Airbus and supplier Thales have uncovered an interesting assembly line defect that could be affecting angle-of-attack data on some of the OEM's long-range aircraft: dirty oil.
During handover flight tests, Airbus discovered that angle-of-attack (AOA) data on two different aircraft were inaccurate. Airbus traced the problem to oil residue on the Thales-supplied AOA probe. Quoting an EASA AD:
Investigation conducted by Thales on the removed probes revealed oil residue between the stator and the rotor parts of the AoA vane position resolvers. This oil residue was due to incorrect cleaning of the machining oil during the manufacturing process of the AoA resolvers. At low
temperatures, this oil residue becomes viscous (typically in cruise) causing lag of AoA vane movement.
The AD (2010-0016R1
) orders replacements of the affected AOA probes on A330s and A340s by April 30. The directive is a revision of one published last month; the revision specifies that aircraft maintenance records can be used in lieu of a visual inspection to pinpoint affected probes.