Newsletter 6
Summer 2004
Updated on 10Jul2004

Published by the Hawker Association for the Members.
Contents © Hawker Association

Pegasus Gyroscopic Demonstration Model
from Roy Whitehead
Our section within the Hawker Experimental Department at Richmond Road was mainly concerned with flight test instrumentation. However, we were constantly asked to tackle jobs for which no other department had the necessary resources. One such job that came our way in 1958 was to make a small model to demonstrate the adverse gyroscopic effects of a large rotating mass on the motion of a manoeuvring aircraft, and a solution to the problem.

The simple model we produced consisted of two very small electric motors with flywheels, mounted close together in tandem on a common axis. They were freely supported on a simple bracket on flexible wires that carried the operating current from a battery. Switches enabled the motors to be rotated either both in the same direction or contra-rotating.
With the motors rotating in the same direction it was possible to demonstrate that if they were gently tilted or turned there would also be a precession effect causing unwanted turning or tilting of the axis of the motors at right angles to the desired direction. With contra-rotation selected little or no precession was exhibited.

I presume the model was intended to demonstrate to Bristols the advantage of contra-rotating the fan and compressor spools of the engine that was to become the Pegasus. Perhaps someone can confirm this.

Postscript from the Editor. When I joined Hawkers in 1960 as a graduate trainee I spent a few weeks in the Apprentice Training School. A similar model was worked on there for John Fozard but this one had an 'airframe' consisting of an 18" long silhouette of the P.1127 fuselage with two co-axial electric motors and flywheels (painted with black and yellow spirals to show the direction of rotation) on the longitudinal axis, and flat plate representations of the wings and tailplane. The whole was suspended in some sort of gimballed frame so the model could be rolled, pitched or yawed with the flywheels contra- or co-rotating to demonstrate the precessional gyroscopic effects. Does anyone remember this