a light cabin monoplane
LIGHT 'PLANE TYPES
A LIGHT CABIN MONOPLANE
The "Hornet-" engined Civilian Coupe.
HEN its development elsewhere is considered, the enclosed small aeroplane has been rather slow in materialising in this country, but now that it has been taken up seriously by our leading manufacturers it is safe to foretell that within the next
few years it will be the predominant type.
The most obvious advantage of the cabin machine is that it affords a great increase in comfort to the occupants, making special kit unnecessary, and conversation without the use of telephones possible. But apart from these features, the typical high-wing monoplane, when combined with the cabin arrangement, can be designed so as to give a particularly clean exterior with a consequent reduction in air resistance and drag and therefore a high performance ; good visibility for the pilot can be arranged, and a normal and easy access and egress can also be provided by a door at the side of the fuselage—a palpable improvement on the clambering-up-and-squeezing-in business necessary with open cockpit machines.
These points, are of course, apparent to everyone now, but credit is due to Mr. H. Boultbee, the designer of the Civilian Coupe machine here described, for realising them as long ago, as 1926, for it was then that this 'plane, which has only recently been placed on the market, was first evolved.
Incidentally, while the Civilian machine is a definite newcomer, it is interesting to recall that Mr. Boultbee has been associated with aviation for over twenty years, and was for a considerable period connected with the Handley-Page concern. As can be seen from the accompanying illustrations, the Civilian is a monoplane with the mainplane braced by "V "lift struts. In construction it follows orthodox practice, incorporating spruce box spars and three-ply and spruce ribs. The wing section adopted is said to have a very high stalling angle, and the wing tips are tapered with the object of giving a large degree of lateral control. The covering is of three-ply, reinforced
at the leading edge to prevent any deformation. The wings are made to fold, and are attached at their roots to the fuselage by simple but robust fittings ; they are anchored to a steel tube structure which forms the top half of the cabin framework.
The folding procedure is particularly easy, and can be done single-handed without disturbing the lift struts or aileron controls. No jury struts are necessary for supporting the wings when in the folded position, and the locking-pins on the front spar fittings have double safety catches.
The fuselage is of composite construction, the rear part being built up in box girder fashion, with spruce longerons and members and three-ply covering. The front section, which includes the cabin and engine mounting, is of steel tubes bolted together with simple joints. The interior of the rear end of the structure is readily accessible for inspection or attention through a detachable fairing.
The tail unit of the Civilian is very neat and clean in appearance, being devoid of all exterior bracing, cranks or king posts. Both the elevator and fin are of full cantilever construction and the complete empennage, comprising rudder, fin, tail plane and elevator are secured to the fuselage by four bolts. As in the case of the main planes, the covering is of plywood.
The control mechanism is rather unusual ; no cables are used, the connection between the stick and rudder bar to the various controlling surfaces being by pull-andpush rods. Ball-bearings and oil-less bushes are used throughout, and by cutting fulcrums and cranks down to a minimum, waste action is obviated. All control levers are concealed, giving unbroken surfaces to the tail and ailerons. The undercarriage, in keeping with modern ideas, is of the axle-less type, with a wide track (6 feet 6 inches) Landing shocks are taken by rubber absorbers, in compression, and the whole arrangement of the components is covered by neat streamline fairing pieces. The top ends of the legs are attached to the top longeron and the " V " radius rods pivot on ball joints, which are enclosed in grease covers, on the bottom members. T h e under carriage is equipped as standard with Dunlop wheels, fitted with Bendix brakes. These are operated independently f o r taxying, by the rudder bar, or together by a
convenient hand-lever. On the production models of the Civilian, a small wheel replaces the tail skid ; this renders a trolley unnecessary when the machine is being moved about in the hangar, and at the same time, lessens the strains imposed on the fuselage in landings. The cabin accommodates two people, the pilot's seat being on the port side. They are carefully designed to give a really -restful position, and are fitted with air cushions. Removal of the passenger's seat leaves a space of 10 cubic feet, and quite large and bulky goods can be easily loaded through the wide side doors. The furnishing of the cabin interior is well carried out, the walls being covered with either hide or cloth. Handrails and a foot rest for the passenger are fitted as standard. The instruments are neatly arranged on a facia board, and a locker is provided for maps. Besides the extra space made possible by removing the passenger seat, ample room is also available within the cabin to the rear of the pilot. Golf clubs, fishing tackle and the •
like can be housed in a locker beneath the fairing to the rear of the cockpit. Naturally, a 11 windows have safety glass, and one of the outstanding features of the machine is the exceptionally good view above, in front at the sides and behind.
The standard power unit installed in the Civilian is the well-known A. B. C. 75 h.p. " Hornet " flat
four. It is supported on a steel tubular mounting, so arranged as to minimise any vibration being transmitted to the rest of the machine. The throttle and ignition controls oil gauge, and revolution indicator are all conveniently grouped so as to simplify matters when the unit is taken out for overhaul, and the engine itself is secured by four conveniently-situated bolts. A fireproof bulkhead is built into the nose, at the rear of the engine, and behind th1/4 is the oil tank.
Peed to the carburetter is by gravity, the fuel tank being situated in the port wing, near the root ; it has a capacity of twenty gallons. This gives a range at cruising speed of about 360 miles (4i hours).
Under test the experimental machine, which was first built in 1929, shows good all round qualities with a top speed of 102 m.p.h., a cruising speed of 85 m.p.h. and landing speed of 36 m.p.h. The rate of climb is 550 feet per minute, and its ceiling is about 16,000 feet.