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Aviation History
2003
2003 - 1815.PDF
Military trainers: PI mounted accessory gearboxes driving two 300A DC generators provide electrical power. Distribution is via dual Pilatus- developed buses, each capable of driving all essential systems. Batteries provide engine start and drive the mission system before engine start. Pilatus expects many of its PC-21 deals to involve service provision - it will be contracted to provide a fixed number of aircraft or annual flying hours. Finite ele ment modelling has been used to consider through-life costs, as well as a design tool and for virtual static and fatigue testing. POl is equipped with strain gauges to allow load measurement and ensure that predicted loads match reality. Two more test airframes will be built: SOI for ulti mate load trials and S02 for fatigue testing. Pilatus has applied for a patent for the PC-21 wing leading edge, which is designed to dissipate the energy of a birdstrike span- wise, preventing birds from penetrating deep into the wing structure, which reduces the need for costly and lengthy repairs. Birdstrike requirements and a desire to have no forward canopy arch to impair the pilots' forward view meant the canopy was redesigned using tapered stretched acrylic and a slightly altered shape. The high speed sledge test of the crew escape system is planned for next month at Martin Baker's Northern Ireland facility in the UK. In another move to identify life-cycle costs early, Pilatus assembled the first wing PILATUS PC-21 SPECIFICATIONS by fitting all the internal systems, then removing them, adding the top skin and reassembling the system through the access panels to prove the maintenance concepts. Aluminium structure The PC-21 is predominately aluminium, with carbonfibre used "where there is an advantage". The material has not been used in the primary structure, but has been used in the wing/fuselage fairing, around the engine cowling and ahead of the cockpit where the ability to create three-dimen sional composite structures is an advantage, says Cervia. A PC-21 wing can be built in one-fifth of the time it takes to build a PC-9 wing, says Smith. Pilatus has an annual pro duction capacity for 40 PC-21s in place. Computerised design tools also helped reduce the cost of prototype aircraft as dig ital mock-ups and dynamic models were used, allowing Pilatus to delay the start of the first aircraft production until later in the design evolution. POl parts manufac ture started in April 2000 with assembly beginning in January the following year. "That makes it more [production] repre sentative and therefore cheaper to build," says Smith, adding that POl was built on production tooling. PC-21 build time is expected to be half that of the PC-9. Computational fluid dynamics (CFD) was coupled with windtunnel tests to develop aerodynamics. The CFD code was used in an engineering flight simulator so Ml Powerplant 1,600shp 1 x P&WC PT6A-68B Wing span (m) 8.8 OEW (kg) 2,250 Maximum take-off weight (kg) 4,250 Maximum load (kg) 2,00 Maximum external load (kg) Cruise (kt) We have kept the first aircraft flying constantly. We wouldn't gain a lot from the second aircraft" JOHN SENIOR, PILATUS pilots could evaluate stalls and spins two years before metal was cut, says Smith. Data from the PoC aircraft was used to prove the engineering simulator and fine- tune it, he adds. Pilatus plans the first flight of the second PC-21 towards the middle of 2004. The company decided last year to delay the first flight of P02 as it felt it would gain little in terms of manufacturing knowledge by building the second aircraft early. Senior says: "We have kept the first aircraft flying constantly. We wouldn't gain a lot from the second aircraft." The second aircraft will now be built close to or after final design freeze and will be "more or less a production aircraft", he adds. This removes potential certification issues with two non-production representa tive aircraft, says Senior. POl is essentially an aerodynamic test airframe, while P02 is the systems test prototype. Delaying P02 means the "impact on development costs is dramatic", adds Smith. He says P02 will have minor differences from the first aircraft, including some structural strengthening as "P02 is to last longer than POl". Ramseier adds that the second PC-21 will have an autopilot and FMS, not fitted in POl. The autopilot will allow single-pilot IFR operation modern air traffic management regimes. Ramseier says these aids will be useful when air forces deploy the aircraft any dis tance that requires operation in civil air ways. Wainwright adds that flying training is not just about producing fast jet pilots, and that PC-21s will train pilots destined for multi-engined aircraft. "We have to be smart and reflect the wider requirement," he says, noting that modern transport and maritime patrol aircraft are fitted with HUDs, FMS, and glass cockpits. Smith says two customer evaluations have "substan tially confirmed the state performance and its fitness for purpose" for Phase II, III, and some elements of Phase IV. The company believes it can sell at least 300 aircraft over 20 years. • www.flightinternational.com FLIGHT INTERNATIONAL 15-21 JULY 2003 37
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