Introduction
On 4 July 2018, a Britten-Norman BN-2B-21 Islander, registration VP-AEJ, experienced a serious incident during approach to Robert L. Bradshaw Airport in Saint Kitts. The aircraft was operating a commercial air transport passenger flight between Saint Eustatius and Saint Kitts in the Caribbean. The sole pilot and four passengers were unharmed, and the aircraft sustained damage to the aileron drive rod.
History of the Flight
The flight departed from Runway 06 at F. D. Roosevelt Airport on Saint Eustatius at 1930 UTC. Shortly after takeoff, the pilot noticed that the ailerons felt “sluggish” during a right turn. Given the short flight duration of approximately 10 to 12 minutes, the pilot continued to Saint Kitts and landed safely at 1942 UTC. The passengers disembarked normally. During a post-flight walk-around inspection, the pilot discovered that the right aileron drive rod had fractured. The maintenance organisation was informed.
Examination
On the evening of the incident, maintenance personnel replaced the broken aileron drive rod in the right wing. An examination of the failed rod revealed that the spherical bearing at the rod end connecting to the aileron was heavily corroded and had seized. The rod had fractured due to overload approximately 70 mm from the rod end, at a riveted area.
Analysis
The aircraft manufacturer assessed that the failure was initiated by bearing corrosion, which led to seizure. Under normal operational loads applied to the aileron drive mechanism, the seized bearing caused the rod to become overloaded and fracture. The manufacturer issued Service Letter SL 127, “Greasing of Aileron Rod End Bearings,” to remind operators of greasing requirements and gather feedback on bearing corrosion.
The maintenance organisation noted that the Caribbean coastline had recently experienced large quantities of decomposing Sargassum seaweed, which releases hydrogen sulphide. Combined with recent storms and hurricanes, these environmental factors may have accelerated corrosion in certain components. The aircraft’s maintenance programme specified a lubrication interval of 1,000 hours, but the organisation reduced this to 100 hours to prevent recurrence. A fleet-wide inspection of all drive rods and bearings was also initiated.
Conclusion
The serious incident occurred because an aileron drive rod bearing corroded and seized, causing the drive rod to overload and fail under normal operational loads. The operating environment may have been more corrosive than anticipated when the lubrication tasks were defined in the aircraft maintenance programme.
Safety Actions
The aircraft manufacturer published Service Letter SL127 to emphasise greasing requirements and solicit feedback. The maintenance organisation reduced the lubrication interval for aileron drive rod bearings from 1,000 hours to 100 hours and initiated a fleet-wide corrosion inspection of all drive rod and bearing assemblies.