Updated in paragraph 12 to include comments from Boeing.
The US National Transportation Safety Board (NTSB) is recommending that regulators address newly-disclosed problems with the Boeing 787’s cockpit voice and data recorder.
In a report released 1 December, the safety agency has urged the Federal Aviation Administration (FAA) to “take appropriate measures to correct any problems found” with the 787’s General Electric-made “enhanced airborne flight recorders” (EAFR), which record flight data and cockpit voices.
The report also urges the FAA to require operators of 787s to update maintenance manuals with guidance that would prevent so-called “stale data” from being using for maintenance activities.
The NTSB uncovered problems with the 787’s EAFRs during its investigation into the 7 January 2013 lithium-ion battery fire aboard a Japan Airlines 787 in Boston.
The 1 December report attributes the fire to a thermal runaway resulting from faulty oversight and manufacturing issues.
But the investigation was hindered by problems with the aircraft’s two EAFRs, which recorded seemingly valid data after the source stopped providing valid data, says the NTSB.
It notes that the system is designed so that a “flight data acquisition function” receives data from various sources, then sends the data at scheduled intervals to the EAFR’s flight data recorder function.
However, if the flight data acquisition function does not receive new data, it continues to transmit the last-received data, which can generate what the NTSB calls “stale data”, according to the report.
The system flags some, but not all, of the data that might be stale, it adds.
“The recording of stale data impacted the early stages of this investigation because significant additional effort was required to identify stale data when possible as well as those parameters for which it was not possible to determine whether the data samples were stale,” says the board.
“This process delayed the NTSB’s complete understanding of the recorded data,” it adds.
Boeing tells Flightglobal it is examining the NTSB’s recommendation and will take appropriate action if needed, noting that the recording equipment played no role in the fire.
GE did not immediately responded to a request for comment from Flightglobal.
The NTSB report says the fault could also mislead aircraft maintenance personnel, resulting in decisions based on incorrect data.
“The safe operation of an aircraft could be impacted if stale EAFR data were unintentionally used by an operator to assess and resolve maintenance issues,” writes the NTSB.
The board also found problems with the EAFR’s cockpit voice recorder function, although voice recordings were not central to its investigation.
“During the airborne portion of the flight that was captured on the recording, almost all of the individual crew conversations were completely obscured by the ambient cockpit noise,” says the NTSB.
The report recommends that the FAA require Boeing to improve the quality of the microphones and that the agency issue specific recorder-related guidance.