The
aeroplane would then be said to be ``nose-heavy.''
A 1/4-inch area in the stagger will make a very considerable
difference to the longitudinal stability.
2. If the angle of incidence of the main surface is not right,
it will have a bad effect, especially in the case of an aeroplane
with a lifting tail-plane.
If the angle is too great, it will produce an excess of lift,
and that may lift up the nose of the aeroplane and result in
a tendency to fly ``tail-down.'' If the angle is too small,
it will produce a decreased lift, and the aeroplane may have a
tendency to fly ``nose-down.''
3. The fuselage may have become warped upward or
downward, thus giving the tail-plane an incorrect angle of
incidence. If it has too much angle, it will lift too much,
and the aeroplane will be ``nose-heavy.'' If it has too little
angle, then it will not lift enough, and the aeroplane will be
``tail-heavy.''
4. (The least likely reason.) The tail-plane may be
mounted upon the fuselage at a wrong angle of incidence,
in which case it must be corrected. If nose-heavy, it should
be given a smaller angle of incidence. If tail-heavy, it should
be given a larger angle; but care should be taken not to give
it too great an angle, because the longitudinal stability
entirely depends upon the tail-plane being set at a much
smaller angle of incidence than is the main surface, and if
that difference is decreased too much, the aeroplane will
become uncontrollable longitudinally.
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