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364,065. Cooling Cylinders.. Fedden. A. H. R. and Bristol Aeroplane Co., Ltd., Filton House, Bristol. Sept. 30, 1930, No. 29337. [Class 7 (ii).]

WHEN I was honoured with an invitation to give a paper before this Fifth International Air Congress, I received also a letter from a member of the committee, who is a famous power in aviation in your country, asking if it would be possible for me to say something about air‐cooled compression ignition engines for aircraft, and whether they are likely to play an important part in the aircraft development of the near future.

An aircraft or other vehicle in which a stream of air taken in from the surrounding atmosphere is passed through a duct to cool the cooling surfaces placed therein of the engine and in which stream a conversion of energy into pressure takes place before the cooling surfaces arc reached and a conversion of pressure into kinetic energy of the stream at its discharge is raised by transferring to the stream waste heat from the engine at a position behind the cooling surfaces and before further loss of pressure is sustained beyond that involved in passing the stream over the cooling surfaces. The above means are adapted to assist propulsion. In one form, an engine a is mounted in a wing b. Engine radiators bl, b2 are mounted in ducts b3, b1 the leading edges of which are in front or behind the leading edge of the wing. Exhaust manifolds c, c1 are provided with fins c0 and are mounted in the ducts to heat the stream. Hinged flaps c3 are provided at the rear of the ducts. In a modification the duct is situated beneath an engine disposed at the front end of the fuselage and a fan forces air through the duct. The invention may be applied to air‐cooled engines. Specification 447,283 is referred to.

FROM the conventional wartime under‐carriage consisting of a straight through axle suspended on bracing struts by shock absorber cord has developed the complex modern undercarriage which is required to absorb the energy of descent, provide smooth taxying and the braking effort, and disappear when not in use. These requirements have brought in their trail a collection of hydraulic, pneumatic and electrical auxiliaries and a comprehensive treatment of the subject would assume some magnitude. This paper therefore summarises existing practice to some extent, and presents some notes on various design aspects which, it is hoped, will prove informative.

A gyroscopic control system for aeroplanes and other dirigible objects comprises (1) a pendulous gyroscope having its centre of gravity below the roll axis of the aeroplane, and comprising a frame 7, an outer gimbal ring 5 mounted to turn about the horizontal roll axis on the frame 7, an inner gimbal ring 3 mounted to turn about a normally vertical axis on the outer ring and a motor 1 mounted in the ring 3 to rotate about a normally horizontal spin axis normal to the roll axis; (2) means for operating ailerons in accordance with deviation of the ring 5 relative to the frame about the roll axis; (3) means operable, when the ring 3 precesses from a normal position, relatively to the outer ring 5, to apply, between the outer ring 5 and the frame 7, a torque of a corresponding sign to the relative movement between the rings in a direction to produce a counter‐precession of the inner ring and (4) restoring means for applying a torque between the rings 3, 5 when the inner ring processes relatively to the outer ring in the opposite direction to the direction of precession. The movement of the gyroscope and the angular momentum of its rotor are so related to the forward velocity of the aeroplane, that the gyroscope will, when the aeroplane moves on a curved path, precess in azimuth under the influence of centrifugal force at approximately the same angular velocity as the aeroplane is turning, to maintain the relative relationship between the gyroscope axis and the aeroplane. As shown, the frame 7 is pivoted in a frame 9 mounted on the aeroplane on the same roll axis as the ring 5 which carries a weight 10. (2) Relative movement between the ring 5 and the frame 7 operates due to relative movement between the gyroscope and aeroplane, through a link 21 connected to the ring 5, a piston valve 22 mounted on the frame 7 to supply compressed air to a servo‐motor 27, which operates the ailerons. A lever 29 pivoted on the aeroplane and having a bifurcated end which engages the ring 7 and which is connected to the piston‐rod 28 of the servo‐motor provides a follow‐up mechanism. (3) Relative movement between the rings 3, 5 operates through a link 14 connected to the ring 3 a piston valve 13 to cause a piston 18 mounted on the ring 5 and connected to the frame 7 by a link 19 to apply a torque reaction between the frame 7 and the ring 5 in such a sense as to oppose the gravity torque due to the pendulous weight to limit the relative azimuthal precession of the ring 3. (4) A spring 20 mounted on the ring 5 applies a restoring torque through the link 14 to the ring 3 to cause a precession of the ring 5 about its fore‐and‐aft roll axis and thus return the ring 5 and the weight 10 back to the vertical plane. The mechanism will cause an aeroplane to fly on a curved course without appreciable banking. The apparatus may be modified so that the aeroplane is banked to the appropriate extent in curved flight by providing a torque between the frame 7 and the ring 5 which is proportional to the angular velocity at which the aeroplane is turning.

