PPRuNe Forums - View Single Post - Feathering props
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Old 23rd Feb 2017, 02:53
  #7 (permalink)  
FGD135
 
Join Date: Apr 2008
Location: Australia
Posts: 663
... is that because of the drag it causes - resulting in a lot of yaw towards the dead engine?
Yes, the drag is so significant on all such twin engine types that the aircraft cannot maintain its altitude. All propeller powered aircraft (with 2 or more engines) have the ability to feather the props of failed engines for this reason.

Yes, there is yaw towards the dead engine.

... why would you ever want auto-feather disengaged?
Things get very interesting when you try to answer this question. From what I have read in this thread, it appears this operator had a policy of taking off with autofeather (AFX) disengaged - for the reason that other King Airs in their fleet were not AFX equipped and they wanted the takeoff procedure to be standard across the fleet. There are sound safety arguments behind this approach.

But, on the other hand, it can be said that to intentionally disable a major safety feature such as AFX is foolhardy! Takeoff is the phase of flight for which the AFX is primarily intended.

Is there a time that, if the engine fails, you wouldn't want it to feather?
Yes, after takeoff, when the aircraft has climbed to a comfortable altitude (say 5000-10,000 feet). In this case, with the possibility of being able to restart the engine, it is more simple to do it with the propeller windmilling, rather than feathered.
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