trim tab profile

[rans6andrew]

I have noticed that the in-flight adjustable trim tabs on some aircraft are not "razor sharp" along their trailing edges but have been deliberately made with a lip on both faces. They seem to be made from a double thickness of sheet aluminium and the edges are splayed apart for the final quarter of an inch (6.4mm) at about 90 degrees. Is this done for some aerodynamic reason or is just to stiffen the edge?

Anyone have further to add?

Thanks,

Andrew Cattell

[David Hardaker]

AIUI it's to reduce the "dead" band around neutral...
d

[gasax]

It reduces the tendency for flutter to occur by always ensuring that the airflow from the rear of the tab detaches in the same place.

(FWIW the original Sierra had issues in crosswinds for exactly the same reason, the slipstream detached at different points depending what the crosswind was - giving a tendency for it to wriggle. This was 'fixed' by small spoiler on the rear most window surround!)