Peninsula Airways Fairchild SA227-AC incident

The pilot of the nonscheduled cargo flight reported that during taxi for takeoff the airplane encountered a 68-knot wind gust, and he returned to the gate to examine the rudder. Finding no damage, he continued the flight. After takeoff, the pilot said there was very little left rudder control. An examination of the rudder was made after the airplane landed at its destination. From the pilot's rudder pedals, the rudder is controlled by a cable which makes a 180-degree turn toward the tail via two phenolic pulleys. Each pulley has two guard pins, which keep the cable from jumping off the pulleys if the cable becomes slack. The inspection showed that the cable had jumped off the upper pulley. The pulley's upper guard pin had retracted, and did not prevent the cable from jumping off the pulley. The guard pin has a perforated and deformed end, giving it a spring action which secures the pin after passing through the holes on either side of the pulley bracket. No service difficulty reports were found for the pins, and the pins do not have any service life limits. An examination of the operator's other, similar model airplanes, showed that several of their guard pins had also retracted. Evidence suggests that the pin's locking action becomes weakened and ineffective by repeated use. The operator submitted a service difficulty report, and as a result of this incident, the manufacturer has published service letters 226-SL-037, 227-SL052, and CC7-SL-045. The service letters indicate that the pins should be inspected, and that all pins should be replaced with improved pins, and secured with cotter pins.

Verbatim NTSB analysis and probable cause from the NTSB dataset