NYC00IA231

During decent for landing, the flight crew experienced a temporary inadvertent deployment of the left engine thrust reverser. The flight crew declared an emergency and diverted to a nearby airport, where the airplane landed without further incident. Examination of the thrust reverser control system revealed that if thrust lever was moved aggressively to the aft stop, the left engine's thrust reverser switch could actuate. Additionally, faults were observed in left main landing gear Ground/Flight (G/F) switch, and the left engine thrust reverser deploy switch. After the left main landing gear G/F switch and the thrust lever switchbox were replaced, the airplane's thrust reverser system tested "ok."

On August 17, 2000, about 1510 eastern daylight time, a Fokker F-100, N860US, operated by US Airways as flight 471, experienced an in-flight deployment of the number one (left) engine thrust reverser during a descent in the vicinity of Norfolk, Virginia. The 2 airline transport-rated flight crewmembers, 3 flight attendants, and 52 passengers were not injured. Visual meteorological conditions prevailed and an instrument flight rules flight plan had been filed for the flight that departed LaGuardia Airport (LGA), Flushing, New York, destined for the Richmond International Airport (RIC), Richmond, Virginia. The scheduled domestic passenger flight was conducted under 14 CFR Part 121.

According to the flight crew, the takeoff, climb, and cruise portion of the flight were normal. They leveled off at a cruise altitude of about 26,000 feet and were using the auto-throttles and autopilot, which operated normally. During the descent for landing, about 18,000 feet and an airspeed of about 290 knots, they observed an amber colored warning displayed on the multi-function display unit (MFDU) that read "REVERSER ENG 1", and heard a two-bell chime. The airplane then began to buffet, and yawed to the left. The pilot-in-command (PIC) disconnected the auto-throttle system manually and pulled both throttles to the idle position. He also disconnected the autopilot and slowed the airplane's speed to 190 knots. The flight crew declared an emergency to air traffic control (ATC), and asked for clearance directly to Norfolk, Virginia (ORF). About 1 minute after the event began, the buffeting stopped, the amber warning on the MFDU turned to a white color, and all systems appeared normal.

About 9,000 feet, during the descent for landing at Norfolk, the crew elected to shut down the number one engine to avoid a possible reoccurrence when the airplane was slowed for the approach and at a lower altitude. The airplane landed at ORF without further incident.

Examination of the airplane by Safety Board personnel revealed a fault present in the left main landing gear Ground/Flight (G/F) switch and the left engine thrust reverser deploy switch ("S9"). Additionally, it was discovered that moving the thrust lever aggressively to the aft stop could actuate the left engine's thrust reverser switch.

After the left main landing gear G/F switch and the thrust lever switchbox were replaced, the airplane tested "ok." Both the left main landing gear G/F switch and the thrust reverser control box were retained for further examination. In addition, the airplane was equipped with a flight data recorder (FDR), which was removed and sent to the Safety Board's Vehicle Recorders Laboratory, Washington, DC, for readout.

The FDR data indicated that approximately 32 minutes and 40 seconds after take-off from LGA, while descending through a pressure altitude of 20,461 feet, on a magnetic heading of approximately 219 degrees, an indicated airspeed of 310 knots, and the advanced flight control actuation system (AFCAS) discrete indicated autopilot, the Thrust Reverser Engine 1 discrete changed from "stow" to "transit." Less than a second later, the Master Caution discrete indicated "warning," and 0.12 seconds later the Thrust Reverser Engine 1 discrete changed to "deploy." Approximately 3 seconds later, the Master caution discrete indicated "normal," and 0.14 seconds later, the AFCAS changed to Flight Director (FltDir). Less than 3 seconds later, the Master Caution discrete indicated "warning." Approximately 41 seconds later, the Thrust Reverser Engine 1 changed to "transit" (this occurred 47 seconds after the Thrust Reverser Engine 1 discrete first indicated "deploy"). Then approximately 33 seconds later, the Thrust Reverser Engine 1 discrete changed to "stow". Less than a second later, the Master Caution discrete indicated "normal." The airplane landed about 14 minutes later.

Further examination of the left main landing gear G/F switch and the left thrust reverser switch box was performed by Fokker Services in the Netherlands. Examination of the G/F switch revealed that the Deck 1 contacts did not function properly. Examination of the switchbox revealed that the "S9" switch was out of tolerance and there was play at the switchbox lower attachment point.