View Full Version : Climb rate - normal and inverted

11-26-2005, 08:14 AM
Playing IL-2 for years now, few weeks ago I noticed that flying inverted does not reduce aircraft performance as it should. Just to test my observations I tried climb rate on FW-190 A-9. I measured time to altitude in 5 flights and got some interesting results:

Flying normally

time from 1000 m to 3000 m - between 2min 22 sec and 2 min 30 sec
time from 3000 m to 5000 m - between 2min 15 sec and 2 min 24 sec

Flying inverted

time from 1000 m to 3000 m - between 2 min 31 sec and 2 min 35 sec
time from 3000 m to 5000 m - between 2 min 21 sec and 2 min 23 sec

Flight parameters were the same for normal and inverted flights: power 105%, pitch 95%, air speed 250 km/h (+/- 10 km/h). Each flight started from the runway, with 50% fuel. As you see, in this flight sim it almost doesn't matter if you climb flying normally or inverted.

In reality, I think, flight performance should significantly degrade if you are flying on your back, especially because WW II fighters were not designed (optimized) for performance when inverted (it would require symetrical airfoil to acheive that and only specialized aerobatic aircraft use that type of airfoil).

I tried that only with FW-190 A-9. If anyone would like to try the other planes, please do, I think results could be interesting.

11-26-2005, 10:29 AM
I tried it with the G.50 and it didn't go so well http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

11-26-2005, 03:09 PM
g50 engine cuts out http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif?

11-26-2005, 04:07 PM
Interesting observation.

How long could WW2 prop fighters fly inverted for?

IIRC the F-14A could only do it for a matter of minutes.

11-26-2005, 05:33 PM
Originally posted by p1ngu666:
g50 engine cuts out http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif?


11-26-2005, 05:52 PM
How long could WW2 prop fighters fly inverted for?

Minutes generally. You run into all sorts of problems with fuel feed. A "rest" period is generally required once positive g flight is resumed in order to allow the inverted flight system to recuperate.

In addition, when the fuel tanks are almost empty you can run into problems much sooner.

11-26-2005, 06:38 PM
P-38 inverted time is like 10 seconds, IIRC. The oil drains to a bottom sump where it is
taken back out of except when inverted. So many seconds and the journal bearings go dry.
This wasn't a problem with most other US fighters. I dunno about fuel though.

11-26-2005, 10:51 PM
its a problem with nearly every plane max, just HOW much of a problem... http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

ye olde rotaries didnt have that problem http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

11-27-2005, 03:24 AM
da question is..

is that from 4.02 patch or from old days?

11-28-2005, 04:54 AM

pecnik, next time try to use ".50" somewhere in the text http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

11-28-2005, 12:42 PM
Really this is something that is probably beyond the bounds of the current modelling
method. There is no direct modelling of airflow over surfaces and it appears that
there may be no seperate wing characteristics for inverted flight but really how much
can you ask considering the number of planes and environment? I guess that when asking,
there is no limit.

It'd be nice to have engines that starve, etc, and we do have some of that.

It's just... how much realism is it fair to ask for? When is it unfair to the point
of taking shots at what can't be done?

11-29-2005, 12:54 AM
well.. AT least Oleg could put in FM that after 10-20 seconds of inverted flight your engine starts dying.. simple as that.

11-29-2005, 04:20 PM
The point is surely 'how long can a pilot survive flying inverted?' My guess is that the engine might still be going long after the pilot has passed out from the effect of the harness cutting off blood flow in the neck area.

In real life, that is.

11-29-2005, 04:37 PM
Great ideas Pecnik. And thanks for the tests.

Also, when you fly inverted you must push stick forward to compensate so that should effect at least level speed maybe.

11-29-2005, 11:44 PM
How long could WW2 prop fighters fly inverted for?

Erm... 2 weeks?

PS. Sorry.

11-30-2005, 03:41 PM
In Warbirds, the oil pressure dropped in in inverted flight and even more in negative loops and turns. On the other hand, it recovered quicker while pulling some Gs. Too low oil pressure would seize the engine.

12-01-2005, 11:27 AM
I am glad that my test led to nice discussion.
Flying inverted poses great discomfort to the pilot, and it is much easier to cope with positive then with negative G acceleration.
Also, how long can airplane fly inverted depends strictly on design fuel feeding system and engine lubrication system. For instance, on Cessna's engine lubrication is almost the same as in car engine, with wet carter, so when you turn engine upside down... it runs out of oil and stops in matter of seconds.
But that was not my area of interest (in this simm it would require few dozen lines of programming code to fix that out). I was primarily interested in aerodynamics. It is obvious that flight performance could not be the same if you fly normally or inverted. With regular airfoil amount of lift generated when inverted is significantly smaller (with big increase in drag), attitude of fuselage is completely different and so on...
I guess that software modifications to deal with presented problem would not be that simple.
But on the other hand, who would think that some simm junkie would even consider testing climb rate in inverted flight???

12-01-2005, 02:35 PM
u can trim to fly upside down luthor http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

12-01-2005, 10:30 PM
Originally posted by Genie-:
well.. AT least Oleg could put in FM that after 10-20 seconds of inverted flight your engine starts dying.. simple as that.
Good idea. Would work relatively well for inline engines, but what about radials? They don't rely on oil being at the bottom of the pan to collect.

Also, and I don't know if these existed in WW2 aircraft, what about the possibility of dry sump engines?

12-01-2005, 11:02 PM
warspite, various oil related systems (pumps?) rely on gravity, u can run upside down for 20seconds or so, but longer than that u should be looking to fly level or push G, which would have the same effect