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Final Report

Summary

On 20 June 2016, a captain and first officer, employed by Cobham Aviation Services, prepared to conduct a QantasLink flight from Canberra Airport, Australian Capital Territory, to Sydney Airport, New South Wales, in a Boeing 717-200 aircraft, registered VH-YQV.

During pre-flight planning, the flight crew entered the take-off data into the flight management system (FMS). Before they completed the cockpit checklist, a member of the cabin crew advised them that an extra 22 passengers would be boarding the flight.

The first officer recalculated the take-off data and wrote the new flex temperature of 34° on the take-off and landing data card (TOLD) card, and the associated EPR of 1.41. However, the revised flex temperature was not entered into the FMS.

The captain commenced the take-off at about 0812 Eastern Standard Time, moved the thrust levers forward and checked for an even spool-up of the engines to an EPR of 1.2. The captain then called ‘auto flight’ and the first officer engaged the auto-flight system. This action caused the thrust levers to move to a position where the EPR from the FMS was achieved. The captain then called ‘check thrust’ and the first officer saw that the EPR was 1.38, instead of the 1.41 as written on the TOLD card. In accordance with standard procedures, the first officer then moved the thrust levers forward to achieve 1.41 EPR.

The flight crew thought that the aircraft was then correctly configured for the take-off, with the correct EPR, and the captain continued the flight. However, after about 4 seconds at 1.41, the EPR returned to 1.38 for the take-off as the thrust lever position returned to that set by the auto-flight system based on the EPR value in the FMS.

Inaccurate take-off reference data has potentially serious consequences. ATSB Aviation Research and Analysis Report AR-2009-052 (Take-off performance calculation and entry errors: A global perspective) concludes:

… it is imperative that the aviation industry continues to explore solutions to firstly minimise the opportunities for take‑off performance parameter errors from occurring and secondly, maximise the chance that any errors that do occur are detected and/or do not lead to negative consequences.

 

Aviation Short Investigations Bulletin- Issue 52

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