question for RotaryWingBob

eLiz

Filing Flight Plan
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Feb 25, 2006
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eLiz
Why is aft cyclic the proper response to unloading the rotor in order to prevent mast bumping?
 
eLiz said:
Why is aft cyclic the proper response to unloading the rotor in order to prevent mast bumping?
Actually, aft cyclic reloads the rotor system. But the story is more complicated.

The problem originates in a low G situation. This can be caused by turbulence or by a cyclic pushover -- for example, clearing a ridge and then shoving the cyclic forward to hug the other side.

The only thing which keeps the fusilage and the rotor system aligned properly is gravity. Remove the gravity and everything is free to move around.

In the low G situation, the tail rotor wants to roll the a/c to the right, in the case of Robinsons, very rapidly. If the pilot tries to stop the roll with left cyclic a mast bump is likely because there's no gravity to keep things lined up.

When you first feel that you're getting light, the proper response to reweight everything by pulling pitch. If you don't respond and the ship starts to roll, that's when you have to reweight using aft cyclic before trying to deal with the roll.

It is very dangerous to let the situation develop to the point that you get a roll. If you feel light in the seat of the pants, raise the collective and all will be fine.

Hope that helps.
 
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