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Aviation History
1965
1965 - 0175.PDF
The Sk35C trainer cockpit shows the distinctively sharply raked ejection seats, inner blast screen recessed to take the periscope mounted in the black centre canopy panel, the access ladder and the extended ram-air turbine aft of the nosewheel leg. The Sk3SC carries neither radar nor missiles SAAB DRAKEN in the Air ... An outstanding feature of Draken operation has been the use of extremely low approach speeds well up the back of the drag curve, a procedure requiring delicate and constant management of throttle and careful control of angle of attack. Now, following a number of undershoot incidents, approach speeds have been slightly increased and the target touch-down speed is equivalent to 140kt, with experi- enced pilots closing the throttle as they cross the runway threshold. The a.s.i. of all Drakens has a white band extending downwards from a speed at which the angle of attack is sufficient to touch the tail on the runway. In the Sk35C the band starts at 260km/hr (140kt) though some pilots say they can touch down safely at 240km/hr (13Okt). Trainees are taught to set up the appropriate angle of attack early—by eye, because there is no angle of attack indicator—and to drive the aeroplane on to the runway without flaring or reducing power. Basic systems of the Sk35C are straightforward and conventional. Groups of integral and bag tanks in the fuselage and inner wings are supplemented by additional tanks replacing the two 30mm Aden guns. Fuel tankage is divided into front and rear groups whose contents are individually shown on a two-needle gauge marked in percentages. Transfer is automatic. Target fuel contents for landing is 20 per cent, but a go-around is feasible with 10 per cent. Electrical power is provided by d.c. generator and constant-speed alternator, with a ram-air turbine-driven generator for emergency power in most later Drakens. Otherwise the aircraft battery has sufficient capacity to maintain vital loads during an engine-out approach. Hydraulic power is by conventional two-pump, two- circuit system operating powered controls, airbrakes, undercarriage, wheelbrakes and nosewheel steering. The last-named is controlled by a tiller wheel on the right-hand console and the brakes are applied by toe pedals. The ram-air turbine also drives a hydraulic pump. Engine handling is, in Rolls-Royce tradition, very straight- forward. For starting, low-pressure cocks for engine and afterburner are opened by switches, the battery is switched on, the throttle moved out of the h.p. cock gate and the starter button pressed for 2sec to initiate the i.p.n. starter turbine. After being switched on at 27 per cent r.p.m., the generator can handle normal loads, but it is standard practice for a ground generator driven from the front of the standard ground-support truck to be coupled to the aircraft for as long as necessary to ensure that the radar is functioning in a stand-by condition and the instrument gyros are spun-up ready for instant getaway. Full cold thrust is reached at 100 per cent r.p.m., after which the throttle can be pushed through a detent to light the afterburner. A 9 per cent r.p.m. range is then available to vary thrust for formation flying. The 100 per cent cold power can be restored by extinguishing the afterburner with a switch just within reach of the left finger tips when the throttle lever is in the afterburner range. The engine can be throttled right back at any Mach number and the afterburner can be lit at any speed. An automatic j.p.t. limiting system is disengaged whenever the nosewheel is extended to prevent inadvertent loss of take-off power. The rear cockpit of the Sk35C is equipped only with minimum instrumentation, including a conventional electric artificial horizon, combined Machmeter/a.s.i. and other basic dials. Virtually all switches, systems, and navigation equipment, undercarriage and drag-chute are controlled exclusively from the front cockpit. The rear pilot has little more than throttle, stick, pedals, brakes and canopy jettison. Background colour is green and night lighting is very effectively provided by red bulbs behind a metal screen at least I'm clear of the main instrument panels. The cutouts through which the dials are viewed are carefully angled to allow for parallax and avoid unwanted cut-off. In the J35A simulator this form of lighting proved extremely effective. The RSAF is possibly one of the two Air Forces in Europe still to use metric measurements for flight instrumentation. (Is there, I wondered, a kilometre Centigrade, according to which one Megameter would always equal Mach 1. For once, the metric system has not tied everything neatly together.) If the rear cockpit of the Sk35C is stark, that of the J35A is hardly complicated. Dominant central positions are taken by the weapon sight and the interception radar scope. Flight instruments are traditional except for the metric measurements, but a v.s.i. is conspicuously absent. The altimeter has zero at the bottom of the dial and no third needle to indicate above 10,000m. This appears extraordinary to one used to altimeters in feet, but the difference between 32,800ft (10,000m) and zero is a great deal more readily sensed by a.s.i., Machmeter and other indications than 10,000ft. Nevertheless, some pilots have misread it. The simulator has a perfectly plain gyro-magnetic compass with fixed dial face and rotating indicator needle, a layout demand- ing inverted thinking when flying in a southerly direction. Much more advanced is the use of a Swedish ASA twin-gyro reference with a Sperry globe horizon combined with Sperry Zero Reader.
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