70.1 Wednesday, Jan. 6 Mechanisms of takeoff and landing flight BERG, Angela M*; BIEWENER, Andrew A; Harvard Univ; Harvard Univ firstname.lastname@example.org
Takeoff and landing are essential elements of flight for birds. During takeoff, birds accelerate forward to attain cruising speed; during landing, birds decelerate to zero velocity. These accelerations are the result of the interaction of moving wings and surrounding air. To understand how birds use their wings to accelerate and decelerate, we investigated short flights of pigeons from multiple perspectives. Birds were filmed with high-speed video to collect kinematic data. We used sonomicrometry to record muscle strain and EMG to record muscle activation. Using DPIV, we measured airflow around the birds and estimated aerodynamic parameters. Implementing these methods allowed us to link kinematics, muscle function, and aerodynamics to create an integrated understanding of takeoff and landing flight. We found that most of the acceleration during takeoff and landing occurred when the bird was not in contact with the perch, demonstrating that the wings, rather than the legs, provided most of the acceleration. Body, tail, and wing angles increased dramatically from takeoff to landing. During takeoff and midflight, the stroke plane angle tilted downward, but during landing, the stroke plane angle tilted upward. We therefore hypothesized that the wingstroke pushes air rearward during takeoff, but forward during landing. Our aerodynamic results support these hypotheses and suggest that the direction of the net airflow due to a wingstroke is roughly normal to the stroke plane. Wingbeat amplitude was greater during takeoff and landing than during midflight. Pectoralis strain changes reflect this pattern. Differences in muscle function among flight modes in the biceps, scapulotriceps, and humerotriceps were more subtle and variable. The biceps and humerotriceps appear to contribute to wing stability during the downstroke.