LEARJET HAS SHIFTED flutter testing of the Learjet 45 business jet to the second prototype, to avoid grounding the first aircraft. The move has delayed the first flight of the Learjet 45-002, but has allowed flight-testing of aircraft -001 to continue, the company says.
Wichita, Kansas-based Learjet says that some 160h have been flown with -001, 66% more flying hours than projected for this stage of the test programme. Rather than ground this aircraft for installation of the flutter exciters, the company has decided to shift testing, to the -002, which is now expected to be flown "within the next few weeks".
Testing accomplished with the -001 includes roll-control disconnects, to prove aileron and spoileron effectiveness in the event of a control jam, and both starter-assisted and windmill air-starts of the AlliedSignal TFE731-20 turbofans, to 35,000ft (10,700m).
The company has also tested battery-only starts down to -18¡C and, within a few weeks, plans to evaluate ground power-unit starting tests down to -40¡C. Thrust reversers have also been tested to maximum thrust for two- and single-engined landings. Aircraft control under both conditions was "very good", says the company.
The aircraft has been flown to the maximum Mach of 0.81.
Changes made include improvement of the gear-retraction time to around 8s, typical of other Learjets. The company says that the third of five flight-test aircraft will be flown soon after the -002, as it requires less post-production modification. Certification is still scheduled for the end of 1996 and first deliveries for January 1997, Learjet says.
Source: Flight International
