F6F Top Speed

[Shuckins]

Several months ago I participated in a post where the topic was the Hellcat's top speed.  There was considerable debate about whether or not it was correctly modeled in AH.  

Several people took part.  F4UDOA quoted airspeed charts published by Chance Vought which tested the Hellcat's performance versus that of the F4U.  These charts indicated that the Hellcat had a top speed above 400 mph.  Other sources, such as NAS Patuxent and Grumman, were also quoted.  All these sources agreed that the top speed of the F6F was greater than that posted by the Navy.  The posts in that thread were cordial and very interesting.  Several of us hoped that HTC would take notice and tweak the Hellcat's flight model.

Since that time I have run across other sources, such as Dean's tome America's Hundred Thousand , which indicate the Hellcat was a true 400 mph fighter.  

My question is, has anyone done any flight test on the new Hellcat flight model in AH II to see if it's performance has indeed been tweaked?  What other changes in the flight model have you noticed?

Regards, Shuckins/Leggern

[ra]

FWIW, Corky Meyer, Grumman test pilot, claims that the reason the F6F is listed as being slower than the F4U had to do with the fact that the F6F airspeed indicator was reading a bit slow due to some quirk in the pitot static system.

ra

[Rafe35]

A pair of Corsair took on two Grumman Hellcat NOTE Navy Flier Edward "Butch" O'Hare piloted one of the Hellcats, and later flew the Corsair. Observers said the Hellcat was no match for F4U-1.

[MAC]

Amen Rafe35

My thought is, if the F6F was the better, faster fighter, why did they spend the millions of dollars to develop the F4U?

SIDENOTE ALERT!: Sometimes it seems like the F6F and F4F are indestructible. I fly the Corsair exclusively and sometimes 2 or 3 pings from the aforementioned craft will cut off my wing, yet I will spend the majority of 1200 rounds @ less than 400 yards on either one and they fly away with at most, a trail of smoke.  I ask again, if they are hardier and faster planes, why design another?

[Shuckins]

Rafe,

I've never heard that story before.  Have you got a source?


Captain Eric Brown, in his book Duels in the Sky compared the F4U-1 and the F6F-3 to the Fw-190A.  Being one of the top test pilots for the RNAF he had flown all three aircraft extensively.  Being British, he had no personal biases favoring either of the American aircraft. He stated that the "FW-190 could not be bested by the Corsair."  In comparing the FW with the Hellcat he said "Danger to the Hellcat would be severe.  This was a contest that was so finely balanced that pilot ability would determine the outcome."

That is quite a different assessment than the one offered in your account.

Regards, Shuckins/Leggern

[Shuckins]

Mac,

The Corsair and Hellcat were designed to meet the same Naval contract specifications for a new shipboard fighter.  The Hellcat was originally intended to be powerd by a different engine than the Pratt and Whitney R2800 allocated to the Corsair.  The Hellcat was designed to be a backup for the Corsair in case it failed to meet Naval carrier qualification trials.  This was a fortuitous move by the Navy, for the Corsair failed to become carrier qualified until the last 9 months of the war.  

The Hellcat was not faster than the Corsair, but the speed differential was substantial.  The biggest advantage that the Hellcat had over the Corsair was its vice free handling at high speeds and in carrier landings at low speed.  The Corsair, in early attempts to utilize it in carrier operations, earned the nickname "Ensign Eliminator" because of its quirky, deadlying handling characteristics at low speeds.  

Because of its superlative handling, the Hellcat was ideally suited for the needs of carrier squadrons largely manned by new pilots fresh out of flight school.

Regards, Shuckins/Leggern

[Rafe35]

Originally posted by Shuckins
Rafe,

I've never heard that story before.  Have you got a source?


Captain Eric Brown, in his book Duels in the Sky compared the F4U-1 and the F6F-3 to the Fw-190A.  Being one of the top test pilots for the RNAF he had flown all three aircraft extensively.  Being British, he had no personal biases favoring either of the American aircraft. He stated that the "FW-190 could not be bested by the Corsair."  In comparing the FW with the Hellcat he said "Danger to the Hellcat would be severe.  This was a contest that was so finely balanced that pilot ability would determine the outcome."

That is quite a different assessment than the one offered in your account.

