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Aviation History
1936
1936 - 0694.PDF
MARCH 19, i936- FLIGHT. •301 demonstration pilot, can make the new Envoy do some eTy remarkable things, but, at the Heston demonstration last week, at least two pilots having no previous experience of the machine made approaches and short landings which would not have disgraced the pilot of a light aeroplane. Despite the many statements made by research experts, Mr Errington, the chief test pilot, claims that the flaps- down stall is quite innocuous and that the Envoy, which has in addition, rather pronouncedly tapered wings, does not'tend to drop a wing even from a full stall. The loss of height, he says, is quite a lot less than in the case of the unflapped type—approximately 300 ft. as compared with 500 ft. indicated on a sensitive altimeter. If the machine is trimmed correctly for a 65 m.p.h. glide the effect of lowering the flaps is merely to depress the nose with no change in the indicated air speed. Aileron control remains down to the moment of stall. The normal hydraulic gear which is used for the retract able undercarriage is also used for the flap operation. It may be remembered that, on previous Envoys, a pump handle and a change-over lever are placed to the right of the pilot. With the Series II a third lever is placed on the pilot's left, beside the tail-trimming wheel; according to of the Envoy, incidentally, is that the take-off is best made tail down—with the trimmer wound well back. As soon as the machine leaves the ground the wheel car. be wound forward again before attending to the under carriage pump. The particular machine used for the demonstration was fitted with Wolseley Scorpio engines which, when turning over at 2,200 r.p.m. gave a cruising speed of approximately 150 m.p.h. The Rotax electric starters were noticeably quiet and efficient in action. High performance for a modest power expenditure has been a feature of all Airspeed machines since Messrs. Tilt- man and Norway first introduced the Courier some years ago. That machine, it may be remembered, was the first British low-wing monoplane to be fitted with a retractable undercarriage, and showed the way to still greater effi ciency. The maximum speed of 173 m.p.h. with two Wolseley Scorpio engines corresponds to an Everling high speed figure of 23.7, which must be regarded as good for a twin-engine type. At the same time the structural effi ciency is good at 1.63, showing that, when equipped for passenger carrying, the Envoy carries as disposable load 63 per cent, of its own weight. Safe and slow : Fit. Lt. Colman makes a demonstration landing just over the Heston boundary marks. In the heading picture the new Envoy is shown in cruising trim. (Flight photographs.) its position the normal " up or down " control and the pump handle operate either the undercarriage or the flaps. In the experimental mode], at least, the flap position is indicated by means of a pointer on the right-hand side of the control cabin. In the air there is little chance that the pilot might make a mistake, since, with the undercarriage still Up, the warning syren would indicate the fact as soon as the engines were throttled back, and, in fny case> feel, sound and sight would tell him that the flaps, rather than the undercarriage, were being lowered. A +vTy C^reless Pilot might possibly pump tne undercarriage up while the machine ^as on the ground, but in just the same way, he might also do a number of other 'oonsh things in any aeroplane. One of e more interesting flying characteristics In three sections extending right across the centre section, the Airspeed split flaps are hydraulically operated. (Flight photograph.)
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