Boeing 787 Dreamliner - Mark Wagner [75]
Chapter 8
TESTING TIMES
LONG BEFORE THE FIRST PARTS AND SYSTEMS FOR THE 787 WERE EVEN DESIGNED, let alone being built, Boeing was pondering the equally massive challenge of test and certification. The large amounts of composites and advanced, more-electric systems demanded an unprecedented number of new tests and, in some cases, adherence to whole new standards of certification.
Boeing began the process when it applied to the FAA for type certification of the 787-8 on March 28, 2003. “When you make the application to the FAA, that freezes the rules at that point, except for special conditions,” said Jeff Hawk, the 787 director of government, environment, and certification. Boeing’s plan was to get as much of a head start as possible on testing and preparing for certification, particularly “special conditions.”
These were issued by U.S. or European air-worthiness authorities in cases where the new aircraft was so different, or had some particular design feature, that it was not covered by the existing regulations. Boeing did not want any surprises and did not want to find itself in the position that Airbus was in 2005 with the A380, of still receiving notification of special conditions in the midst of flight tests.
Boeing met with FAA and EASA officials on a more or less continuous basis from 2003 onward to clear its certification plan by early 2006. But no matter how many meetings, Boeing knew it still would have to contend with a series of special conditions. However, even by mid-2005 Hawk believed there would be no “showstoppers” among them. “We may see one for lightning strike associated with composites, and perhaps others to do with the use of composites and electric systems,” he said at the time.
Structure around passenger and cargo doors was given additional plies of composite to help protect against “ramp rash,” the day-to-day damage from inadvertent collisions with service vehicles that all jetliners experience in airline operation. Mark Wagner
Concurrently with preparing for tests of all the novel elements, Boeing also was developing the design to meet all the usual safety standards. “Is the design criteria different because of composites? Yes,” said 787 Engineering and Technology Vice President Randy Harley. “But we still have to define internal and external loads, static strength, crash-worthiness, and producibility as well as make it fail-safe, maintainable, repairable, and inspectable.”
Boeing’s priorities for testing composites focused on fatigue and corrosion, damage tolerance, crashworthiness, and producibility. All of these issues were generally well understood with conventional aluminum, “but with a composite they get more emphasis,” said Harley. Damage tolerance, for example, demanded new tests for hail and bird strikes as well as lightning protection.
Building on experience gained with certification of the 777’s largely composite empennage, and working closely with their military counterparts who had composite technology experience through involvement with the B-2, F-22, and X-32, among others, the Boeing 787 team developed a pyramid approach to testing and proving the airliner’s composite materials and structure. The base of the pyramid was formed with a broad set of small coupon tests of the materials, most of them only two to three inches wide by ten inches long. Next was a series of element tests that covered slightly larger pieces, such as shear panels, representative of those to be used in the structural makeup of the airframe. On top of this were tests of a number of larger-scale subcomponents, such as complete wing skin panels. Above this were tests of even bigger components, such as complete fuselage barrel sections and tail units. Finally, on the top of the pyramid were full-scale static and fatigue ground tests as well as flight tests themselves.
The good in-service performance of the composite parts on the 777 gave Boeing