Flight, August 1923

THE "WREN" LIGHT 'PLANE

   IN our issue for April 12 last we published a photograph of, and made brief reference to, the remarkable little light 'plane built to the designs of Mr. W. O. Manning by the English Electric Company, Ltd., of Preston, and known as the "Wren." Since that time the "Wren" has made numerous successful flights, and has been taken over by the Air Ministry, for whom it was built. This first experimental machine having more than fulfilled its designer's expectations, an demonstrated its practicability, it has been decided to put the "Wren" into production, and offer it to the public as a really low-powered light 'plane, easy to fly and cheap to maintain, at the low price of ?350.
   We therefore give this week further details of the "Wren," together with illustrations and general arrangement drawings.
   The production model now offered is practically identical with the original machine, the only alterations being of a minor nature in the detail construction, tending to improve durability and to facilitate the quick attachment and detachment of the main planes, etc.
   All parts have been designed and passed to the standard safety factors of the Air Ministry. The power available is quite adequate for cross-country flying except in very strong opposing winds, and is sufficient for a quick get-off from a reasonably level field.
   The “Wren" is very easy to fly, and handles remarkably well in the air. Various pilots who have flown it have reported very favourably indeed on its performance. It has an excellent gliding angle, thus enabling full advantage to be taken of favourable winds.
   Particular attention is called to the arrangement of the landing wheels, which eliminates the usual type of projecting undercarriage. This not only reduces head resistance, by enabling the wheels to be partially enclosed in the fuselage, but enables the machine to be landed on rough ground, ploughed fields, or gorse bushes, etc., without any risk of turning over, which would be almost inevitable with the usual type of landing gear. The fuselage bottom is reinforced with a three-ply rubbing surface over a large area forward, and in the event of a forced landing on bad ground this acts as a braking surface. This, together with the low landing speed (25 m.p.h.), enables the machine to be brought to a standstill in a few yards.
   Another noteworthy feature is the fact that its 3 h.p. A.B.C. engine is run at a comparatively low speed, thus ensuring reliability and durability. In motor-cycle racing this type of engine is frequently run at 4,000 to 4,500 revolutions per minute, whereas in this machine its maximum speed is only about 2,700 r.p.m., equivalent to a speed of just over 35 m.p.h. on the motor-cycle. When once the machine is in the air the engine can be throttled down to half power, which is ample to sustain level flight. It will thus be seen that the engine is not required to run under any more arduous conditions than usual, while the cooling is naturally much more efficient.
   The "Wren" should especially appeal to those in out-of-the-way parts of the Dominions and Colonies, who have thus placed within their reach the means of travelling over wide stretches of country with inferior roads, or even no roads at all, at a speed equal to an express train, and at a practically negligible cost.
   It should be noted that the "Wren" is in every way suitable and eligible for the forthcoming light aeroplane competitions for the Duke of Sutherland's ?500 and Daily Mail ?1,000 prizes, etc.
   The fuselage of the "Wren" is of orthodox box girder construction, reinforced at points of attachment of main planes, landing wheels, etc. The tubular axle of the landing gear is fitted with two pneumatic-tyred wheels and is attached to the lower longerons of the fuselage with shock-absorber cord. A swiveling tail skid sprung with shock-absorber cord is fitted.
   The main planes are of the cantilever type, thus eliminating outside struts and bracing wires. A special high-lift section is used. The main spars, of substantial box section, are of spruce, and a special form of internal bracing is used, giving great torsional stiffness. Quick detachable joints are provided between the two planes and to the fuselage. The leading edge is covered with three-ply on the upper surface.
   A special light fabric is used for the covering, doped with Titanine "glider dope," finished in aluminium colour.
   Tail plane, elevator, fin and rudder are of substantial build, and follow standard constructional methods. The controls follow approved standard practice, and are exceptionally efficient in operation.
   The engine is a 3 h.p., O.H.V., 398 c.c. flat twin A.B.C., motor-cycle type, specially adapted for aircraft work. It is mounted on the top of the nose of the fuselage, and drives direct a two-bladed tractor screw made from four laminations of selected Honduras mahogany. This airscrew looks an almost ridiculously small affair, measuring as it does only some 3 ft. 6 ins. in diameter, but it has been found in practice to be quite efficient.
   The pilot sits in the nose of the fuselage immediately behind the engine, and with his head level with the leading edge of the main plane, a portion of the latter being cut away to house the "brain" of the machine. From this position the pilot obtains an excellent view in all directions, it being quite easy to look past the engine and its mounting, which is very narrow, while the downward slope of the front portion of the deck enables him to look over the nose. For landing the machine should be as nearly "fool proof" as makes no difference, as the pilot can see the ground quite clearly, while the low position of the nose of the machine effectively prevents overturning on landing.
   The controls are of usual type, with a "joy-stick" for elevator and ailerons and a foot-bar for the rudder. As distinct from the experience of many of the competitors at Itford last year, the "Wren" has been found to answer her controls well, both under power and when gliding with the engine throttled right down. Manoeuvres such as vertical banks have already been executed on the machine, and it seems quite probable that the "Wren" would loop, although considerable caution should be used in stunting such a machine. Owing to the low resistance a very high speed can probably be attained in a dive, and a too sudden flattening out might consequently impose very severe stresses on the structure.
   It may be mentioned incidentally that two "Wrens" will be entered for the forthcoming competitions at Lympne, one of which will be piloted by Squadron-Leader Maurice Wright, who put the first "Wren" through its tests, and the second by Flight-Lieut. Longton, whose flying in recent races and exhibitions at the Pageant have made him known to and popular among wide circles of aviation enthusiasts.
   Following are the main characteristics of the "Wren": Length, o.a., 24 ft. 3 ins.; span, 37 ft.; weight of machine empty, 232 lbs.; engine, 3 h.p., 398 c.c., A.B.C. flat twin; fuel capacity, 1 gallon of petrol and 1 pint of oil; duration, 1 1/2 hours; instruments fitted, Smith's air speed indicator and cross level; revolution counter and altimeter can be fitted if desired. The maximum speed is 50 m.p.h., and the landing speed about 25 m.p.h. The machine can be stored in a shed 24 ft. 6 ins. long, 8 ft. 6 ins. wide, and 5 ft. 6 ins. high.