Fig. 8. The implications of the differential pressure measurements of the five sites towards the leading edge of the wing (P8, P7, P4, S1 and S7), and the downstroke kinematics, during the earlier two of the middle three flaps (complete flap cycles are required). (A) Differential pressures. (B) The variation in wing stroke angle during downstroke within the x-z plane, i.e. when observed from front-on (_x-z), is shown in black, the angle within the stroke plane () in red. (C) The calculated geometric velocity (including forward flight speed) for each wing section. Mean section forces assuming that the measured point pressures can be taken as mean pressures for relevant wing sections of known area (D) are combined, and their orientations to the vertical are taken into account when calculating contribution to weight (BW) support (E). The effective moment arm for the aerodynamic force on the wing (R_eff), or the effective centre of pressure, acts approximately half way along the wing (F). Instantaneous muscle-mass specific powers (G) are calculated assuming that the pectoralis dominates downstroke power, and constitutes 18% of body mass. Means ± S.D. for weight support, effective moment arm and powers, are calculated from appropriate individual average measurements of differential pressure, kinematics and morphology; averaging is performed as the final step.