4.11 and Engine Overheat

[Pips]

Originally Posted by Whacker

I have the actual pilot manual for the F4U-1 series open right now, revision 1944.

The climb section calls for the following:

Max continuous normal rated power calls for 44" MAP at 2550 RPM, with the blower shift from neutral to low when MAP drops to 41.5" between 5500 and 7000 ft. above MSL.

Military power climb calls for 2700 RPM at 52.5" MAP, shifting to low blower when MAP drops to 45" between 1700 and 5500 ft. above MSL.

Whacker, does the manual make any mention of radiator settings for the above? Does it also cover temps and times at certain RPM before overheating sets in? Cheers.

[Whacker]

Originally Posted by Pips

Whacker, does the manual make any mention of radiator settings for the above? Does it also cover temps and times at certain RPM before overheating sets in? Cheers.

No specific radiator settings are mentioned for those two profiles. Also no clear answer to your second question. Here's some data that seems to be relevant.

- There's no air speed restriction regarding any of the cooling flaps (cowl, intercooler, oil cooler) and apparently they can be open at any speed up to Vne, and are covered by some kind of "relief system".

- Max open cowl flaps can lead to some buffeting at the tail, so it's recommended they only be full open on the ground. Take off and climb are recommended at 2/3 open, and high speed or cruising are recommended full closed.

- Max cyl head temp *period* seems to be 260 degrees C (500 F), and the manual says at several places *never* to exceed that under any circumstances.

- Max rated continuous power cyl head temp is stated to be 232 degrees C, with the provision that 260 never be exceed as per previous bullet point.

- Take off and Emergency War Power engine profiles are to be used for no more than 5 minutes.

- Re: Emergency War Power, it doesn't say whether this is 5 minutes max per flight (and between ground servicing) or if it can be used multiple times. I imagine the Wasp radial ground service manual would be the authority for this. It's also clearly limited by the amount of water in the water tanks, but I can't determine if the total water capacity would be used up during that 5 minutes or not.

- Military Power is to be utilized for no more than 30 minutes. Again it doesn't say if this is the total per flight or if it can be used, let to cool down, then used again.

- If I had to make a semi-educated guess given what I know about radials, the 5 min/30 min limits for those power profiles is per flight, with some ground maintenance and checks that need to occur before the engine can be used again. Radials had rather low mean time between overhauls, and higher power settings and temperatures are going to cause rapidly increased wear and tear the worse it gets.

[-)-MAILMAN-]

Here is a link to the film used for pilot training for flying the F4U-1 Corsair from wing fold, start up, takeoff, climb, and landing. the narrator gives the Manifold Air Pressure, Propeller RPM, Radiator settings and altitudes that the supercharger shifts. At the normal rated power climb neutral blower is used, 43.5" MAP at 2550 RPM and shifts from neutral blower to low blower at "approximately" 8,000 feet. Viewing the film is free. In the past you had to use Real Player to view the film, but there are now new choices, I used WMP. Over the last few years I have watched the Hellcat, Thunderbolt, P-40, P-39 and P-38. This was the first reference I had seen to 44" (43.5" to be exact) up to 8,000 feet.

The film is using the F4U-1 with the framed canopy at a time frame when the six position national insignia was being used.

http://www.zenoswarbirdvideos.com/F4U.html

[Robo.]

Originally Posted by -)-MAILMAN-

43.5" MAP at 2550 RPM and shifts from neutral blower to low blower at "approximately" 8,000 feet. (...) This was the first reference I had seen to 44" (43.5" to be exact) up to 8,000 feet.
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Very interesting movie, thanks for that. As it seems, the devs seemed to stick to the actual manual which states 5500ft. It is not unusual to see different sources stating different values, it is hard to make a decision then. In this case, the movie happens to be the only source refering to 8000ft. Both US and British manuals state 5500ft.

As long as you can fly the a/c as per book (and you certainly can as I described above), I don't see any problem.

[Bolelas]

Not a question about the game itself, but as real life aircraft behaved: In a dive, in a over-rev situation (lets say i cut throttle but forgot to pitch back), does the plane heat the same way as if i was adding more fuel? (with less pitch). I know compressed air heats, plus there is fuel going in (the idle fuel), and also friction, but should it overheat slowly?
Hope you people can understand question, because it is a little confusing.
I have not much knowledge about engine, just what i read in foruns, books etc. Also in the spitfire manual it says that in a dive they could do a little over-rev, but had to add at least one third of throttle : Was this to lubbricate pistons?

