Hinge offset?

[maxtork]

Hi All,

I was hoping one of you could help educate me a bit. I've followed many threads here and have seen reference to hinge offset. I'm curious s to what exactly this means. Are we refering to the spanwise distance if any between the flapping and the lead-lag hinges? Or are we talking about the angular offset of the flapping hinge from the hub like we see on a Bell style tail rotor or a Kmax type rotorhead? If it isn't too much trouble can you explain how this effects how things work? I know large hinge offsets allow different things like high speed maneuvering but I just can't figure out how.

Thanks
Max

[[email protected]]

Max - the hinge offset is the distance between the flapping hinge and the rotor mast and is effectively the length of the lever that the blade uses to exert force to move the fuselage. Thus a 2 bladed teetering rotor head has no hinge offset and an articulated rotor head has some hinge offset.

With semi-rigid rotors where some of the mechanical hinges are replaced with composite materials, the exact position of the flapping hinge can be difficult to determine but an 'effective hinge offset' is calculated that equates the actual control power to that which would be achieved with a mecahnical hinge in the same position. For example, the Lynx (with a titanium rotor hub)has an effective hinge offset of 17% which means that the fuselage responds to a cyclic input the same way as it would if a mechanical flapping hinge was located 17% of the distance between the rotor hub and the blade tip.

By control power, I mean how much fuselage response you get to a given cyclic input.

[maxtork]

Brilliant Crab!

You must be a rich guy being able to turn something as clear as mud into crystal clear.

Thanks
Max

[oldbeefer]

'You must be a rich guy being able to turn something as clear as mud into crystal clear'

No, just a product of what was (at the time Crab went through) one of the best pilot and instructor training courses in the world!

[[email protected]]

Yes, but they didn't teach me how to spell mechanical though:)(3rd line 2nd para)