Editing Speed to fly (section)

== History ==
The first documented use of speed to fly theory was by [[Wolfgang Späte]], who used a table of speeds to fly for different climb rates to help him win the 1938 Rhön competition flying a [[DFS Reiher]].<ref>{{cite journal
  | last = Wills
  | first = Chris
  | title = Letters
  | journal = VGC News
  | issue = 94
  | pages = 36
  | publisher = The Vintage Glider Club
  | date = Summer 1998
  | url=https://www.sailplaneandgliding.co.uk/archive-item/no-94-summer-1998
  }}</ref><ref>{{cite journal
  | last = Pettersson
  | first = Åke
  | title = Letters
  | journal = Sailplane & Gliding
  | volume = 57
  | issue = 5
  | pages = 6
  | publisher = British Gliding Association
  | date = October–November 2006
  | url=https://www.sailplaneandgliding.co.uk/archive-item/volume-57-no-5-october-november-2006
  }}</ref> Späte is thought to have used a simplified form of the general theory that did not account for sinking air between thermals.<ref>{{cite journal
  | last = Edwards
  | first = Anthony
  | title = Letters
  | journal = Sailplane & Gliding
  | volume = 57
  | issue = 6
  | pages = 7
  | publisher = British Gliding Association
  | date = December 2006 – January 2007
  | url=https://www.sailplaneandgliding.co.uk/archive-item/volume-57-no-6-december-2006-january-2007
  }}</ref> 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.<ref>{{cite journal
  | last = Reichmann
  | first = Helmut
  | title = Letters
  | journal = Sailplane & Gliding
  | volume = 30
  | issue = 6
  | pages = 312
  | publisher = British Gliding Association
  | date = December 1979 – January 1980
  | url=https://www.sailplaneandgliding.co.uk/archive-item/volume-30-no-6-dec-jan-1979-80
  }}</ref><ref name=Irving>{{cite book
  |title=The Paths of Soaring Flight
  |date=1999
  |publisher=Imperial College Press
  |isbn=1-86094-055-2
  |pages=65–74
  | url=https://www.sailplaneandgliding.co.uk/archive-item/the-paths-of-soaring-flight
  }}</ref> The simplified (no-sink) analysis was first published in English by Philip Wills in 1940, writing under the pen-name “Corunus”.<ref>{{cite journal
  | last = Wills
  | first = Philip
  | title = Cruising speeds
  | journal = Sailplane & Glider
  | volume = 11
  | issue = 2
  | pages = 22
  | publisher = British Gliding Association
  | date = March–April 1940
  | url=https://www.sailplaneandgliding.co.uk/archive-item/volume-11-no-2-mar-apr-1940
  }}</ref> 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,<ref>{{cite journal
  | last = Pirie
  | first = George
  | title = Best Flying Speeds
  | journal = Sailplane & Glider
  | volume = 15
  | issue = 6
  | pages = 3–4
  | publisher = Glider Press Ltd
  | date = June 1947
  | url=https://www.sailplaneandgliding.co.uk/archive-item/volume-57-no-5-october-november-2006
  }}</ref> a graduate who had flown with Cambridge University Gliding Club, and Ernest Dewing,<ref>{{cite journal
  | last = Dewing
  | first = Ernest
  | title = Letters
  | journal = Sailplane & Glider
  | volume = 15
  | issue = 6
  | pages = 22–23
  | publisher = Glider Press Ltd
  | date = June 1947
  | url=https://www.sailplaneandgliding.co.uk/archive-item/volume-15-no-6-jun-1947
  }}</ref> an undergraduate who flew at Dunstable after graduating. They both noticed, Pirie by direct argument and Dewing with mathematics, that the solution involved adding the average rate of climb in the thermal to the instantaneous rate of sink being experienced in the glide in order to find the corresponding best speed to fly.<ref>{{cite journal
  | last = Edwards
  | first = Anthony
  | title = Standing the Test of Time
  | journal = Sailplane & Gliding
  | volume = 66
  | issue = 3
  | pages = 46–49
  | publisher = British Gliding Association
  | date = June–July 2015
  | url=https://www.sailplaneandgliding.co.uk/archive-item/volume-xlv-no-6-december-1994-january-1995
  }}</ref> Karl Nickel and [[Paul MacCready]] published separate articles (in German) describing the same theory in Swiss Aero-Revue in 1949.<ref>{{cite journal
  | last = Nickel
  | first = Karl
  | title = The Best Speed for Cross-country Soaring (translated from "Die beste Streckenfluggeschwindigkeit", Swiss Aero-Revue, Vol. 24, No. 12 December 1949, p478)
  | journal = Sailplane & Gliding
  | volume = 45
  | issue = 6
  | pages = 329
  | publisher = British Gliding Association
  | date = October–November 2006
  | url=https://www.sailplaneandgliding.co.uk/archive-item/volume-xlv-no-6-december-1994-january-1995
  }}</ref><ref>{{cite journal
  | last = Edwards
  | first = Anthony
  | title = Why does the Best-Speed-to-Fly construction work? (With a little history thrown in)
  | journal = Sailplane & Gliding
  | volume = 31
  | issue = 3
  | pages = 126–127
  | publisher = British Gliding Association
  | date = June–July 1980
  | url=https://www.sailplaneandgliding.co.uk/archive-item/volume-31-no-3-jun-jul-1980
  }}</ref>

In 1954, [[Paul MacCready]] described an Optimum Airspeed Selector, that he had been using since 1947.   According to MacCready, the crosscountry airspeed selector is "a simple device that indicates the optimum speed at which a sailplane should be flown between [[thermal]]s.  On a day with weak thermals and weak downcurrents, a pilot should fly between thermals at a velocity near that for [[polar curve (aerodynamics)|best gliding angle]] of the sailplane...If the next thermal to be encountered is expected to be strong, the pilot should dive toward it at high velocity in order to reach it as fast as possible.  Note the magnitude of the wind is of no concern when considering thermals which move with the air mass.  For the derivation of the airspeed selector one minimizes the time for the sailplane to reach a thermal and regain the original height."<ref>{{cite journal |last1=MacCready |first1=Paul |title=Optimum Airspeed Selector |journal=Soaring |date=1954 |volume=18 |issue=2 |pages=8–9 |publisher=Soaring Society of America |url=https://soaringweb.org/Soaring_Index/1954/PDF/1954_Mar-Apr_08.html}}</ref>

According to Bob Wander, "The principal advantage of making a rotatable speed-to-fly ring for your total energy variometer is that cross-country speeds in gliding can be optimized when we factor the strength of thermals into the speed-to-fly process.  For instance, when thermals are weak, then it pays to fly conservatively...[[polar curve (aerodynamics)|minimum sinking speed]]...We are able to cruise faster between thermals when lift is strong because it is so easy to get altitude back in strong lift".<ref name="bw">{{cite book |last1=Wander |first1=Bob |title=Glider Polars and Speed-To-Fly...Made Easy! |date=2003 |publisher=Bob Wander's Soaring Books & Supplies |location=Minneapolis |page=23}}</ref>