Industri Pesawat Terbang Nusantara (IPTN) is making minor changes to the fly-by-wire (FBW) flight-control system (FCS) of the N-250, Indonesia's first fully indigenously designed airliner, following early flight tests.

IPTN test pilot Erwin Danoewinata says that the general handling characteristics are "very satisfactory", and that the FCS is "-better than expected". A programme is under way, however, to "-improve the feel system in pitch and yaw with the FBW system".

"Some stability issues" will be tackled by changes to the "Q" feel schedule of the FBW system. The ailerons and elevators are active FBW, with stand-by, mechanically signalled, modes, while the rudder has both active and stand-by FBW modes and the spoilers and flaps are all FBW. "In general, the N-250 handles like a much smaller aircraft," adds Danoewinata. "Field performance is better than expected due to better CLmax [coefficient of lift]. Time to climb to 25,000ft [7,600m] is 15min, and IPTN is "-working with Allison to improve high altitude capability". Other flight-control modifications are being introduced as a result of stall testing. "The aircraft required an artificial stall-warning system, though there was no deep stall tendency. The attitude for recovery was too steep in our opinion," comments Danoewinata.

Following a delay in the first flight of its second prototype - a 64-seat production-representative N250-100 - to December, IPTN now expects to aim for Indonesian certification at the end of 1997. US Federal Aviation Administration certification is now expected around mid-1998.

Source: Flight International