PDA

View Full Version : [Que] Engine damage and RPM runaway



Alexi_Alx_Anova
10-22-2004, 05:57 AM
One of my biggest dreads in FB, and it continues to be in PF, is to attack planes with rear gunners. I appreciate that your engine and the rear gunner are pointing at each other and so engine damage is very likely. However, it seems to me that almost all bullets that make it to your engine cause the RPM to run away. Sometimes you can do nothing about it, other times you can decrease throttle and/or prop pitch and keep the engine quiet for a while. Very occasionally the bullet causes a dead stop.

I have a question to those who know something about engines (Cajun76 out there?)

What part or parts of the engine would cause the RPM to go mad if it was damaged?
I suppose there are a number of systems that go togther to control/limit the engine's/prop's RPM.
Are these areas a major proportion of the engine's area?

What I'm getting at is if the probablity of receiving engine damage that casues runaway RPM is modeled realistically. At the moment it feels to me that this type of damage happens far too often, but I don't know anything about engines.

I ask this now because I was hoping it would not be so common in PF, but it looks like nothing has changed. The rear gunners are still snipers (and they can still shoot down through the floorboards http://forums.ubi.com/images/smilies/cry.gif ) and the first hit they score on you seems to invariably break your engine and causes the RPM to go up disasterously. If this is realistic, I'll live with it and try to perfect my attacks from below. But if it's too simplistic a damage model....

Alexi

Alexi_Alx_Anova
10-22-2004, 05:57 AM
One of my biggest dreads in FB, and it continues to be in PF, is to attack planes with rear gunners. I appreciate that your engine and the rear gunner are pointing at each other and so engine damage is very likely. However, it seems to me that almost all bullets that make it to your engine cause the RPM to run away. Sometimes you can do nothing about it, other times you can decrease throttle and/or prop pitch and keep the engine quiet for a while. Very occasionally the bullet causes a dead stop.

I have a question to those who know something about engines (Cajun76 out there?)

What part or parts of the engine would cause the RPM to go mad if it was damaged?
I suppose there are a number of systems that go togther to control/limit the engine's/prop's RPM.
Are these areas a major proportion of the engine's area?

What I'm getting at is if the probablity of receiving engine damage that casues runaway RPM is modeled realistically. At the moment it feels to me that this type of damage happens far too often, but I don't know anything about engines.

I ask this now because I was hoping it would not be so common in PF, but it looks like nothing has changed. The rear gunners are still snipers (and they can still shoot down through the floorboards http://forums.ubi.com/images/smilies/cry.gif ) and the first hit they score on you seems to invariably break your engine and causes the RPM to go up disasterously. If this is realistic, I'll live with it and try to perfect my attacks from below. But if it's too simplistic a damage model....

Alexi

Fennec_P
10-22-2004, 06:14 AM
Ive noticed that too. For me, it seems to happen almost exclusively for the Hurricane and Spitfire.

At a guess I'd say it is caused by damage to a propeller component.

One explanation could be the loss of oil pressure. In a constant speed propeller, the blade pitch is kept constant by pressurized oil. If that leaks out, the blades will default to the full fine position, and cause the engine to overrev if you don't throttle down.

Its techically correct, but it does seem to happen way too often. Only an extremely fluky hit to a vulnerable part should disable the CSP entirely, but it seems to happen every single time, and only with certain planes.

http://www.avweb.com/newspics/185000_constant-speed_prop.jpg

weasel75
10-22-2004, 06:41 AM
With the P-40 it happens too, at a "good" rate.

Tully__
10-22-2004, 06:57 AM
Most likely component is the constant speed propellor pitch/rpm governor. Some types go full fine if the oil pressure used to control pitch is lost, which would result in runaway rpm with any sort of airspeed much above stall speed.

bolox00
10-22-2004, 07:41 AM
from my understanding of r/l engines variable prop single engine aircraft are usually designed to fail in the fully fine position to give the pilot maximum power available while landing- something to be done asap-try a go around in corse pitch!!. multi engine planes are usually designed to fail in coarse/feathered position to reduce drag and give the best single/whatever engine reformance- making it easier again to get your plane down in one piece.
as the mechanism is usually in the prop hub/spinner it isn't unreasonable to expect a fair proportion of fire from a rear gunner to hit this area if you are coming in dead 6 o'clock- but as to the failure being quite so abrupt in the aircraft it is modelled in is perhaps debatable - but i think a resonable attempt at what could happen in real life- and good reason not to park on a bomber's six http://forums.ubi.com/images/smilies/35.gif
slashing/head on attacks are less risky - but difficult to get good results- my shooting still sucks http://forums.ubi.com/images/smilies/16x16_smiley-surprised.gif
if/when you get hit like this do 2 things immediately: kill your throttle, pull up sharply.
convert your airspeed to altitude and level off at~ 200kph -add as much power as you can get away with - usually not much- and trim for a long slow flight home- hoping the engine didn't take a hit too!

Alexi_Alx_Anova
10-23-2004, 05:54 AM
I hadn't thought of the pitch etc. being controlled by a hydraulic system. It makes sense. There sure must be a lot of oil pipes under the engine cowling http://forums.ubi.com/images/smilies/16x16_smiley-indifferent.gif

Alexi