Corsair and Hellcat in Europe (1 Viewer)

wuzak · Jul 17, 2018

BiffF15 said:
Wuzak,

If I understand you correctly going up in octane lowers FTH, however the engine will still make more power at all altitudes than with the lower octane fuel?...

Cheers,
Biff

Between the new and old FTH the power will be increased. Above the old FTH the power is the same.

Let's use an example of a Merlin cleared for +21psi boost on 100/150 fuel. Let's say its full throttle height is X ft.

Normal max power on 100/130 fuel is +18psi boost at Y ft.

Operating with 100/150 fuel boost can be kept at +21psi boost to X ft. Power increases as the altitude increases because there are less pumping losses as the throttle opens. Peak power is at FTH.

Above FTH, the boost will drop, and will continue to drop until it is +18psi at Y ft. So, between X and Y altitude, more boost is available and more power. From Y ft upwards, the power is the same whether the fuel is 100/150 or 100/130, and ADi does not help.

On 100/130 fuel the throttle is still part closed between X and Y altitude, as it is still maintaining +18psi boost.

Hope that helps?

wuzak · Jul 17, 2018

This chart shows it graphically.

http://www.spitfireperformance.com/merlin66hpchart.jpg

The diagonal lines rising from left to right are constant boost. The diagonal lines decreasing from left to right are the full throttle lines.

You can see that in S (fully supercharged/hi) gear the FTH for +25psi boost is ~14,000ft. From there the boost (and power) falls until it meets the +18psi line at ~20,000ft.

Similarly for +28psi boost and MS (medium supercharged/lo) gear.

BiffF15 · Jul 17, 2018

Wuzak,

I think I've got it but one or three more questions to confirm. Assuming an engine could handle the power (is strong enough) and your fuel was of such a high octane you could theoretically have FTH of sea level correct? And if so power above it's lower octane FTH would remain the same? And the reason is the engines limitation is not octane but airflow?

Cheers,
Biff

wuzak · Jul 17, 2018

BiffF15 said:
Wuzak,

I think I've got it but one or three more questions to confirm. Assuming an engine could handle the power (is strong enough) and your fuel was of such a high octane you could theoretically have FTH of sea level correct? And if so power above it's lower octane FTH would remain the same? And the reason is the engines limitation is not octane but airflow?

Cheers,
Biff

Yes, you certainly can have sea level FTH.

You could even have a FTH below sea level - the supercharger can't produce the boost at sea level.

And, yes, the power above the FTH would remain the same.

This post earlier in this thread is a good example.

The R-2800 in the F6F and F4U is called a 2 speed 2 stage engine, but in effect it is 3 speed. The main supercharger has a fixed gearing ratio to the engine. The Auxiliary supercharger has neutral, low gear and high gear.

On the blue line (60inHg MAP), you can see the speed increases with altitude from 0ft to 1,000ft, then decreases to 3,000ft. This is with the Auxiliary stage in neutral.

On the red line (65inHg MAP), the speed is decreasing from 0ft to 2,000ft. This suggests that the FTH with the auxiliary supercharger in neutral is 0ft at 65inHg MAP.

Dawncaster said:
Good example for 60 to 65"hg manifold pressure.

case of F4U-1.

View attachment 501911

The maximum speed improvement was not great, and the most distant altitude was about 17,000 ft with a speed increase of approx 18 mph. the reduction in critical altitude was about 2,000 ft. One model had low-type cabin(birdcage canopy), so this could have had some effect.

Special overboosting by improved water injector was tested by F6F-3 and F4U-1 until 1945. The reports on both models did not specify a definite manifold pressure(reports used the carburetor impact pressure instead), but likewise the top speed improvements were not large.

I think the P-47 is more advantageous because it uses a turbocharger.

The limitation is the performance characteristics of the supercharger - that is the mass air flow and the pressure ratio.

Here is a post by SR6 a couple of years ago with a compressor map.

What was the problem with the allison engine?

parsifal · Jul 17, 2018

Zipper730 · Jul 17, 2018

GregP said:
Yeah, the old A-6 was a very good aircraft. Basically all it lacked in my mind was some forward firing weapon(s)

I felt the same thing

MIflyer · Jul 17, 2018

Here's a chart shown in Bill Gunston's book on the development of piston aero engines that helps show why a turbosupercharger can be so useful.