[Whacker]

Originally Posted by Bolelas

Not a question about the game itself, but as real life aircraft behaved: In a dive, in a over-rev situation (lets say i cut throttle but forgot to pitch back), does the plane heat the same way as if i was adding more fuel? (with less pitch). I know compressed air heats, plus there is fuel going in (the idle fuel), and also friction, but should it overheat slowly?
Hope you people can understand question, because it is a little confusing.
I have not much knowledge about engine, just what i read in foruns, books etc. Also in the spitfire manual it says that in a dive they could do a little over-rev, but had to add at least one third of throttle : Was this to lubbricate pistons?

Over-revving any engine is very, very bad for it. It creates a lot of heat very rapidly (mostly from friction, not combustion), and it pushes parts of the engine far beyond what they were designed to work at.

Some common failures include piston rods breaking ("throwing a rod"), cam and crankshaft bearings rapidly being burnt out and seizing up, valve heads colliding with pistons, etc. Even if everything manages to hold together, it can also cause critical "soft" components like gaskets to fail, which may not cause an immediate seize-up but could cause other things to fail in a chain reaction.

It's very complicated and I don't pretend to understand the actual ways and means of doing it, but calculating a particular engine's red-line rev rating is done based on it's design. Beyond that red-line the probability of partial or total failure rapidly goes up to where it's essentially guaranteed.

Lastly, keep in mind this was almost 80 years ago. Aeronautics was a very young field and technology was pushing boundaries once held to be insurmountable. Warbird engines were pushed to their absolute limits and designed to run at just below those with minimal safety cushions. Overspeeding your prop and motor will invariably give you those really bad results, and the game seems to do a great job of simulating that as best as it can.

Hope that helps.

[K_Freddie]

So what were saying here is... a slower revving engine is a lot cooler, whether it be driven by wind or combustion.

Common sense says that combustion would be hotter

[Crumpp]

Also in the spitfire manual it says that in a dive they could do a little over-rev,

The Spitfire manual does not say to over-rev the engine in a dive. It says to keep the throttle 1/3 open in a dive to maintain 3000 rpm. Do not use the propeller rpm control to maintain rpm, adjust the throttle (manifold pressure) to maintain rpm.

That the correct way to operate a constant speed propeller while maneuvering in any aircraft. You adjust manifold pressure to maintain rpm. On many manifold pressure gauges, a green arc is provided to assist the pilot in keeping the engine within limits to maintain that required rpm while maneuvering.

http://images.search.yahoo.com/image...1pdac1f&fr=sfp

[Pips]

That's interesting - that the throttle should be adjusted during manoeuvering, but not the prop. Does the manual state what the prop setting should be during manoeuvering?

[julian265]

Originally Posted by Arrow

I don't agree that it is proportional to MAP. Take the prop away from an engine and run it even on low MAP, you will see that it will overheat and explode just in seconds.

If you have killed an engine in a few seconds by over-revving it, then the engine has suffered mechanical failure, which in this case has nothing to do with coolant or oil temperature.

Originally Posted by greybeard1

Actually, heat to waste in internal combustion engine is about three times power developed and this latter is directly proportional to MAP, not to RPM, which is a consequence (that's to say an output, not an input) and, secondarily, by mixture, that contributes to take away some warm before the cooling system does.

I agree... in the scope of normal operating speeds.

Imagine two identical engines, each producing the SAME SHAFT POWER. One is running at 2500 RPM, and higher MAP, the other at 3000 RPM, and lower MAP.
The engine running at 3000 rpm will be producing more heat, due mainly to decreased efficiency at the higher rpm. It is the efficiency change which determines how much more heat is generated. Without knowing what it is, we're all just guessing, however I don't think the difference between 2500 and 3000 would be more than around 20%, meaning that MAP is still the main factor in heat generation... Which is why i disagree with "Pre 4.11 engine temps were effected more by manifold pressure than by engine RPMs or mixture settings, which simply is not realistic at all.".

Does anyone have an efficiency (or BSFC) chart for one of these aero engines?