4.11 and Engine Overheat

[-)-MAILMAN-]

The release notes state that we should be flying all of the planes at approximately 70% throttle and 70% prop pitch to avoid over heating. It also states that the gages are not to be relied upon.

The F4U Corsair and the F6F Hellcat had a manually operated mechanical two stage, two speed supercharger. I will make a couple of assumptions. I have assumed that in the game supercharger one is neutral blower, supercharger 2 is low blower and supercharger 3 is high blower. In previous versions of the game I could switch supercharger to maintain the correct manifold air pressure as I changed altitudes.

I fly the F4U and F6F a lot. I flew them with historical power settings prior to this latest release even though it would take me a bit longer to get to the combat area. Normally it gave me an edge by giving me a longer duration at high performance because I started combat at cooler engine temperature. I would exceed these settings only when engaged in combat.

The F4U had a normal continuous power setting of 2550 RPM (93% prop pitch in the game) and 44" MAP from Sea Level to 8000 feet with supercharger one and cowl flaps 2/3 open (position 6 in game). The throttle would have to be increased continuously as I climbed. At 8000 ft I would have to exceed 100% throttle to maintain the 44" MAP so I would switch to supercharger two, lower the throttle setting to maintain 48" MAP and continue to climb. At approximately 18,500 feet I would have to exceed 100% throttle to maintain 48" MAP so I would switch to supercharger three and reduce the throttle and maintain 48" and continue to climb where eventually the altitude would not allow me to maintain the 48" MAP. These settings coincided with the actually flight data for the F4U-1 Corsairs. For additional proof go to Zeno's Warbirds Web page and view the movie for flying the F4U-1 Corsair. It describes in detail all of the settings for Normal Power Climb as well as power settings for Military and Cruise. Normal continuous is just that, they could run the power settings like this forever with deviations due to geographical locations where the temperatures would be considerably higher on average. This is not cruise or maximum cruise.

With this latest release you cannot follow the actual flight manual or the official documentation any longer. In previous releases operating with a normal power setting you could easily extend away in a 1000 foot/min climb from a Zero or Oscar and eventually from the Ki-61 unless they went to military or war emergency power. With this release you can no longer maintain the correct manifold pressure settings as you climb below 8000 feet. You reach 100% throttle below 5000 feet and have to exceed 100% to keep 44" manifold air pressure which causes you to overheat prior to reaching 8000 feet where you will switch to supercharger two. The plane then appears to revert to the old engine performance above 8000 feet. The F4U-1 uses the Pratt & Whitney R-2800-8 and later -8W engine.

The F6F which uses the Pratt & Whitney R-2800-10 and later -10W engine and a different carburetor (may explain the different MAP setting) than that used on the F4U has the same issues. A normal power climb in the F6F would use an RPM setting of 2550 RPM and 44" MAP using supercharger position one from Sea Level up to 7,000 feet. As you continued to climb you would would maintain 49.5" MAP and change supercharger settings all the way up to critical altitude. You cannot maintain 49.5" MAP all the way up to7,000 feet without exceeding 100% throttle and overheating the engine.

Taking away water injection on the Corsair MkI (F4U-1) & F6F-3 Late should have no bearing on heating issues nor should it change the performance parameters for normal power settings.

At least in the previous versions of the game you could fly by the gages (flight envelope) and not have to rely on the text telling you what percentage of throttle to have. Why have the gages if they aren't reliable?

[Gabelschwanz Teufel]

That is one excellent post.

[Robo.]

Originally Posted by -)-MAILMAN-

With this latest release you cannot follow the actual flight manual or the official documentation any longer. In previous releases operating with a normal power setting you could easily extend away in a 1000 foot/min climb from a Zero or Oscar and eventually from the Ki-61 unless they went to military or war emergency power. With this release you can no longer maintain the correct manifold pressure settings as you climb below 8000 feet. You reach 100% throttle below 5000 feet and have to exceed 100% to keep 44" manifold air pressure which causes you to overheat prior to reaching 8000 feet where you will switch to supercharger two. The plane then appears to revert to the old engine performance above 8000 feet. The F4U-1 uses the Pratt & Whitney R-2800-8 and later -8W engine.

The F6F which uses the Pratt & Whitney R-2800-10 and later -10W engine and a different carburetor (may explain the different MAP setting) than that used on the F4U has the same issues. A normal power climb in the F6F would use an RPM setting of 2550 RPM and 44" MAP using supercharger position one from Sea Level up to 7,000 feet. As you continued to climb you would would maintain 49.5" MAP and change supercharger settings all the way up to critical altitude. You cannot maintain 49.5" MAP all the way up to7,000 feet without exceeding 100% throttle and overheating the engine.

Taking away water injection on the Corsair MkI (F4U-1) & F6F-3 Late should have no bearing on heating issues nor should it change the performance parameters for normal power settings.

At least in the previous versions of the game you could fly by the gages (flight envelope) and not have to rely on the text telling you what percentage of throttle to have. Why have the gages if they aren't reliable?

Hi Mailman - very good post. Regarding the F4U and 4.11 Il2 compare, the issue seems to be that the altitude for 2nd blower is actualy around 5000-5500ft (cca 1800m as per Il-2 compare graph). I just did a quick test in WIP 4.11.1 and you definitely will be able to fly her by the book now - cold start, taking off at full power (99p no ADI), maintaining climb power of ''44 @ 2550RPM to 5000ft... Exact alt very much depends on the map (atm. pressure etc) as it did in RL, so I simply tend to switch the blower when my throttle hits the limit. Then ''48 @ 2550RPM... With my climb speed reasonably high (around 160MPH IAS), cowling flaps 2/3 open, CHT around 200C, oil temp around 100, slightly lower when I get higher up, switching to high blower appropriately (around 15k) and no issue with overheating whatsoever.

