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BOEING COMPLETES TWO LIFETIMES OF TESTS ON 777 STRUCTURES; PROGRESS ALSO ON 777 FLIGHT CONTROLS TESTING

BOEING COMPLETES TWO LIFETIMES OF TESTS ON 777 STRUCTURES; PROGRESS ALSO ON
    777 FLIGHT CONTROLS TESTING
    SEATTLE, July 7 /PRNewswire/ -- The Boeing 777 may not be slated for first flight until mid-1994, but two developmental components for the new airplane already have completed the equivalent of two lifetimes of simulated takeoffs, flight loads and landings, Boeing Commercial Airplane Group said today.
    As part of the 777's extensive ground and flight testing program, tests on an all-composite, 44-foot (13.4-meter) developmental version of the aircraft's horizontal tail and a 21-foot-long (6.4-meter-long) test section of the 777 fuselage began in October 1991 and February 1992, respectively.  The fatigue and static structural testing, which will continue through the end of the year, is being conducted at the Boeing Developmental Center in south Seattle.
    "These tests are part of the most comprehensive structural validation program on any Boeing aircraft," said Rudy Schaad, 777 Structures chief engineer.  "Our goal is to validate structural reliability and intended function, and provide a smooth transition into service.
    To achieve the two lifetimes milestone, the fuselage section was pressurized and loaded to simulate typical flight cycles from takeoff through landing.  One lifetime equals 44,000 flight cycles on the 777, Schaad said.
    The portion of 777 test fuselage will undergo additional pressurized cycles before Boeing test engineers purposely damage the section by inflicting structural cracks, dents and holes.  The structure will undergo another "half lifetime" of pressure tests in this damaged condition, allowing engineers to evaluate damage tolerance and repairability.  The full test program will subject the section to 120,000 flight cycles of simulated operation.
    In the two lifetimes of fatigue tests on the developmental horizontal stabilizer, varied loads that simulate takeoffs, flight and landings were applied to the structure.  Made of carbon fibers embedded in a new, toughened epoxy resin, the stabilizer will be subjected to static loads that put a continually increasing stress on the structure up to its design limit.  Next, the structure will be stressed to its "ultimate load," which is one-and-a-half times greater than what is ever expected in airline operation.
    Damage then will be intentionally inflicted on the structure, followed by additional fatigue tests of 10,000 equivalent flight cycle.  Following damage tolerance verification, the horizontal stabilizer will be repaired and the final test will stress the structure beyond the ultimate load to the point of destruction. Schaad said this last test will determine the structure's maximum strength capability.
    Schaad credited three organizations within Boeing Commercial Airplane Group for the success of the structural tests:  777 Division Structures Engineering, Fabrication Division's Developmental Manufacturing and central Engineering's Structures Laboratory.
    In other testing related to the newest Boeing jetliner, Capt. John Cashman, 777 chief pilot, reported that 39 flights have been completed in a 757 airplane modified with systems to emulate the 777's flight control system.  (The flights totaled 119 hours, 39 minutes and included 257 landings.)
    Cashman and 777 senior project pilots, Capts. Frank Santoni Jr. and Joe MacDonald, started flying the 757 test bed March 11 and are continuing to validate the new airplane's "flight control laws" -- the software programs that regulate the response and stability of the airplane in flight.
    Other Boeing pilots as well as pilots from 777 customer airlines and regulatory agencies will be involved in future flights in the modified 757, with testing continuing through September, Cashman said.
    Major assembly of the newest Boeing jetliner gets under way early next year.  Delivery of the first 777 to United Airlines is scheduled for May 1995.
    -0-             07/07/92
    CONTACT: Barbara Murphy of Boeing Commercial Airplane Group, 206-965-3345
    (BA) CO:  BOEING COMMERCIAL AIRPLANE GROUP IN:  AIR ST:  WA -- SE004 -- X773  07/07/92
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Publication:PR Newswire
Date:Jul 7, 1992
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