The UK Air Accidents Investigation Branch (AAIB) last month issued a sweeping recommendation that the EASA, FAA, Transport Canada and other aviation agencies amend requirements for the design and installation of electronic components in aircraft so that fluid and moisture contamination, as a source of common cause failures, is specifically taken into account. This recommendation stems from a November 2005 incident involving a 2004 Bombardier Challenger 604 (registration VP-BJM) that experienced stabilizer pitch trim failure due to corrosion of the horizontal stabilizer trim control unit (HSTCU) circuit board. The airplane had logged only 202 flying hours at the time of the incident.
According to the AAIB, moisture created by humid air condensing on the cooling motherboard during repeated prolonged flight at altitude over time corroded the solder, leading to the HSTCU’s eventual failure. The AAIB is concerned that avionics motherboards on other aircraft could be affected in a similar manner.
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