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Aviation History
1941
1941 - 2353.PDF
OCTOBER gva, 1941. FLIGHT TEACHING AEROPLANES TO FLY airscrew and partly to bleed the airscrew of any air which may be trapped in the system. With the airscrew lever in the maximum r.p.m. position the throttle is opened up to rated boost and the r.p.m. checked again. Before throttling back the magneto drops are checked, (Each magneto switched off in turn and the drop in r.p.m. noted.) 12. While warming or running up, the engine is tried on alternative fuel tanks and the fuel pressures noted. 13. After completing the engine run, and having waved the chocks away, the brakes are tested, while taxying, for pressure and grip and after rubbing the brakes during two or three minutes' taxying the aircraft is brought to rest and the static grip of the brakes tested. Incidentally, all brake tests should be carried out on tarmac or dry grass to eliminate wheel slip. While faxying, a rough check should be made of the blind-fling instruments. B. During Flight After having taken off and set the undercarriage, flaps, airscrews, throttles and cooling gills in the correct climbing position, a climb is made, if weather permits, to the rated altitude. When climbing the following checks are made : — 1. Generator charging rate and correct discharge for various electrical gear. 2. Air compressor building up satisfactorily. 3. If the best climbing speed is not above the maximum speed at which the undercarriage will retract, or above the maximum speed at which it is permissible to lower it, the chassis tests may be done on the climb. If the under- carriage appears to be working satisfactorily it should be raised and lowered three of four times on each set of under- carriage indicators. A pressure gauge must be fitted to enable hydraulic faults to be more easily located. The gauge is removed after the test flight. 4. During the climb tfie usual temperatures and pres- sures are watched, but unless they are abnormal they are not usually recorded until the rated altitude is reached. This is the height at which the rated boost begins to fall off. From the altitude at which this fall-off in boost occurs, the pilot can tell whether the automatic boost control is working properly, and whether the pipe-line from the super- charger casing to the boost gauge is free from leaks. Many engines are fitted with a cut-out on the boost con- trol, and, if the boost is low, this cut-out can be used to determine whether the control is at fault or whether the low boost reading is due to a leak. If, on pulling the cut- out, the boost rises and remains steady, it will be the automatic.control which is at fault; if the boost does not rise, however, it will indicate a leak. This test has, of course, to be carried out just below rated altitude, as other- wise the boost will not rise in any case. It is usual to continue to climb and check the operation of the two-speed supercharger by making several changes and noting the increase in boost and the response of the automatic boost control to this sudden increase. On a percentage of aircraft the maximum power altitude is found. This is the maximum height at which full throttle boost at maximum r.p.m. is obtainable in level flight. On all other aircraft a five minutes' level flight at full throttle is done just below the average maximum power altitude and all temperatures and pressures recorded to- gether with A.S.I, reading. At this height, or above, the engines are checked for weak mixture while lunning at various combinations of boost and r.p.m On fighters it is usual to make an additional weak-mixture check by doing steep turns while running in weak, as this increases the severity of the test when applied to certain engines. A few aircraft out of the week's Many are the dials, levers, instruments and gadgets which have to be checked on a modern aeroplane. shown above is an example of a modern machine. The Hampden cockpit
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