Guy Norris / Seattle
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| Boeing says the tests on the 777 will be “significantly different” to those carried out on a 757 for the 777’s FCS. |
Boeing has leased a 777-200ER from American Airlines to test and validate the control laws of the 787’s flight control system (FCS).
The 787 has a more elaborate, full-authority fly-by-wire system providing directional and lateral control as well as the longitudinal control offered by the 777 system. Boeing, which has leased the aircraft for 10 months, has worked with BAE Systems to develop the digital FCS system, which allows the 787 laws to be gradually introduced and tested in flight.
“Using this, we turn them on one by one as we fly,” says 787 systems chief engineer Mike Sinnett, who adds that functionality is being increased steadily after initial tests in ground laboratories, a simulator and finally the testbed aircraft. “Each time we have a bit more of the 787 FCS functionality. In straight and level flight, we turn on the functionality and gradually expand the flight envelope. We are now most of the way through the flying and we’re really happy with the way it’s going.”
Although Boeing used a 757 to develop the hardware and software for the 777 FCS, these tests are significantly different, says Sinnett. “This time we don’t have to do anything like that – we’re just expanding the envelope.” Described as the concept validation and risk reduction (CV & RR) tests, the work aims to avoid the “downstream risk of finding stuff in the demonstration and production flight programme”, he adds.
The 787 FCS is also designed to help reduce the structural weight of the outboard wing by shifting the lift distribution inboard using manoeuvre load alleviation control laws to move ailerons, spoilers and flaperons. Boeing is developing a similar system for the 777F and plans to use the CV & RR test aircraft in June to test FCS software for the new freighter.
Source: Flight International
