On Sep 28, 11:15*am, 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?)?

Normally the angle of incidence is relative to a datum reference on
the fuselage. The wing is usually described as a positive angle (if
the leading edge is raised above the trailing edge of the chord) and
the tailplane is a negative (if the leading edge is down relative to
the trailing edge).

The angle of decalage is usually described as the relative angle
between the chord line of the wing and the chordline of the tailplane
(or other surface). No reference to the fuselage datum is made.

Mike