adjusting plane

from The Collaborative International Dictionary of English v.0.48

Adjusting plane \Adjusting plane\, Adjusting surface \Adjusting
surface\ (A["e]ronautics)
   A small plane or surface, usually capable of adjustment but
   not of manipulation, for preserving lateral balance in an
   a["e]roplane or flying machine.
   [Webster 1913 Suppl.]