On 28 Sep 2009 18:15:03 GMT, Nyal Williams
wrote:

Is there a term for the difference between the angle of incidence of the
wing and the angle of incidence of the tailplane? I have heard/read
decalage used this way; however, wikipedia says decalage means the
difference between the angles of incidence between the two wings of a
bi-plane. (Thinking of that makes me think that extending Fowler flaps
turns the aircraft into a bi-plane).

Is there a separate term? Is this usage correct (Is Wikipedia just
incomplete?)?

Yes, Wikipedia is incomplete. Decalage can refer to a difference in
incidence angle between any two aerodynamic surfaces.

rj