Speed to fly

MacCready speed to fly ring for a variometer. The outer ring show various airspeeds, while the variometer shows climb rate. The index arrow, white triangle, on the ring is placed against the expected rate of climb at the next thermal. The variometer needle will then point to the optimum airspeed, listed on the ring, to be flown to that thermal. The greater the expected rate of climb, the more clockwise the ring is rotated, and the faster is the optimum airspeed.[1]

Speed to fly is a principle used by soaring pilots when flying between sources of lift, usually thermals, ridge lift and wave. The aim is to maximize the average cross-country speed by optimizing the airspeed in both rising and sinking air. The optimal airspeed is independent of the wind speed, because the fastest average speed achievable through the airmass corresponds to the fastest achievable average groundspeed.[2]

The speed to fly is the optimum speed through sinking or rising air mass to achieve either the furthest glide, or fastest average cross-country speed.[1]

Most speed to fly setups use units of either airspeed in kilometers per hour (km/h) and climb rate in meters per second (m/s), or airspeed in knots (kn) and climb rate in feet per minute (ft/min).

  1. ^ a b Glider Flying Handbook, FAA-H-8083-13. U.S. Department of Transportation, FAA. 2003. pp. 4–8, G-4. ISBN 9780160514197.
  2. ^ Modern Elementary Gliding, British Gliding Association, n.d. Appendix D: "Making the Most of it".