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Aviation History
1967
1967 - 0762.PDF
FLIGHT International, May 11 HANDLEY PAGE JETSTREAM . . . Undercarriage The tricycle undercarriage is designed and made by Electro-Hydraulics Ltd, with tyres, wheels and anti- skid brakes by Dunlop. The single mainwheels are the same size as those of the HS.125, but larger section tyres at com- paratively low pressure (521b/sq in) are designed for operation off grass. An inwardly retracting arrangement was chosen so that stowage was as nearly as possible within the basic shape of the aeroplane. Steerable, and fully castoring in operation, the twin-wheeled nose undercarriage is forward-retracting. The fairing doors which cover the retracted undercarriage legs also cover the bays when the wheels are down. Testing A comprehensive structural test programme is being undertaken to clear the aircraft for its full expected life. Much of this will be complete before the certificate of airworthiness is granted. The third of the five development airframes now in final construction will soon begin fatigue testing. The wing and fuselage unit will first of all be statically pressure tested up to 1.33 times the design differential of 6.51b/sq in. Fatigue testing under pressurisation, air and inertia loads, will then begin in the water tank with 25,000 ground and flight cycles, followed by limit loading both with and without cabin pressurisation. Further fatigue and fail-safe testing will continue the torturing of that specimen. A pressure cabin and empennage specimen will be static load tested to twice the design cabin pressurisation, with empennage loads simulated at various centre of pressure positions. This specimen will also be tested for fail-safe survival. The third major structural component to be put through the full routine will be an engine bearer assembly. Systems Whereas in all of the areas of technical design described so far Handley Page's approach to the Jetstream has been to follow the well defined paths of good aeronautical practice, it is in the matter of equipment and systems, design, installa- tion and serviceability that the special requirements of the market have called for a new kind of approach. Here the primary criterion has been to find the best blend of British and American equipment dependent upon its availability, reliability and its manufacturers' guaranteed worldwide after- sales service and product support. Whilst the basic equipment problem is to ensure that it will be properly supported in the field with spares and technical service, much has also been done to ensure the easy servicing and reliability of the selected equipment. Flying controls All the main control surfaces are manually operated from dual control wheels in the cockpit through cable and push-rod systems. Aerodynamic balance on the ailerons is by set-back hinges and geared tab (starboard tab for trimming only), on the elevator by set-back hinge, unshielded horn and geared tab; and on the rudder by unshielded horn and spring tab. Although in their most recent aircraft Handley Page have tended to favour the use of push-pull rod systems, these are almost unheard of on light aircraft in America; so for the most part cables with standard American end fittings were chosen. The trim tabs on the control surfaces are operated manually from pedestal-mounted control wheels connected by cables to irreversible screw jacks. Provision is also made for a Bendix electrical actuator to supplement the manually operated pitch trim circuit; the switch for this would be on each pilot's control wheel. With planned up-grading of the airworthiness to FAR Part 25 and BCAR Section D it is expected that the trim circuits will suffice for the total control system to be considered fail-safe. Fuel The engine fuel system consists essentially of two integral wing tanks, each of 195 Imp gal capacity. Each tank is divided by diaphragm ribs into five cells and these feed through non-return flapper valves into the innermost cell, which serves as a collector tank. Situated in each collector bay are duplicate booster pumps, with integral non-return valves, and from these fuel is fed to each engine through an individual line with a filter-cum-negative-g-tank, a low-pressure cock and a fuel flowmeter. To ensure the maximum amount of usable fuel in the tanks, there is a jet scavenge pump in the inner- most cells. There is a crossfeed line and cock. One filler cap for gravity refuelling is provided on each wing tank. Contents indication is by capacitance-type system; there is provision for drip-sticks to special order. Stack pipes leading from the outermost end of each wing tank allow venting. Filter de-icing using methanol injection is provided and a warning lamp system indicates low pressure at the engine pump inlet. Air Conditioning and Pressurisation is provided for the entire volume of the fuselage given over to crew and payload accommodation. Air is tapped from the engine compressors, each of which feeds a separate cold-air unit package so arranged that one unit supplies the flight deck and the other the cabin—or either unit serves both areas. Thus, each area can be kept at required temperatures—a difficult problem with a single system. In the case of the Jetstream, any one system can maintain full pressurisation (6.51b/sq in differential for an 8,000ft cabin altitude at 30,000ft) and full temperature control. The two identical cold-air units comprise AiResearch off-the- shelf components and the system is assembled and tested in America. The design requirements for the unit include tem- perature control in the cabin between +15°C and +30°C with the ambient temperature range from arctic minimum and tropical maximum over the altitude range of sea level to 30,000ft. Recirculator fans at each end of the cabin enable some cabin air to be mixed and re-circulated with the con- ditioned supply. Air conditioning is available on the ground as well as in flight; a Kollsman automatic pressurisation controller is fitted to give the pilot a choice of automatically maintained cabin altitudes up to 8,000ft. Two safety relief valves give protection against over-boosting, and two inward valves against negative differential. Indication is provided of the cabin altitude, pressure differential, and rate of change of cabin pressure, with warning lights for over- and under-pressurisation. All aircraft are fitted with an emergency oxygen supply as basic equipment and there are two standard variations for the crew. For passengers in the Jetstream under third-level and air taxi rules there is provision for two portable oxygen packs. For executive versions there is a ring main system which provides every passenger with an oxygen point and mask. Hydraulics The raising and lowering of the undercarriage and wing flaps, the steering of the nosewheels and the operation of the brakes are effected hydraulically. The 2,0001b/sq in system is supplied from two engine-driven pumps. A Skydrol 500A fluid system is optionally available. Totally independent hand-pump operated systems are provided for the emergency lowering of the undercarriage and flaps. Ice and Rain Protection Airframe and propeller de-icing equipment is optionally available, but a gold-film electrically de-iced Triplex windscreen, fitted also with wipers, is standard. The engine intake (hot air) de-icing is an integral part of the basic powerplant. Goodrich inflatable rubber boots are being engineered to fit the wing leading edge outboard of the engines and for the fin and tailplane. Air pressure for inflating the boots is tapped from both engine compressors while the pulsation cycles are determined by solenoid distribution valves triggered by an electronic timer—one in the circuit to the wings and the other in the circuit to the empennage. The system will be cleared for operation of up to two hours' duration. Jet pump ejectors provide a small vacuum to constrain the boots to the normal aerofoil contour when they are not being used. Electrical de- icing of propeller blades and spinners is optionally available. The de-icing equipment of the Jetstream will be cleared for operation in severe icing. Wind tunnel tests have been made with simulated heavy icing build-ups on the flying surfaces. Electrics Two electrical generating systems are provided: each engine is fitted with 9kVA 200V 400c /s alternator and 3kW 28V d.c. starter/generator. The former supply power
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