Flight, February 1932
GERMAN AIR UNION'S TWO STANDARD PLANES FOR HOME CONSTRUCTION
By EDWIN P. A. HEINZE
Handicapped by lack of funds, German light plane clubs have held, a competition for designs for machines suitable for construction by club members. Two such designs
have now been approved, and the machines are described below
THE German aviation clubs are handicapped compared with those of other nations by having to rely entirely on their own means for the acquirement of aircraft. Owing to the Peace Treaty, the German Government is not allowed to subsidise the clubs. This, naturally, is a heavy drawback to the whole movement, but it cannot quench the enthusiasm of German youth. For some years past now the German aviation clubs have successfully built their own gliders and sailplanes, and the experience in handicrafts thus obtained has encouraged the German Air Union, with which the majority of clubs are affiliated, to develop motor-driven machines, which the club members can build in their club workshops. Last year the Union held a design competition intended to develop a single-seater practice aircraft, and two of the most promising designs were adopted and have now been completed by the designers under the auspices of the Union. The trial machines were demonstrated for the first time at the Central Airport of Berlin before members of the Press on February 9, and created an exceedingly good impression. The designers are the well-known sailplane constructor Mayer, formerly assistant tutor at the Aachen College of Engineering (now tutor at the Stettin College of Engineering) and a group of students at the Berlin College of Engineering.
The plane designed by Mayer is a robust structure entirely built of wood. It is remarkable to note that both Mayer and the student group have selected as the most suitable type of machine a parasol monoplane with strut-braced wings. Whereas the Berlin student group, however, has designed a rather elegant machine of considerable aerodynamical merits requiring no little skill in the making, Mayer has purposely designed his plane along somewhat rougher lines, keeping in mind primarily ease of construction and avoiding all parts requiring particular skill or experience. The wing of his machine has the same section all through, so that a single jig will serve to construct all ribs. Also the wing has the same camber below as above, i.e., it is symmetrical, so that, incidentally this machine, given an engine of about 40 h.p., is fully capable of stunt flying, inverted flying, etc. The wing consists of two sections, which can be taken down and hung up on the side of the fuselage, where special fittings are provided for this purpose. Owing to the double camber, the wing is very stiff. It has one spar and, except for the trailing edge, it is covered with veneer, the trailing edge and ailerons being fabric covered.
Curious also is that both Mayer and the student group, working entirely independent of one another, have adopted almost exactly the same type of fuselage, which has hexagonal section, and is entirely made of wood. The hexagonal form is aerodynamically very good, as it gives the machines a slim shape. Also it offers good possibilities for fixing the under-carriage and empennage.
In point of appearance, the second plane, developed by the student group, is rather superior. As already indicated, the details of this machine are more finely worked out. It requires more care and skill to build, and is not quite so robust. The wing consists of three sections, the middle one being fixed over the fuselage, while the side portions are pivoted so that they can be swung back against the fuselage. The struts are of steel. To give the pilot a good view, the centre section has a shorter chord than the end sections, the reduction in lifting surface being compensated by an increased angle of incidence. The wings have two box spars, which are joined at their lower surface by plywood. The usual internal bracing is dispensed with, its place being taken by two simple box ribs in the end sections. For the rest, the wing has fabric skin.
The span of this machine, which has the same size and type of engine as the other, is 29 1/2 ft., and its lifting area 107.6 sq. ft. The weight only amounts to 407 lb. and, like the other machine, it will take a load of 220 lb., including 33 lb. of fuel and a parachute.
Performance figures have not yet been ascertained, because neither of these machines has yet completed the official tests. On a fair estimate, however, the speed of Mayer's plane amounts to about 72 m.p.h. and that of the student group to 78 m.p.h. with the small engines now fitted. The machines are, in the first place, intended for practice flights over the home ports of the clubs, and, therefore, high speed is not essential. Two-seater planes for home construction are soon to be developed by the German Air Union, too, so that clubs will at no distant date be able to come cheaply in possession of badly-needed aircraft.