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Tandem Rotor helicopters


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I wanted to stop hijacking the other thread. So, as you may know, they do things totally different than single rotor helicopters. If you have any questions, I will answer them as best as I can.

 

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I work as an A&P on the CH-46, and I've always wondered how the aerodynamics of the fwd rotor effect the aft rotor, and do the aft blades effect the fwd blades where they intermesh over the sync shaft tunnel? Does lift from the fwd rotor act as a relative wind for the aft rotor? If so can variations in the lift from the fwd rotor change the angle of that relative wind and subsequently effect the angle of attack and lift of the aft rotor blades? Or is that over thinking it? Tandem rotor aerodynamics sounds like an interesting ground school lesson. I'd also imagine that with a lack of tail rotor, that a hover could be done with less worry of wind direction?

 

Of all things to ask, the aerodynamics of those things is what I'm curious of, probably because I don't know and that kind of technical stuff just interests me.

Edited by superstallion6113
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In the 47 the aft rotor always does more work. It also has to fly thru the air disturbed by the forward rotor. Since the aircraft uses differential collective pitch, the DAFCS computers make any adjustments they need to the controls to keep the aircraft happy. Wind direction at a hover matters almost nothing at all, but the aircraft will weathervane in large crosswinds (its 60 feet long).

 

Tandem rotor aerodynamics are different. Recovering from VRS is different.

Turning the DAFCS off induces flying the aircraft by hand, in all its glory. Power changes will disrupt the equilibrium greatly, so the key is to set the power and leave it.

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