i8 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 62 



head resistance of the aeroplane moving at these attitudes and with 

 these speeds was computed from : 



where D is drift on model at 30 miles per hour, and T total thrust 

 required. 



so Q, 



Fig. 6. — Characteristic performance curves. 



The effective horse-power required, angle of wing chord to wand 

 and thrust required are plotted as " characteristic performance 

 curves " on figure 6. 



§8. AXES AND NOTATION 



We shall adopt a notation similar to IJairstow's for the study of 

 dynamical stability. The normal attitude of the aeroplane is its 

 position when in steady flight in a straight line. We select rectan- 

 gular axes with origin at the center of gravity and fixed in the aero- 



