Wind-tunnel investigations of instability in a cable-towed body system

Abstract

A brief investigation was made in R.A.E. wind tunnels into instability of a body towed by a helicopter. This was undertaken after an incident in which a divergent oscillation led to cable failure in flight. Stability boundaries in terms of cable length and forward speed were determined for the original cable/body system. The effects of various body and suspension modifications were then studied. Existing theory was compared with the experimental results and both were used in forecasting the behaviour of a new cable/body system. Subsequent experimental work elsewhere confirmed the validity of these estimates. Enhanced stability of the system was observed at short cable lengths and a possible explanation is suggested.