Hanriot HD.15

Flight, August 1922

THE HANRIOT TWO-SEATER FIGHTER, TYPE H. 15
An Interesting French All-Metal Machine

   AT the last Paris Aero Show there was exhibited on the Hanriot stand a very business-like racing monoplane, with cantilever wings, remarkable for its aerodynamic cleanness of design no less than on account of its all-metal construction. Certain of its details were not, perhaps, all that they might have been, but, generally speaking, the machine, which had been designed for last year's Coupe Deutsch, was one of very considerable interest. The racer was not finished in time to take part in the race, and we have not up to the present heard of it being tested in flight. However that may be, the Hanriot Works are carrying on with all-metal construction, and one of the latest to issue from the works for flying tests is the type H.15, for the illustrations and characteristics of which we are indebted to our excellent French contemporary L'Adronautique.
   Designed for the Section Technique, the Hanriot 15 is an all-metal two-seater fighter of unorthodox design. The power plant is a 300 h.p. Hispano-Suiza, and a Rateau supercharger is fitted, as the machine is intended to operate at great altitudes. As to how far the estimated performance will be realised, no information is as yet available. In the meantime, it is of interest to note that the calculated speed at the height at which the H.15 is intended to operate (23,000 ft.) is 143 m.p.h. The theoretical ceiling (on the assumption that the supercharger works perfectly) is 33,600 ft., and it is estimated that the climb to 23,000 ft. will be accomplished in 25 minutes. It will thus be seen that, assuming the estimated performance to be attained, the Hanriot 15 should be a very useful machine for military purposes.
   As regards general design and detail construction, the former is shown by the accompanying photograph to be a considerable departure from orthodox lines, with its very unusual wing bracing, while some of the wing details are shown in the sketches. The fuselage construction consists of tubular longerons with triangular bracing, also of tubular construction. The front portion of the fuselage is covered with aluminium, but fabric is used from the pilot's cockpit to the stern post.

Wing Construction

   Apart from the fact that it is fitted with a supercharger, the Hanriot 15 is chiefly interesting on account of the all-metal wing design, the fuselage construction showing fewer points of interest. From the accompanying sketches, it will be seen that each wing has one main spar only, but that this single spar is reinforced against torsion by two tubular auxiliary spars. The latter do not appear to be intended to take any part of the bending stresses. The main spar is of Duralumin, apparently of box section, terminating at the tip in a wooden end piece so as to avoid shaping the Duralumin box. The wing section is deep, so as to allow of a good spar depth, but apparently the wing does not taper either in chord or thickness. The auxiliary spars are in the form of Duralumin tubes, and bolted to them, and passing through the main spar, are the tubular compression struts of the internal drag bracing. The ribs are built up of Duralumin tubing, this material being used both for flanges and triangulated webs, as shown in the sketch.
   The wing bracing is unusual in that the single struts are arranged to act as lift and anti-lift members at the same time. From a short distance out on the lower plane a strut runs to the top longeron of the fuselage, while another strut slopes outward and upward to the top plane. The outer end of the lower plane is supported by a sloping strut running to the top centre section, crossing the lift strut en route. To reduce the bending moment on the fairly long bay in the top plane a wire is taken from the point where the main struts cross each other to the top spar, while from the same point on the struts an external drag wire runs to the nose of the fuselage.
   The incidence of the outer portion of the wings is adjusted by means of the members running from the auxiliary spars to the main struts, but, owing to the obliquity of these struts, it might be imagined that considerable stress would be put on the spars and ribs with travel of the centre of pressure.
   Contrasted with the tendency in British design towards a duplication of parts and relatively small factors of safety on each, the Hanriot wing bracing is interesting as an example of the opposite method : as few parts as possible, and these of necessity highly stressed. It would appear that a lucky shot in one of the main inter-plane struts might seriously endanger the strength of the wing structure, as might also a shot in one of the single main spars.
   The main characteristics of the Hanriot 15 are as follows :- Length o.a, 25 ft. 7 ins. Span, 35 ft. Wing area, 300 sq. ft. Height 9 ft 10 ins. Gap, 5 ft. 3 ins. Weight, empty, 2,300 lbs. Weight of fuel, 660 lbs. Useful load, 880 lbs. Total loaded weight, 3,840 lbs. Wing loading, 12-8 lbs./sq. ft. Power loading, 12-8 lbs./h.p. Speed at 23,000 ft. (estimated), 143 m.p.h. Climb to 23,000 ft. in 25 mins. Theoretical ceiling, 33,600 ft.