BiffF15 · Jul 17, 2018

Just when I thought I understood...

Thanks Wuzak and SR6!

Navalwarrior · Jul 19, 2018

Milosh said:
Didn't some F6Fs take on some Luftwaffe a/c? Med and/or off Norway, iirc.

Resp:
I read that during the MTO landings of Allied forces in Southern France (not Italy), US Navy Hellcats were flown inland for Photo-Recon duties, but were fired upon by Allied forces due to their similarity in profile (and dark paint scheme) to the FW-190. Not sure how many sorties were flown or whether there was any air-to-air engagements.

Drphloxx · Jul 19, 2018

GregP said:
The Chance-Cought (actually Vought-Sikorsky ... all the drawings start with "VS" anyway) F4U Corsair gave the Japanese a nasty surprise. I was a very good fighter and, in its later versions, was simply outstanding by any measure of success of fighter prowess.

What do you think might have happened if it had been used in the ETO versus the Luftwaffe, combined with the all-time best kill ratio fighter of WWII, the F6F Hellcat? If the two of them had been deployed to Europe when they historically could have been, what might the result be?

It's OK to speculate the Pacific would not have gone as well without the two deployed in the same numbers as they were in real life, but remember the P-38 was there, too, and was not mach limited versus the Japanese in most cases.

Grumman's chief test pilot, Corky Meyer, has said in print (Flight Journal) that the Hellcat and Corsair flew side by side when at the same power levels when HE tested it except in the main stage (where it was 5 - 6 mph slower since the Hellcat didn't use ram air to avoid carburetor icing, and the same speed in low or high blower stages), and surmised the difference in airspeed was pitot tube placement on the Corsair since they verified the speed of the Hellcat with rigorous means. He says the Corsair was "optimistic" on airspeed and the Hellcat wasn't. Read the article ... but I can't remember the exact issue description. About 10 years ago or more, maybe 15 years ... can't remember.

I can't really say since our pilots at the Planes of Fame have never raced the two, but they fly side by side at the same power level when we DO fly them side by side (same rpm and MP). Same engine (basically, different dash number) and same prop in the early versions (same prop part number and diameter). Our Corsair is the oldest one in flying condition (tail number 799) and HAS the same prop as a Hellcat (F6F-3) ... and IT flies the same speed as a Hellcat at the same power levels in the same blower stages ± a few mph. Both gain or lose slightly, and not the same plane every time.

Corky seems to be right. What do you think?

MIflyer · Jul 19, 2018

Capt Eric Brown was of the opinion that the F4U would have fared poorly against the FW-190. And he had plenty of experience with both.

Macandy · Jul 19, 2018

Last Fleet Air Atrm kills in the ETO were by by Wildcats supporting anti shipping strikes off Norway on 26 March 1945. 4 Wildcats. Vs 8 Bf109Gs. 3 109s shot down for no loss.

Navalwarrior · Jul 19, 2018

MIflyer said:
Capt Eric Brown was of the opinion that the F4U would have fared poorly against the FW-190. And he had plenty of experience with both.

Resp:
I want to say the report was dated Jan 1944, that an F4U (likely an -1A) was flown against a captured FW190. Keep in mind that both were using the latest octane fuel in the US. In these tests, the F4U outmaneuvered the 190 in almost all areas. The one thing I do remember is that the F4U could snap roll and easily get on the 190's tail. The report also advised pilots both the attributes and 'no go' traits in dealing the 190. I cannot recall the maximum altitudes these tests flights were made, but likely were below the higher altitudes of the ETO.

DarrenW · Jul 19, 2018

Navalwarrior said:
Resp:
I read that during the MTO landings of Allied forces in Italy (or sometime later), US Navy Hellcats were flown inland for Photo-Recon duties, but were fired upon by Allied forces due to their similarity in profile (and dark paint scheme) to the FW-190. Not sure how many sorties were flown or whether there was any air-to-air engagements.

