Weltensegler Feldberg
Страна: Германия
Год: 1921

M.Simons The World's Vintage Sailplanes 1908-45

M.Simons The World's Vintage Sailplanes 1908-45


  Friedrich Wenk had experimented with tailless models since he was sixteen and had discovered the secret of stability for such aircraft; a sweptback wing and a centre of gravity positioned well forward. During the First World War he made friends with Fritz Peschkes, a pilot. In peacetime, nearly penniless, they joined forces to build a tailless glider which Peschkes flew over the slopes of the Feldberg in 1920. He crashed, but the resulting publicity attracted the attention of Alexander Steinmetz, a prosperous businessman who formed the Weltensegler Company, with Wenk and Peschkes as chief designer and test pilot respectively. This ‘World-sailer’ firm was the first commercial venture of its kind to appear on the gliding scene. Workshops were established in Baden Baden and in 1921 they set up a large shed and dormitory on the Wasserkuppe in time for the second Rhoen contest.
  Wenk’s new design was a 16 metre span, tailless glider quite unlike anything else that had been seen. Apart from the lack of a tail, the Weltensegler had other unusual features. The wing was given pronounced dihedral over the inner portions and anhedral toward the tips. This was the origin of the cranked or ‘gull-winged’ form that later became very fashionable. In Wenk’s glider, the outer parts of the wing were supposed to act both as controls and as stabilisers, but at the same time were intended to flex in response to wind gusts, to give some dynamic propulsion and extra lift. They had a marked twist almost like propeller blades and were swept back like the outer feathers of a bird’s wing. A kind of derrick mast stuck out at an oblique angle from the bridge-like structure below the main wing, and this was attached to the leading edge of the outer, flexible tip section, about half way along its length. The idea was that a gust of wind would twist the flimsy tip ‘feathers’ to a different angle of attack, then they would return to their normal trailing position, imparting a little of the gust energy to the glider as they did so. Springs were placed so as to return them to normal.
  The usual control system for aircraft of this period was to have a continuous loop of cable over pulleys, with tensioning turnbuckles to take up any slack. For Wenk’s tailless glider this would not do. Not only did he want the ailerons to act as elevators, but also had this notion of extracting gust energy, to do which it was thought necessary for the wing tip ‘feathers’ to move independently, not only of one another, but independently of the pilot too. to some extent. Instead of a continuous loop, Wenk provided the pilot with only one cable, running to the warping wingtip. Thus, the pilot could warp one wingtip down on one side, while the other floated more or less freely. This would tum the glider. Or he could pull both down together, pitching the nose down. If he relaxed all pressures, the control surfaces would float to a position controlled only by the springs and the local direction of the airflow, for the Weltensegler was trimmed to fly stably in this configuration.
  The wing was braced by a complex but extremely light truss structure underneath, and the pilot was housed in a flimsy, streamlined gondola under the centre section. The Weltensegler was very large for its time, but astonishingly light, weighing only 45 kg without pilot.
  On 14th August 1921 it was brought out of the workshops and taken to the western slopes of the mountain. A breeze was blowing up the slope and it was hoped that someone would manage an extended soaring flight. No-one had done it before, except the Wrights at Kitty Hawk. Peter Riedel, one of the spectators, had noticed already that the control system relied on spring tension and wondered what would happen if the springs proved inadequate to restore the very flexible vanes to neutral against the pressure of the airflow. His friend, an admirer of Wenk, assured him that the designer would have allowed for that. A few minutes later Riedel was to see his fears justified. Wenk's pilot was Willy Leusch, and the method of launching him was unusual. Four men of the Weltensegler team grasped the under-wing strutwork, lifted the glider, pilot and all, bodily into the air, holding it there momentarily with the wind blowing over the wings already supporting the weight. It was poised for all the world like a big model glider being hand launched. The crew gave an extra push and the Weltensegler was suddenly flying gracefully forward over the slope, and began to ascend. The watchers were utterly amazed to see the great white, tailless, bird-like sailplane rising higher and higher as it floated out over the valley, until it reached a height of about 80 metres above the start, much higher over the sloping ground in front of them. Wenk was congratulated on the proof of his theories as his creation gained altitude. Then, at a considerable height, the Weltensegler turned to the left and entered a spiral, picking up speed. No-one really knows what happened next. If Leusch pulled the stick hard back, the cables simply went slack and only the airflow and the feeble springs of the system were capable of restoring the control surfaces to the neutral position. They obviously failed to do so because now the airspeed was dangerously higher and probably the whole light wing structure was twisting and perhaps even fluttering. The dive became steeper and steeper, and then with a loud crack the wing broke. The little gondola fell like a stone to the ground, with the wings trailing like two long white banners attached to it. Joy turned to horror, for there was no chance that Leusch could have survived. What might have been the first long soaring flight by a sailplane had ended in tragedy.
  Just as in the previous Wasserkuppe meeting, after an unpromising start, the first hopeful flight had resulted in a fatal accident. It seems surprising that the enthusiasts persisted at all, but persist they did. Many people never forgot the sight of the Weltensegler's ascent. It haunted and fascinated them. Alexander Lippisch in particular was greatly impressed by the Wenk designs, and pursued research into tailless gliders and aeroplanes for many years, with increasing success. When, in the early thirties, Wolf Hirth wanted a new, stable sailplane, he called Wenk in to design the wing for him. The result was the Moazagotl, which had sharply swept back outer wing panels and a cranked ‘gull' wing like the ill-fated Weltensegler. It also had a tail, and orthodox ailerons.
The Rhon Soaring Competition: View of the "Weltensegler" (world-soarer) in flight. A few minutes after this photograph was taken the machine did a righthand turn, got into a nose-dive, and crashed, the pilot (Willy Leusch) dying from his injuries later.
The Weltensegler preparing to take off. The flag indicates a steady breeze blowing up the slope. The cumulus clouds, hardly understood in 1921, indicated that there was strong convective activity. It is generally believed now that Leusch was launched straight into a thermal which reinforced the slope lift and helped him to gain height rapidly. The upper surfaces of the Weltensegler were decorated with a design apparently intended to represent a moth or butterfly wing, the dark spot visible on the outer wing being part of this design.
Another photograph of Leusch preparing to enter the gondola of the Weltensegler, with members of the factory team standing by ready to throw him into the air.
The Rhon Soaring Competition: The series machine of the Segelflugzeug Werke Baden-Baden. Note the unusual arrangement of the wing-tips.