Data Safety Assurance

Boeing 737-33A at Chambery Airport, France
Domain: Air
Year: 2012
Data Categories: Dynamic
Properties Lost: Timeliness, Suppression, Lifetime

Summary:

Boeing 737-33A at Chambery Airport, France

Details:

On the 14 April 2012 and prior to departing Chambery Airport in France, the crew of a Boeing 737 used an Electronic Flight Bag (EFB) computer to calculate the aircraft’s take-off performance. During the use of the software application the commander omitted to input the aircraft’s take-off weight and it defaulted to the previous flight’s data. Compounding the issue was that none of the crew undertook a cross-check of the EFB’s output and the pilot subsequently employed incorrect speed and thrust information for the take-off. The consequence of using the incorrect information was that the calculation of the required airspeed for rotation was too low and the pilot continued to increase the aircraft’s pitch angle to the point whereby the tail hit the runway. There were no injuries sustained in this incident but the aircraft suffered damage.

Following its investigation, which examined the wider employment of computers to derive aircraft performance information, the Air Accident Investigation Branch (AAIB) identified that there had been “a number” of previous accidents and incidents attributable to the “incorrect calculation of take-off performance”; and that due to the potential for degraded climb performance a catastrophic outcome could be envisaged. The AAIB also recognized that “take-off under-performance” is subtle and many other events of this nature may have been experienced but never reported. In its conclusions the AAIB acknowledged that using computers has “brought about improvements in accuracy and ease with which aircraft performance requirements can be made”. However, there are “continued vulnerabilities” associated with the use of incorrect data that it is essential to control through “appropriately designed software and hardware”. Although there were no injuries in this instance, this incident and the conclusions of the AAIB highlight some important points for “Safety-related Information Systems”. A clear chain of events was established that involved the use of incorrect information as a causal factor leading to an incident, which had the potential to be of a catastrophic nature; • This was not an isolated incident; • The crew did not appreciate the criticality of the EFB’s information and it was used without validation; • The AAIB recognized the essential need for appropriate system development. It is often recognized that data must be up to date, but the explicit need to prevent the use of old data can be omitted from the safety requirements. This incident illustrates the importance of the properties Timeliness, Suppression and Lifetime.

Links:

• http://www.aaib.gov.uk/publications/bulletins/april_2013.cfm
  (accessed 17 January 2021)