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334,405. Aircraft structures. Wallis, B. N., of Vickers (Aviation), Ltd., Weybridge Works, Byfleet Road, Weybridge, Surrey. Sept. 26, 1929, Nos. 29167 and 39440. [Class 4.]

EVER since the days of LORD BEAVERBROOK (“big bombs— beautiful bombs”) the bomb has, in the mind of the British public, been surrounded by an aura of glamour and each larger missile that has been produced has been received with a flood of lyrical eulogies in the Press. We would not wish it to be thought that by writing in this way ,we are belittling the ingenuity of those like MR. B. N. WALLIS (on whom we are delighted to see has been conferred the honour of Fellowship of the Royal Society, in common with another great figure in British Aeronautics MR. W. S. FARREN—warm congratulations to both) who have successfully surmounted the many technical snags in designing successively larger bombs. Indeed, it is quite obvious that aerodynamically their latest effort, the 22,000‐pounder, is a big advance on any of its recent predecessors—themselves brobdingnagian in size—to which it is the immediate successor since in shape it more resembles the smaller bombs of earlier war days. It is fitted with the most interesting aerofoil‐sectioned fins which must result in remarkably steady flight and is of a streamline shape that must give it an extremely small drag factor, apart from allowing it to fit astonishingly snugly along the underside of the Lancaster fuselage.

THERE are two outstanding principles which underlie all airship design, two criteria by which everything undertaken may bo judged. The first is that the body produced shall offer a minimum of resistance to propulsion through the air; the second is that, having shaped a body in that way, it shall give a maximum of disposable lift for a given volume. An airship also, at the present time at least, must be produced for a minimum of cost. For this reason every effort must be made to design the structure as cheaply, as economically, and as quickly as possible.

THERE have been two previous James Forrest Lectures dealing with aeronautics. In 1912, Mr. Mallock addressed this Institution on “Aerial Flight,” and in 1914, Dr. Lanchcster took as his subject “The Flying‐Machine from an Engineering Standpoint.”

In order to maintain the hinge moments of a combined pair of aircraft ailerons as low as possible each aileron is constructed so that when it is depressed to increase the camber of the wing its own camber is simultaneously increased. As shown, this is effected by making the aileron in two parts a, b hinged together at e, the leading portion a being adapted to be depressed whenever the aileron as a whole is depressed about the hinges c at the rear ends of brackets d. The dipping of the portion a is effected by a link t connected to a non‐rotatable nut r working on a threaded rod k, at the upper end of which is a pulley m actuated by a cable n that passes into the wing structure at a point in line with the axis c. A cable o which serves to vary the camber of the wing is associated with the cable n through a gearing‐up pulleys p, q.

A supporting surface I for aircraft is provided with a control surface II adjustable on the surface I and an auxiliary surface III adjustable on the lower side of the surface II and adapted to participate in the adjustment of the surface II and also throughout at least part of its movement to be adjusted independently of the surface II; the surface II is adjustable so that it is given a motion compounded of a rotation and a fore‐and‐aft displacement. In one form, an auxiliary surface III is nested normally on a control surface II and is connected thereto by links 2, 3 and a tension spring. The surfaces II, III are simultaneously operated from a crank 4 through a link 6 and the surface III is adjustable independently of the surface II from a crank 7 through a link 9. In a modification, the surface II is connected by links to out‐riggers on the wing I so that the surfaces II, III are adjustable together and are moved rearwardly and downwardly. In a further modification, the abutting surfaces of the wing 1 and the surface II are so shaped as to leave a slot when the surface II is moved. The surface III may be arranged so that when in its extreme adjusted position it closes the slot formed at its leading edge during its initial movement. In another form, the surfaces II, III are operated by means concentric with the axis of articulation of the control surface II and in a modification the surface III is operable by cam means and only after a predetermined adjustment of the surface II. In a further form, the surfaces II, III are housed normally in a recess 23 at the rear of a wing. The surface III is again connected to the surface II on outriggers connected thereto by links 3, 2. The surfaces are adjustable as one by a rack 19 and a pinion 22. After the surfaces have been fully adjusted towards the rear, the surface III is independently adjustable through a rack and pinion. The leading edge of the surface III is shaped so that on adjustment of the surface III a slot between the surface II and the wing is uncovered. In a modification, the link 2 is replaced by a pin‐and‐slot and the rack for adjusting the surface III only engages with its pinion when the rack 19 has been disengaged, due to rearward adjustment of the surfaces. In a further modification, the surface III is adjusted by an endless band connected to the pin moving in the slot. In a further modification, the surface II comprises two portions separated by a slot and the surfaces II, III are nested normally in the underside of a wing. In a still further modification, the recess 23 is closed when the surfaces have been adjusted rearwardly by a surface IV and a slot forming slat 47 is adjusted concurrently with the surface III, this is effected by a rope 50 carrying a pin 56 which engages in a slot 55 in discs 57 connected to the slat 47 by a link 59 when the surface III is in position prior to adjustment, In a still further form, the surface II is connected to outriggers 63 by links 66, 64 and 69, 67 connected and operated from a link 71 as shown. The surface III is adjusted by rotation of the pivot axis 76 or through links from a rod rotatable in the surface II. In a still further form, the adjusting mechanism is carried by the leading edge of the surface II.

