STEWART PENNEY /STANS
Swiss manufacturer addresses design issues and prepares to wrap up second set of trials with hot-weather flights
Pilatus is preparing for the final elements of the second phase of the PC-21 flight-test programme, with the next step in the four-part programme for the turboprop-powered trainer to begin in July.
Kevin Smith, Pilatus managing director strategic projects, says since the PC-21's first flight last July the aircraft has clocked up more than 125h. Swiss FOCA civil aviation authority certification is planned for December next year, he adds.
Smith says phase two testing has concentrated on envelope expansion, proof of design and problem identification. Phase three will test fixes and tune the aircraft, he adds, while phase four next year will concentrate on certification. The second aircraft, which will be production representative, will also fly in 2004.
Some issues have been addressed, including raising the floor in the rear cockpit and a rudder change, both implemented during down periods caused by bad weather.
None of the issues "are outside the 'tuneability' or adjustment of the system - we don't need to remanufacture parts", says Smith.
Also in the next few weeks Pilatus will equip aircraft P01 with a head-up display, while the navigation system will also be upgraded. The aircraft has an an attitude and heading reference system, as Pilatus was "let down badly by BAE [Systems]", which was to have supplied a GPS-satellite/inertial navigation system, says Smith.
Pilatus chief test pilot Andreas Ramseier says a 10-flight spin programme and initial hot-weather trials in Grenada, Spain, will be completed in June as Phase 2 concludes.
Ramseier says Phase 3 will start at the end of June and flight control optimisation will begin. Changes will include tuning gearing ratios, which have been "keep quite stiff to avoid PIO [pilot induced optimisation]", and maintain flight safety during initial envelope expansion, says Ramseier. Smith adds "getting the gearing right is making sure the aircraft is fit for purpose".
Ramseier says flight testing, based at Pilatus Stans facility in eastern Switzerland, will cover around 450h to achieve civil visual flight rules certification.
In September, the power management system - taken from a lighter proof-of-concept (PoC) aircraft without modification -will be rescheduled, providing 1,080shp (800kW)on take-off up to 70kt (130km/h), as opposed to today's 900shp, after which power increases until1,600shp is available at 200kt rather than today's 220kt, says Ramseier.
Pilatus has been able to make the change as the aircraft is "docile...quite benign" during take-off and the additional power means improved take-off and initial rate of climb performance, says Smith. As a knock-on effect, the carbonfibre propeller's diameter will be increased 50mm (2in) to 2,390mm.
Phase 1 flight trials used a Pilatus PC-7Mk2-based PoC aircraft to test the high wing-loading and other items planned for the PC-21. PoC first flight was in November 1997, and concluded after a 210h programme in December last year. The PoC aircraft had two of the PC-21's three 150 x 200mm cockpit displays, the engine power management system, and reduced-span wing and spoiler-boosted roll control system, both used to replicate jet-like handling, a key aim of the PC-21 programme.
Source: Flight International
