M.Simons The World's Vintage Sailplanes 1908-45
THE HUETTER H-28
Continuing their development of small sailplanes. Wolfgang and Ulrich Huetter after the H-17, went on to produce the H-28, a high performance type. To cut down the length of each member for building in small workshops, the ДальшеMore>>>
fuselage centre section was made 1.32 metres wide, which also permitted a carefully constructed wing root junction and fairing. Each wing was thus 5.3 metres long. On the prototype the wing was straight, but the centre section was inclined at an angle so that when the wings were in place a ‘gull’ bend appeared near the root, without the usual complications of building a curved mainspar. Otherwise the wing structure was orthodox, rigged by means of two horizontal pins, at top and bottom of the main spar, with a third pin at the rear drag attachment. Aileron connection was automatic. The aerofoil used was the Goettingen 535, but slightly thinned, and tapering at the tip to a symmetrical profile.
The cockpit was not large but was carefully laid out, with a parachute box, space on the panel for four or five instruments, and a retractable venturi to provide suction power to drive a turn-and-slip indicator for cloud flying. An outstanding feature was the one-piece, moulded plastic cockpit canopy, one of the first ever produced. It was specially made at Darmstadt, which had then, as now, an important plastics research department in the Technical University.
The tail unit was so small that the tailplane was hardly wider than the fuselage centre section, so it was normally left in place during road transport.
Test flights were successful. The glide polar was measured and the maximum glide ratio was found to be 23.4, which occurred at about 80 km/h. Although the 28 in the name stood for the expected glide ratio, it was not altered after the flight tests.
The Huetters marketed plans, as they had for the H-17 and several more Huetter 28s were built. These all had ‘gull’ wings. Two of these were German and three others were built in Denmark. One competed in the Swiss championships and remained in service for many years, appearing at the vintage rally on the Wasserkuppe in 1974, flown expertly by its owner, Herr Aeberli.
The Huetter 28/3 was designed later and one was built. It had a span of 13.5 metres and a longer fuselage. The old-fashioned Goettingen 535 aerofoil was replaced by one calculated according to the Joukowsky formula. The glide ratio was improved to 27.2, which closely approached the intended figure. The type was not marketed.
Two H-28s survive, one in Switzerland and one in the USA.
Technical data:
H-28: Span, 12 m. Wing area, 7.6 sq m. Aspect ratio, 18.46. Empty weight, 88 kg. Flying weight, 178 kg. Wing loading, 23 kg/sq m. Aerofoil, Goettingen 535 modified with symmetrical tip. Best glide ratio. 1 : 23.4 at 90 km/h. Minimum sink speed, 0.86 m/sec at 70 km/h.
The surviving airworthy Huetter 28, flown here by its owner, Eugen Aeberli, at the Wasserkuppe vintage rally in 1974. Since the Huetter design was later developed into the H-30, and then a glass-reinforced plastic version which led to the H-301 Libelle 15-metre sailplane, the H-28 may be regarded as the direct ancestor of one of the most successful glass-fibre sailplanes of modern times.
The Swiss Huetter 28, HB-223, in an early paint scheme.
The surviving H-28 in 1974. All H-28s except the prototype were built with curved spars to give the fashionable ‘gull wing' shape. The drawing shows the prototype in straight-winged form.
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