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Aviation History
1947
1947 - 1851.PDF
OCTOBER 23RD, I947 48r Some Impressions from the Pilot's Viewpoint : Good Basic Characteristics Flying the Ambassador dTHE prototype Airspee - bassador has now completed forty hours of test flying, and this might be a suitable moment to pause and summarize a few of the air- craft's salient flying characteristics. This particular moment will be all the more appropriate because, during the last ten hours in the air, opportunities have been given to unbiased and ex- perienced outside observers to assess some of these characteristics for them- selves, and all the opinions have been very encouraging. Indeed, the Ambassador has several features which we have tended to accept as being natural and necessary vir- tues in any aircraft, but which we knew to be almost unique. It was, perhaps, natural when assessing a proto- type on which so much depended, to be over-critical. Now, with the initial period of test flying behind us and the resultant minor modifications in hand,,it is possible to view the Ambassador's characteristics as a complete picture rather than in sections, and to feel a confidence" which may previously have been overlaid by our concen- tration on relatively unimportant faults. From the point of view of a- pilot flying the aircraft for the first time, four features will appear to be out- standing—and all four of them survive both detailed assess- ment and a study of any test reports which have been made since the first flight. Three of these characteristics will be of vital importance in all-weather airline operation and the fourth will add to the comfort of the passenger. Most important, perhaps, is the aircraft's stability in all axes, and particularly in pitch. In all flying conditions and at all speeds the fore-and-aft stability is markedly good, without being too positive, and there is no tendency to '' hunt'' or for the effect to vary with different power settings. Even in very bumpy conditions the elevator con- trol, too, is quite definite, and there is no need for the pilot to '' chase'' the control when making an approach in rough weather with the flaps down. In particular, the aircraft gives the impression of being a very steady platform at all times, with little wing or fuselage flexing. In association with this stability is the unusual fact that there is relatively little change of trim between extremes of speed and power. So much so that the aircraft can be held without retrimming, when the engines are opened up to take-off power after a full-flap engine-off approach. Neither the amount of power used nor the speed makes very considerable differences to the trim, though there naturally is a nose-down bias when the flaps are fully lowered. This bias can, if necessary, be held manually—a feature which will form a valuable safety factor in day- to-day operation. The third important characteristic of the Ambassador is its viceless stall—which is, again, one that applies in T HIS Ambassador Progress Report, issued ' by Airspeed Ltd., is published exactly as received. The writer of it is well known to us, and we are quite certain that it errs on the side of modesty. Although there are minor teething troubles still to be rectified, the flying qualities of this new type are by way of being outstanding, and the moderate tone makes the Report all the more convincing. all conditions of power and flap-set- ting. There is no tendency for a wing to drop, and. when held at the stall the aircraft simply rocks fore and aft, with a slight buffeting as the nose falls away. Most important of all, full aileron and rudder can be applied without ill-effect when the aircraft is in this stalled condition. The ailerons remain effective, and their use does npt tend to stall a wing. Approaches can consequently be made safely at low speed and with no particular need for the use of power. Finally, even in its unfurnished test-shell form, the Ambassador—thanks largely to the low tip-speeds of the airscrews and to the over-wing exhaust-manifold outlets —is remarkably quiet inside. Conversations can be carried on in more or less normal tones, and the noise-level should be very low indeed when the aircraft has been furnished. It is early yet to make any useful comments on the Ambassador's asymmetric flying qualities. New rudders, with additional geared-tab area to compensate for the de- letion of the original spring tab, are being fitted now that the preliminary handling trials have been completed. These should be considerably lighter in action and will permit the completion of the single-engine flying tests. Already, however, a number of hours of asymmetric flying have been put in at medium powers, and the results have been very satisfactory—especially where the all-important minimum control-speed characteristics are concerned. Some very provisional figures obtained show, in some cases, an im- provement on those previously estimated. A feature of the Ambassador which has a good incidental effect on engine-failure safety is its low span-loading. The aircraft, when flying engines-off, gives an impression of unusuarbuoyanty. This is borhe^out in practice by the low rate-of-descent figures recorded in this condition. These figures show an L/D ratio of 17.5 even at a gliding speed as low as 106 m.p.h. (170 km./h.). In practice it simply means that there is nothing critical about the hand- ling qualities in emergency conditions. From the pilot's point of view the Ambassador's control cabin layout is unusually good, and the "drill" is sim- plified to the point of demanding only a minimum amount of memory-jogging. The steerable nosewheel and pilot- operated control locks greatly ease the crew's labours while taxying, and the view from the control cabin is well above average transport aircraft standards. The layout of this cabin is, in fact, such that the pilot is given a valuable impression of being part of the machine. He is not merely someone conducting an aircraft with the aid of a number of ill-disposed controls and from a some- what indifferent grandstand—an unfortunate impression often gained when flying an aircraft for the first time H. A. T.
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