dhawald3
Topic Author
Posts: 16
Joined: Tue Jun 28, 2011 3:10 pm

Gyroscopic Effect Of Turbo Fan Engines

Mon Jan 07, 2013 7:10 am

Hi there!

the gyroscopic effect due to the rotating mass affects engines, it is more pronounced in turbo prop engines due to a larger fan.

Even though it is less in turbofan engines is there anything done to counteract it in modern turbofan engines?
 
rwessel
Posts: 2448
Joined: Tue Jan 16, 2007 3:47 pm

RE: Gyroscopic Effect Of Turbo Fan Engines

Mon Jan 07, 2013 9:36 am

Not really. Compared to the mass of the aircraft, the effect is pretty small, particularly since much of the rotating mass is in the relatively small diameter section of the engine. Some engines do have counter-rotating shafts, and that will obviously reduce the effect, but it's not a prime consideration.
 
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Starlionblue
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Joined: Fri Feb 27, 2004 9:54 pm

RE: Gyroscopic Effect Of Turbo Fan Engines

Mon Jan 07, 2013 10:16 am

Quoting rwessel (Reply 1):
Some engines do have counter-rotating shafts, and that will obviously reduce the effect, but it's not a prime consideration.

Counter rotating shafts mitigate torque, not gyroscopic effects (rigidity in space and precession). Though I guess you get precession in opposite directions when the engines changes direction.

[Edited 2013-01-07 02:17:28]

[Edited 2013-01-07 02:18:17]
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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Jetlagged
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RE: Gyroscopic Effect Of Turbo Fan Engines

Mon Jan 07, 2013 4:27 pm

For a V/STOL aircraft like the Harrier gyroscopic precession is important as it adversely affects hovering stability. That's why the Pegasus engine has counter-rotating shafts. Counter rotating shafts in engines like the RR Trent are more for aerodynamic reasons than to reduce precession torque. Airliners don't usually pitch or yaw at high rates so any precession torque will be relatively low, but it is taken into account when stressing the engine mountings. It's more likely to be significant in a military fighter as a rapid pitch up will create a yawing moment.
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