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Aviation History
1975
1975 - 0083.PDF
RIGHT International, 9 January 1975 level flight. In the case of the Triplane it is no good using only "aileron" to pick up a wing and neither is it any use kicking on rudder as this just yaws the nose up above the horizon with a loss of airspeed. In contrast if the Boxkite drops a wing it is best to hold the rudder still and pick up the wing with aileron, accepting the inevitable heading change. In these early machines the pilot is much more Of a passenger, accepting the fact that the machine takes him where it wants to go, and agrees only reluctantly to respond to the pilot's increasingly desperate demands. The most important instrument on the Boxkite is nine inches of waxed string tied to a crosswire under the foreplane; when it streams straight back all systems are "go", but if it gets 10° out of line, beware! There is also good reason for placing a great deal of credence on the old aviators' stories like "there isn't much lift in the air today." Instructors at the Central Flying School not so many years ago discussed the old chestnut: "If you turn down wind, do you lose airspeed?" "Impossible," said the theor ists, brushing aside the assertions of the early aviators; "the aeroplane operates within a moving mass of air and doesn't respond in the manner suggested." Shuttleworth pilots on the other hand will be adamant that speed is indeed lost when turning downwind, as is dramatically demonstrated with the veteran aeroplanes, and these reports are now backed by the latest theory from a well known aerodynamicist. The business of being "forced down" has puzzled many modern aviators, but the culprit is rapid and relatively large changes in induced and profile drag caused by Below, "when the Avro Triplane encounters a bump the pilot may expect a second . . . as the tailplane encounters the disturbance"; below right, the Sopwith Pup: "fly the aeroplane" 47 pump in the cockpit produces 2-51b/sq in of air pressure in the fuel tank, and when this is achieved the blow-off valve hisses away merrily. This together with the array of pipes and levers gives the impression that the whole device is probably powered by steam. A single brass igni tion switch and a "blip" cutout button on the stick com pletes the list of controls. To start a rotary, such as the Le Rhone in the Pup, each cylinder is primed with a large and wicked-looking syringe and the engine is pulled over with that asthmatic wheeze peculiar to rotaries. With chocks in position and a pair of brawny mechanics on the tail the air lever is opened half-way, fine adjustment closed and the ignition switched on. The mechanic at the bows gives the propeller a mighty heave and with a cough, a splutter and a great hissing roar the engine catches, immersing the entire aeroplane in a cloud of blue smoke rich with the tang of burnt castor oil. The inexperienced aviator will attempt to "catch" the engine on the fine adjustment, but this will flood the whole thing and bring it to a grinding halt. One must have patience; the priming fuel is soon exhausted and the engine cuts (a lean cut this time) and now we can leisurely open the fine adjustment. There is plenty of time, because of the tremendous flywheel effect of the rotating engine. Again the engine coughs and picks up, this time on the main fuel system, but one has to balance that elusive mixture setting. Careful, the air pressure is falling and this needs three or four quick strokes of the handpump; in the air the wind-driven pump will take care of it, but we will still have to monitor it and perhaps adjust the blow-off valve. Oil is now pulsing in the glass bowl— there is no pressure gauge—indeed on earlier machines one had to meter the oil flow, as on ancient motor cycles. Now the power is slowly brought back from our original full-power start setting to a "dot and carry" spluttering if \ I* I h * u I* turbulence and also the extra trim drag during attempted corrections. Hence the expression "no lift in the air today." The problems of flying these ancient machines are matched only by the difficulties in persuading a rotary engine to keep running. For example, the engine controls in the Sopwith Pup would defeat any modern pilot. There is no fuel cock visible, and the throttle quadrant is graced by two levers of which the larger controls the air passing through the choke while the smaller meters the fuel via a needle valve. They are known as the "air lever" and "fine adjustment" respectively. Originally the air lever was used more or less as a throttle, but this was not very efficient, and one really has to balance the mixture continuously as engine conditions change. A large hand-
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