THE hull of R 100 is a sixteen‐sided polygon, measuring 709 ft. in length, with a maximum diameter, situated about two diameters, 266 ft., from the nose, of 133 ft., the height of the gas‐space within the framework being about 128 ft. at the maximum diameter. It is built up on a framework of 16 triangular longitudinals with 15 transverse frames, also triangular. No intermediate longitudinals or transverse rings are fitted. Along the centre runs an axial girder, taking the place of the wire rope used in Zeppelin construction, to which is brought the radial wiring forming the bulkhead between each of the gas‐bags. The gas capacity is 5,600,000 cub. ft., giving a gross lift of 160 tons. The transverse frames are not, as in R 101, of the “space frame” type, inherently stiff without bracing (in R 101 the triangular frames have a depth of 10 ft. 6 in.), but are only 2 ft. 6 in. deep, braced by the radial wiring. There are 15 gas‐bags, Nos. 14–15 being interconnected. In accordance with normal Zeppelin practice, automatic valves are fitted at the bottoms of the bags, discharging into fabric trunks leading to the upper surface. Hand‐operated valves are fitted at the top of 11 of the bags. Back as far as Frame 13 the axial girder is of triangular section, but from there aft it is square and forms an integral part of the cruciform fin structure. All girders, from which the longitudinals, transverse frames and axial girder are built up, are composed of Duralumin strip wound and riveted into tubes connected by stamped Duralumin bracing pieces.

It was reported in last month's AIRCRAFT ENGINEERING (Orders and Contracts) that orders for conversion kits worth nearly £3 million to Rolls‐Royce Ltd. had been placed by Trans‐Texas Airways of Houston, Texas, and Central Airlines of Fort Worth, Texas, for Dart R.Da.10 turboprop conversions of thirty‐five Convair 240 airliners.

A variable‐pitch airscrew includes a differential screw mechanism connected with two skew gear‐wheels of opposite sense, mounted coaxially of the airscrew shaft, said skew wheels being adapted to be restrained against rotation for the purpose of altering the pitch of the propeller blades. Within the hollow driving shaft of a propeller are two coaxial shafts 17, 18 having at their inner ends spur wheels 23, 24 which are in mesh with corresponding teeth formed on two brake drums 23a, 24a that are furnished with brake bands 23b, 24b controlled by a lever 26c. The outer ends of the shafts 17, 18 carry skew gear wheels 29, 30 of opposite sense which engage permanently pairs of gear wheels 31, 32, and 33, 34 mounted on parallel transverse shafts 35, 36 and 37, 38. The shafts 35, 37 are connected by means of right and left‐hand skew gears 39, 40 with a transverse rotatable sleeve 41 splined on to a shaft 44. This shaft 44 bears two differential screw threads 45, 46, the smaller of which 46 engages a threaded boss 47, whilst the other engages a screwed lug 48 on a slidable sleeve 55 having an open jaw member 57 which engages an eccentric pin 58 at the root of a blade. When the hand lever 26c is moved to brake one or other of the wheels 23, 24 one or other of the skew gears is given a relative rotation and a corresponding movement takes place of the shaft 44 whereby the blade is altered in pitch. As an alternative to the brake drums the shafts 17, 18 may be furnished with notched discs adapted to be engaged by spring‐influenced pawls carried by a lever similar to the lever 26c.

In a retractable aircraft undercarriage having a plurality of points of application of operative force constrained to move at varying rates, a differential device, adapted to allow for the relative rate of movement between the points of application, is provided in the transmission means. In one form, a landing‐wheel 5 is supported on resilient compression members 1 spaced apart to receive between them the wheel and pivoted to a supporting‐frame 6 also pivoted to a lever 8 rigid with a double‐grooved pulley 11. Retraction of the landing‐gear is accomplished by winding a cable 25 on to a drum 26. The cable is connected through a spring 24 to a pulley 23 over which and pulleys 22, 29, 30, 31 passes a cable 21, 21B secured at one end to the rod 6 and at the other to the pulley 11. Initial tension rotates the drum 11 anticlockwise which, through frictional engagement, rotates a lever to disengage a catch 14 co‐operating with a detent 16 having a slot 19 adapted to engage a pin 7A connecting the frame 6 and lever 8 for locking the landing‐gear in its operative position. Continued winding forces the pulley 31 and lever 8 anticlockwise, rotates the pulley 11 and pulls on the frame 6; thus the joint 7 is freed and moves past the line joining the pivot of the pulley 11 and the wheel axle 4. During retraction the pulley 23 allows for the varying rates of movement of the pulley 11 and the point of attachment to the frame 6. The landing‐gear is extended by rotation of a drum 27 integral with the drum 26 to wind up a cable 28 which has during the process of retraction been wound on the pulley 11. The cable 28 is secured to the pulley 11 or is made continuous with the cable 21B and secured to the pulley 11. The spring 24 allows for slight inequalities in the rate of paying out of cable 28 and hauling in of cable 25. The spring 24 may be omitted, in which case the drums 26, 27 are connected by a torsion spring. A brush for cleaning the landing‐wheel is provided. In a modification, a lever 51 connected to the frame 6 and the shock‐absorbers 1 are rotated for retraction or extension of the landing gear through gearing and toothed quadrants from a differential gear which is driven from a sprocket wheel 44, the quadrant on the lever 51 being driven from the differential through a chain 46 and a sprocket 47. The frame 6 is pivoted to a member 53 slidable in a bearing in the lever and provided with a rubber buffer 54 which bears, when the landing‐gear is operative, in a recess 55 in an anchorage secured to the rear wing spar. The wheels may project slightly when retracted.