On 13 October 2010, a Boeing 717-200 (717), registered VH-NXD, was being operated by Cobham Aviation Services Australia, on a scheduled passenger flight from Perth to Kalgoorlie, Western Australia. On board were 97 passengers, three cabin crew and two flight crew.
During the approach to land on runway 29 at Kalgoorlie Airport, the stickshaker activated. The copilot, who was the pilot flying, reduced the aircraft's pitch angle and continued the turn onto final. About a minute later, the approach was no longer stabilised and the flight crew conducted a go-around. On the second approach to land and after turning onto final, the copilot noted that the aircraft was below the required profile. As the copilot increased the aircraft's pitch attitude, the stickshaker activated for about 2 seconds. Following recovery actions, a go-around was conducted. The third approach was conducted by the pilot in command at an airspeed that was about 15 kts higher than the previous approaches.
The investigation found that the stickshaker activations were primarily a result of an incorrect approach speed. The approach speed generated by the flight management system (FMS) was based on a landing weight that was 9,415 kg less than the aircraft's actual weight. Prior to departure, the flight crew had inadvertently entered the aircraft's operating weight in lieu of the aircraft's zero fuel weight (ZFW) into the FMS. The data entry error also influenced the aircraft's take-off weight (TOW) in the FMS. The error went unnoticed and did not manifest as an operational problem until the approach into Kalgoorlie.
The investigation identified several organisational issues that had the potential to adversely affect the safety of future operations. Those issues related to the format of the aircraft load sheet, the verification check by the flight crew of the TOW against the load sheet and the lack of an independent validation check of the FMS-generated landing weight. In response, the operator has made a number of enhancements to the format of the 717 load sheet, the FMS weight data entry and verification procedures, the weight validation checks and the 717 simulator training in respect of recovery from stickshaker activation.
The application of correct operating data is a foundational and critical element of flight safety. In January 2011, the ATSB released a research report titled Take-off performance calculation and entry errors: A global perspective.
The operator's procedure for confirming the validity of the flight management system generated take-off weight did not place sufficient emphasis on the check against the load sheet.
|Date:||13 October 2010||Investigation status:||Completed|
|Time:||1313 WST||Investigation level:||Complex - click for an explanation of investigation levels|
|State:||Western Australia||Occurrence type:||Stall warning|
|Release date:||09 February 2012||Occurrence category:||Serious Incident|
|Report status:||Final||Highest injury level:||None|
|Aircraft manufacturer||The Boeing Company|
|Type of operation||Air Transport High Capacity|
|Damage to aircraft||Nil|
|Departure point||Perth, WA|