mast moment indicator

[jagannath]

sir
with reference to the above subject, I would like to know the significance of mast moment warning system installed in some of the eurocopter helicopters. Why this warning system is optional in some of the helicopters. Is this warning system really required in hingeless rotors. Of course I feel mast moment is nothing but a pitching moment in rotating co-ordinate system or mast moment is the resultant of pitching and rolling moment, please clarify. Is there any empirical formula in deriving mast moment.


thanks in advance
Jagannath

[QTG]

It's a Wheatstone Bridge installed vertically inside the rotor mast, the varying resistance measured across it being directly proportional to the bending moment applied to the mast. It's a valuable tool which tells the pilot when he is approaching the point of knackering the mast, for example when landing on sloping ground.
It's usually optional because, if slope limits are observed, and correct landing technique employed, the mast should not become knackered anyway.

[NR DROOP]

It is not the mast that gets damaged it it the blade cuffs. These are the vulnerable part of the system and must be inspected if the MMI is exceeded. The EC-135 that slide down the hill in the snow shows how fragile that portion of the blade can be. If no MMI is fitted or if it is unserviceable then the a/c has a limit on the slope it can land on. Even so damage can be done if the cyclic is mishandled.

[skadi]

It is not the mast that gets damaged it it the blade cuffs.

OK for the EC135, but not for BO105/BK117 , they dont have bladecuffs...

When MM is exceeded, the dilatation bolts between mast and titan rotorhead have to be checked

skadi

[QTG]

......and the BO 105's different too. Perhaps I should have said "...the mast and associated bits and pieces should not become knackered anyway".