Specs allowed single engine turns, so we could get in and out of the back country places faster than the competition.
Cheers,
Wes

 

[jetcal1]

Just curious, were those engines in an "on condition" maintenance program? Our turboprops at the commuter came from the factory with 5300 hour TBOs, but went "on condition" immediately, and most were still on their original airframes when the company went T.U., some with 20K+ hours/cycles. Our average leg was 50-55 min, so time and cycles tracked pretty close. We did a lot of single engine turns in the Podunk airports, so you could usually tell which side of the plane an engine came from by its hours/cycles ratio. We were the only operator in our neck of the woods whose Ops Specs allowed single engine turns, so we could get in and out of the back country places faster than the competition.
Cheers,
Wes

I do not believe they were on condition. I do know in one case the engines had 8000 + hours (Don't remember cycles and the RR people were quoting just over $1.3 mil each to overhaul

 

[XBe02Drvr]

I do not believe they were on condition. I do know in one case the engines had 8000 + hours (Don't remember cycles and the RR people were quoting just over $1.3 mil each to overhaul

Speys? Or Tays? RRs are pricey beasts. The Darts on our Fokkers cost near twice/flt hour compared to the GEs on the SAABs that replaced them. The extra 12 seats on the Fokker only paid for the extra cost if you could fill them on every leg. How do I, a lowly wrench twister, know all this? My then girlfriend, now ex-wife, was the Manager of Purchasing and a former wrench twister herself.
Cheers,
Wes

 

[jetcal1]

Speys? Or Tays? RRs are pricey beasts. The Darts on our Fokkers cost near twice/flt hour compared to the GEs on the SAABs that replaced them. The extra 12 seats on the Fokker only paid for the extra cost if you could fill them on every leg. How do I, a lowly wrench twister, know all this? My then girlfriend, now ex-wife, was the Manager of Purchasing and a former wrench twister herself.
Cheers,
Wes

Due to NDA's, I don't to get into a lot of details. (Geez,I feel like a prick writing htat.) BR710's

 

[Navalwarrior]

It is and it isn't. While Naval warrior's post certainly goes into detail, it doesn't in fact dispute my question of who was to use it at the time in the ETO. By 1944 the desire for a long range escort was being met by the P-51, P-47 and P-38, ground attack was being handled by aircraft like the Beaufighter and Typhoon, with the Tempest as a supreme low altitude fighter entering service and the likes of the Spitfire XIV on the way as a great all rounder, excellent performance down low and up top, the Allies have some serious capability at their disposal. Now sure, every airframe counts and there's no doubt the Corsair would have been welcome in larger numbers, but if Corsairs were being diverted to the ETO, where are they not being used? There was a need for them in the Pacific, so that's where they were best served. Not even a Corsair can be in two places at once.

Cont:
My theory was based on a relatively small number of F4Us being used as a stopgap measure for the period of June to Nov/Dec 1943. It was available during this this time as they US was furnishing them to the FAA and later the NZAF. 8th AF in the ETO was losing a lot of B-17/B-24s during this pre-P-51 operation time period. I recently came across a currently produced profile print of an F4U painted as if operating as a P-47 unit. Just brought back thoughts on this discussion.

 

[DarrenW]

he F6F had 250 gallons and had less one way range than the P-47D. It could carry a lot more for ferry but once the xternals are gone you have to come home with what you have internally

would stick to using them to escort the 1943 B17/B24 raids.

I've evaluated the high altitude escort radius of the F6F and determined that with the 150 gallon belly tank the range was about equal to P-47 with the early ferry tank filled with 100 gallons of fuel. The 150 gallon drop tank utilized by the Hellcat was much more streamlined than the ferry tank and should have provided more range if total air frame drag between the two aircraft were similar (each aircraft having a total of about 400 gallons). It wasn't because the Hellcat's wing was both larger and thicker than the Thunderbolt's and created even more induced drag as altitude increased (due to inherent increases in wing AoA). This was one reason why it wasn't as efficient and burned more fuel for a given cruise profile, even with similar drop tank configurations. The engine driven supercharger also robbed valuable power and required more boost pressure than the turbocharger for the same output power.

