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Aviation History
1963
1963 - 0993.PDF
962 FLIGHT International, 20 June 1963 IN TH E PARIS AIR . . . Though the pilot need not know the numerical values of the angles, he has to observe the lights to avoid excessive angles of attack and to achieve best performance. The aircraft will lose speed in a turn with more than the green light showing; and speed is critical for an interception and hard to recover at above Mach 1.0. I asked what happened if the pilot pulled into the red sector and kept on pulling, but was told only that the maximum angle of attack would be exceeded. When I later pulled back hard into the red sector at about 400kt at 10,000ft I could only find a rough buzz of buffeting and no sign of any breakaway or sudden pitching. The Mirage has an artificial-feel system intended to maintain an approximately constant gradient of stick force per g throughout the flight envelope, starting at about 6.61b/g; but there is also a little hydraulic chap, called Oscar, who applies a progressive additional resistance as the load factor increases. He does not intervene suddenly like the F-104G's stick thruster; nor is there any stick-shaker. Continuous pitch autostabilization is applied through the small trim-flaps inboard of the elevons, which electronically follow up the pitch—not roll—effort of the elevons and are biassed over ±2° movement by a rate gyro. Rudder control is electro-hydraulic, the pilot's input being sensed in an open scissor link and fed elec trically to the powered control as a computed signal modified by a yaw stabilizer. Should the electronic system fail, the scissor link immediately closes to establish direct mechanical control. Aileron response at subsonic speeds is extremely high and there appears to be little or no artificial feel. Rates of roll of 300°/sec can easily be achieved, though only three consecutive rolls at such rates are allowed, in order to avoid inertia coupling. A very useful 120°/sec rate of roll is available at supersonic speed. The control column is short and "broken," giving pleasantly small manual movements. One can comfortably rest one's forearm on one's thigh during high-g manoeuvres. Undercarriage control is by a normal lever on the left, with a tiny "three greens, one red" indicator on the main panel. There are, of course, no flaps; and the airbrakes are controlled from a press-switch on the tip of the throttle lever. Gentle pressure extends the airbrakes only so long as the button is kept pressed. Additional pressure will lock the switch. The instantaneous control is most useful for very brief braking during formation flying or rapid vertical manoeu vring, when retardation can be applied for a second and immed iately released again. I found it very useful when trying to remain subsonic during the latter part of the flight at lower levels. The airbrakes can, incidentally, be extended under any conditions and at any speeds, though they are not normally used with the gear down. Capt Varin extended them as a demonstration at Mach 2, although the deceleration derived from simply cutting off the after burner is far greater at such speeds. There are two more automatic flight control modes in the oper ational Mirage HI, though neither was fitted in the particular air craft I flew. The first is the so-called auto-commande, a short-term autopilot which is used as the standard flight mode. The pilot has to exert the normal control forces, but as soon as he releases the stick it stays put and that flight attitude will be held constant for up to two minutes, regardless of trim-changes introduced by passing Mach 1 or changing configuration. Thus the pilot has a form of stick-steering autopilot which can greatly ease his task, when he is Capt Varin in the front seat, Mark Lambert in the back. Note the rear gunsight, blast shield and unusually low coaming occupied with radar and weapons. The second system is the auto- power control, which has proved very helpful during the approach. Because the Mirage normally approaches "on the back of the drag curve," the main control during landing is the throttle. It is normal to set up a constant angle of attack and motor in with the throttle alone, knowing that increased power is likely to decrease speed rather than increase it. The normal GCA approach speed is in the Adhemar constant- yellow attitude and, with the auto-power system, the pilot simply sets a datum power of between 7,400 and 7,800 r.p.m. and keeps the attitude and heading correct. Auto-power then varies the after burner nozzle aperture to adjust the thrust of the engine (without moving the throttle) and maintain constant i.a.s. Speed during a GCA is 180kt, reducing to 160kt over the approach lights and about 145kt at touch-down. The powered hydraulic brakes have the Mini-stop anti-skid system and the cruciform braking parachute can be streamed with the nosewheel still off the ground. Cockpit pressurization appeared to be excellent, with no sudden pressure changes and a remarkably stable atmosphere even at the highest rates of climb. A very powerful temperature control system is provided to keep the pilot cool despite airframe heating. Engine, afterburner and fuel controls are extremely simple. The normal internal fuel load, including the tank which replaces the rocket motor, is split into left and right halves with automatic flow-proportioner and manual stand-by cross-feed. Total capacity is 590 Imp gal. A tiny panel of four transfer lights shows correct feeding, a light warns of 600 litres remaining, a veeder counter shows total litres consumed at any moment and two needles on a single gauge register the amount remaining on each side. Engine instru ments are a j.p.t. gauge, two-needle r.p.m. gauge and lights showing afterburner fuel feed and ignition. The afterburner is engaged by snapping the throttle lever up over a detent, whereupon fully variable afterburner power can be applied to raise the thrust of the SNECMA Atar 09Cfrom 11,0001b to 14,1001b. There are two hydraulic systems, one for the servos alone and the other for servos and utilities. The supplies can be switched from the cockpit and there is an "intelligent reservoir" which will auto matically cut off flow to the gear and airbrakes if a fluid leak becomes apparent. Emergency wheel-brake pressure can be applied pro gressively to both mainwheels together in case of brake failure. Steering on the ground is by differential braking. The airbrake switch is normally pin-locked on the ground to avoid damaging groundcrew working on or under the wing. A central warning panel is associated with an alarming attention-getting klaxon. There is no forward view through the rear gunsight, but the in structor can manoeuvre a target spot in the pupil's sight and observe his tracking of it. Although the Mirage III has flown a few tenths beyond Mach 2, normal squadron machines reach just above or below Mach 2. The limiting factor is heating of the engine compressor face. Having absorbed this information during an extended cockpit briefing, I strapped in, the canopy hummed down and Capt Varin started the engine by high-pressure air. Every second counted now and, after my ride in the Lightning last year (Flight International for May 31, 1962), I was prepared for a pretty hot get-away. Our take-off weight was 18,0401b. Varin taxied out, lined up, went to full cold thrust, said a few words over the radio and let go the brakes. A second later I felt an unusually gentle thump as the afterburner lit; then we really shot forward. At 120kt Varin raised the nosewheel, set 10° nose-up attitude by the boule and lifted off at 160kt only 14sec after brakes off. Eleven seconds later he cut the afterburner at 280kt and we accelerated in a steep turn to come back over the field. I now give the total elapsed times from brakes-off as recorded on the ground. At lmin 5sec, heading back for the field at 500ft and 380kt, Varin relit the afterburner. With insistent urge we accelerated to 600kt in 19sec and pulled up into a 30° climb at Mach 0.9—this was lmin 24sec after brakes off. We passed 20,000ft at 2min 4sec, 30,000ft at 2min 30sec, 33,000ft at 2min 37sec and began a forward pushover at 35,000ft at 2min 46sec. Thus, time from 500ft to 35,000ft was lmin 22sec. Most of the way up I was resisting the rapid pressure changes while Capt Varin climbed inverted to show me the pretty clouds receding below us. He turned on full cooling to anticipate the heating of the
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