Gases to be silenced are caused to partake of a whirling motion close to the inner surface and past the reticulations of the reticulated wall of a chamber arranged within an outer casing. Substantially the whole of the gases flow past the reticulations from a relatively restricted inlet to an outlet, and the whirling motion may be imparted by a deflector plate or curved vane or by a tangential inlet. A casing 1 has at one end a portion 50 terminating in a hemispherical cap 51 with inlet 54, and at the other end a plate 3 with eccentric outlet 5 and a pipe 9 attached thereto. The interior of portion 50 is separated from the interior of the rest of the casing by a plate 2 having an eccentric aperture 4 behind which is a deflector plate 10. Within the portion 50 are hollow conical frusta 52, 53 abutting at their larger ends. The small end of frustum 52 is connected to the inlet 54, while the small end of frustum 53 is connected to the aperture 4. Within the casing 1 are a pair of frustoconical chambers 6, 7 with reticulated walls, the smaller end of chamber (5 entering the larger end of chamber 7 eccentrically, and the smaller end of chamber 7 terminating in the outlet pipe 9. The deflector plate 10, adapted to whirl the gases, is located close to the wall of chamber 6 and comprises a portion 11 inclined to the longitudinal axis of the casing with an edge in contact with the internal surface of chamber 6, and a portion 12 arranged parallel to the axis of the chamber. A similar plate is located behind the entrance to chamber 7. The spaces between the frusta 52, 53 and the outer casing are filled with sound‐absorbing material 57 such as asbestos or coke, or, alternatively, sheet asbestos may be wound round the frusta. The space between the chambers 6, 7 and the casing serves as a cushioning space and may also be filled with sound‐absorbing material such as steel wool, or fibrous asbestos or with material adapted to absorb poisonous gases. An opening 13 may be provided for the removal of solid matter. In a modification (Fig. 2) the inlet pipe 59 is secured to an end plate 58 forming the base of the conical chamber 60, the smaller end of which passes through an eccentric opening in diaphragm 2 into a cylindrical reticulated chamber 15 supported by a diaphragm 16, and is extended by a pipe 62 adapted to direct the gases on to a portion 20 of a deflector plate on the side remote from an aperture 21. The gases then pass through aperture 21 and flow along the inner surface of the chamber with a gyratory motion. A second deflector plate 22, similar to the first, is situated in the chamber 15. In both constructions, the second deflector plate may produce whirling in the same or an opposite direction to the first. In a modification, the reticulated chambers are of spherical form. In Fig. 4 gases enter the chambers 38 tangentially by a pipe 39 and leave by pipes 40, 41. In Figs. 5 to 8 (not shown) different arrangements and combinations of chambers within the casing are described, and in two of the forms, suitable for aircraft, the casing is conical and provided at its rearward or smaller end with a number of perforations to give a gradual outlet. Specification 366,257 is referred to in the Provisional Specification.

IT has been stated above that the rate of heat transfer is closely proportional to the temperature difference between the plate and the free air stream, and over the laminar portion it will also be proportional to the conductivity of the air. It remains to consider to what extent the actual temperature of the air in the boundary layer will influence the rate of heat transfer. The conductivity of air increases with temperature by reason of the increased molecular velocities, and we might expect, therefore, that the hotter the surface the greater will be the rate of heat transfer per unit of temperature difference above that of the air. This is, in fact, found to be the case.

THE following notes, principally for the use of ground engineers, refer to the super‐charging of the four‐stroke cycle petrol engine; two‐stroke cycle engines and compression ignition engines are not here dealt with.

The pitch of the blades of an air‐screw is adjustable by means of a movable cylinder which is mounted beyond the end of the hub and moves over a fixed piston to either side of which an actuating liquid is conveyed down the hollow airscrew shaft and the cylinder has an axial extension which takes a bearing inside that shaft. The air screw shaft a4 is hollow and driven by gearing from the engine shaft a2. Inside the shaft are fitted two concentric tubes ƒ, ƒ1 of which the tube ƒ is secured to the shaft a4 by teeth ƒ2 and the mounting includes steady bearings ƒ6 which are serrated to allow oil to pass, and further steady sleeves between the two tubes are provided at ƒ3. The outer end of tube ƒ is attached to a piston g secured thereto by a nut g1. Over the piston is a cylinder h having a closed end h1 and an inner axial extension sleeve h2 which takes a bearing on the outside of the pipe ƒ on annular rings h3 and also on the inside of the shaft h4. The end of the space between the concentric tubes is closed by a plug h3. When liquid pressure is applied to either side of the piston, movement of the cylinder is transmitted to the pins m4 on the blade roots by the bolts m and links m3, the connection of the two linkages is formed as a slipper movable within a guide m5. For the purpose of ensuring oil tightness the junctions of the supply pipes j1, j2 with the supply tubes ƒ, ƒ1 are formed with spring‐held glands j4, j5, j10, j9.

COMING from the company which produced the famous range of “gull‐wing” fighters, something unconventional was to be expected from this new bomber. The lay‐out follows, in general, that adopted for the French multiplaces de combat; but the lines are more refined and the machine is of smaller overall dimensions than these. The main plane is set rather low on the fuselage, between the true low‐wing and the middle‐wing positions. It is of low aspect‐ratio, a very modern feature, and set unusually close to the tail unit. A point of particular note is to be found in the crew arrangement, which is similar to that of the Fokker T.5 [Aircraft Engineer‐ing, March, 1938, page 83] and several other new designs from various countries. The machine is to be commanded by the front‐gunner‐bomb‐aimer‐navigator, with the pilot as a subordinate member of the crew. This idea, which is reminiscent of the early days of warships, when the commander was a soldier and the captain a very inferior person, was used by the German Feldtfliegertruppen during the Great War and is being revived in the Royal Air Force and other services where N.C.O. pilots are being introduced in the majority.