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Aviation History
1923
1923 - 0020.PDF
IT* JANUARY II, 1923 and sprockets. The leading edge of the aileron is a rectangular section Duralumin tube. The wing bracing of the Hanriot " H.26 " is unusual, inasmuch as it does not incorporate any struts, although the wings are not entirely cantilever beams on account of a single lift wire, running from the rear strut of the under- carriage to the top plane, passing en route to a fitting over the lower plane main spar. Both this fitting and the corres- ponding one on the top plane are of sheet metal: It is stated that the factor of safety on the wings is 12, loaded in the normal way. As regards torsional stresses and down loads such as may occur during a nose drive, the factor of safety may be considerably smaller, although this form of construc- tion, with but single spars, has been used on the Hanriot " H.D.15 " with, so far as we are aware, good results. That machine had, however, interplane struts to assist in resisting torsional stresses. To a certain extent, the fact that leading edge and false rear spar are secured to the fuselage should help matters, although, in view of the relatively small width of the fuselage, these points lie fairly close together and a long way from the wing tips. In pure bending, there is little m m B m m H H H E H El El H El El H El F. KOOLHOVEN, ROTTERDAM AFTER having been away from active participation in aircraft construction for several years, Mr. F. Koolhoven made his re-entry into aviation at the Paris Salon with a small parasol monoplane two-seater fighter, the " F.K.31." Having succeeded in forming a company in Holland, known as the N. V. Nationale Vliegtuig Industrie, of Rotterdam, one of the directors of which is Colonel Wallaardt Sacre, who built-up and was head of the Dutch Air Service, Mr. Kool- hoven had but a few weeks in which to build his machine, and even then strikes in certain departments delayed matters considerably. Consequently, the finish of the " F.K.31 " was not all that it might have been, but when one is told that the machine was built in three weeks, the lack of finish may easily be forgiven. The "F.K.31," as already stated, is a parasol monoplane two-seater fighter, the chief object of the designer having been to obtain a good view and a free field of fire for both pilot and observer, as well as great manoeuvrability. The former has resulted in the choice of the parasol monoplane design, and the latter in a high-lift wing-section, giving a The Hanriot school machine, type H.14. El El H, El El El H doubt that the wings are amply strong, and it appears probable that the figure 12, given as the factor of safety, relates to pure fbending only. The undercarriage, also a Duralumin structure, is of some- what unusual design, inasmuch as there is a set of struts forming a letter N in side view, linking the lower portion of the undercarriage to the fuselage. These " N's," however, are reinforced by a single strut on each side, running from the shock-absorber attachments to the main spar of the top plane, at the point where this is attached to the fuselage. It will thus be seen that the long single struts do not lie in the same plane as that of the " N " struts, and a form of triangulation, as seen in front view, is obtained. This accounts for the fact that there is no transverse wire bracing in the undercarriage. A small wing section encloses the transverse tubes and axle of the chassis. The axle does not run right through, but is divided, a short length of fixed tube resting inside the fairing, with two short axles hinged to its ends. From the axle hinges wires run to the fuselage fitting on the lower longeron, at the point where the lower plane front spar is attached. Whatever one may think of the design of the Hanriot " H.26," especially as regards its wing structure, the work- manship is excellent, and the finish, made complete by some form of spraying with metal, above even the high average French standard. The main characteristics of the Hanriot " H.26 " are :— Length b.a., 7 -35 ms. (24 ft. 2 ins.) ; span, 9 ms. (29 ft. 6 ins.); height, 2 -5 ms. (8 ft. 3 ins.) ; wing area, 18 sq. ms. (194 sq. ft.) ; weight, empty, 820 kgs. (1,800 lbs.) ; weight of fuel (3 hrs.), 180 kgs. (396 lbs.) ; useful load, 80 kgs. (176 lbs.) ; total loaded weight, 1,080 kgs. (2,372 lbs.) ; power loading, 9-14 lb./h:p. ; wing loading, 12-25 lb./sq. ft. Estimated performance: Maximum speed near ground, 260 kms. (161 miles) per hour ; speed at 2,000 ms. 255 kms. (158 miles) per hour; ceiling, 8,500 ms. (28,000 ft.). small overall size without unduly putting up the landing speed. In the machine exhibited, the fuselage was of metal con- struction, while the wing was of wood. In future editions, however, we understand*that probably the wing also will be of metal construction. The fuselage, which is of ap- proximately rectangular section, although slightly rounded, is built-up of steel tubes, braced by tie-rods. From an external view, it might be concluded that the main fuselage structure is very deep. This is not, however, the case, as much of the depth is made up of light stringers and formers, placed outside the main framework. The rear portion of the fuselage is covered with fabric, while in front the covering is in the form of aluminium sheet, the attachment of which to the fuselage structure is by a few bolts, the heads of which are of streamline shape and form handles. By undoing a few of these, the entire covering on both sides of the front portion can be removed, exposing the internal framework for inspection or overhaul. The operation of removing the covering occupies but a few minutes. The pilot's cockpit is in front, and access to it is gained by removing a sliding panel on the side of the fuselage. A circular opening in the wing enables the pilot to look either over or under the plane, the central portion of which is thinned down for the purpose. Immediately behind the pilot's cockpit is that of the observer or gunner. This cockpit is divided into two separate compartments, one of - which contains the gunner's seat, gun mounting, etc, while the other accommodates the wireless, photographic apparatus, etc. The gun mounting is unusual, and incorporates a sloping telescopic tube, with a spring which just balances the weight of the guns. By releasing a catch, the guns can be swung rapidly in any direction, elevated or depressed, and this with a minimum of exertion on the part of the gunner. As the trailing edge of the wing is cut away in the centre, the gunner obtains a particularly free field of vision, 20
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