BOEING 787-8 — London, GB, 2014-10-10

NTSB summary

Based on crew reports and verified with images from the crew and the EAFR, the flight crew lost the use of three of the five head down displays following a lightning strike.  The crew followed published procedures, however the procedures did not contain a checklist related to a partial loss of displays.  After the crew elected to follow the "Loss of All Displays Checklist", none of the affected displays recovered to an operational state.  The crew did land the aircraft successfully using the remaining displays available to the crew.  All of the displays did recover normal operation after accomplishing a power cycle to the displays while the aircraft was on the ground.  No procedures existed for a power reset of the displays to occur while in flight, which most likely would have resulted in a restoration of the displays. Reviewing the design and display certification requirements, the displays passed their respective certification testing required by the FAA.   Supplemental testing by the investigation also showed the displays operating satisfactorily at testing levels that were above levels specified in the original certification of the aircraft and system.  However, when subjecting the displays to testing that was based on different standardized system level testing (typically associated with military aircraft) that was not required to be conducted for display unit or aircraft certification, the failure could be repeated.  This failure was attributed to the display's response to a rapid transient radiated electric field.  The electrical field analysis of the aircraft cockpit confirmed that similar electrical transients can be present during certain lightning strikes experienced by an aircraft.  Although the displays passed the required certification testing required by the FAA, it was determined that certain environmental conditions exist that could cause adverse conditions of the display operation resulting in a loss of the display.

Probable cause

A shutdown of the displays due to the inability to operate through a rapid transient radiated electric field brought on by a near field lightning strike. Contributing to the loss of displays for the remainder of the flight was the lack of guidance to the crew to perform a controlled power reset to the display.

Sequence of events (FDR factual report)

Recorder documents in the docket

Docket: data.ntsb.gov/Docket/?NTSBNumber=ENG15IA037. This brief is an analytical aid assembled from public records; it is not an investigative finding.