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Aviation History
1948
1948 - 0629.PDF
MAY 6TH, 1944s FLIGHT 501 The rotor head and stabilizing bar of the 47B are shown on the left, while the right-hand picture shows the hub of the tail rotor and its cable-operated pitch-control. banks gave an indication of accurate control, an accom- plishment not acquired until after considerable practice, but it was noted that Mr. Youell did not wear that intently- staring look, with eyes glued on the rotor rev. counter, which so often characterizes the pilot of a helicopter. He found plenty of time to look around, turn his head to talk to us, and generally seemed to have mastered the 47B so thoroughly that all control movements had become just as instinctive as do those of a fixed-wing aircraft. Very Complete Equipment The cabin is comfortable both as regards seating and view, and the instrument panel is well laid out and very complete, even to the carrying of radio and night-flying navigation lights. The flight instruments are clearly marked to indicate the limits permitted. For example, the airspeed indicator has a red mark at 92 m.p.h. indicated air speed ; the dual engine and rotor revs, indicator has a green STABILIZER BAR segment between 285 and 350 rotor r.p.m., the minimumand maximum rotor speeds, and a red division at each end of the green segment. Similarly, the cylinder-headtemperature indicator has a green segment between 100 and 230 deg. C. The same arrangement is adopted for theoil pressures and temperatures and for the petrol pressure. The controls (dual) are of orthodox type, with slopingcolumns for collective pitch control and vertical columns for cyclic pitch control. On the former is a twist-gripthrottle and the latter has a friction adjustment to eliminate fatigue on long flights. Directional control is by pedalswhich operate the pitch of the tail rotor. Power is supplied by a Franklin flat-six • air-cooledengine, mounted with its crankshaft vertical, immediately below the rotor shaft or mast. There is a two-stage plane-tary reduction gear, which provides a ratio of 9 to 1 for the main rotor. The tail rotor gear is higher, the ratio being1.667 to 1. There is a centrifugal clutch which engages at about 1,500 r.p.m., and a free-wheel coupling. Should the en- gine stop, the freewheel couplingdisconnects it from the rotor, and the tail rotor is then driven bythe main rotor so that full direc- tional control is maintained inautorotative flight. Fuel is carried in two tanks, one forward contain-ing nine gallons and one aft hold- ing 23 gallons (American, ofcourse). Action of the stabilizer bar usedon the Irvin-Bell 47B is somewhat difficult to explain in full detail, HOKQUE I* CONTROL. CYCLIC PITCH CONTROL COLLECTIVE PITCH CONTROL WITH AUTOMATIC 'THROTTLE CONTROL ABOVE, a part-sectioned view ot the 47B showing general layout of com- ponents. On the right, the controls and instrument panel. I, map compart- ment ; 2, starter button ; 3, compass-card holder ; 4, compass ; S, ignition ^witch ; 6, master switch ; 7, radio control pane! ; 8, loudspeaker ; 9, airspeed indicator ; 10, altimeter ; 11, cylinder-head temperature gauge ; 12, ammeter ; '3, microphone button ; 14, cyclic pitch control stick ; 15, friction adjustment ; 16, tail-rotor control pedals ; 17, circuit breaker (instrument light) ; 18, circuit breaker (radio); 19, carburettor heat control; 20, throttle; 21, collective Pitch control ; 22, fuel " on-off " valve ; 23, oil-temperature selector switch ; 24, carburettor mixture control ; 25, position-light switch ; 26, fuel level indicator ; 27, oil-temperature and fuel pressure gauge ; 28, manifold-pressure puge.; 29, rotor and engine rev. indicator ; 30, circuit breaker (instruments); :. auxiliary fuel pump switch. L
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