Regards, Shuckins/Leggern

Shuckins,
 
I got that story from another book which I don't remember what the name of that book and it was from early 1970s where couple US Navy books come around.  I might have to re-check that book from the Library where I got it from and most of them detail I got it from Vought after I email them for questions.  I still copy most important info what did the author write about F4U and the rest of US aircraft and I still got this:

"In early January, 1943, a captured Japanese Zero was put up against an F4U-1, with the Corsair proving superior in most respects. Against a P-51 Mustang, the Corsair outfought the Army craft above 12,000 feet, and was considered evenly matched below that altitude. A pair of Corsair took on two Grumman Hellcat NOTE Navy Flier Edward "Butch" O'Hare piloted one of the Hellcats, and later flew the Corsair. Observers said the Hellcat was no match for F4U-1. On May 21, 1943 a fighter evaluation meeting took place at Eglin Air Base in Florida. Army pilots flying the Corsair for the first time were high in their praise. Dogfights were held with P-47, P-51, P-38, and P-39 Army fighters and all resulted favorably for the Corsair."

It was really intresting that I found that old book and I might get it tomorrow if Library open tomorrow or not.  

Rafe

[Rasker]

Picked up a used copy of "Duels in the Sky" thru the Barnes and Noble website for a bit over six bucks, including shipping.  The others they had for sale cost a bit more; Zeno's site sells new copies for $20 or thereabouts.

[joeblogs]

There is a discrepancy between the standard navy characteristics charts and some of the numbers reported by Grumman and referenced by guys like Barett Tilman.

I am somewhat skeptical of claims the F6f is as fast as the F4u-1 on a few grounds.

First the model of the r2800 used in F6f engine might not have been as powerful at high altitudes as the one in the F4u-1. The difference might be as simple as supercharger settings or carburation, I don't know. I think the effect is rather small though.

Second, the F6f wing area is substantially larger than the F4u, as is total "wetted area" - the surface of the plane exposed to the airstream. That usually means more drag. Also I'll bet the F6f has a lower lift-drag coefficient (someone can check that with Francis Dean or Loftin I believe). These effects should matter a lot.

Finally, while I haven't surveyed all the charts, it appears the F6f weighed no less than the f4u-1.

I've never understood this pitot tube argument. All navy fighters had an airspeed adjustment chart in their manuals so they knew these weren't perfect. On a one-off flight I can see this being a problem.

What I don't believe is Grumman or the U.S. Navy running repeated tests without good instruments that are improperly calibrated.

Variation in measurement would more likely result from different a/c weights or failing to convert actual weather conditions into standard atmosphere.

-blogs

Originally posted by Shuckins
Several months ago I participated in a post where the topic was the Hellcat's top speed.  There was considerable debate about whether or not it was correctly modeled in AH.  

Several people took part.  F4UDOA quoted airspeed charts published by Chance Vought which tested the Hellcat's performance versus that of the F4U.  These charts indicated that the Hellcat had a top speed above 400 mph.  Other sources, such as NAS Patuxent and Grumman, were also quoted.  All these sources agreed that the top speed of the F6F was greater than that posted by the Navy.  The posts in that thread were cordial and very interesting.  Several of us hoped that HTC would take notice and tweak the Hellcat's flight model.

Since that time I have run across other sources, such as Dean's tome America's Hundred Thousand , which indicate the Hellcat was a true 400 mph fighter.  

My question is, has anyone done any flight test on the new Hellcat flight model in AH II to see if it's performance has indeed been tweaked?  What other changes in the flight model have you noticed?

Regards, Shuckins/Leggern

[Shuckins]

joeblogs,

The versions of the Corsair that saw the most combat were the F4U-1A and the F4U-1D.  The -1D was powered by the R2800-8W engine, which produced 2000hp at sea-level, 2135hp under wep at 12,400 feet, and 1650hp at 21,000 feet.

The F6F-3 was powered by by the R2800-10 engine.  The F6F-5 had the same engine with water-injection added.  It produced 2000hp at sea-level, 2135hp at 15,000 ft., and 1650hp at 22,500 feet.

The baseline weights of the -1D Corsair and the -5 Hellcat were almost identical at about 12,300 lbs., hardly surprising when one considers that the two aircraft were designed to meet the same navy specifications for performance, range, ordnance, top-speed, etc.  Power loadings at all altitudes were also practically identical.  Both aircraft used the same 3-bladed Hamilton-Standard propeller.

As one can imagine, given the above data, climb rates were nearly identical as well, when combat loadings were similar.

Drag coefficients were very similar, with the Corsair possessing a slight edge.  The drag coefficient of the F4U-1D was .0267.  That of the F6F-3 was .0272.  The coefficient of the F6F-5 was slightly less than that of the -3 because of a redesigned engine cowling, but I have no figures for its exact coefficient.  The Hellcat's wing did give it more substantial flat plate area, 9.08 sq. ft. compared to the Corsair's 8.58 sq. ft.

