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Aviation History
2003
2003 - 1811.PDF
Military trainers: Phase II has a higher rate of roll and has more equip ment to emulate frontline aircraft, says Smith. "A core objective is an aerodynamic capability greater than any other turboprop for training". However, the company's pre dictions mean "PC-21 acquisition and life- cycle costs are the not the most expensive for a turboprop", says Smith. Pilatus benchmarks the PC-9 as 1, with jet trainers being 3-6:1 in cost terms. A frontline fighter is 30-60:1, with the odd example reaching 100:1. "We can argue that you can do 5h on the turboprop for the same cost as an hour on a jet," he says. Jet trainers now in development are aimed at pushing capability into the oper ational conversion unit training role. But these aircraft will need an enhanced turbo prop to improve the interface with the jet. Pilatus believes the PC-21 can be used for much of the traditional six phases of train ing, promoting the turboprop for Phase II basic, Phase III advanced and some of Phase IV fighter lead-in. For Phase IV, a typ ical ground-attack profile includes a l-1.5min target run, regardless of whether it is flown at 300kt or 600kt, says Smith, adding: "There is a difference between the two, but it is not worth worrying about." What is not possible to train in a turbo prop, he acknowledges, is advanced air defence where high specific energy manoeuvres are part of the course. He says some air forces are considering removal of Phase I ab initio and replacing it with a combination of synthetic devices and the basic turboprop. Inclusion of advanced avionics will allow air forces to start instilling frontline ethos - such as setting the correct jettison package in case of engine failure on take-off, or turn ing the master-arming switch on - from the first day. "Training is not for fun, but to learn frontline skills," says Smith. Development of the PC-21 officially began in January 1999, although the team had been put together in the last days of the preceding year. On 1 May 2002, an "inter nal roll-out" of the first aircraft, POl, was held in Stans and, after two months of ground tests, it made its first flight on 1 July at the hands of Tyndall. Smith says the intention had then been to accrue 50h and attend the Royal International Air Tattoo and Farnborough air show in the UK. Weather problems restricted flying to lOh, "all fault free". As a result, FOCA, the Swiss airworthiness regu lator, permitted Pilatus to fly to the UK pro vided relights and other safety-critical func tionality were demonstrated. This was done and the aircraft flew to the UK that day. Flying has continued since the aircraft returned from Farnborough, "with no show stoppers". As with all flight-test pro grammes, problems have been found, inc luding too-light rudder pedal forces. Although Pilatus concentrated on problem identification during phase 2 testing, this was changed while the aircraft was grounded by bad weather. Another "safe change" introduced in this way was the raising of the rear cockpit floor. Pilatus plans a 450h flight-test pro gramme to achieve FOCA VFR certification by late next year. Smith says solutions have not been introduced as soon as problems have been identified because the company wants to understand all the issues and make sure that by fixing one problem it does not create others. Phase II testing included flow visualisa tion up to 25,000ft; flutter up to VD and M0.76 at 18,000ft; stability and control including low and high weight aft centre- of-gravity; and load factors up to 8g. The aircraft is due to be cleared for +8/-4#. A key system allowing the PC-21 to be used over the broad expanse of the training cycle is the power management system, which controls the output of the l,600shp Pratt & Whitney Canada PT6A-68B. This was proven on the PoC aircraft and used unmodified in the initial phase of PC-21 flight testing. The system restricts available power at the end of the runway to 900shp, steadily increasing to the full l,600shp at 230kt, making the take-off and initial accel eration easier to manage and reducing the www.flightinternational.com FLIGHT INTERNATIONAL 15-21 JULY 2003 33
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