Trim Tabs

[R22DRIVER]

One for the Techies.....

I have always wondered about the tim tabs on the trailing edges of a main rotor blade.

What are they for and how do they work?
R22

[sir.pratt]

um - for trimming? they work to aerodynamically trim the blade so the 2 blades are aerodynamically balanced.

[MightyGem]

To help adjust the blade tracking in conjuncton with the adjustment of the pitch change rods. On our aircraft some of them are fixed, but the others can be bent(using a precision bending tool!) for fine adjustment.

[paco]

Umm.. actually, they don't work aerodynamically, but produce a twisting moment. You bend it down to make the blade fly down.

Phil

[Blind Bob]

Umm.....actually, they do work aerodynamically! Trim tabs are initally set by the manufacturer to make the blade fly the same as the master in their whirl tower. When the blade is installed track adjustments will be made using the pitch change rods. However all things not being equal due to age and wear etc.., some blades will change there track position with increase in airspeed. To compensate for this the trim tabs are then adjusted.

[paco]

Beg to differ. If you were trying to make the blade fly up aerodynamically, you would bend the tab downwards, but you bend it up to fly up. Of course, it may create enough of a twist to change the angle of attack indirectly.

Phil