Ulrich Schäfer, now employed at the Fachhochschule Aachen (working with Professor Röger, well-known for his research in glider rescue and crash safety), still plans to continue his work by designing a high-performance 'Horten'-like motorglider. Although the little 'Aachen' has not been flown for some time, the flight testing of this flying wing produced some interesting information about this category of aircraft.

Ulrich Schäfer learnt about the design theory of flying wings by corresponding with Reimar Horten for eight years before Horten's death in 1993, and a visit to Argentina completed his knowledge of the Horten design philosophy. During this visit, Reimar Horten assisted the 'Project Aachen' design by giving a lot of helpful advice. Christiani Wassertechnik, a factory which had built a reputation for making water-cleaning devices, enabled Schäfer to build the proof-of-concept prototype called Project 'Aachen'. This prototype made its successful maiden flight in early 1995.

The Aachen is conventionally designed around a swept-back wooden wing featuring a Schäfer-designed airfoil and a steel tube centre section. The lift distribution over the span follows the Horten 'bell' theory of predominantly producing lift in the centre section and nearly no lift at the wingtips. Ailerons and elevator are combined in the 'elevons', and instead of the old Horten wingtip airbrakes, two small differential operating rudders are mounted on the wings, just in front of the elevons. Their movement out towards the wingtip is greater than towards the centre, and this gives an extra 'braking moment' supporting the steering moment. In spite of being a prototype and a microlight, the whole aircraft makes a perfect, robust impression and shows excellent craftsmanship. The fixed tricycle undercarriage consists of a GRP-covered steel tube frame with two main wheels equipped with brakes, and a steerable front wheel, operated by direct connection to the rudder pedals. The cockpit is built from steel tubes and is GRP-covered, and a BRS aircraft rescue system is fitted to the bottom of the centre section.

A 36hp two-cylinder two-stroke Göbler-Hirth engine, situated just behind the pilot, powers the Aachen. This engine is equipped with double ignition and drives the four-blade folding prop via belt reduction. However, this fuselage section has not been optimised for performance, as the designer did not want to build a fast racer, but rather a safe and easy-to-maintain test platform.

Entering the cockpit is easy via a black wing root walk-way. The seat originates from a microlight and also acts as the fuel tank for 25 litres of two-stroke fuel, while the four-point harness is from a sports car and has the shoulder belts permanently connected to the lower belts on each side. They hold you comfortably in the seat, but it is difficult to strap them on without help in the narrow cockpit.

Inside the cockpit, it feels like a normal motorglider, although there are some significant differences. For example, the ailerons do not move if the stick is fully back, and the stick does not go fully back if aileron is applied. These two points remind you of the fact that you are sitting in an 'elevon-controlled' flying wing. Due to the pilot's high position and the big canopy, the view from the cockpit is excellent except in a downward direction, as you are sitting above the wing.

The little Göbler-Hirth engine starts well and runs very smoothly and quietly. Taxying is easy with the steerable front wheel and the good suspension and damping characteristics of the undercarriage give a comfortable ride on the ground. Unfortunately, the bicycle-type wheel brake lever is hidden in front of the throttle and is difficult to reach. The elevator trim is distinctly prototype-like: the elevator bar is pulled up by a rubber-cable connected to a small metal chain which can be fixed in different positions on the instrument panel! The 'zero'-position for take-off is reached when both elevons are being pulled up about an inch-and-a-half above the trailing edge. During flight, the elevons also remain 'up' this is a small correction to the original Horten flying wing theory as to how much wash-out is needed. After magneto check, engine check, fuel pump on, and pulling out the safety pin of the BRS, the Aachen is ready for take-off.

Acceleration is good and the ground run very stable. It is not possible to lift the front wheel until the airspeed is a little above minimum flying speed. From smooth runways, the wing reaches its element by doing a little 'jump', the angle of attack on the ground seems a little too low to reach the shortest possible ground run. On rough ground, the take-off run is shorter. A good speed for the climb is 43-45 knots, with the variometer indicating around 500ft/min. The longitudinal stability at all speeds is good and well damped, although the feeling when flying through turbulence and thermals is unusual. First the nose rises, then the rest comes up. Just imagine that you are sitting in a small boat and going against the waves on the sea, and you have got the feeling! Some pilots try to correct these movements using the elevator, and although this is possible, I think it is rather pointless. Why apply two drag-producing elevator movements (down and up) if ultimately none is needed?

The Aachen is certainly not over-powered, but it is well-balanced. Indeed, changing the power setting causes no changes in the trimmed speed. For example, if the stick is free the addition of power simply causes the Aachen to climb at the trimmed speed. Unfortunately, with the (not optimised) propeller used during the test flights, the maximum cruise speed is only around 60 knots. Some modifications, specifically to the propeller, should help to make the Wing a bit faster.

From a handling perspective, the stick and rudder are well co-ordinated, with light operating loads and a responsive feeling. Rolling using full rudder and aileron shows almost no tendency to sideslip. When circling, a little bit of opposite aileron (against the turning direction) is needed. Changing from 45° to 45° needs about 5.5 seconds at 45 knots. While this is not too bad when compared with many microlights, it is rather slow for a 13.5m glider. This, and the fact that the elevator is full up at 45° bank and 45 knots, may be improved by increasing the washout of the outer wing section. Only applying aileron causes the Aachen to turn 10°-15° in the opposite direction: this adverse yaw is caused by the aileron drag. When the intended bank angle is reached, the Aachen soon starts circling without further sideslip and also without use of the rudder. Turning her with the rudder only is also possible the swept-back wing banks the aircraft without problems. Sideslipping is possible with about 20°-25° and nearly no bank, but it is completely ineffective as there is no significant fuselage surface to disturb the airflow over the wing. Seen from the ground, this looks very odd. From the pilot's viewpoint it makes sense, allowing landings even in strong crosswind conditions.

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