The Boeing Canard Rotor Wing (CRW) Dragonfly demonstrator (Flight International,23-29 April) is described as using side directional-control nozzles for "anti-torque control". Since the rotor is tip-driven by flow from the Williams turbofan and thus has no "twiddle at the middle" - as Dr George Hislop of Fairey Aviation called helicopters with shaft-driven rotors - there must be an unusual amount of friction torque to counteract!
Older readers may recall the Fairey Ultra-Light helicopter (1955) and the SNCASO SO 1221 Djinn (1953) also used engine compressor flow to turn their rotors, having cyclic pitch for directional control. Since the Dragonfly apparently lacks cyclic pitch, the side nozzles (puff pipes?) are doubtless used for steering while in vertical, hovering or transitional flight up to the point where the rudders become effective.
David WH Godfrey
Ontario, Canada
Source: Flight International
