AD NUMBER: 2009-04-07
MANUFACTURER: Airbus
SUBJECT: Airworthiness Directive 2009-04-07
SUMMARY: We are adopting a new airworthiness directive (AD) for the products listed above. This AD results from mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAIdescribes the unsafe condition as: An A330 aircraft experienced a sudden [uncommanded] nosedown order [event] while in cruise. This order was preceded by an automatic autopilot disconnection and triggering of the "NAV IR1 FAULT" Electronic Centralised Aircraft Monitor (ECAM) Caution. Investigations highlighted that at time of the event the Air Data Reference 1 (ADR) part of ADIRU1 [Air Data Inertial Reference Unit] was providing erroneous and temporary wrong parameters in a random manner. This abnormal behaviour of the ADR1 led to several consequences such as unjustified stall and over speed warnings, loss of attitude information on captain Primary Flight Display (PFD) and several ECAM warnings. Among the abnormal parameters, the provided Angle of Attack (AoA) value was such that the flight control computers commanded a sudden nose down aircraft movement, which constitutes an unsafe condition. * * ** * * * * These anomalies could result in high pilot workload, deviation from the intended flight path, and possible loss of control of the airplane. This AD requires actions that are intended to address the unsafe condition described in the MCAI.

FMI: www.faa.gov/regulations_policies/airworthiness_directives/