Pivotal altitude

For any given ground speed there is a specific height above the ground at which an aircraft will orbit, or pivot, around the point which is directly abeam in the direction of the lowered wing.  This is true for any bank angle.  While it is customary to refer to this as pivotal altitude, it is actually the height above the pivot point which is critical. The calculated pivot height must be added to the elevation of the ground at the pivot point to obtain the proper MSL altitude.  (The indicated altitude with the proper local altimeter setting.)

In the above diagram, the extension of the abeam line towards the low wing intersects level ground at an angle equal to the bank angle,  theta.  Since the weight vector and centrifugal force vector form a right triangle which is similar to the right triangle formed by the radius of turn and the height, we can write:

Since weight is mass times the acceleration of gravity,

with velocity in ft/sec.

For velocity in knots, the equation becomes: