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Aviation History
1974
1974 - 0010.PDF
10 Civil Lynx from Westland FLIGHT International. 3 January 1974 By the Technical Editor WESTLAND HELICOPTERS is well advanced with plans to build a 12-passenger version of the Lynx helicopter, with deliveries planned to begin during 1976. Aimed primarily at the rapidly growing oil drilling rig market, the Lynx will also be offered with an eight-seat executive interior. The major structural design is virtually complete, detailing has begun, an engineering and cus tomer mock-up is to be built shortly, and a schedule for GAA certification has been drawn up. The nominal mission calls for the aircraft to ferry a 12-man crew to a rig 150 n.m. away at 150kt and pick up a shore-leave crew for the return journey, without intermediate refuelling. Single-pilot operation in IMC, both inside and outside airways, is being promoted as one of the main marketing attractions, and will read across directly from the military versions. The commercial possibilities of such a helicopter were recognised when the requirements for the third of the Anglo-French helicopters were being studied in the mid- 1960s. They called for a substantial improvement in reliability, safety and poor-weather performance, and were met basically by the adoption of a mechanically simple hingeless rotor driven by two engines, an advanced auto pilot with two-channel autostability, and a comprehensive navigation system. The commercial Lynx was first schemed as an air taxi helicopter, but for some time now the implications of a long-term global energy crisis have thrown the offshore oil and natural-gas rig-servicing markets into sharp relief. Large-scale surveys are being conducted in the North Sea, the Persian Gulf, the Gulf of Texas, Alaska, Indonesia and elsewhere, and all the signs are that oil extraction from increasingly inaccessible sites will continue to grow in importance. Helicopter operations in support of the drilling industry are already widespread, but they are based in many cases on types with limited bad-weather performance, and there are signs that rig-supply operators will push strongly for speed and airline-style dependability and productivity. Westland's surveys of the North Sea situation show that the average oil rig is manned by between 50 and 90 people working a three-week cycle (two weeks on the rig alterna ting with a week ashore), so that one-third of the staff is changed each week. On this basis, the ability to ferry 12-man teams over 150 n.m. was adopted as a reasonable target. Development of the military versions has already cleared the Lynx to operate at an all up-weight of 9,5001b (the original design figure was 8,0001b). To cash in on this, and to make adequate room for a 12-man team (plus two pilots), the fuselage was lengthened by the insertion of 12 10- S 6 50 100 150 200 250 300 350 400 Range- n.m. a 30.5cm bay immediately aft of the cockpit section. The extra cabin length will enable up to three stretchers to be loaded fore and aft, necessitating only the removal of one row of seats and obviating the untidy diagonal stowage which would have been necessary with a shorter fuselage. Besides the stretcher cases, four seated casualties and a medical attendant can also be carried in the casevac role. Other seating options are possible, e.g. by leaving a row of four seats immediately behind the flight deck, allowing a mixed passenger and freight layout. Each row of seats has its own window. This is one indication of some careful thinking by Westland to secure an attractive layout. Small helicopters are usually bought in penny packets, and frequently the choice of type depends just as much on styling and appearance as it does on speed or productivity. Sales of commercial helicopters have been slow to build up and it has to be admitted that a given speed, payload and range still comes more expensive in rotary wings than with fixed ones. Also in many cases the layout adopted to suit a given military role does not lend itself to easy or attractive conversion. Almost all the commercial heli copters now flying have been launched on the backs of military programmes (a situation that is not likely to change yet), so the commercial operators are heavily reliant on the equipment ordered by the Services. However, many of the ideas held by the Military are now veering in the direction of those held by civil users. Speed, twin- engined reliability, lack of vibration and noise, and service ability, for example, now rank high in military thinking as represented by new designs such as the Bolkow 105, Agusta 109, the Uttas projects and the Lynx. Until recent years operators tended to regard the helicopter's relatively low speed and other deficiencies as wholly justified by its unique Vtol ability, but this outlook is changing rapidly. Only recently have the problems of all-weather helicopter operations been studied in any depth, but the implications are now fairly well understood. Satisfactory all-weather flight calls for good handling qualities, adequate de-icing and anti-icing, and the integration of a compre hensive set of navigation and approach aids with the flight- control system so as to prevent the crew's job from becoming too difficult when conditions get tough. Compre hensive avionics are needed not just for poor-weather flying, but to enatile the aircraft to fit in with ATC pro cedures. The hingeless rotor has a lot of control power available and gives rapid response to pilot or autopilot demands. In a word, the handling is crisp. However, a reasonably advanced automatic flight-control system is required to make the most of the performance available, and the Elliott AFCS now being developed in the military prototypes and also specified equipment for the civil Lynx, contains a duplicated autostability system. The latter contains dupli cated pitch, roll and yaw channels driven from two vertical gyros and two rate gyros, and a heading hold signalled from the compass. Trials with the ten prototypes so far built have shown that the AFCS permits the aircraft to be flown hands-ofT throughout its forward speed envelope at all altitudes and in the worst weather which has so far been encountered. Anti-icing is applied to engines, engine intakes, the main windscreens and the two pitot heads. Development flying so far indicates that the ice-shedding characteristics of the main- and tail rotors will keep them free and no protection system is planned at present. Trials in more severe icing conditions will be needed to verify this. In the military utility versions the navigation and approach equipment will comprise VOR/DME and ILS, the Decca Tans (Tactical Air Navigation System) and Madge (Microwave Aircraft Digital Guidance Equipment) made by MEL of Crawley. By virtue of the considerable space needed to accommodate the military requirements, and particularly those of the two navies, there is plenty
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