By F. G. Irving
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Extra resources for An Introduction to the Longitudinal Static Stability of Low-Speed Aircraft
In this simple treatment, the trim condition merely GENERAL STABILITY CONSIDERATIONS 39 defines CLT. The quantity dCLJdCL is the only aerodynamic expression in eqn. 13) which might be affected by the trim condition and in incompressible flow it is constant for a given aeroplane, as will be seen later. It is clear from eqn. 14) this particular value of A being given the symbol hN. g. were hNc aft of the datum, the static margin would be zero and the aeroplane would have neutral static stability.
The only significant aerodynamic tail parameter is the overall lift-curve slope al9 which is primarily determined by the geometry of the complete horizontal tail. To a first order, features such as the ratio of elevator chord to total chord are of no consequence. In the stick-free case, an increase in tail incidence <5αΓ results in an increment of lift coefficient a1 δατ and, since the elevator will float up a little so as to keep CH = 0, there will also be a decrease in tail lift coefficient due to this elevator deflection, of magnitude (a2b1/b2)ôocT.
9) are those appropriate to the prevailing conditions. e. γ-^α2δηίΗηχ, *« = -^ 0 = - K r f l 2 è? (610) which is the result given by eqn. 3). S. This result is essential to the analysis of trim curves obtained in flight, which are rarely straight lines in practice. The consequences of eqn. 10) are noticed by the pilot as a variation of stick position with speed. This is shown in the following analysis. Write dltrlm dr 1trim dCL -dîï—dëT-dïT (611) For an aeroplane in steady level flight at an equivalent airspeed K .
An Introduction to the Longitudinal Static Stability of Low-Speed Aircraft by F. G. Irving