Guy Norris/LOS ANGELES
Boeing revealed several last minute aircraft and engine modifications to the 717-200 regional aircraft on the eve of its planned roll-out on 10 June. Despite the problems, the company still hopes to achieve a first flight for the aircraft in early September, according to programme manager Jim Phillips.
One of the most significant engine problems is the redesign of the fan containment system, which will be tested in a full-up engine blade-off test in July. "In the rig tests, this is something which we were not satisfied with, so we are doing that change now and are on track for tests in July," says Phillips.
The suspected problems with the containment system appeared about two months ago on rig tests with a BMW Rolls-Royce BR715 fan case. "The case showed fracture points," says Phillips, who adds that BMW R-R has subsequently "-gone for a conservative design fix. We have the option to refine it later". The engine maker is thickening the gauge of the aluminium fan case, but the "-weight penalty is still within the contingency envelope," says Phillips. Boeing "still feels good about it", he adds.
The other widely reported problem of cracking of the engine's third-stage high-pressure compressor blades has been resolved and a modification, involving changes to the blades and variable stator scheduling system, is being validated. "You could fly with these engines, but we're going all out for safety," he adds.
Other problems are related to "integration issues" with the aircraft's avionics and flight control systems. The company has encountered a software problem in the flight management system housed within the Versatile Integrated Avionics (VIA) processors. These Honeywell-developed computers are the centrepiece of the 717's advanced avionics suite.
The company has also run into problems with the aircraft's electrically signalled (fly-by-wire) spoiler system. In tests it was discovered that the spoilers (two panels per side) were prone to inadvertent deployment under rare conditions. Boeing plans to redesign them.
The resulting delay means that flight tests are not expected until early September, almost three months behind the original schedule. Using three test aircraft and the first production standard 717, Boeing hopes to compress the original 10-month test programme into eight months and catch up on its summer 1999 target delivery date to launch customer AirTran.
Tests totalling up to 1,600h are expected, including a week's worth of flight operations with P-1 (the first production aircraft), which will take part in a service-ready demonstration with AirTran in the first quarter of 1999.
Source: Flight International
