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What happened

On 1 August 2014 a Qantas Airways Ltd. (Qantas) Boeing 737-838 aircraft (registered VH-VZR and operated as QF842) commenced take-off from Sydney Airport, New South Wales. The flight was a scheduled passenger service from Sydney to Darwin, Northern Territory.

While the aircraft was climbing to cruise level, a cabin crew member reported hearing a ‘squeak’ during rotation. Suspecting a tailstrike, the flight crew conducted the tailstrike checklist and contacted the operator’s maintenance support. With no indication of a tailstrike, they continued to Darwin and landed normally.

After landing, the captain noticed some paint was scraped off the protective tailskid. This indicated the aircraft’s tail only just contacted the ground during take-off.

What the ATSB found

The ATSB found the tailstrike was the result of two independent and inadvertent data entry errors in calculating the take-off performance data. As a result, the take-off weight used was 10 tonne lower than the actual weight. This resulted in the take-off speeds and engine thrust setting calculated and used for the take-off being too low. As a result, when the aircraft was rotated, it overpitched and contacted the runway.

The ATSB also identified that the Qantas procedure for conducting a check of the Vref40 speed could be misinterpreted. This negated the effectiveness of that check as a defence for identifying data entry errors.

What's been done as a result

Qantas has advised that, in response to this occurrence, the Central Display Unit pre-flight procedure has been modified. This modification requires that, after the take-off data has been compared/verified by both flight crew, they are to check the ‘APPROACH REF’ page and verify the Vref40 speed.

In addition, Qantas also advised that the Flight Crew Operating Manual was amended to include a check that the take-off weight in the flight management computer matched that from the final loadsheet. This check was also to ensure the take-off weight from the final loadsheet was not greater than that used for calculating the take-off performance data.

Safety message

Data input errors can occur irrespective of pilot experience, operator, aircraft type, location or take-off performance calculation method.

Effective management and systems can significantly reduce the risk of data input errors. Good communication and independent cross-checks between pilots, effective operating procedures, improved aircraft automation systems and software design, and clear and complete flight documentation will all help prevent or uncover data entry errors.

The application of correct operating data is a foundational and critical element of flight safety, but errors in the calculation, entry and checking of data are not uncommon.

Data input errors remain one of the ATSB’s top safety concerns for the travelling public. More information is available from the ATSB’s SafetyWatch initiative.


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Safety issue

AO-2014-162-SI-01 -  

Flight crew operating manual procedure for Vref40 check

The Flight Crew Operating Manual procedure for crew comparison of the calculated Vref40 speed, while designed to assist in identifying a data entry error, could be misinterpreted, thereby negating the effectiveness of the check.

Safety issue details
Issue number:AO-2014-162-SI-01
Who it affects:All Qantas Boeing 737 pilots
Status:Adequately addressed

General details
Date: 01 Aug 2014 Investigation status: Completed 
Time: 1034 EST Investigation type: Occurrence Investigation 
Location   (show map):Sydney Airport Occurrence type:Aircraft preparation 
State: New South Wales Occurrence class: Operational 
Release date: 16 Nov 2015 Occurrence category: Incident 
Report status: Final Highest injury level: None 
Aircraft details
Aircraft manufacturer: The Boeing Company 
Aircraft model: 737-838 
Aircraft registration: VH-VZR 
Serial number: 34193 
Operator: Qantas 
Type of operation: Air Transport High Capacity 
Sector: Jet 
Damage to aircraft: Nil 
Departure point:Sydney, NSW
Destination:Darwin, NT
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Last update 10 March 2016