Schempp-Hirth Discus

{{Short description|German single-seat glider, 1984}} {{More citations needed|date=May 2009}}  {{Infobox aircraft |name=Discus |image=Discus 800.jpg |caption= |type=[[FAI Standard Class|Standard-class]] sailplane |manufacturer=[[Schempp-Hirth]] |designer=[[Klaus Holighaus]] |first_flight=1984 |introduction= |retired= |status= |primary_user= |more_users= |produced= |number_built=>850 |variants= }} The '''Schempp-Hirth Discus''' is a [[Glider competition classes|Standard Class]] [[Glider (sailplane)|glider]] designed by [[Schempp-Hirth]]. It was produced in [[Germany]] between 1984 and 1995 but has continued in production in the [[Czech Republic]]. It replaced the [[Schempp-Hirth Standard Cirrus|Standard Cirrus]]. It was designed by [[Klaus Holighaus]].

==Design and development== The Discus was the first production sailplane to have a distinctive swept-back leading edge. This is now common in contemporary sailplanes.

Studies had long shown that the ideal wing for minimizing [[induced drag]] should be an elliptic planform. To keep production costs down, a triple-trapezoidal approximation of this shape was adopted for the Discus. The wing section was also new. [[Wingtip device|Winglets]] were only available towards the end of the production run, though many have been retro-fitted. The fuselage and tail were adapted from the [[Schempp-Hirth Ventus]]. A version with a narrow fuselage is called the Discus 'a' and the wider fuselage version is called the 'b'. The fuselage is made of [[glass-reinforced plastic]] around a steel tube frame. The wings and tail surfaces are also fiberglass with the exception of the main wing spar, which is made of [[carbon fiber]]. There is a {{convert|6.5|L|USgal impgal|abbr=on}} water ballast tank in the fin for trimming purposes when the main wing mounted ballast tanks are in use (184 L combined) for a maximum wing-loading of {{convert|50|kg/m2|lb/sqft|abbr=on|}}

===Competition use=== The Discus dominated standard class sailplane racing throughout the 1980s, winning six [[World Gliding Championships]] in a row from 1985 to 1995.

===Performance=== The best measured [[glide ratio]] is 42.5:1. Though it is considered a high performance sailplane, its handling is well within the capabilities of inexperienced pilots. With no bad manners, powerful airbrakes and a low landing speed, the Discus is popular with clubs. Discuses are easy gliders to assemble, having light wings, automatic control hookups and a single pin securing the wings.

===Production=== Over 850 Discuses had been built by 2004 and it remains in production today despite the introduction of its successor, the [[Schempp-Hirth Discus-2]]. About 12 per year are built under license by Schempp-Hirth Vyroba in the [[Czech Republic]] as the Discus CS. Some models are fitted with small sustaining engines (turbos) and are designated Discus T.

==Variants== ;Discus a: Short fuselage and narrow cockpit optimized for smaller pilots, utilising the fuselage and tail of the [[Schempp-Hirth Ventus|Ventus a]]. ;Discus b:Standard production model utilizing the fuselage and tail of the [[Schempp-Hirth Ventus|Ventus b]]. ;Discus bT:Discus b with a retractable sustainer motor ;Discus bM:Motor-glider with retractable engine ;Discus CS:Continued production in the [[Czech Republic]] ;Discus K: Aerobatic version first flown on 18 November 1987. This was, due to disappointing performance in aerobatic, later converted back to a standard version.<ref>{{Cite web| title=Discus | author=Thomas Bergmann | language=de | url=https://www.segelfliegen-magazin.de/wp-content/uploads/2013/05/discus.pdf | archive-url=https://web.archive.org/web/20190401074802/https://www.segelfliegen-magazin.de/wp-content/uploads/2013/05/discus.pdf | archive-date=2019-04-01}}</ref>

==Specifications (Discus b) == [[File:Discus CS panel.jpg|thumb|Instrument panel in a Discus CS.]] {{Aircraft specs |ref=''Jane's All the World's Aircraft 1988-89'' <ref name=JAWA88-89>{{cite book |title=Jane's All the World's Aircraft 1988-89 |year=1988 |publisher=Jane's Information Group |location=London |isbn=0-7106-0867-5 |editor=John W.R. Taylor|pages=630}}</ref> |prime units?=met  |crew=1 |length m=6.68 |length note= |span m=15 |span note= |height m=1.27 |wing area sqm=10.58 |wing area note= |aspect ratio=21.3 |airfoil= |empty weight kg=233 |empty weight note= |max takeoff weight kg=525 |more general= *'''Water ballast:''' {{convert|180|L|USgal impgal|abbr=on}}  |stall speed kmh=66 |never exceed speed kmh=250 |never exceed speed note=in smooth air ::::{{convert|200|kph|kn mph|abbr=on}} in rough air ::::{{convert|180|kph|kn mph|abbr=on}} on aero-tow ::::{{convert|150|kph|kn mph|abbr=on}} on winch launch |g limits=+5.3 - 2.65 |glide ratio=45:1 at {{convert|100|kph|kn mph|abbr=on}} |sink rate ms=0.59 |sink rate note=at {{convert|78|kph|kn mph|abbr=on}} |lift to drag= |wing loading kg/m2=49.62 |more performance= |avionics= }}

==See also== {{aircontent  |see also= |related= |similar aircraft= *[[Glaser-Dirks DG-300]] *[[PZL Bielsko SZD-55]] *[[Rolladen-Schneider LS4]] *[[Schleicher ASW 24]] |lists= *[[List of gliders]] }}

==References== {{reflist}}

* {{cite book |last=Simons |first=Martin |title=Sailplanes 1965-2000 |year=2005 |publisher=EQIP Werbung und Verlag G.m.b.H. |location=Königswinter |isbn=978-3-9808838-1-8 |edition=2nd revised}}

==External links== {{Commons category}} *[http://www.schempp-hirth.com/ Schempp-Hirth Website] *[http://www.harrishillsoaring.org/doc/discus_johnson.pdf A Flight Test Evaluation of the Discus Sailplane, by R.H. Johnson, published in Soaring Magazine, February 1986] *[http://www.gliding.co.uk/bgainfo/technical/datasheets/discus.pdf British Gliding Association, Discus datasheet] *[https://web.archive.org/web/20051102092646/http://www.sailplanedirectory.com/PlaneDetails.cfm?planeID=87 Specifications of Schempp-Hirth Discus]

[[Category:1980s German sailplanes]] [[Category:Schempp-Hirth aircraft|Discus]] [[Category:T-tail aircraft]] [[Category:Aircraft first flown in 1984]]