Event
An airplane was in flight when it experienced an abrupt nose-down pitch. This was caused by an inflight failure of the horizontal stabilizer's trim actuator jack screw. The crew responded by exerting a large amount of back pressure on the control wheel and adding nearly full engine power. Through these actions, the crew was able to maintain control of the airplane and make a successful landing.
Examination
Following the incident, an examination of the actuator was conducted. The examination revealed an inadequate amount of lubricating grease and excessive part wear. The jack screw, a component of the actuator, had suffered from insufficient lubrication and subsequent wear.
Crew Actions
The crew's prompt and effective actions were key to the safe outcome. They applied sustained back pressure on the control wheel and increased engine power to nearly full, which compensated for the loss of trim authority and allowed them to fly the aircraft to a landing.