What happened
During the final approach at an altitude of 30 to 50 feet, the captain moved both power levers to the flight idle position. The captain reported hearing both engines transition into a ground idle state. After verifying that both power levers remained forward of the gate, the crew noted an increase in the sink rate. The aircraft bounced during the landing process.
Upon touchdown, which occurred 484 feet from the approach end of the runway, the captain moved both power levers to the ground idle position. Following this action, the airplane veered to the right. The crew attempted to maintain the runway centerline using asymmetric reverse thrust, but the aircraft continued to veer off the right side of the runway. Analysis of gouges in the runway caused by the right propeller indicated a ground speed of 92 knots at the time of the incident.
The investigation
An examination of the aircraft revealed compression wrinkles on the lower wing skin located at the wing splice location. A rigging check performed on both engine controls showed no evidence of improper rigging while in the flight idle position. However, investigators identified improper rigging at the low and high reverse positions for the right engine. Records indicated that previous discrepancies had been documented regarding asymmetric reverse thrust. There were no prior reports of high rates of descent occurring when power levers were moved to the flight idle position.