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Data input errors

By Martin Dolan, Chief CommissionerMartin Dolan

As humans, we’re all prone to making simple mistakes—be it a typo in a document or pressing a wrong digit when dialling a phone number.

While most of these mistakes are harmless in everyday life, they are potentially dangerous if done by pilots flying aircraft. 

A good example of how a simple, inadvertent, and undetected mistake can lead to a serious aviation accident is the March 2009 Emirates A340 tailstrike and runway overrun at Melbourne airport. 

Our investigation into that accident found that the tailstrike resulted from the crew using incorrect take-off performance parameters. The initial error was likely due to mistyping, when a weight of 262.9 tonnes, instead of the intended 362.9 tonnes, was entered into a laptop computer (or 'electronic flight bag') to calculate the aircraft's take-off settings. The error passed through several subsequent checks without detection.

Worryingly, we found that this type of accident was not a unique event. Similar events continue to occur throughout the world. 

The ATSB has highlighted the safety risks surrounding data input errors in our SafetyWatch initiative.

Data errors—such as the wrong figure being used as well as data being entered incorrectly, not being updated, or being excluded—happen for many different reasons. The consequences of these sorts of errors can range from aborted take-offs through to collisions with the ground. Errors can occur irrespective of pilot experience, operator, aircraft type, location and take-off performance calculation method.

While no one is immune from data input errors, risk can be significantly reduced through effective management and systems. 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 ATSB has highlighted the safety risks surrounding data input errors in our SafetyWatch initiative. The Data input errors priority on our SafetyWatch web page provides useful strategies for aviation operators to help manage risk along with links to safety resources. I encourage anyone involved with managing risks associated with data input errors to check it out. 

Written by Martin Dolan, Chief Commissioner at 2:05 PM


Sylvia Else said...

During the takeoff roll, there is a fairly simple relationship between thrust, airspeed (relates to drag), acceleration, and mass. Of these, the thrust is predicted from the thrust settings, and the airspeed and accleration can be measured. Thus once the aircraft is accelerating, it is possible to calculate the mass, and compare it with the value specified to the flight management system. It would appear that modern FBW aircraft already have all the required hardware in place, and only a sofware modification would be required to warn the pilots, long before V1, that the aircraft is not performing as expected.

May 2, 2013 15:06
Tony Taggart said...

I still write cheques. So you know how old I am!!
because I still write cheques I have to enter BOTH words and figures. Perhaps we need a checking system where the numbers are critical - such as the tail strike with 262 and not the correct 362- that requires BOTH numbers in figures and in words. This could eliminate such serious errors.
Best wishes

May 2, 2013 15:54
Dave Lochbaum said...

In this case, it was reported that the data entry error went through several subsequent checks without detection. Since each of these checks was presumably conducted to detect and correct such errors, it's prudent to examine why each failed. Had just one of these checks worked as intended, disaster would have been averted. Boosting the effectiveness of each barrier lessens the chances that all fail.

May 2, 2013 22:35
Martin Dolan, Chief Commissioner (author) said...

In response to our report on the Emirates accident, Airbus informed us it has work under way to develop take-off performance monitoring; the European Aviation Safety Agency is also examining the certification standards that would be required for such systems. While things are less advanced with other manufacturers and regulators, we welcome the efforts that are in train to develop the sort of modification that Sy has in mind.

As regards Tony’s and Dave’s comments, we learned a number of things (also in our report) about what can reduce the effectiveness of cross-checking arrangements, including in this case distractions during pre-flight preparation; the format of the documents and screen layouts for entering and presenting the data; and the challenges of cross-crew qualifications in mixed fleets. Emirates have taken a number of safety improvement steps appropriate to their circumstances as a result of the accident.

That said, we will continue to stress that the underlying problem applies to a large range of aircraft and of operators. Operational and aircraft differences mean that each operator needs to assess the risks that data entry errors pose for their circumstances and consider whether they need to do more.

May 6, 2013 15:48
Bill Pickering said...

Can I please add my belated comment. While I agree with Sy with regard to a last line of safety defence, I believe that the first risk mitigation priority and emphasis should be given to strict uninterrupted FMC data entry procedure sequence, for a two or three crew cross checking system SOP, for either a computer or manually generated load sheet. That is, the FMC computed Gross TOW must be cross checked with the load sheet Gross TOW figure before executing the entry in the FMC, followed by similar cross checking of the entered MACTOW index and stab trim setting within authorized limits. It is extremely important and critical that execution of the Actual ZFW is only done after this procedural step. Non critical cockpit distractions during this short processing time can be avoided by placing such distractions on hold or standby. I would also strongly recommend the use of strong printer ink and bolded characters in appropriate larger font size for the respective actual ZFW, TOW, LW, MACTOW and STAB TRIM for computer load sheets,to mitigate further risk. Ultimately, the preference for manual load sheets must be weighed up against the risk mitigation benefits of computer generated load sheets.

May 31, 2013 12:01