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Aviation History
1963
1963 - 1225.PDF
r ^r ONE-ELEVEN To provide variable tailplane incidence, both hydraulic systems are used, each supplying identical circuits and motors; the motors drive a gearbox coupled to the screwjack moving the tailplane. Selection is mechanical through a conventional trim wheel in the flight deck operating a cable linked to the servo valves of the hydraulic motors. The rate of change of incidence is two-thirds of a degree per second with either both or one motor operating. Should a motor or servo valve fail, a collapsible strut "breaks" under excessive load, causing a valve to cut the hydraulic supply and a micro-switch to operate a warning light on the flight deck. The pilot can then isolate the fault by cutting the hydraulic supply to the flying control services in the associated hydraulic system. Rudder control is through two independent hydraulic jacks located in the base of the fin, each operated by separate hydraulic systems, governed by cables connecting the pilot's rudder bar to the servo valves of the jacks. Interposed between the rudder bar and the servo valves is a duplicated hydraulic artificial-feel unit, and also a yaw-damper actuator powered by No. 2 system. If a servo valve jams, a break-out strut automatically off-loads the jack and operates a flight-deck light warning the pilot to isolaje the associated hydraulic circuit. Should both systems fail, sufficient manual control will be available for the pilot to manoeuvre the aircraft. On each wing there are two spoiler/airbrake surfaces. The inboard spoilers on each wing are hydraulically connected and are operated by individual servo-controlled hydraulic jacks, supplied by No. 2 system. Similarly, the outboard spoilers are powered by the No. 1 system. When used as spoilers, the surfaces move upwards in conjunction with the uprising aileron and remain stationary on the other wing. As airbrakes, all four spoiler surfaces rise simultaneously. If a servo valve jams in the extended position, a collapsible strut will "break" operating a light warning the pilot to isolate the associated hydraulic circuit. This allows the spoiler to blow back FLIGHT International, II July 1963 through ram effect, the hydraulic fluid from the jack exhausting to the system reservoir. Should the aircraft speed exceed the design speed for spoiler extension, the spoiler will blow back automatically and the displaced hydraulic fluid will be absorbed by the associated system accumulator. In this event the warning light will not operate. Hydraulically powered artificial-feel units are built into the rudder and elevator circuits. These provide both pilot and auto-pilot with an accurately calibrated relationship between control forces and applied control movements appropriate to the conditions of flight. This gives a positive feel to the controls and helps to prevent overdressing the structure through over-controlling. The forces applied by the pilots are resisted by hydraulic jacks to simulate the loads imposed by the airstream on the control surfaces. Landing gear retraction time is approximately 8 sec plus a further 2 sec required for main undercarriage doors closing. Wheel brakes are applied automatically throughout the retraction cycle, and are released by depressurization, down, or free-fall selection. Hydraulic power for nosewheel steering is supplied by No. 1 system and becomes available only when the nose undercarriage is locked down. Supply is automatically cut when the nose under carriage retracts. There are two wheel brake circuits, "foot" and "hand," and both are powered by No. 2 hydraulic system. In each circuit there is an Accumulator which independently stores sufficient energy to supply six full brake applications. The foot brake system accumulator ensures a minimum of one anti-skid stop under the most adverse conditions. The foot brakes are progressive in action and are applied by means of pedals giving differential response. The hydraulic system connecting the pedals to the brake control valve is independent of the main hydraulic system. The foot brake system includes an anti-skid device. The hand brake system is also progressive in action but does not incorporate an anti-skid device. It is operated by mechanical levers, one available to each pilot. Fluid reservoirs, main filters, main system accumulators, power FLIGHT International, 11 July 1963 shut-off valves and other equipment concerned with system supply are located on the rear bulkheads of the main undercarriage bays. Equipment associated with flaps, spoiler/airbrakes, and wheel brakes is also located in the undercarriage bay. No hydraulic piping or components are located within passenger or flight crew compartments except the low-pressure lines associated with the brake master cylinders on the rudder pedals. Fuel System Fuel is Stored in two main integral wing tanks formed by the wing torsion box. The wing centre section can be adapted to form a third tank. Small vent tanks, one in each wing extremity, are incorporated to collect fuel entering the venting system during manoeuvres. The wing construction of webs and ribs prevents rapid shifts of fuel within the tanks and enables variations of the centre of gravity position to be maintained within acceptable limits. The fuel capacity is 2,200 Imp gal (2,640 US) equally divided between the two wing tanks, plus 850 Imp gal (1,020 US) in the centre section tank. A single pressure refuelling point, located on the starboard side of the fuselage under the wing leading edge, is of the international standard 2Jin, bayonet self-sealing type. The control panel is approximately 3ft forward of the connection in the fuselage side. From it, and without need for steps or staging, the whole refuelling operation can be carried out. The maximum refuelling rate is 410 Imp gal/min at 501b/sq in, 150 gal/min delivery into each of the wing tanks and HOgal/min into the centre section tank. Defuelling, similarly, is either automatically or manually controlled. The One-Eleven can also be refuelled through overwing filler caps. Under normal conditions each main tank will supply the engine on its own side. The system also provides for feeding both engines from one tank or a single engine from both tanks. When the centre section tank is used its content is not fed direct to the engines but is transferred to the main tanks by pilot selection, using electric transfer pumps. Two electric booster pumps are fitted in each main tank. During take-off and landing all pumps will be in use; at other times only one on either side is required. The fuel is taken to the engines through two pipes which pass under the floors one Throughout the design of the One-Eleven the British Aircraft Corporation have been able to draw upon experience with turbine-engined airliners in short-haul operation which far exceeds that ofany other manufacturer. The fruits of this experience will be especially obvious to airline engineering staff, some of whom will come to know the equipment bay around the main chassis stowage. Here, looking for ward are found: 7, brake accumulator charging panel; 8, bay light; and 9, air-conditioning equipment If one turns around within the'same bay to look aft one comes upon: I, ax. motor and hydraulic pumps; 2, d.c. motor and hydraulic pump; 3, main hydraulics reservoir; 4, flap motor and gearbox; 5, primary flap torque shaft; and 6, secondary flap torque shaft. The bay is reached via a service door within the main landing-gear door, and the engineer whose outline is included in the sketch is about Sft lOin tall and standing on the ground A view looking down the rear ventral passenger stair, showing the following: I, engine fire bottles; 2, autopilot elevator servo; 3,control cables; 4, ventral-stair operating handle In this view of the external ventral surface the keyed items are repeated for clarity in the small inset at lower right; the main droning is, of course, looking forward. There are numerous aerials and other items distributed along the underside, but these are all indicated in the main cutaway drawing overleaf
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