The Australian Transport Safety Bureau did not conduct an on-scene investigation of this occurrence. The report presented below was prepared principally from information supplied to the Bureau.
On 13 March 2003, while on final approach during a training flight, the crew of a Lear 45 aircraft, registered VH-SQR, reported feeling a severe vibration through their respective control columns, followed by a rapid 10 to15 degree nose-down pitch change. Attempts to manually trim the nose of the aircraft up failed, with both crew members required to pull back on the control columns in order to regain control of the aircraft.
A subsequent inspection of the aircraft by the operator's engineers revealed that the aircraft's horizontal stabiliser could be moved by hand, vertically, approximately four inches at the leading edge. On examination, the horizontal stabiliser actuator appeared normal, with all attachments in place. However, the actuator was found to have free movement of its shaft in and out of the actuator body. Further detailed examination indicated that the actuator's primary `Acme screw' had failed. With this screw failed, the horizontal stabiliser load should have been retained through a secondary rod, however, the threaded retaining nut had unscrewed from the rod.
The United States National Transportation Safety Board (NTSB) advised the Australian Transport Safety Bureau (ATSB) that they were conducting an investigation into the failure of the horizontal stabiliser actuator, and the ATSB appointed an Accredited Representative to that investigation.
As a result of the incident, the US Federal Aviation Administration (FAA) issued emergency Airworthiness Directive (AD) 2003-06-51, on 20 March 2003, requiring operators to conduct an immediate inspection of Lear 45 aircraft horizontal stabiliser actuators and to remove from service any actuators that were the same part number as the failed one.
The Australian Civil Aviation Safety Authority issued Airworthiness Directive 5/2003, on 21 March 2003, requiring all Australian Lear 45 operators to comply with the requirements of the FAA AD. Additionally, the actuator manufacturer completed a new actuator design and has since had the new actuator certified for fitment to all affected Lear 45 aircraft.
The US NTSB is yet to publish its final investigation report (number ENG03WA011).
|Date:||13 March 2003||Investigation status:||Completed|
|Time:||1615 hours EST|
|State:||Queensland||Occurrence type:||Flight control systems|
|Release date:||06 May 2005||Occurrence class:||Technical|
|Report status:||Final||Occurrence category:||Incident|
|Highest injury level:||None|
|Aircraft manufacturer||Gates Learjet Corp|
|Type of operation||Flying Training|
|Damage to aircraft||Nil|
|Departure point||Brisbane, QLD|
|Departure time||1530 hours EST|