Retractable engine

from Wikipedia, the free encyclopedia
Folding engine with 5-blade folding propeller, Oehler system
ASH 26E with unfolded Wankel engine and fixed propeller

A retractable engine is in gliding sports one in the fuselage of a glider retractable drive , so motor with propeller to the start not to start winds to rely or aero tow or to longer distances without usable thermals to bridge up to the next possible landing site. This is then a landing on a glider airfield or an outside landing on a suitable agricultural area , but not an emergency or safety landing

Principle of the folding engine

The reason for sinking in the fuselage of the glider is to avoid unnecessary drag in pure gliding. Are usually for reasons of weight two-stroke or rotary engines with timing belts reducers used for propeller. Depending on the power of the engine, one type of aircraft is approved for self-launch or exclusively as a " lull pusher " to get to the next airfield or to enable an outside landing . In Germany, gliders with auxiliary power units have an D-Kaircraft registration number beginning with followed by three more letters.

Individual types

Many current gliders are optionally available with a retractable engine, such as the ASG 32 , ASH 31 , ASH 30 and ASW 28 from Alexander Schleicher , or the types Quintus , Arcus , Duo Discus , Ventus 2 and Discus 2 from the competitor Schempp-Hirth .

Alternative principles

Stemme S10 with the propeller gap open in powered flight

The Stemme S10 uses a different principle, here a mid-engine drives a two-bladed propeller in the nose of the fuselage via a remote shaft. If this is not running, the propeller blades are folded in and the propeller gap is closed. Turbines are also occasionally used, for example in the Jonker JS1 , Schempp-Hirth offers a system called FES (“Front Electric Sustainer”) with an electric motor for the Discus type, in which the propeller is folded onto the hull when not in use.

Problems

Due to an accumulation of accidents during the operation of gliders with retractable engines registered in Germany, the Federal Bureau of Aircraft Accident Investigation (BFU) issued a corresponding information letter; According to the BFU, the reason for the increase in accidents is that if the engine does not work, "it makes the situation from which it was supposed to help more difficult". According to the BFU, there were 103 accidents with such aircraft from 2005 to 2012, in which the engine did not work as expected in 30 incidents and a decision to land outside was made too late.

Individual evidence

  1. ^ Long-distance shafts - propellers - mid-engine. Stemme, accessed on May 10, 2019 .
  2. ↑ Jonkers JS1 - drive. Jonker Sailplanes, accessed October 4, 2016 .
  3. ↑ Discus 2c FES. In: schempp-hirth.com. Schempp-Hirth, accessed on May 10, 2019 .
  4. ↑ Risk of a retractable engine? (PDF) In: Federal Office for Aircraft Accident Investigation. May 2012, accessed October 4, 2016 .