Flight, October 1923

THE AVRO LIGHT MONOPLANE, TYPE 560
700 c.c. Blackburne Engine.

   THE Avro type 560, built for the competitions at Lympne, is a cantilever monoplane which, although in external appearance following the usual practice, has several unusual constructional features.
   The fuselage is of somewhat similar construction to that employed in the biplane, although the external shape is rather different. The four longerons are of spruce with spruce struts running diagonally to form a Warren girder, the struts being attached to the longerons by means of three-ply "biscuits" glued and nailed in position. As in the case of the biplane fuselage, the covering is fabric throughout, longitudinal stringers keeping this clear of the struts, etc. Except for the fact that it is practically flat-sided and with flat deck and bottom, the fuselage of the Avro monoplane is of very good streamline form, and should offer very little resistance.
   The monoplane wing has a pronounced taper both in chord and thickness, and is built in two halves. At the root the wing spars project a considerable distance beyond the inner rib, and fit into openings in the fuselage, where they are bolted together by means of special joint plates to form a continuous girder. The wing section used is of the bi-convex type, somewhat similar to some of the American sections described in FLIGHT of May 24, 1923. The spars are built-up box-sections, with flanges of solid spruce and walls of double diagonal spruce skins. This form of construction has been found to give an extremely rigid spar. The ribs have T-section spruce flanges tied together by means of corrugated Duralumin struts and ties. The drag bracing is formed of spruce struts and ties arranged in the form of a Warren girder and attached to the spare by means of three-ply "biscuits." The wing covering is of special light linen fabric, doped with Titanine glider dope.
   The tail plane is made in two parts, which fit into suitable attachments inside the rear end of the fuselage, the two halves of the tail being fastened together so as to form a continuous member, and no external bracing is required. It is quite evident that considerable care has been taken in designing the tail unit so as to make it offer as little resistance as possible. The elevators are of the unbalanced type, hinged to the rear spar of the fixed tail plane. The rudder is of the balanced type, with a strong box-section main spar and spruce ribs. The ailerons and elevators are operated by a walnut joy-stick mounted on a universal joint at its lower end. The aileron control is by means of cables, but the elevators are operated by a long push-and-pull rod. As in the biplane, the rudder is operated by means of pedals.
   The 700 c.c. Blackburne engine is mounted on an engine plate of the simplest possible form, i.e., a flat plate of 8 gauge Duralumin, to which the engine is bolted direct by the horizontal bolts through the lugs on the crank-case. Direct drive is employed, a ball thrust bearing being housed in a cage on the front end of the crank-case. The petrol tank is mounted just under the deck of the fuselage, immediately ahead of the front spar, and a specially long induction pipe has been fitted so as to give direct gravity feed to the carburettor.
   The undercarriage is of very simple form, and consists of two light wooden wheels mounted on a steel tube axle. This axle is supported from the fuselage by two struts on each side. These struts are placed some considerable distance apart, so as to provide space for the rubber shock absorbers, which, with the rest of the struts, are streamlined by covering the space between the struts with metal over the lower portion and three-ply over the upper. The struts are braced laterally by short tubes running diagonally to the centre of the fuselage.
   The pilot's cockpit is arranged between the front and rear spars of the wing, and an interesting feature is that the airspeed indicator is mounted in the root of the wing, so that when the machine is dismantled for transport the instrument is removed with the wing without the necessity for breaking the connections. The tail skid is in the form of a bent steel tube mounted in vertical bearings, and the landing shocks are taken by a coil spring.
   The main characteristics of the Avro monoplane type 560 are as follows: Length, o.a., 21 ft.; span, 36 ft.; maximum chord, 5 ft. 4 1/2 ins.; minimum chord, 3 ft.; wing area, 138 sq. ft. The weight of machine empty is 285 lbs., and it will carry a load of 180 to 200 lbs. The wing loading is 3-4 lbs. per sq. ft., and the power loading 23-5 lbs, per h.p., with the engine developing 20 h.p. at 3,200 r.p.m.