super puma MR mast/ pof

[lars1]

Why is the mr mast tilted forward? -what would have been different if it was not tilted?

:ok:

[jayteeto]

A simple back of fag packet not fully technical answer: In PofF, one of the limits to forward speed is amount of disc tilt available in the rotor head. 5deg or so is a good start. Avoids nose down in the cruise as well.

[lars1]

The attitude of the AC depends on the relationship between CG/CP location, right? Would it matter on the attitude of the aircraft (make any difference to the tilted version) if the rotormast was regular, and the swashplate was tilted 5degrees more fwd..?

But, I`ll buy that one with you might run out of cyclic authority.

My thoughts around this is that the puma is a cruiser, and you want to have a swashplate with as little offset as possible during cruise to prevent vibrations and mechanical wear..? just a thought..

[jayteeto]

Lots of small things add up. You are not wrong. CofG does affect position as well as disc tilt. Puma hovers nose up, but thats another story. The tilt fwd affects that as well as other effects.

[HeliComparator]

Whenever the rotor disc is not at right angles to the rotor mast, the mast receives a cyclical bending moment which causes stress. By tilting the mast forward, the maximum value of that stress is reduced - you get a bit of stress in the cruise and a bit of stress in the hover. If the mast were upright you would get less stress in the hover but a whole lot more in the cruise (of course in the cruise the disc is tilted forward so that the rotor thrust is tilted forward to overcome fuselage drag).

HC

[ericferret]

The Bell 47 makes an good example as the early versions did not have the controllable elevator at the back. Note the use of the word elevator not stabiliser. This lifted the tail and therefore increased the tilt of the mast giving a higher forward speed.

The elevator was coupled to the fore and aft cyclic system.

[ShyTorque]

Ah yes, we used to taunt Wessex pilots: "The Puma is a flying machine that hovers; the Wessex is a hovering machine that flies..."