The best configuration for the Hellcat would be the 150 gallon belly tank and 100 gallon wing tank. This gives a perfect 250 internal/250 external fuel load. By my estimations (using metrics provided by Bill) the conservative ETO escort radius would have been about 265 miles, allowing for the outskirts of Aachen to be reached. This was only marginally better than a P-47D equipped with a 75 gallon belly tank and roughly equal in range if the 108 gallon belly tank was installed so there's really no need whatsoever to consider using Hellcats for escort in place of the Thunderbolt during the summer of '43. Besides, during this time they were needed in significant numbers in the PTO, as was the Corsair.

 

[swampyankee]

An interesting thing was MacD / Boeing had gone to the USAF asking for money plus an old Eagle so they could test it to destruction to determine its actual failure point in hours. The USAF said nope, so the engineers did some calculations to determine best guess when the average jet would fail. They had a formula that included hours, over Gs plus who knows what else. They came up with 12000 hours. The MOGUARD Eagle that broke up in mid air was put thru the formula and was determined to have about 11700 hours ish on it when it failed with a defective structural part.

Not bad hypothesizing on the engineers part, that includes the guys who designed and built as well as their protégés who figured out the failure formula.

Cheers,
Biff

This was one of the sorts of tasks I did when I was a test engineer at Sikorsky. During thar time, AHS did a study where they sent fatigue test data for a component to the big helicopter makers, Bell, Boeing, Sikorsky, and Aerospatiale. Same part, same data, and the results differed by a factor of about 500. I don't remember the ranking

 

[wuzak]

I've evaluated the high altitude escort radius of the F6F and determined that with the 150 gallon belly tank the range was about equal to P-47 with the early ferry tank filled with 100 gallons of fuel. The 150 gallon drop tank utilized by the Hellcat was much more streamlined than the ferry tank and should have provided more range if total air frame drag between the two aircraft were similar (each aircraft having a total of about 400 gallons). It wasn't because the Hellcat's wing was both larger and thicker than the Thunderbolt's and created even more induced drag as altitude increased (due to inherent increases in wing AoA). This was one reason why it wasn't as efficient and burned more fuel for a given cruise profile, even with similar drop tank configurations. The engine driven supercharger also robbed valuable power and required more boost pressure than the turbocharger for the same output power.

The best configuration for the Hellcat would be the 150 gallon belly tank and 100 gallon wing tank. This gives a perfect 250 internal/250 external fuel load. By my estimations (using metrics provided by Bill) the conservative ETO escort radius would have been about 265 miles, allowing for the outskirts of Aachen to be reached. This was only marginally better than a P-47D equipped with a 75 gallon belly tank and roughly equal in range if the 108 gallon belly tank was installed so there's really no need whatsoever to consider using Hellcats for escort in place of the Thunderbolt during the summer of '43. Besides, during this time they were needed in significant numbers in the PTO, as was the Corsair.

What is the "high altitude" you speak of?

What speed is it cruising at?

 

[DarrenW]

What is the "high altitude" you speak of?

What speed is it cruising at?

25,000 feet and a cruise speed of 283 mph (from pilot's manual).

I compared the F6F with a 150 gallon drop tank to the P-47 with a ferry tank at this altitude and the two airplanes have roughly the same cruise speed, range, and fuel burn rates.

AC / altitude / engine output / RPM / MP / fuel setting / fuel use rate / airspeed / max. range

P-47D / 25,000ft / 1200hp / 2250rpm / 32" Hg / auto lean / 105gph / 295 mph / 960 miles / 2.81 mpg

F6F-5 / 25,000ft / 1225hp (Low Blower) / 2300rpm / 36" Hg / auto lean / 106gph / 283 mph / 935 miles / 2.67 mpg

At 30,000ft things are even a bit closer:

AC / altitude / engine output / RPM / MP / fuel setting / fuel use rate / airspeed / max. range

P-47D / 30,000ft / 1200hp (est.) / 2250rpm / 32" Hg / auto lean / 110gph / 303 mph / 960 miles / 2.75 mpg

F6F-5 / 30,000ft / 1125hp (High Blower) / 2300rpm / 34" Hg / auto lean / 111gph / 299 mph / 935 miles / 2.67 mpg

 

[Navalwarrior]

25,000 feet and a cruise speed of 283 mph (from pilot's manual).

I compared the F6F with a 150 gallon drop tank to the P-47 with a ferry tank at this altitude and the two airplanes have roughly the same cruise speed, range, and fuel burn rates.

Resp:
This same issue applies to the F4U. Initially I didn't figure in the speed necessary that the escort fighters had to maintain with the bombers in order to effectively intercept the Lufwaffe. My fuel consumption figures did not take the aforementioned into account.