Flight, July 1924
THE SHORT "LIGHT 'PLANE TWO-SEATER
Bristol "Cherub" Engine
GRADUALLY the machines being built for this year's light 'plane competitions at Lympne are beginning to take form. We believe that three or four are almost finished, and are
only waiting for engines, while others are in various stages of progress, ranging from those designed but the construction of which has not been begun, to those nearing completion. By the courtesy of Short Brothers of Rochester, we are able to lay before our readers this week the first illustrated description to be published of the Short monoplane two-seater, which this firm has designed and is constructing at their Rochester works.
The Short light 'plane two-seater is an ordinary monoplane, if by "ordinary" one understands a monoplane in which the wing is neither of the "parasol" nor of the "low" type. Apart from the fact that the machine is a cantilever monoplane, i.e., without external wing bracing, the Short machine is of interest on account of the fact that the fuselage is built entirely of Duralumin, following the same method that has been successfully employed in the Short "Silver Streak," "Springbok," and, more recently, in the little twin-engined light flying boat described and illustrated in FLIGHT on April 17, 1924. By this form of construction, originated by Mr. Oswald Short, the outer covering, which is of Duralumin sheet, is riveted to circular or elliptical rings of L-section which form the "frames" of the structure, the outer covering or planking resisting the stresses, assisted by longitudinal stiffening strips, which do not, however, run through from end to end, but are interrupted at the frames. In the two-seater light 'plane the fuselage is of elliptical cross-section, and should have a very low head resistance, as the shape is particularly smooth.
The wings of the first machine have spar flanges of laminated mahogany, with three-ply walls, but later machines of this type will probably have spars built up of high-tensile steel strip, thus making it entirely metallic, with the exception of the fabric wing covering. The ribs are also of Duralumin, in the form of sections built up to form a "Warren girder." The two halves of the monoplane wing are bolted to strong fuselage frames by fish-plates and large-diameter hinge pins so as to facilitate dismantling. The wing section employed is a high-speed section over the outer half of the wing, gradually changing into a deep section at the root, where the maximum stresses occur. The ailerons extend the whole length of the wings, and are operated by torsion tubes and rods. A variable camber device is fitted which enables both ailerons to be pulled down together, while still retaining their differential aileron action. The controls for varying the camber, as well as the usual aeroplane and engine controls, are in duplicate, so that the machine may be piloted from either cockpit.
The undercarriage is of simple V-type, with shock-absorbers in the form of rubber blocks in compression, incorporated in the front "legs." The wheels are standard "Palmer" type, measuring 450 mm. by 60 mm.
The Bristol "Cherub" engine is mounted in the nose of the fuselage, on an aluminium alloy casting, and the whole cowled-in to give a clean entry for the air. The small-diameter propeller is fitted with a spinner. Behind the engine there is a fire-proof bulkhead, aft of which are mounted the petrol and oil tanks. Fuel supply is by gravity feed. The capacity of the petrol tank is approximately 3 1/2 gallons.
Later on we hope to have an opportunity of publishing a more detailed description of this interesting machine, illustrated by sketches and photographs. In the meantime the following brief specification may be of interest: Length, o.a., 23 ft. 9 ins.; wing span, 34 ft.; chord, 5 ft. 6 ins.; wing area, 168 sq. ft.; weight of machine empty, 483 lbs.; useful load, 367 lbs.; total loaded weight, 850 lbs.; wing loading, 5.05 lbs./sq. ft.; power loading, 30-4 lbs./b.h.p. The estimated top speed is 73 m.p.h. and the stalling speed 37 m.p.h. It would appear that both are very conservative estimates.
Flight, September 1924
THE SHORT LIGHT MONOPLANE (No. 8)
Bristol "Cherub" Engine
THE very pretty monoplane entered by Short Brothers of Rochester is already known to readers of FLIGHT, a description and a full-page scale drawing having been published in our issue of July 24, 1924. The machine is a "normal" (i.e., neither "high-wing" nor "low-wing") monoplane two-seater, fitted with Bristol "Cherub" engine. From the accompanying illustrations it will be seen that the machine is of exceptionally clean lines, the photographs particularly illustrating this point. Aerodynamically, therefore, the machine should be very efficient, and the estimated performance figures published in our previous article will in all probability be considerably improved upon during actual flying tests.
Constructionally the machine is of more than usual interest on account of the all-metal fuselage, which incorporates features similar to those of the famous Short "Silver Streak" and "Springbok" larger aeroplanes. This form of construction, which has not been developed as rapidly as it might have been on account of the Air Ministry's objection to the use of Duralumin in aircraft construction, is remarkably simple, and certainly appears to provide a "cleaner" structure, with a minimum of parts, than the more usual forms of metal construction.
