Cessna T182T N93CL incident near Cahokia, Illinois

Probable cause

The mechanic’s improper installation of the elevator trim actuator, which resulted in reversed elevator trim control, and his subsequent failure to detect the misrigging of the elevator cables during the postmaintenance inspection.

NTSB analysis

The pilot was conducting a postmaintenance test flight. He reported that the airplane was about 900 ft above ground level in the crosswind turn after takeoff when it "began to pitch steeply toward the ground." The airplane lost about 200 to 300 ft of altitude. He pulled hard aft on the yoke to keep the nose level, and he confirmed that the autopilot was not engaged. He called for the pilot-certificated passenger to assist him in pulling aft on the yoke, which required "extreme back pressure." The pilot maneuvered the airplane to land on the longest and widest runway available. During the flight, the pilot incrementally added nose-up elevator trim in an effort to relieve the nose-down pressure; however, this had no effect. The manual elevator trim wheel indicated that the trim was in the full nose-up trim position. The pilot turned the airplane onto the base leg and was still unable to relieve the "extremely strong" nose-down tendency. He remembered that maintenance had been performed on the elevator trim system and thought that there might be some kind of control-reversal problem. While on the base leg of the approach, he decided to apply nose-down trim using the electric trim on the control yoke. The nose-down control forces lessened, and he immediately realized that there was a control reversal. The pilot proceeded to make a normal approach and landed without incident.

The examination of the airplane's elevator trim system revealed that moving the elevator trim wheel to the full nose-down position resulted in the elevator trim tab moving to the down position, which would place the airplane in a nose-up configuration and indicated that the elevator trim control was reversed. The airframe and powerplant mechanic who had performed the maintenance on the airplane, which included replacing the elevator trim actuator, inadvertently misrigged the elevator control cables. The airplane's maintenance manual instructed mechanics to "make sure that the trim tab moves in the correct direction when it is operated by the trim wheel" and contained a note stating that "nose down trim corresponds to the tab UP position." The mechanic did not ensure that the trim tabs moved in the correct direction during his postmaintenance inspection after he installed the elevator trim actuator.

Text from the NTSB. Open the NTSB docket for CEN15IA079 for the full record.