Why re-invent the wheel??? Read what R. Leonard and others had to say about the Hellcat's contributions in Europe (I recommend it):

American Hellcats vs the LW

The only service the Hellcat saw outside of the PTO was off Norway with the FAA and during the Allied landings in Southern France during 1944. While there were Hellcats based out of Corsica during this operation, they didn't fly missions into Italy. The Wildcat however did see action in the MTO.

wuzak · Jul 19, 2018

Macandy said:
Last Fleet Air Atrm kills in the ETO were by by Wildcats supporting anti shipping strikes off Norway on 26 March 1945. 4 Wildcats. Vs 8 Bf109Gs. 3 109s shot down for no loss.

A good example of the importance of the quality of the pilots.

swampyankee · Jul 19, 2018

wuzak said:
A good example of the importance of the quality of the pilots.

....and that the Wildcat was probably not quite so outmatched by anything with a Balkenkreuz as some would have everyone believe.

wuzak · Jul 19, 2018

swampyankee said:
....and that the Wildcat was probably not quite so outmatched by anything with a Balkenkreuz as some would have everyone believe.

4 Wildcats should have been outmatched by 8 Bf 109s.

swampyankee · Jul 19, 2018

wuzak said:
4 Wildcats should have been outmatched by 8 Bf 109s.

They should also have been able to break off combat.

I'll stand by my statement that the Bf109s weren't as much better as some people claim.

Dawncaster · Jul 20, 2018

MIflyer said:
Capt Eric Brown was of the opinion that the F4U would have fared poorly against the FW-190. And he had plenty of experience with both.

In another book(Wings of the Navy) he said he had an uncomfortable experience with Corsair. He was a test pilot for the Corsair I JT118 in early 1944. he said because of his short stature of 170 cm, Corsair's wide cockpit - tailored to Vought's 193 cm chief test pilot, gave him poor vision and control. and the 'Corsair I' was also a model with a Birdcage canopy that offered the lowest and deepest cockpit position and poor visibility among the all Corsairs. (meanwhile another British pilots who boarded the 'Corsair II' praised the Corsair's wide cockpit.)

Brown also said that the aileron was moderately light and the elevator was heavy, and Corsair had poor control harmony. extremely light stick force for aileron/elevator with good control harmony that the USN's inspection reports and other pilots pointed out were not found in his book. His small body has sometime resulted in low test results compared to other test pilots as was the case in other book(Wings on my Sleeve). perhaps he would not have used the Corsair's full agility.

His 'verdict' in 'Duels in the Sky' was seems based on his mind for Corsair in 'Wings of the Navy'.

"I was never to achieve any Sort of rapport"

Navalwarrior · Jul 20, 2018

Dawncaster said:
In another book(Wings of the Navy) he said he had an uncomfortable experience with Corsair. He was a test pilot for the Corsair I JT118 in early 1944. he said because of his short stature of 170 cm, Corsair's wide cockpit - tailored to Vought's 193 cm chief test pilot, gave him poor vision and control. and the 'Corsair I' was also a model with a Birdcage canopy that offered the lowest and deepest cockpit position and poor visibility among the all Corsairs. (meanwhile another British pilots who boarded the 'Corsair II' praised the Corsair's wide cockpit.)

Brown also said that the aileron was moderately light and the elevator was heavy, and Corsair had poor control harmony. extremely light stick force for aileron/elevator with good control harmony that the USN's inspection reports and other pilots pointed out were not found in his book. His small body has sometime resulted in low test results compared to other test pilots as was the case in other book(Wings on my Sleeve). perhaps he would not have used the Corsair's full agility.

His 'verdict' in 'Duels in the Sky' was seems based on his mind for Corsair in 'Wings of the Navy'.

"I was never to achieve any Sort of rapport"

Resp:
A friend of mine's Dad flew Wildcats as a Marine Aviator in 1943 as fleet CAP. He returned to the States in Jan 1944 where he instructed cadets for 12 mos on the Corsair, flying every variant (F4U-1, -1A, FG-1, and F3A). He never had a problem with any Corsair variant, nor did any of his fellow instructors. He returned to the Pacific flying CAP for the Fleet, where he shot down two Kamikazes in the F4U-1D/FG-1D. He was recalled to Korea the first few mos of the conflict, where he flew the F4U-4. He never had to abort due to mechanical issues. He later flew the Hellcat and Tigercat (in training following WWII) and thought both excellent, but still favored the Corsair.

Corsair and Hellcat in Europe (1 Viewer)

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