has completed initial airworthiness tests of the stretched and accumulated more than 40 flight hours in the run-up to the start of flutter tests, which are expected to begin later this month.
Initial aircraft handling qualities are good and systems appear to be robust, says 787 Chief Pilot Randy Neville. In an interview with Aviation Week, Neville said that progress has been rapid thanks to careful pre-flight test preparations, lessons learned from the 787-8 and good performance of systems during four days of “gauntlet” ground tests, which simulated flight operations in the run-up to the maiden flight on Sept. 17.
The first aircraft, ZB001, is now being used for the first phase of stability and control testing and on Oct. 2 conducted its first flight with a full complement of flight-test engineers. Until now, initial airworthiness has been conducted with two flight crew only. Phase one stability and control focuses on lateral stability and the performance of the primary flight-control system.
The initial handling work assesses the baseline safety of the aircraft and includes initial stall testing at various center of gravity positions (cg) and flap settings.
The 787-9, which is stretched by five frames forward and five frames aft for a total of 20 additional feet in length over the baseline model, has a slightly larger cg range to test, as well as added flap settings. These include a “deeper” flap 30 setting for higher lift, as well as added detents at 10, 17 and 18 deg.
The 30 flap setting is designed to optimize performance in some gross weight conditions and field lengths. Although originally indicative of actual flap angles, the detent positions on more-recent generation Boeing aircraft are simply representative of pre-set positions for takeoff and landing.
Flaps 1 on the 787-8 indicates the leading edge slats are extended, but trailing edge fully retracted, while Flaps 5-20 are currently takeoff flap settings with leading edge slats extended and increasing amounts of trailing edge flap.
“The airplane has been flying regularly, with just a day for initial checks between the first and second flights, as planned. As of this morning, the 787-9 had racked up more than 40 hr. in the air and has completed initial airworthiness testing,” saysVice President, Marketing Randy Tinseth.
Flutter tests lie immediately ahead and will evaluate the aeroelastic characteristics of the airframe and the 787-9’s latest generation of composite primary structure wing. Flutter testing is a critical part of the envelope expansion for any new aircraft and, until the work is complete, the 787-9 is limited to lower speeds, altitudes and weights.
During the testing, the crew will introduce a range of vibration frequencies to the flight control surfaces by physically hitting the yoke or by computer input. The tests will ensure that the aircraft structure naturally dampens out the oscillations without further input from the pilots, and without amplifying into potentially destructive open-loop feedback oscillations.
The flutter test phase, which also includes additional primary flight-control system evaluation, is expected to be followed by a further period of stability and control tests.
The certification campaign is scheduled to be completed in the second quarter of 2014, with delivery to launch customerset for mid-year. In addition to the ZB001 and the second test aircraft ZB002—both of which are powered by the latest “Package C” version of the —the test program includes a third airframe, ZB021, which will be powered by ’s -1B.