Fundamentally, the Short method of fuselage construction (and the same principles are now being applied to flying boat hull construction) consists in making the outer skin or covering part of the stress-resisting structure. The skin, of sheet Duralumin, is applied in short panels which wrap around the fuselage contour (of elliptical cross-section) and is attached to "L"-section rings or formers lying in a transverse vertical plane. The fact that it is impossible, without beating or some other form of shaping, to bend sheet material around a sphere, although it bends, of course, readily around a cylinder, necessarily means that the Short fuselage is not really in the form of a smooth curve, longitudinally, but is in a series of straight lines. The angle which adjacent straight lines make with each other are, however, so flat that to all intents and purposes the outward form is a curve. Where a sharp change in the direction of the curve occurs the covering sheets are kept very narrow, as indicated in the general arrangement drawings, while a gentle curve allows of using wider sheets. The sheets are riveted to the "L"-section formers, and, in order to stiffen the skin against compression loads, "V"-section stringers are riveted to the skin between the rings or formers. These stringers do not, however, run through from end to end, as in a flying boat, for instance, but are interrupted at the formers. Owing to the curvature of the fuselage, which already by itself stiffens the skin considerably against compression loads, the fact that the stringers are not continuous probably does not matter in the slightest, and the resultant simplicity of construction would appear to be well worth, if necessary, a little extra thickness in the skin. Certainly we have never, in any country, seen a fuselage structure more free from projections, bracing and other encumbrances than that of the Short "Satellite." Whether the particular form is as light as it might be for such a small machine is, perhaps, open to discussion, but that the system is well worth developing for larger machines there cannot be the slightest doubt. Even in this small size the weight of the fuselage is by no means prohibitive, although some of the machines entered have managed to reduce their fuselage weight below that of the Short.
We have devoted rather a large amount of space to the fuselage, but we feel that we need not apologise for doing so, as the construction is unusually interesting.
The monoplane wing of the competition machine is built over wood spars, but it appears likely that subsequent machines of this type will have spars made from high-tensile steel strip so as to make the entire construction metallic. In the Lympne machine the spars have flanges of laminated mahogany with walls of three-ply. The ribs are made of Duralumin, built up in the form of a Warren girder. The two wing halves are bolted to strong fuselage frames by fishplates and large-diameter hinge pins so as to facilitate dismantling. The ailerons extend the whole length of the wing, and are operated by torsion tubes and rods. A variable camber device is fitted, which allows of depressing both ailerons together, the differential aileron action being retained.
The undercarriage is of vee type, with rubber shock absorbers in the form of compression blocks incorporated in the front "legs." The axle as well as the telescopic struts is enclosed in streamline casings, as shown in one of our sketches. The front chassis struts are bolted to a strong fitting immediately below the front spar attachment.
The Bristol "Cherub" is mounted on a particularly neat aluminium alloy casting, shown in a sketch. Direct loads are taken by this mounting, assisted by sloping steel tube bracing struts as shown, while torque loads are taken care of by the casting itself. The whole forms a very simple mounting, making the engine readily accessible and allowing of removing the engine in a very short space of time. Behind the engine there is a fireproof bulkhead, aft of which are mounted the petrol and oil tanks. Direct gravity feed is employed.
The photographs on p. 613, which were taken from above, give an excellent idea of the arrangement of the two cockpits in tandem. Owing to the fact that the front cockpit is ahead of the wing root, the view from here should be unrivalled, as the pilot can look straight down past the sides of the fuselage, and the only direction in which there is any obstruction is diagonally downwards and aft. Even from the rear cockpit the view is better than in the majority of machines, and altogether the question of view appears to have been most happily solved in the Short "Satellite."
The controls are of usual type, and in conformity with the regulations they are in duplicate. This applies not only to the normal flying controls, but also the gear operating the variable camber device, which can be worked from either cockpit.
Flight, September 1926
British Light ‘Plane Development & Lympne Meeting
THE 1926 MACHINES
No. 15. The Short "Satellite" (A.B.C. "Scorpion Mark II")
The machines carrying the numbers 15 and 16 in the competition have been entered by the members of the "Seven Aeroplane Club." This club was formed originally at Eastchurch, and received its title from the fact that there were seven founder-members of the club.
The Short "Satellite" is unaltered as regards the machine itself, but the members of the Seven Aeroplane Club have fitted an A.B.C. "Scorpion Mark II" in place of the original Bristol "Cherub." This engine has passed its Air Ministry type tests, but has not as yet had an opportunity to show what it can do when installed in a machine. The performance of the "Satellite" with its new power plant will be watched with interest.