The Special Case of the Voyager

The 1986 nonstop round-the-world flight of Burt Rutan’s Voyager brought deserved high praise for its designer and courageous flight crew. However, the account of that historic flight shows that the pilots were handicapped by the instability of the airplane at high gross weights. The Voyager is a canard configuration whose tips were joined to the main wing by parallel fuselages (Yeager, Rutan, and Patton, 1987). The statement is made, “Hand-flying Voyager required almost all our concentration, and flying it on autopilot still required most of our concentration.”

A note from Brent W. Silver, a consulting member of the Voyager design team, points to a likely cause of this problem. Apparently, bending of the Voyager’s main wing in turbulence coupled into the canard tips through the parallel fuselages. This caused canard twisting in phase with main wing bending and considerable pitch changes. The same main wing flexibility in a conventional tail-last arrangement should have not caused such a pitch reaction.