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Aviation History
1933
1933 - 0453.PDF
57 AUGUST 31, 1933 THE AIRCRAFT ENGINEER SUPPLEMENT TO FLIGHT Fig. 13.—Zap Flap Installation on Starboard Upper Wing landing. This would be admitted if it were not for the fact that the increased lift permits a speed along the flight path so materially reduced that from actual ex perience, there have been no adverse comments by pilots. There has been instances of aeroplanes being equipped with airbrakes but without the necessary increases in lift. The result has been that, as the aeroplane must be dived at the ground at a sharp angle and at an unreduced minimum Speed, the rate of descent is so great as to be quite disconcerting. The reaction is caused by the necessary sharp flaring action close to the ground and the short time interval aggravated by the high vertical velocity. With the modern aeroplane, whose cleanness has gone so far beyond the aeroplane of several years ago, the addition of the drag imposed by a flap does nothing more than bring the gliding angle back to what we were accustomed to and eliminates the bad floating characteristics. If an aeroplane were infinitely dirty from a drag standpoint and had a high wing loading and flaps in addition, it would be con ceivable that the aeroplane would have to be dived at the ground at a 50 to 60 degree angle and the transition from this attitude to the 12 to 15 degree angle of attack for landing would quite complicate the technique of landing. Here we come to the problem that is often advanced by the automatic landing proponents. It is the writer's opinion that flying will not reach popular enthusiasm sufficiently to warrant a large industry until the human element of flying has been reduced far beyond what it is to-day. The place where the greatest human judgment is necessary is in that transition which takes place when the aeroplane comes in at a given negative angle in a glide and must be levelled off with the angular attitude changing to 12 or 15 degrees positive. It would be most desirable to build an aeroplane in which the pilot could wind a crank adjustment to a point where an indicator WOHW designate -" la«ding attitude," pull back his throttle and let the aeroplane do the rest. There are certain things, however, which make this difficult at this time and, under certain commercial operating con ditions, will be difficult to meet in the future. This is qualified, however, by considering only existing practical high lift devices. Rates of descent beyond 12 or 15 ft. a second are going to be difficult to take care of except in a very awkward type of landing gear. A rate of descent of 12 ft. a second at or near maximum lift can only be accomplished at the present time with a lightly loaded aeroplane of clean lines and with flaps, or slots and flaps. As the wing loading is increased, the velocity along any given flight path very adversely affects the rate of descent and the total overall L/D of the aero plane with retracted flaps must be very good in order not to have too steep an angular gliding attitude for Fig. 14.—The X0J.1 fitted with Zap Flaps and Ailerons 870 e
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