Fig. 7. Expansion of Fig. 6 for the middle three flaps: non-acceleration-compensated pressures for eight sites (P8, P7, P4, P3, S1, S2, S6, S7) along and across the wing. Six pigeon outlines relate to the same timing as the plots, and are labelled a-f. Each tracing is separated in time by an interval of approximately 16 ms (although the rest of the timing remains normalised to the cycle as defined by the synchronising accelerometer peaks). Positions (a) and (f) are the upstroke/downstroke transition, and occur just after the trough in synchronising accelerometer signal. Position (b) indicates mid downstroke, a period of little wing acceleration, coinciding with peak pressure for sites along the leading edge. Position (c) is towards the end of downstroke, when the synchronising accelerometer is being accelerated upwards. Position (d) relates to a downwards acceleration of the proximal wing, after which the distal wing opens up (position e), completing upstroke. LE, leading edge; TE, trailing edge.