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MD-90 PROTOTYPE PASSES MAJOR FLIGHT TEST

 LONG BEACH, Calif., April 12 /PRNewswire/ -- In-flight tests pushing McDonnell Douglas' new commercial twin jet to its design limits, the MD-90 has proven its airframe is flutter-free at all speeds and altitudes within the design envelope.
 With the critical speeds of 395 knots and a Mach speed of 0.895 converging just below 21,000 feet, the MD-90 flew at the planned limit of its design speed envelope with no adverse effects.
 The 395 knots measures air speed in nautical miles and is equivalent to 630 miles per hour at 20,724 feet. Mach speed relates to the speed of sound, which increases as altitude increases for the same indicated air speed.
 A team of McDonnell Douglas flight test engineers and their design-and-technology counterparts monitored the structural aerodynamic damping (SAD) tests from the Douglas Aircraft Co. telemetry center in Long Beach.
 With statistical information provided by the telemetry system, the team cleared the MD-90 from one speed to the next, with each level carefully monitored as the state-of-the-art twin jet reached its design limits.
 At 11,000 feet, the MD-90 cleared its first hurdle of 395 knots. At 35,000 feet, the aircraft cleared the second hurdle of 0.895 Mach. Subsequently, the MD-90 flew to 20,724 feet where the "knee of the curve" was attained -- the level where both 395 knots and 0.895 Mach speed coincide.
 At this point, the MD-90 proved its airframe could dampen any induced vibration at these speeds and altitudes as it is designed to do. This includes pilot-induced vibrations to purposely force the airframe to stressful conditions. In each instance of vibration, the MD-90 airframe was unaffected by the induced conditions and maintained excellent damping ratios.
 This testing verifies the MD-90's handling at its design speed limits and provides necessary information on aircraft handling characteristics.
 Preston Henne, MD-90 program manager said, "This is one of the most difficult portions of flight test requirements and the aircraft has proven our design is sound."
 In keeping with previous program achievements, Henne said, the successful completion of the SAD tests was accomplished ahead of schedule.
 At the controls for these critical tests was MD-90 chief test pilot, Capt. Bill Jones, who successfully flew the aircraft on its inaugural flight Feb. 22. With that 4-hour and 56-minute flight, the MD-90 now holds the Douglas Aircraft commercial twin-jet record for the longest first flight.
 The flight tests were conducted from the Mojave Airport, 90 miles north of Los Angeles.
 The MD-90 flight test program now continues with U.S. Federal Aviation Administration (FAA) participation which began at the end of March. The agency issued a "Type Inspection Authorization," which permits FAA personnel to fly the aircraft and to observe and perform tests.
 The MD-90 is McDonnell Douglas' newest twin-engine jetliner, designed to carry 153 passengers in a typical two-class seating arrangement over non-stop distances of 2,600 statute miles. It is powered by two International Aero Engines V2500 turbofan engines, rated at 28,000 pounds of thrust. The engines will make the MD-90 the quietest and cleanest aircraft in its class.
 McDonnell Douglas has 77 firm orders and 102 other commitments for the MD-90. FAA certification of the aircraft is expected in the third quarter of 1994, with first deliveries to customers in the fourth quarter of 1994.
 -0- 4/12/93
 /CONTACT: Don Hanson of Douglas Aircraft Co., 310-593-4710/
 (MD)


CO: McDonnell Douglas; Douglas Aircraft Co. ST: California IN: ARO SU:

EH -- LA018 -- 4726 04/12/93 11:34 EDT
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Date:Apr 12, 1993
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