Testing Times Ahead
Dec 14, 2009
Guy Norris/Everett
With only a few minor exceptions, Boeing says the flight test plan for the 787 remains broadly identical to the one outlined in May before the six-month hiatus caused by the side-of-body modification work. Boeing's hope is therefore to stay on track to earn type certification in around eight and half to nine months, followed immediately afterwards by first of model type testing.
Although first flight in December marks the start of flight testing, the road to full up certification will not begin until the aircraft is given type inspection authorization, the milestone denoting the start of full-time FAA involvement. This is expected around February 2010.
Boeing plans to conduct the test and certification program in a relatively swift fashion compared to earlier programs with around-the-clock test operations that will see the six-strong test fleet flown and maintained under an almost airline-like schedule. The basic 24/7 routine will involve 16 hr. of maintenance and 8 hr of testing, with daylight hours reserved for the latter. Within these windows, the aircraft will be released for flight testing by 0700 and be back in the hands of the ground crew after 1500 each day. Maintenance will carry on through midnight until the early hours when aircraft release begins for the next round of flight testing. The cycle begins anew at 0600 when the test crew starts work.
Unlike the 777 where test crews remained with specific aircraft, the test pilots and engineers will be allocated to whatever aircraft is available to perform tests on the day. "We're moving to a fleet management process to make sure we've got the right 787 flying on a daily basis. So we're expecting to do that and keep the test program going," said Boeing flight test operations director Frank Rasor during an interview conducted in May.
Although the basic plan compresses the flight test schedule by almost 20%, the actual period devoted to flying the 787 test fleet remains comparable with other programs. Between them the four Rolls-Royce Trent 1000 powered 787s and two General Electric GEnx-1B powered 787s were originally expected to accumulate an estimated 3,100 flight hours, of which 2,430 hr was to be dedicated to the Trent-powered versions. There is nothing to indicate so far that Boeing expects these estimates to change radically. Similarly total ground test hours will likely stack up to around 3,700 of which all but 600 hr will be the Rolls fleet.
The compressed schedule means the ground test and layup phases will now occupy around 40% of the whole test program, rather than almost 50% in previous campaigns. Ice shapes have been pre-fabricated ahead of time, and a pressure belt has already been prepared for load tests. Items such as these historically took around 30 days to fit, but this time is expected to be cut to about seven days using the new procedures. Ground test work will also move increasingly into second shift, giving the third shift more time perform maintenance, repairs and turn the aircraft.
Although certain aircraft within the fleet will have specific test duties, such as ZA003 which will dedicated largely to interior testing work on the cabin, noise, flight deck and systems, the plan includes making more use of each test asset per flight.
Test Roles By Aircraft:
ZA001
The first 787 to fly, ZA001, or sometimes simply Airplane 1 (AP1), will be used to prove initial airworthiness qualities, basic low-speed stability and control and its flutter limits. Assuming no adverse flutter is discovered, high-speed stability and control testing will get underway around late January or early February, with FAA/EASA certification testing expected to begin shortly after.
For the remainder of its flight tests from this point on ZA001 will be fitted with new Trent 1000s incorporating full performance measurement rakes. The first engines do not have these features to enable thrust reversers to be used in early tests.
On and off through April to June, ZA001 is scheduled to be temporarily based at Edwards AFB, Calif., and Roswell, N.M. The first stint at EAFB in the April timeframe will focus on takeoff and landing validation and certification work, with a break for ice shapes certification back in Seattle the following month. The ice shapes simulate worst case icing conditions, with real icing tests to be undertaken using ZA002 and ZA005, both of which will be specially fitted with ice probes.
With the six month schedule slide, Boeing has once again been forced to shuffle the pack on where best to perform hot and cold weather test work. The mid-2009 start schedule provided opportunities for hot weather tests in the deserts of the U.S. southwest as well as cold weather somewhere in North America towards the end of the schedule. Now the test team will likely be forced to hunt for cold conditions in the southern hemisphere, though Boeing is yet to confirm this. Basic certification will cover temperatures to around -35 deg C, but Transport Canada requires tests down to -55 deg C.
ZA001 will also fly back down to EAFB and on to Roswell for rejected take-off and other high-speed brake certification tests, as well as for phase two of the stability and control program. This will continue into July-August 2010, with the first customer pilot demonstration flights set to take place in the July timeframe. Final test items in the last two months will include main landing gear actuation certification, as well as more refinement of the primary flight control system and the collection of data on flight characteristics for 787 simulators.
As well as a full data system, ZA001 will additionally incorporate special instrumentation for gear actuation, engine performance instrumentation, inertial measurement units (IMUs) to monitor fuselage body bending and a telemetry system to download flight test data to Boeing's ground station in real-time.
ZA002
ZA002 may join the test program before year-end and will also be outfitted with a set of special instruments in addition to the full data system. These will include IMUs to measure the exact twist angles of the all-composite wing, load banks to absorb excess electrical energy created by the engines and auxiliary power unit (APU), instruments for APU monitoring, and the icing probe. The load banks are required because ZA002 will be the first 787 partly dedicated to tests of the engines as well as the many electrically driven systems. The aircraft's fuel tank system will be specially equipped with an oxygen analyzer and fiber optic temperature sensor to monitor tank conditions.
ZA003
The third aircraft is configured with a representative interior, rather than a full-up production cabin, and will be used for testing systems, noise, flight deck, avionics and electro-magnetic/high-intensity radiated fields, as well as for smoke penetration and evacuation work. Special equipment on this aircraft will include test instrumentation to measure flow in the environmental control system ducting, an in-service data system as well as instruments to measure temperature.
ZA004
Line number four will be the first NAMS (nautical air miles) test aircraft and will measure efficiency with "pristine engines." It will also be used for the flight loads survey, a role that has assumed even more significance since the structural reinforcement issue as it will validate design assumptions. It will therefore be equipped with IMUs, pressure belts and static data flush ports to gather loads data during the flight loads survey.
ZA004 will enter flight tests powered by Trent 1000 engines 10021 and 10023, but will be re-engined in mid-year with the improved Package B Trents. The new engines will be used for a second phase of NAMS tests, having flown the original NAMS flights earlier in 2010 with the baseline engines. Additional NAMS tests for the initial production batch will also be undertaken using ZA100, the re-numbered seventh line aircraft and the first to incorporate structural weight improvements. A further round of range performance tests is scheduled to occur using Line 20 which will feature a second wave of production upgrades.
ZA005
The first General Electric GEnx-1B powered 787 test aircraft, ZA005, is expected to join the test program by the end of February and will be equipped with load banks and an icing probe like ZA002 as well as GE-specific performance measuring instruments. Tasks will include flutter tests, aerodynamic performance, stability and control, flight controls, propulsion and avionics tests. The first GE-powered 787 will also undertake community noise work as well as ETOPS tests. It will also be fitted with a full data system.
ZA006
ZA006 will be fitted with an engine vibration monitor and interior noise recording data array. The GE-aircraft will also repeat baseline airworthiness tests as well as GEnx-specific work and conduct lightning and high intensity radiated field testing.
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