On August 28, 2001, a DE Havilland DHC-8-102 (registration N827PH) operated by Horizon Air Inc was involved in an aviation accident near Portland, OR. Investigators recorded the probable cause as: Improper tension of the right control yoke chain; a worn right aileron spring tab hinge bearing; improper tension of the left aileron spring tab aft spring and worn contact stud; improper tension of the right aileron spring tab and a worn contact stud; a worn… This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
After departure, crew experienced stiff roll controls that increased with airspeed. Post-flight inspection revealed multiple discrepancies in aileron and spring tab systems.
Sequence of Events
The operator reported that soon after departure, the first officer noticed stiffness in the flight controls when attempting to bank the aircraft left. The captain assessed the situation and opted to continue the climb. After leveling off, the crew observed that the stiffness grew more pronounced as airspeed increased. This behavior persisted during descent; the first officer noted that resistance to left roll inputs intensified as the aircraft accelerated. The captain attempted to relieve the pressure using aileron trim. When the trim indicator reached the first mark, the control wheel suddenly moved approximately 25 degrees, causing the aircraft to bank right. As the aircraft decelerated on approach, the roll control stiffness decreased. Following landing, the crew performed a full control check and found no abnormal indications with the ailerons or spoilers.
Post-Flight Inspection Findings
A post-flight inspection disclosed several discrepancies that were believed to have contributed to the stiff flight controls. These items included: high tension in the right control yoke chain; the right aileron spring tab hinge bearing did not rotate freely; low tension in the left aileron spring tab aft spring, accompanied by a worn contact stud; low tension in the right aileron spring tab and a worn contact stud; and the left aileron hinge bearing did not rotate freely.