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Aviation History
1937
1937 - 1668.PDF
624 - FLIGHT. JUNE 24, 1937. but only at speeds in excess of 200 m.p.h. is the airflow and engine noise really marked, and at 140 m.p.h., throttled well back, it is as quiet as one could wish. If passengers were to be carried it would be a simple matter to hunt out the origins of the various organ-pipe and other noises. After the two Mercury VIIIs (each 840 h.p. at 14,000ft.) have been run up and the cowling gills opened by means of a hand-wheel to the right of and slightly behind the pilot, the rudder and elevator trimming wheels (placed to gether on the right) are adjusted so that the dashboard indicators show that the tabs are approximately in the neutral position, according to the load, and the hydraulic- ally operated flaps are set in the 30-degree take-off position. In order to save later explanation, it may be as well to sav that there are three vertically operated push -pull levers in a, bank on the pilot's right, one to set the undercarriage jack in motion, another to operate the flaps, and a third, 01 "selector," to transfer the oil pressure, when necessary, from these to the jack which raises or lowers the rear gun turret. The necessary oil pressure is supplied by an engine- driven pump, and there is an auxiliary hand-operated pump, with a lever on the pilot's right, in case trouble is experienced with either the particular engine concerned, the pump itself, or the pressure lead system. The flap and undercarriage indicators are on the port side of the control cabin, the former showing particularly the " up," A plan view of the Blenheim's control cabin, showing the tidy instrument panel and giving some idea of the range of view provided for the pilot and bomber-naviga tor. On the right of the pilot's seat can be seen one of the two trimming wheels and the three hydraulic control plungers in line behind it; the trimming indicators are on the right side of the dash, while those for the undercarriage and flaps are on the left side of the cabin. "take-off" and "landing" posi tions, and the latter incorporat ing a red and green warning light system. All the indica tors are of the sliding-signal type, and there is the usual buzzer warning device which comes into action when the throttles are closed with the undercarriage retracted. Just as soon as the machine has left the ground the under carriage control valve is pulled up and the elevator tab wheel rotated to adjust the natural change of trim as the jacks do their work. The acceleration is most marked. Then the flaps are raised by pulling the second plunger (there is a momentary , sink—rather like a pronounced down bump in a machine with this performance), and the three controls set in the "off," or neutral, position. Somewhat behind the pilot and on his left are the two D.H. airscrew pitch-changing plungers; these are pulled out with the expected "gear-change" effects. We are most definitely on our way —upward as well as forwards. Even in coarse pitch and at an air speed of 140 m.p.h. the climb is phenomenal, though the engines, fully supercharged as they are, do not develop their maximum power until the machine has reached 14,000ft. Hence the desirability for the use of two-speed blowers in machines of this description. By the time that 7,000ft. has been reached one has had a chance of realising just what good forward visibility means. In a military machine the need is obvious, but it is no less necessary in the case of civil machines. The field of view in the Blenheim is almost completely hemi spherical, and as we cruised over the docks at Avonmouth I looked through floor windows and realised just how efficient as a piece of long-range artillery this Blenheim is. Only to port and starboard, where the big radials obstruct the view, is there a blind spot for the pilot— and the rear gunner will take care of that. As a flying machine the Blenheim appears to be all that one should expect nowadays. The ailerons are reason ably light and the machine will turn and change bank accurately without use of the rudder. At cruising speeds she will turn with fair accuracy on the rudder alone, but at high speeds it appears that the machine has pronounced positive stability in the directional plane ; the use of the rudder by itself merely induces a yawing motion while the machine carries on as before with a loss of speed. Inci dentally—and the point might be incorporated in all larger machines—it is possible to adjust the position of the under- slung rudder pedals in relation to the already adjustable
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