Wednesday, February 10, 2010

History gliders (or sailplanes) in 3 pictures. Most distinctive evolution: launching method.

Picture 1. Around 1930. Launching glider with bungees. Two groups of 3 or 4 people pull the glider with 2 bungees from the top of a gently sloping hill.
Picture 2. Year 2005. Launching glider with a winch. The winch pulls the glider with a 1.000 to 1.600 meter cable to height of about 400 to 700 meter.
Picture 3. Year 2009. Launching glider with self-launching engine.

The history of gliders (or sailplanes) and gliding is old. In 1902 the Wright brothers build for the first time a working, true three-axis control. With this glider combined with an engine and propellers they were able to make the first sustained flight with a powered, controlled aircraft. Let's concentrate on gliding as a sport in which pilots fly unpowered aircraft.

What is the most distinctive evolution in the history of gliding as a sport? 
  • You: Glider? JeanD99: Don't look at the airplane. Since 1902 the distance that a glider can fly for each meter it descends is increased up 70:1 - this is the lift-to-drag ratio (L/D) - but gravity is a relentless force because sink is sink for every bird in the sky.
  • You: Skids, wheels, wheelbrakes or withdrawn wheels? JeanD99: I don't think so. The evolution of wheels made the landing easier during history but a landing is still a landing.
  • You: Pilots? Glider-instructors? Training? JeanD99:  Until the 1930's the pilot sat alone in the glider. Once in the sky he/ she was alone with all his/ her happiness, dreams, tears and fears. Making good or bad decisions without someone who could intervene. Later on dual-gliders were developed and training produced better skilled pilots but this didn't change the two critical moments in every flight: its beginning and its end.
  • You: Instrumentation and other technical aids? JeanD99: The first gliders didn't have any instrument at all! They only had three-axis control. Altimeter, airspeed indicator, compass, variometer (measures climb or sink rate of the plane), turn and bank indicator, MacCready ring (indicator for optimal flying for given conditions),  computer with GPS technology (provide the glider's position in 3 dimensions by a moving map display), FLARM (anti-collision device), transponder (help air traffic controllers and other airplanes to identify the aircraft and to maintain separation) etcetera they are a great help for flying long distances. But it's still flying.
  • You: Discovery of the sources of rising air? JeanD99: Gliders can stay for hours airborne if and only if they find sufficient rising air. Most commonly used sources: ridge lift (first used by Klemperer in 1921), thermals (Kronfeld in 1928) and wave lift (Hirth in 1933). This is not the distinctive I'm pointing at.
The most distinctive evolution in the history of gliding as a sport is: 'launching'. The method of launching implies the business on the ground. It implies how many man are involved on the ground. In the first phase, gliders were launched with 2 bungees from the top of a gently sloping hill. A minimum of 7 people (6 pulling and 1 instructor) were involved.
In the second phase, starting somewhere after World War II, gliders are launched with a winch. The winch pulls the glider with a 1.000 to 1.600 meter cable to height of about 400 to 700 meter. This method needs a long airfield and a minimum groundcrew of 5. This phase is still the mainstraim method in presentday sportgliding worldwide. It's a relative cheap method of launching. 

Since a few years we entered, with the self-launching gliders, the third phase. It's an evolution which will have huge impact on the groundcrew and the gliderclubs. In presentday gliding with it's mainstream winch-launching most members on a gliderclub devote whole days around the airfield: flying a few times and most of the day helping out other members of the club. If you scratch my back I'll scratch yours. The self-launching gliders makes it possible to start alone and come back anytime the pilot(s) wants. The need to land the glider not on the homebase ('land out') is largely decreased. This method needs a minimum groundcrew of 1.

And the future? I guess more training on the ground in glider-simulators and more technological improvements: auto-starting, auto-flying and auto-landing.

Picture 4. Launching glider via aerotowing by engined aircraft.

Footnote. You: What about launching a glider via aerotowing by another engined aircraft? JeanD99: This method is being used commonly since the 1940's. This method is relative expensive and not mainstream in the world of gliding.

No comments:

Post a Comment