Flight, August 1931

AN AVRO MAIL PLANE

A.V. ROE & CO., LTD., of Manchester, have just produced one of the first aircraft specially designed in this country for carrying air mails. This is undoubtedly a step in the right direction, particularly as the Avro 627, as it is called, has been built with the specific purpose of catering for Canadian desires.
In its essentials it is reminiscent of the Antelope, but in detail it varies very considerably. From first to last, Mr. Chadwick, the firm's Chief Designer, has worked in cooperation with the Canadian Government officials and those of Canadian Airways, Ltd., the result being that the 627 can definitely be said to represent the type of machine which Canada wants. She is probably not so fast as some of the mail-carrying aircraft used in the United States of America, but undoubtedly satisfies the desiderata of those who will use her, to a far better extent, than the American craft. The construction throughout is of metal, and every precaution has been taken to make her safe, comfortable, and easy to fly in bad and exceptionally cold weather. As befits a modern production, the whole undercarriage can easily be changed for skis or floats, and full night-flying equipment is, of course, fitted. The engine installation includes an electric inertia starter and an engine-driven electric generator. The mail compartment is built up in the manner of our fireproof bulkheads, with asbestos sheeting sandwiched between duralumin plates. A summary of the main conditions which the machine has been designed to fulfil would be high cruising speed, some 600-mile range in still air, ease of maintenance, ease of transport of all replaceable components, and complete equipment for comfortable and regular operation of airmail services under Canadian conditions.

Fuselage

   Following the now accepted Avro practice, the Type 627 fuselage is of welded steel tubing. The main frame is divided into three sections, consisting of the engine mounting, which is of the straightforward tubular type, the middle section, which includes the mail compartment and the pilot's cockpit, and the rear section continuing from behind the pilot to the stern post. As far aft as the pilot's cockpit the fuselage is tubular strut braced, while the rear section is wire braced. Directly behind the engine mounting is the section carrying the two fuel tanks, having a large rectangular one in the middle slung on steel straps, with a shaped gravity tank above it. Abaft this is the mail compartment, which is completely lined with duralumin-asbestos-duralumin, and provides 40 cubic ft. of clear space inside it. A folding lid of the same material opens towards the starboard side of the machine, and provides a large-size entrance for loading. This half of the lid is further divided into halves, so as to incommode the loading operation as little as possible.
   Directly behind the mail compartment is the pilot's cockpit, and, being situated thus far aft, the pilot should have an excellent view in all directions; moreover, his position should make him very safe and give him every chance of surviving in the event of a crash. No pains have been spared to make the pilot's job as comfortable as possible, so that long-distance flights should present no difficulty.
   The seat is adjustable in the same manner as in the Avro Tutor, the operating lever being situated on the right-hand side, the handle part of this lever being, as are all the other handles and levers in the cockpit "Doverised," in order that the pilot should have no trouble through touching cold metal in very low temperatures
   The rudder bar is easily adjustable in flight by means of a small hand wheel mounted directly in line with the pivot, in the same manner as other Avro machines. In the standard position, on the port side of the cockpit, is a wheel for adjusting the tail plane; a refinement is an indicator for showing the tail setting. All fuel system controls are situated on the right-hand side of the cockpit, enabling either or both tanks to be connected direct to the carburettor, and there is also a lever to a hand-worked Vickers pump for use in case the engine pump breaks down. Landing lights, which are fitted in the bottom wings, can be swung down to the landing position by means of another control, and another lever on the same side opens or closes louvres in the engine cowling to regulate the engine temperature. Cockpit heating is provided direct from the exhaust, with openings under either heel board, thus keeping the pilot's feet warm, as well as heating the cockpit. Special instruments include a Pioneer bank and turn indicator, and a climb indicator, a button on the dashboard controlling the Eclipse electric inertia starter. Arrangements are also made for releasing the American-type parachute flares for emergency landing. A receiver for the Western Electric radio beacon is situated on the floor behind the pilot's seat. Following the usual Avro practice, the side fairings of this part of the fuselage are built up of spruce and three-ply, in complete frames, which are easily detachable, thus readily exposing all control rods and wires, which are led outside the actual fuselage frame, when desired, leaving the inside of the cockpit absolutely clean. The front cowling panels just abaft the engine are aluminium, well shaped to work in harmony with the engine cowling and keep the drag of this large-sized fuselage as low as possible. The engine cowling itself will be of the Townend ring type, which should contribute a great deal to the high performance.
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The Power Installation

   The engine mounting is a triangulated welded-up steel tube structure, terminating in a ring to which the engine is mounted in front, and four attachment points on the after end, which are bolted to machined steel fittings on the fuselage. The oil tank is placed in front of the fireproof bulkhead, and lies inside the engine mounting. A unique feature of the power plant is the fitting of an Eclipse Electric Inertia Starter, and the provision of direct drive for the electric generator. The starter may also be worked by hand, for which purpose a hand lever is provided. The engine is an Armstrong-Siddeley "Jaguar Major" of 525 b.h.p. at 2,000 r.p.m., fitted with a geared airscrew running at 0.657 crankshaft speed. The engine is also fitted with a geared fan, maintaining ground level power up to 3,000 ft.
   Fuel tankage is provided for 100 galls., there being 72 galls. in the main tank, which is situated directly behind the fireproof bulkhead, and 28 galls. in the gravity tank above it. Both tanks are built up of welded aluminium sheet of some 16 gauge, thus providing both lightness and strength. The main tank is slung in leather-covered steel straps, and may be removed for repair through the bottom of the fuselage, when necessary. The gravity tank sits on bearers on the top of the fuselage, and is constructed with the diagonal bracing struts of the top centre section, passing through grooves each side of it. The gravity tank has a direct reading contents gauge, and fuel is passed to it from the main tank by the engine-driven pump, which is fitted as standard for emergency use. There is, however, also a hand-worked Vickers pump.
   The oil tank, which, as we have already mentioned, is in the engine mounting, is of cylindrical form, and also constructed of aluminium. Its capacity is 11 galls. One end of it has a special large-diameter drain cock, so that the contents may be emptied quickly and heated before use when operating the aircraft in very cold climates.
   A Vickers-Potts oil cooler is used with a bye-pass, so that it may be cut out of the oil circuit when conditions are particularly cold. The exhaust manifold, placed behind the engine, is of streamline section, with a long tail pipe carried below the pilot's cockpit, and, being in the form of a ring, is designed to work in conjunction with the Townend ring engine cowling. The tail pipe finishes right aft of the pilot's cockpit, and, by means of a muff, supplies air through suitable ducts into the cockpit, the outlets being at the front end of each footboard. A control handle is fitted on the right-hand side of the cockpit for regulating the supply of warm air.
   On Monday, August 10, the "627" was flown at Heston before Col. Shell<...>rdine, the Director of Civil Aviation. In its finished state, and painted brilliant yellow, it makes an imposing aircraft. Its take-off appeared good, as did its top speed. Particularly impressive was the ease with which it could be manoeuvred on the ground without extraneous help.
   The modern arrangement of swivelling tail-wheel together with efficient wheel brakes certainly makes the aircraft nearly as handy on the ground as a motorcar.
   Taken all round, this aircraft would appear to fill the needs of the Canadian market in an admirable manner, that is assuming that a cruising of not more than 147 m.p.h. is what is required, and it undoubtedly provides one of the best equipped and most comfortable cockpits for the pilot that we have seen.