MORRISTOWN, NJ, USA
N792TA
Raytheon 400A
During a descent in preparation for landing, the left wing of the airplane experienced an uncommanded aileron trim input to the up position. Attempts to raise the right wing through the use of the roll trim select switch were unsuccessful on both the pilot and copilot sides of the airplane. The left wing continued to trim up until the left and right trim tabs were fully deflected in opposite directions requiring both pilots to physically control the airplane with full left control column input. The pilots declared an emergency and as airspeed was reduced, controllability improved and an uneventful landing was made. Examination of the roll trim control printed circuit board revealed that the relays on the board had developed a 'time lag,' causing them to stick in the closed position. As of the date of this report, the manufacturer was in the process of redesigning the circuit board.
On October 23, 2000, about 1520 Eastern Daylight Time, a Raytheon 400A, N792TA, operated by Raytheon Travel Air, was not damaged when it experienced an uncommanded aileron trim input while descending through 12,000 feet, 20 miles south of Morristown, New Jersey. There were no injuries to the two certificated airline transport pilots and two passengers. The flight departed the Charlottesville-Albemarle Airport (CHO), Charlottesville, Virginia, and was destined for the Morristown Airport (MMU), Morristown, New Jersey. Visual meteorological conditions prevailed and an instrument flight rules flight plan was filed for the executive transport flight conducted under 14 CFR Part 91. According to the Raytheon Travel Air Incident Report Form, during the descent, at 250 knots, the left wing began to trim up. The pilots were able to stop it initially, and attempted to use the roll trim select switch to raise the right wing. The attempt failed on both the pilot and copilot sides. The left wing continued to trim up until the left and right trim tabs were fully deflected in opposite directions requiring both pilots to physically control the aircraft with full left control column input. The pilots declared an emergency with the MMU tower, and requested vectors direct to MMU for landing on Runway 05. As the airspeed was reduced for landing, the controllability improved, and an uneventful landing was made with 30 degrees of flaps. According to a representative of the operator, several relays on the airplane's roll trim control printed circuit board experienced a malfunction during the flight. The circuit board was removed from the airplane and functionally tested after the incident. The test revealed no abnormalities. Further testing of the relays on the circuit board revealed that a "time lag" had developed, which caused them to stick in the closed position. The "lag" occurred after power had been applied to the circuit boards for more than 10 minutes. As of the date of this report, the manufacturer was in the process of redesigning the roll trim control printed circuit board.
The failure of several relays on the roll trim control printed circuit board, which caused an uncommanded aileron trim input.
Source: NTSB Aviation Accident Database
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