Thursday, February 7, 2013

AIRCRAFT WASHING AND RINSING


                On 27 November 2008, an Airbus A320-200 crashed into the sea off the coast of Perpignan during an airworthiness check flight and was destroyed, killing all 7 occupants.
                     According to the investigation’s report, the accident was caused by the loss of control of the aeroplane by the crew following the improvised demonstration of the functioning of the Angle Of Attack (AOA) protections, which were inoperable at the time because the AOA sensors had jammed making it impossible for the protections to trigger. 
             The jamming of the AOA sensors had been caused by freezing of the water which was 
present as a result of incorrect rinsing procedures being used on the aircraft three days before 
the accident flight. 
          The purpose of this Information Notice is to remind maintenance organisations and other 
organisations which are responsible for washing and rinsing operations on aircraft to adhere 
to approved maintenance procedures specified by the aircraft manufacturer or the type 
certificate holder.
                             Background 
            The aircraft had come to the end of its lease and had been ferried to Perpignan for 
maintenance and painting work. Following completion of this, and in accordance with its end 
of its lease agreement, a check flight was required prior to the return of the aircraft to its 
owners.
                Prior to being painted the aircraft was rinsed with fresh water using a water jet and without the AOA sensors being protected with masking protections. Both of these processes were contrary to the manufacturer’s prescribed procedures in the Aircraft Maintenance Manual. As a result, water penetrated inside at least two of the three AOA sensors. This water remained 
inside the sensors for the three days before the accident flight. The temperatures encountered 
during the check flight caused this water to freeze and the AOA sensors to jam. This in turn 
prevented the AOA protections from triggering during the improvised check of their 
functioning. 
               This accident underlines the importance of adhering to the correct procedures for all aspects of aircraft maintenance. Therefore maintenance organisations and other organisations which carry out washing and rinsing operations on aircraft are reminded to adhere to approved 
maintenance procedures specified by the aircraft manufacturer or the type certificate holder 
with particular regard to the appropriate protection of all sensors during cleaning and painting 
tasks.

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