Three steps of about four and a half seconds each. Step 1, blade section: a two-blade propeller spins on a motor, and its disc is the plane of rotation. A cross-section of one blade is an aerofoil. Its chord line is tilted from the plane of rotation by the blade angle, leading edge first, as the blade moves through the air. Step 2, thrust: the blade turns the air downward, air is drawn into the disc and pushed down below it, and thrust acts upward along the shaft, at right angles to the plane of rotation. Step 3, torque, viewed from above: a quadcopter's diagonal pairs spin in opposite directions, front-left and rear-right clockwise (CW), front-right and rear-left counter-clockwise (CCW). The CW pair pushes the body counter-clockwise and the CCW pair pushes it clockwise. The reactions are equal and opposite, so the torques cancel and the aircraft does not yaw. The still frame shows step 2.
