Langley Memoir on Mechanical Flight, Parts I and II / Smithsonian Contributions to Knowledge, Volume 27 Number 3, Publication 1948, 1911

by S. P. Langley; Charles M. Manly

Let R = distance of CG₂ below CP₂ = ag.

Let S = distance of thrust-line below CP₂ = ad.

If now the aerodrome under the action of the propellers be supposed to turn about the CP₂ (or, a) through an angle α, so that g takes the position g′, we [p049] obtain by the decomposition of the force of gravity an element g′k = W sin α which acts in a direction parallel to the thrust-line.

If we again neglect the horizontal hull resistance, equilibrium will be obtained when

kg′ × ag′ = T × ad′

or

WR sin α = TS

∴ α = sin⁻¹TSWR

Fig. 5. Diagram showing relation under certain conditions of thrust, C. P. and C. G.