Climb vrs Acceleration part Humpty squat

[F4UDOA]

Here is my best "cogent" case.

I have a document from the Brits which is physically to large to fit into my scanner.

It states the differance in climb between the F6F-3 and F4U-1 both no water.

It says that the F6F-3 climbed better because of two reasons.

I'll quote from the document.

As regards to performance, the Corsair giving 343Knots is some 9 Knots faster than the Hellcat at 22,700FT, which is within 100ft of the critical alt of both aircraft. When both Aircraft are at there maximum respective fighter weights, the maximum rate of climb of the Corsair is considerably inferior to the Hellcat. The Corsair is however 340lbs the heavier. The differance in rate of climb is apparently partly due to the superior cooling characteristics of the Hellcat which permit the gills to be closed throughout the climb, where as the Corsairs gills have to be opened at least half-way to ensure adequate cooling.

My point being that any A/C that would have to climb with cowl flaps open would accelerate at a higher rate than it would climb proportionately due to the fact that acceleration in level flight does not require the addition drag of open cowl flaps. Hence climb and acceleration would be linear but not equal relative to the other.

This could apply to any radial engine A/C that climbed in this condition not just the F4U.

How say you??

[Tilt]

Originally posted by F4UDOA


This could apply to any radial engine A/C that climbed in this condition not just the F4U.

How say you??

Didnt some 109's have  large cooling flaps under the wings?

the La7 had 3 such devices........a) shutters around the spinner anulus......b) gills over the exhaust slots c) gill behind the oil cooler. (la 5 had a & b plus its oil cooler was a significant permanent source of drag)

Would this lead to the modelling of cowl/gill drag as the temperature approached the red zone................ it would be quite different for different AC......

Corsair circumferential cooling flaps are fairly prominent I suppose.

However if you modelled this effect to automatically give drag penalty under high engine temperatures what about the ability to manually initiate the drag when you want to scrub e.

[F4UDOA]

Tilt,

It is an interesting topic.

There is also carburator intercoolers to consider. Although I don't know how much they disturbed airflow. I'm not sure how much drag radiator gills opening on A/C such as the 109, P-51 or YAK would make a differance. I wouldlike to see more management of engine temp. I think it would change the way people flew in the MA instead of just cruising around at MIL power all the time.

As far as the ability to slow down on landing or approach the F4U for one had landing gear that doubled as dive flaps so slowing it is the easiest thing to do since you can't damge the A/C even at high speeds. One F4U test pilot Mike Horan was quoted as saying that even at the edge of compressabilty he could use the main gear to slow the A/C.

I wanted to show with this post was the raltive differance in climb vrs acceleration peformance. This is about the 5th post I have done on the subject.

[flakbait]

Yup, the 109 had a pair of "boundry layer" radiators burried in the wings. The cooling "vent" was actually a split flap, where the lower half opened or closed depending on what you set in the cockpit. When you deployed more than half flaps they opened automatically. Hunt around for some pics of a 109 model, some of 'em show the radiator flap arrangement pretty well.

As for cowl flaps, yes they do cause an amazing amount of drag. Not enough to act like an air brake, but they can and do slow you down a bit. Opening them at high speed would probably break the linkage though, slamming them shut; good luck on landing! I'll take my P&W rare, thanks.

Anyway... you'd open 'em up on the ground or on approach, and close 'em in flight. The B-29 had a real fun problem with blowing off cylinder heads due to excess temp (air temp was up near 120º). So crews did a flat climb-out with the cowl flaps wide open until 200mph. At that speed they caused more drag than cooling, so gradually they closed 'em up and started a normal climb. Up high, above 10,000 ft, you wouldn't need 'em because of the cooler air temp.

I noticed the report only says "gills", not which set of "gills". Corsairs (Hellkittens too) had cowl flaps, oil cooler flaps, and intercooler flaps. They could've had any/all of them open for a variety of reasons.



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Flakbait [Delta6]
Delta Six's Flight School
Put the P-61B in Aces High

[ccvi]

If the current climb rates in the game match those of the real aircrafts, and then are reduced by those kinds of "breaks", after adjusting the climb back to the real values that would reduce in increased acceleration.

I think the best solution would be to make cowl flaps be operated manually (or automatic like combat trim).

[MANDOBLE]

If you are climbing at 150/160 mph, a bit more of drag should have little effect.

[F4UDOA]

Mandoble,

I actually have the Navy test docs on climbing the F4U with cowl flaps open 1/3, 2/3 and full open.

The results ranged from 50 to 150FPM at 5K and 100 to 300FPM at 15K.

Most climb figures for the F4U are with clowl flaps open 1/2.

I am king of the esoteric;)

[MANDOBLE]

So, the maximum rate of climb of the Corsair is considerably inferior to the Hellcat should have little relation with cowl flaps.

[F4UDOA]

Your right.

It had to do with an extra 350lbs of fuel. Empty the F4U weights 300LBS less than the Hellcat. So with equal loads the F4U would be 650lbs lighter than the test they ran and 300lbs lighter than the Hellcat.

Remember the test said maximun loaded weights not equal.

However I have very clear charts showing what open cowl flaps do to climb and by proxy acceleration.