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Aviation History
1937
1937 - 0620.PDF
FLIGHT. MARCH II, T^ Two-Speed Gears and V.P. Airscrews IN a De Havilland patent it is proposed to introduce a two-speed or even a vari able-speed gearing between the engine and a v.p. airscrew. In the example in the specification a two-speed gear is employed and either one or other of the gears is engaged by the movement of a clutch member in one direc tion or the other. When a variable-speed gear is used it may be controlled by means connected to the blade-pitch adjustment so that the pitch of the airscrew blades and the speed of the engine are simultaneously adjusted and the best combination always obtained.—Patent No. 454983: Geoffrey de Havitland and The De Havilland Aircraft Company, Ltd. Cooling PATENT No. 454664 deals with the air cooling of engines housed in wing nacelles. Air inlets are provided in the leading edges of the wings and air is led from these inlets by a conduit forward to the engine compartment, after which it passes out through suitable openings in the sides. The air inlets in the wings are so situ ated as to utilise the airscrew as a cool ing fan. They may also be arranged so that the inflow of air is greatest when the machine is climbing, and therefore when the greatest cooling effect is required. The size of the air inlets may be varied at will to control the degree of cooling.—Patent No. 454664: Geoffrey de Havilland and The De Havilland Aircraft Co., Ltd. Shock-Absorber Struts ASHOCK-ABSORBING strut, patented by G. H. Dowty, is composed of two telescoping tubes, one of which (A) slides in the second one (B). A spring (C), mounted in the longer tube (B), abuts against the closed end (D) of the smaller tube (A) and forms the resilient element ol the strut. A closed chamber (E) of some length is formed in the end of the smaller tube (A), bounded at each end of two pack tug glands and this space is filled with liquid. Through this space a hollow tube (F) passes, which is attached to the outer telescopic tube and which carries a fixed piston (G) which works up and down in the liquid-filled space between the two packing glands. Restricted passages are formed in this pis ton, and the liquid has to flow through these when relative move ment between the two main tubes takes place. On one direction oi motion the restricted apertures are closed to give increased damping, the liquid then passing from one side of the piston to the other through holes (H) lead ing to the interior ol this central tube. The novel feature ol the patent is the method of damping used, which can be in corporated in a strut in a simple and economical manner, the whole strut being easily formed in the under carriage structure.— Patent No. 455719: G. H. Dowty. The Dowty strut described in patent No- 455719- Com pactness is one of the outstanding features O The TREND of INVENTION Recent Aeronautical Patents Reviewed \ Geodetic Construction THE present patent is associated with two earlier patents (Nos. 388438 and 412232), both of which relate to Vickers' geo detic construction. This system, as many readers of Flight are aware, consists of longi tudinal members which may form the wing spars, or the longitudinal main frame of a fuselage, in conjunction with two series of bracing members which connect the longi tudinal members and which lie in geodetic lines on the surface of the wing or fuselage structure. These two series of bracing members in tersect each other and are deeper than they are wide and are so curved that their depth is always normal to the surface of the struc ture they form. When they are in this form the twisting and lateral forces produce com pression in one set of members and tension in the other set. As they are rigidly attached at their points of intersection they balance the forces set up by the loading. The present patent is particularly con cerned with the method of securing the members at their points of intersection, gus set plates and angle pieces being used. The method adopted makes the geodetic mem bers continuous between the longitudinals and they are so recessed that they fit into each other and are attached in the manner outlined above.—Patent No. 452726: Vickers (Aviation), Ltd., and B. N. Wallis. Jettisoning Fuel ASHORT BROS, patent covers a jettison valve designed for the rapid discharge of fuel from a tank which cannot, by reason of its position, be emptied by open ing a discharge valve in the tank itself. Bolted to an opening in the tank is the upper end of an outlet pipe, the lower end of which is attached, by means of a hose, to a second outlet pipe which extends ver tically downwards to an opening in the side of the fuselage or wing of the aircraft. On the flange by which the first outlet pipe is attached to the tank a mushroom valve is seated on special packings and the stem of the valve passes through the side of the pipe, which is suitably bent to make this possible, and the valve is opened by a hand wheel and screw gear. In the closed position the pressure of the fuel in the tank assists in effecting a seal.—Patent No. 454820: Short Bros. (Rochester and Bedford), Ltd., and A. Gouge. Flap Load Adjustment I N addition to providing for the hydraulic control of the flaps by the pilot, patent No. 546863 provides means for their auto matic adjustment in accordance with the aerodynamic pressure of the flaps them selves, and therefore according to the speed of the aircraft. This is effected by including in the control system a sealed air chamber which is separated from the operating liquid by a floating piston. The pressure in the air chamber is such that at a given speed of the aircraft the flaps are capable of mov ing into a neutrai position, thus further compressing the air in the chamber, and the energy thus stored returns them to an nn«, tive position when the speed decrea^T Thus, with the aircraft stationary thev^n be set to their maximum displacement TZ as the speed increases so the flam gradually retracted, their position at ^ times being automatically adjusted to th flying conditions at any instant. An alternative method of obtaining ami],, results was described in an earlier nater,? No. 454490.' granted to the same firm but in this earlier method a source of com pressed air was essential, whereas ttY necessity is eliminated in the later scheme - Patent No. 456863: Societe d'Inventions Aeronauttques et Mechaniques. Tail-wheel Mounting ATAIL wheel is mounted in such a way that it is capable of pivoting about an axis whicn is inclined in a'direc tion forward of the vertical, while the main axis of the shock-absorber unit, to which it is attached, is upwardly inclined in the opposite direction, that is, towards the rear In an arrangement of this type the shock- absorber unit takes up the bending and twisting forces and, with the rearward in clination ol the shock-absorber unit, the direction of yielding falls better in the'direc- tion of the shock forces applied to the tail wheel. If with this arrangement the tail wheel pivots about the same axis as the shock absorber, certain disadvantages arise, among which is the fact that the middle position of the tail wheel is unstable. These drawbacks are removed if the axis of rota tion for the tail wheel is inclined slightly forward from the vertical.—Patent No. 454198: Electronmctall G.m.b.H. Undercarriage Retraction T HE object of a forward-retracting under carriage patented by G. H. Dowty is to provide a construction which is easy to install and which will contribute to the general structural strength of adjacent parts without adding substantially to the weight. The accompanying illustration shows that it incorporates one or more shock-absorber struts A and a radius rod B. The top of the strut is attached to a collar C which forms the end of the jack plunger D. This plunger, in addition to sliding in the outer tube of the jack, also slides on a fixed in ternal stem E which is attached to some structural member of the aircraft. At the other end this stem E, which is rigid with the jack cylinder, is attached to some other fixed part F, thus forming a substantial in terconnecting beam between two members of the wing structure. To the part F the radius arm is also pivoted. Movement of the ram of the jack causes retraction to take place in the manner shown. Other forms of construction are shown for rearward retraction, and also for a two-jack forward retraction. In these arrangement- the jack is rigidly supported against loan? due to compression or tension in the radius rod at all points during retraction. It can also form a structural part of the aircraft —Patent No. 455384: G. H. Dowtv. Details of the Dowty retractable undercarriage dealt with in above.
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