moving forwardly, and it swings the forward
end of the frame upwardly, Fig. 20, and we now
have, as in the second figure, a new angle of incidence,
which is 30 degrees, instead of 12. It will
be understood that in order to effect a change in
the position of the machine, the forward end ascends,
as shown by the dotted line A.

_Fig. 20. Action when Propeller ceases to pull._

The weight a having now ascended as far as
possible forward in its swing, and its motion
checked by the banking action of the plan it will
again swing back, and again carry with it the
frame, thus setting up an oscillation, which is extremely
dangerous.

The tail E, with its unchanged angle, does not,
in any degree, aid in maintaining the frame on
an even keel. Being nearly horizontal while in
flight, if not at a negative angle, it actually assists
the forward end of the frame to ascend.

APPLICATION OF THE NEW PRINCIPLE.--Extending
the application of the suggested form, let us see
wherein it will prevent this pendulous motion at
the moment the power ceases to exert a forwardly-
propelling force.

_Fig. 21. Synchronously moving Planes._