|
Contact:
Hal Klopper |
|
|
Contact:
Hal Klopper |
|
FOR IMMEDIATE RELEASE
96-201
MESA, Ariz., Aug. 19, 1996 -- The MD 600N program is back in the air and on track for Federal Aviation Administration (FAA) certification and deliveries later this year.
The program received a major boost on Friday, Aug. 9, when McDonnell Douglas Helicopter Systems test pilot Chan Morse lifted off in the third MD 600N to fly. The program had been delayed following a hard landing May 28 that caused the company's second test aircraft to be destroyed by fire. The third MD 600N replaces that aircraft as the primary development test vehicle.
The MD 600N is an eight-place, stretch-version of the popular MD 520N helicopter.
Last week's flight was the culmination of an intensive effort to complete the aircraft, add design modifications to increase main rotor-blade-to-tailboom clearance, and to install the instrumentation suite required for the resumption of FAA testing.
To date, nearly 75 percent of flight and development testing has been completed, the majority of which will not be repeated, said Carlo Rao, integrated product definition chief engineer at McDonnell Douglas Helicopter Systems.
The new MD 600N will be joined in the flight test program later this month by the original MD 600N prototype.
That aircraft has been undergoing a modification program to bring it up to production configuration. FAA testing is expected to be completed by November, Rao said.
The FAA has reviewed the results of the accident investigation and approved the company's plan for continuation of the MD 600N certification program.
The accident, which delayed the program, occurred in flight during an extreme control reversal in the longitudinal axis while in autorotation at maximum speed and minimum rotor RPM. During this extreme maneuver, designed to determine the maximum flight envelope for the aircraft, the main rotor blade contacted the NOTAR tailboom and cable controlling the thruster and vertical stabilizers. The subsequent damage to the control system forced the pilot to make an emergency landing.
Following an extensive investigation, McDonnell Douglas engineers began testing several improvements to ensure that tailboom and control cable contact is prevented in the future. Final decision on improvements will be made based on the outcome of flight tests, Rao said.
Changes under consideration include:
-- Increasing the minimum main rotor blade RPM in autorotation from 86 to 90 percent.
-- Making a minor adjustment to the forward center of gravity envelope.
-- Changing the downforce on the tailboom by adjusting the horizontal stabilizer (changing the angle of attack) or reversal of the NOTAR thruster, or a combination of both.
-- Moving the empennage control cable from the top of the boom to the side to increase cable/main rotor blade separation.