The Planes

There are no towplanes in Bitterwasser, so all planes are self-launching motorgliders.

Most gliders here are state-of-the art Open Class two seaters. Many of them EB 28 and EB 29 with spans of 28 meters and sometimes even more. As graceful as they are in the air, they are a bear to handle on the ground. Fortunately, the people who planted the first palms 40 years ago were forward thinking and spaced them far enough apart, so the big wing gliders can manouver in the alleys of palm trees. However, there is not much space from the wingtips to the trees. 

The latest and greatest is a brand new ASH 30 which is the successor of the ASH 25. I had a good discussion with the lead designer, Martin Heide (the "H") about the performance goals and handling characteristics they were trying to achieve.

I am surprised to see so many Open Class ships at a place with such strong weather like this. These gliders really excel in weak and moderate conditions where their best L/D of 60+ helps them to minimize thermalling. In conditions where inter-thermal speeds are 110 kts+, less wing and high wing-loading bring the advantage.

The ultimate set-up: One of the big Open Class ships. Note the six wing stands and two double wing wheels. Behind the plane is the owner's Biwa home with the perfect tow vehicle for Africa in the driveway.

We rented an Arcus E, a 20m (span) two seater - the E stands for electric self-launcher. This proved to be an excellent choice. The electric propulsion system is much simpler to operate than an engine. The only control elements for the system is a power lever, like a throttle and a switch to change control between front and back seat. If the motor is needed during flight, all one needs to do is push the power lever all the way forward. The propeller mast will extend within seconds and the motor will spool up to full power. With a conventional self launcher the sequence would be, open fuel valve, extend propeller, turn on ignition, set throttle and possibly choke, push starter - hope that it will fire, warm-up, apply power.

In order to shut down and stow the motor, one just pulls the power leaver all the way back. The motor/propeller stops, the propeller automatically lines up vertically and the whole thing retracts. No cool down, no fiddling with a propeller brake, etc. The only drawback is the limited capacity and the weight of the batteries.

The weight of the batteries in the wings, together with my brother's and my weights with chutes brings us to max gross weight of 810 kg and a wingloading of over 50 kg/sqm. There is no need to put in water but of course, also no ballast we can dump when things get weak. So far, this has not been a problem. Even at max gross weight, the Arcus feels light and nimble on the controls even in tight and lumpy thermals. We typically climb away from 800 - 1000 ft in the morning (winch launch height) to conserve battery capacity. It is amazing how this ship runs. Inter-thermal speed at McReady 4kts is over 100 kts which translates at the altitudes we fly at into a ground speed of 210 - 225 kph.

A few days ago, I had the opportunity to fly back seat in a Nimbus 4DM. It was an older glider with 25m span. I didn't see much of an advantage in the climb, actually I found it hard to roll this big ship into tight thermals but it was clearly slower on the run than the Arcus.