Speed to fly

[5] In the same year two Poles, L. Swarzc and W. Kasprzyk, also published similar results, although there is some debate about whether this included the effect of air mass movement between the thermals.

[8] The full solution incorporating sinking air between thermals was independently published in the June 1947 edition of Sailplane & Glider by two Cambridge University members, George Pirie,[9] a graduate who had flown with Cambridge University Gliding Club, and Ernest Dewing,[10] an undergraduate who flew at Dunstable after graduating.

[11] Karl Nickel and Paul MacCready published separate articles (in German) describing the same theory in Swiss Aero-Revue in 1949.

According to MacCready, the crosscountry airspeed selector is "a simple device that indicates the optimum speed at which a sailplane should be flown between thermals.

For the derivation of the airspeed selector one minimizes the time for the sailplane to reach a thermal and regain the original height.

[17] Electronic versions of the MacCready Ring are built into glide computers that will give audible warnings to the pilot to speed up or slow down.

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 ]