Getting down to brass tacks, the top speeds listed for both aircraft vary considerably, depending on the sources quoted.  The top speeds listed by the manufacturers tended to be more optimistic than those given by the Navy.  I don't know why the discrepancies between the two sources exist, but I strongly suspect it had to do with devotion to maintenance.  The manufacturers undoubtedly kept their test aircraft in superb condition to get as much performance as possible, and the Navy was simply not as devoted to maintenance as the manufacturers were.

The early F4U-1 had a top speed of slightly under 400mph.  The Navy listed the top speed for the -3 Hellcat as being about 380mph.  Later investigations by Grumman revealed that the early Hellcat's air-speed indicator was faulty, consistently showing it to be about 20knots slower than the early model Corsair, even when they were in closely stabilised formation.  Grumman copied the placement for the Corsair's air-speed indicator and thus attained identical readings.  The only real speed advantage enjoyed by the early Corsair was 20knots at altitudes below 5000 feet, because the Corsair's blower received ram-air at those altitudes and the Hellcat's did not.

Maximum speeds vary according to the sources quoted.  Top speed of the F4U-1D under wep is listed as 417mph at 20,000 feet.  The Hellcat's top speed came at almost the same altitude.  Chance Vought was given a Hellcat (A -5 I believe.) to study for the purpose of improving the Corsair's cockpit layout and stall characteristics.  The data they amassed during these tests gives a top speed of near 405mph, which is almost identical to that given by Grumman.  Late in 1944, the NAS at Patuxent, Maryland, tested an F6F-5 against a late model Zero, and listed the Hellcat's top speed as being 409 mph.  (That aircraft must have been in superb condition!)

So as you can see from this data, the performance edge held by the Corsair was real, but was not substantial.

Regards, Shuckins/Leggern

[joeblogs]

Francis Dean covers this debate very well.

I would make only a few qualifications to your argument. First, I am skeptical that USN or Grumman would run repeated flight tests (I am not referring to the Petuxant meeting here) without calibrated instruments. If they did we should assume a big margin of error around any a/c performance numbers we talk about.

That said, the difference between 400 MPH and 380MPH is only 5%. So I can't rule out sampling error.

Second, most comparisons of -8 and -10 Double Wasps use the same performance numbers, but I've seen reports where the superchargers are not the same and hence the critical altitudes are slightly different (only by a few thousand feet). This might explain differences in Vmax. But this is tentative claim; I am trying to match up three different engine numbering systems.

Had either of these engines been geared for fighting at European style altitudes (30+k ft), both planes would have been significantly faster, at least in true airspeed.

Third, while someone else can do the calculations better than I, small differences in drag coefficients, or wing area for that matter, translate into significant differences in drag at high speeds, because drag increases in proportion to the square of velocity.

-Blogs

Originally posted by Shuckins
joeblogs,

The versions of the Corsair that saw the most combat were the F4U-1A and the F4U-1D.  The -1D was powered by the R2800-8W engine, which produced 2000hp at sea-level, 2135hp under wep at 12,400 feet, and 1650hp at 21,000 feet.

The F6F-3 was powered by by the R2800-10 engine.  The F6F-5 had the same engine with water-injection added.  It produced 2000hp at sea-level, 2135hp at 15,000 ft., and 1650hp at 22,500 feet.

The baseline weights of the -1D Corsair and the -5 Hellcat were almost identical at about 12,300 lbs., hardly surprising when one considers that the two aircraft were designed to meet the same navy specifications for performance, range, ordnance, top-speed, etc.  Power loadings at all altitudes were also practically identical.  Both aircraft used the same 3-bladed Hamilton-Standard propeller.

As one can imagine, given the above data, climb rates were nearly identical as well, when combat loadings were similar.

Drag coefficients were very similar, with the Corsair possessing a slight edge.  The drag coefficient of the F4U-1D was .0267.  That of the F6F-3 was .0272.  The coefficient of the F6F-5 was slightly less than that of the -3 because of a redesigned engine cowling, but I have no figures for its exact coefficient.  The Hellcat's wing did give it more substantial flat plate area, 9.08 sq. ft. compared to the Corsair's 8.58 sq. ft.

