Guy Norris/LOS ANGELES
Boeing began the 757-300 flight test and certification programme on 2 August when the stretched twinjet made a 2h first flight from Renton, Washington.
The maiden flight, which was around a month later than originally planned because of the impact of production-related problems at Renton, was marred only by the loss of the static pressure trailing cone. This prevented the collection of calibrated airspeed data leaving Boeing engineers to guess actual indicated airspeed "within ±5kt", says 757-300 chief project and test pilot Leon Robert.
The cone was lost within the first 45min over the mountains of the nearby Olympic Peninsula where most of the test flight was conducted, adds Robert. The take-off was made at reduced weight of 84,600kg (186,400lb) to compensate for Renton's relatively short runway length. The 55m (179ft)- long -300, representing a 7.1m stretch over the -200, was "overspeed a little bit to gain the necessary clearance on take-off", says Robert. Although V1 (decision speed) is close to that of the -200 (at 113kt), the rotation and climb speeds are "two to four knots" faster at 123kt for Vr and 133kt for V2, he adds.
After climbing to a maximum altitude of 16,000ft, Robert and senior project pilot Jerry Whites conducted an initial assessment of handling qualities with different flap configurations. All tests were made at speeds up to 250kt which will remain the limit until flutter clearance work is completed later this month. "We did work on initial sideslip, approach to stall with initial buffet and some flutter work with rudder-type kicks just to excite different modes and responses," says Robert. "It flies very much like a -200," he adds.
The next phase of tests will continue initial handling qualities with more stalls, wind-up turns, full rudder sideslips and varying centre-of-gravity positions. By mid-August, the test team hopes to be working on flutter clearance, which will be undertaken at speeds up to Mach 0.91 (around 400kt plus). At the end of the month the first aircraft, NU701, will make its first visit to Edwards AFB, California where it will undergo runway tests. Robert says the second aircraft, NU721, is also running behind the original schedule and is "four to six weeks behind us" and is now expected to join the programme around October.
The delays to the start of the test flights now mean that even more pressure is on in an effort to meet the January 1999 target delivery date to launch customer Condor.
Source: Flight International