Good news is also that all the temp gauges (all of them, yes- on all aircraft) will be working correctly in 4.11.1. With MFP / RPM setting you state, you will be able to monitor your temps (oil is more likely to give you some grief than CHT here, mind you Corsairs temp gauges are OK already in 4.11). Tested on rather ambient Crimea map using earliest F4U, not sure about hotter environments. I am also not able to comment if the supercharger alts are correct and in match with the manual as I don't have it with me but quick search on WWIIacperformance shows pretty much identical climb curve (ac No 02155)... Can't do the same test with clean 4.11 version at the moment, but I will check that as well later on and come back to you as I am not sure how much of that is related to the take-off issue. Hope that helped.

[-)-MAILMAN-]

Originally Posted by Robo
"I just did a quick test in WIP 4.11.1 and you definitely will be able to fly her by the book now - cold start, taking off at full power (99p no ADI), maintaining climb power of ''44 @ 2550RPM to 5000ft."




5000 feet is still too low to be shifting from supercharger 1 (neutral blower) to supercharger 2 (low blower) in the F4U-1 Corsairs. The Real Life Corsairs (F4U-1/-1A/1C/1D) used the R-2800-8 and -8w engines and maintained 44" MAP up to 8000 feet before shifting from neutral blower to low blower then maintaining 48" MAP. This matches exactly the USN Pilot training film for the Corsairs and until v4.11 the game matched this.

Hellcats used the R-2800-10 and -10W engines and had a different carburetor than those used in the Corsairs. Once source has the Hellcat shifting from neutral blower to low blower at 5500 ft (USN training film uses this altitude) and another source has it at 7000 feet. The Hellcats in versions previous to v4.11 shifted at 5500 feet. Shifting the supercharger at 5000 feet in this version is also too low for the Hellcats.

[Whacker]

Originally Posted by -)-MAILMAN-

Originally Posted by Robo
"I just did a quick test in WIP 4.11.1 and you definitely will be able to fly her by the book now - cold start, taking off at full power (99p no ADI), maintaining climb power of ''44 @ 2550RPM to 5000ft."




5000 feet is still too low to be shifting from supercharger 1 (neutral blower) to supercharger 2 (low blower) in the F4U-1 Corsairs. The Real Life Corsairs (F4U-1/-1A/1C/1D) used the R-2800-8 and -8w engines and maintained 44" MAP up to 8000 feet before shifting from neutral blower to low blower then maintaining 48" MAP. This matches exactly the USN Pilot training film for the Corsairs and until v4.11 the game matched this.

Hellcats used the R-2800-10 and -10W engines and had a different carburetor than those used in the Corsairs. Once source has the Hellcat shifting from neutral blower to low blower at 5500 ft (USN training film uses this altitude) and another source has it at 7000 feet. The Hellcats in versions previous to v4.11 shifted at 5500 feet. Shifting the supercharger at 5000 feet in this version is also too low for the Hellcats.

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.

Edit - I posted this for discussion sake, not to indicate that anyone is wrong or right.

[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.

[Robo.]

Originally Posted by -)-MAILMAN-

5000 feet is still too low to be shifting from supercharger 1 (neutral blower) to supercharger 2 (low blower) in the F4U-1 Corsairs. The Real Life Corsairs (F4U-1/-1A/1C/1D) used the R-2800-8 and -8w engines and maintained 44" MAP up to 8000 feet before shifting from neutral blower to low blower then maintaining 48" MAP. This matches exactly the USN Pilot training film for the Corsairs and until v4.11 the game matched this.

Hi Mailman, I said it was around 5000-5500ft at that particular map (Crimea). The MFP is obviously very much depending on the atmospheric pressure and this is actually modelled in Il-2, e.g. your results may vary on a different map.

44'' up to 8000ft.? Which source is stating this as the alt where pilots normally switched from neutral to low blower?

US manual section b ''Power plant'', page 6:

neutral - S.L - 5500ft
low - 16500ft
high - 22000ft

= exactly what 4.11 Il-2compare states and what is also replicable in game in my climb test including best climbing speed and limit temperatures.

With water injection used, neutral blower only up to 2000ft, low from 2000 up to 15000ft. (e.g. page 24 of the British AP2351A manual)

It seems to me that the blower altitudes in 4.11 are pretty much spot on for Corsairs. Coud you please post some sources (preferably links) stating otherwise?

Originally Posted by -)-MAILMAN-

Hellcats used the R-2800-10 and -10W engines and had a different carburetor than those used in the Corsairs. Once source has the Hellcat shifting from neutral blower to low blower at 5500 ft (USN training film uses this altitude) and another source has it at 7000 feet. The Hellcats in versions previous to v4.11 shifted at 5500 feet. Shifting the supercharger at 5000 feet in this version is also too low for the Hellcats.

I have not tested the F6Fs yet. Again, shifting of blowers was fairly complicated, there were certain restrictions in throttle movement in Low and High blower position especially. Also, pilot had to reduce MFP and desirably RPM when switching, actual reaction time varied from plane to plane, and from the atmospheric conditions, that in the first place. Altitudes at normal rated powers should be as follows:

neutral 2550rpm, 44'' - SL - 7000ft
low 2550rpm, 49.5'' - 7000-22000ft
high 2550rpm, 49.5'' 22000ft up

From what I know from the Hellcat FM development, the 1st blower was impossible to set correctly withinh how the game works (I know nothing about that, sorry), and DT simply focused on getting the actual performance and speeds right at any altitude. The blower alt seems to be about 600m too low which is not a biggie considering you have got correct performance now. Hope that helped.

[-)-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.