Getting down to brass tacks, the top speeds listed for both aircraft vary considerably, depending on the sources quoted.  The top speeds listed by the manufacturers tended to be more optimistic than those given by the Navy.  I don't know why the discrepancies between the two sources exist, but I strongly suspect it had to do with devotion to maintenance.  The manufacturers undoubtedly kept their test aircraft in superb condition to get as much performance as possible, and the Navy was simply not as devoted to maintenance as the manufacturers were.

The early F4U-1 had a top speed of slightly under 400mph.  The Navy listed the top speed for the -3 Hellcat as being about 380mph.  Later investigations by Grumman revealed that the early Hellcat's air-speed indicator was faulty, consistently showing it to be about 20knots slower than the early model Corsair, even when they were in closely stabilised formation.  Grumman copied the placement for the Corsair's air-speed indicator and thus attained identical readings.  The only real speed advantage enjoyed by the early Corsair was 20knots at altitudes below 5000 feet, because the Corsair's blower received ram-air at those altitudes and the Hellcat's did not.

Maximum speeds vary according to the sources quoted.  Top speed of the F4U-1D under wep is listed as 417mph at 20,000 feet.  The Hellcat's top speed came at almost the same altitude.  Chance Vought was given a Hellcat (A -5 I believe.) to study for the purpose of improving the Corsair's cockpit layout and stall characteristics.  The data they amassed during these tests gives a top speed of near 405mph, which is almost identical to that given by Grumman.  Late in 1944, the NAS at Patuxent, Maryland, tested an F6F-5 against a late model Zero, and listed the Hellcat's top speed as being 409 mph.  (That aircraft must have been in superb condition!)

So as you can see from this data, the performance edge held by the Corsair was real, but was not substantial.

Regards, Shuckins/Leggern

[Shuckins]

joebloggs,

I believe you are right.  The difference in drag coefficients would exact a greater penalty in level flight the faster the two aircraft flew.  For instance, the XF6F-6 prototypes had the same engine and propeller as the F4U-4 Corsair and had a top speed at 23,000 feet of 425mph.  That's about 15 to 20 mph less than the F4U-4 at the same altitude, depending on the sources quoted.

If one studies these two designs closely you could find yourself being amazed at how similar they are in weight, power-loadings, range, fire-power, ordnance carrying ability, top speeds, etc.  The only difference between the two that allowed the Hellcat to be readily accepted by the Navy for carrier operations was it's utterly reliable and predictable handling qualities.  The Corsair's dangerous handling vices were not sufficiently rectified to permit it's use on carriers until about January of 1945.

Regards, Shuckins/Leggern

[joeblogs]

Shuckins - Did the production models of these planes use the same propellers? For some reason I thoought the F4u-1 prop was a tad longer. Could just be poor memory.

-Blogs

Originally posted by Shuckins
joebloggs,

I believe you are right.  The difference in drag coefficients would exact a greater penalty in level flight the faster the two aircraft flew.  For instance, the XF6F-6 prototypes had the same engine and propeller as the F4U-4 Corsair and had a top speed at 23,000 feet of 425mph.  That's about 15 to 20 mph less than the F4U-4 at the same altitude, depending on the sources quoted.

If one studies these two designs closely you could find yourself being amazed at how similar they are in weight, power-loadings, range, fire-power, ordnance carrying ability, top speeds, etc.  The only difference between the two that allowed the Hellcat to be readily accepted by the Navy for carrier operations was it's utterly reliable and predictable handling qualities.  The Corsair's dangerous handling vices were not sufficiently rectified to permit it's use on carriers until about January of 1945.

Regards, Shuckins/Leggern

[Shuckins]

Not sure about that joe.  Both models of the Hellcat used the same Hamilton-Standard propeller with 6501 blades that all the -1 Corsairs used.

Corky Meyer, test pilot for Grumman, stated in an article in Flight Journal magazine that the XF6F-6 Hellcat had the same engine and propeller as the F4U-4, so I suppose he knows what he's talking about.

Regards, Shuckins/Leggern

[Rafe35]

Originally posted by Shuckins
Not sure about that joe.  Both models of the Hellcat used the same Hamilton-Standard propeller with 6501 blades that all the -1 Corsairs used.

Corky Meyer, test pilot for Grumman, stated in an article in Flight Journal magazine that the XF6F-6 Hellcat had the same engine and propeller as the F4U-4, so I suppose he knows what he's talking about.

Regards, Shuckins/Leggern

Then later Grumman F8F Bearcat putting Hellcat to retirement home and F8F is pretty faster than almost US Navy planes until F4U-5 came in 1946.