The types of problems raised in recent days with the Boeing 787’s cockpit voice and flight data recorder are not unique to that aircraft, say industry sources and a former accident investigator.
And the issues, which were identified in the US National Transportation Safety Board’s (NTSB) 1 December report on a 2013 Boeing 787 battery fire, will likely be addressed quickly by the industry.
“On relatively new airplanes we have seen [this] before,” John Goglia, a former NTSB board member, tells Flightglobal. “It’s not surprising.”
“When you finally identify an problem and put it on the table, engineers with fix it,” he adds.
Though the NTSB’s report concluded a thermal runaway caused the fire, so-called “stale data” from the aircraft’s enhanced airborne flight recorder (EAFR) delayed the investigation. It adds that stale data could also mislead airline maintenance workers.
As the report explains, stale data is old data, generated by the Japan Airlines (JAL) 787's EAFR when the system stopped receiving new data from data sources.
The system, which records data at predefined intervals, responded by continuing to record the last known data. That data initially seemed valid, but was not, the report says.
The NTSB notes that the JAL EAFR marked some, but not all, stale data as “no source available”.
The board also found issues with the EAFR’s cockpit voice recording function, reporting that radio microphone channels “were very low and used only about 25% of the available total dynamic range”.
Also, audio picked up by the cockpit area microphone was poor in quality. “Almost all of the individual crew conversations were completely obscured by the ambient cockpit noise” during the flight, says the report.
General Electric, which makes the EAFR’s hardware, software and a “configuration tool”, would not specifically address the EAFR issues raised by the NTSB.
Neither would Boeing, although the manufacturer said it “will take any appropriate actions following our review of the report”.
But an industry source who declined to be identified says the stale data issue is not unique to the 787. This person adds that “established methods" existing for validating stale data and describes the NTSB’s comments as a call by the agency to make the data less cumbersome.
Another source who declined to be identified says the EAFR worked as designed.
The source says the system can record the validity (including staleness) of every flight data parameter, but cautions that the JAL EAFR may not have been configured to cover all parameters.
“The system is designed so it can be configured that, in the event a parameter source has stopped providing valid data, it identifies this condition while it continues to record the same value,” says the source.
“It sounds like somebody played with the controls,” says Goglia, noting that the settings can likely be tweaked by airlines.
Still, Goglia thinks stale data issues are “growing pains” associated with the EAFR’s complex software.
He notes other aircraft, like Fokker 100s, Boeing 737-300s and early Airbus models experienced similar issues.
“It [is] a question of getting all of these components… to talk to one another,” he says. “It takes time and use to let them work their way out and [to] identify these problems.”
The unnamed sources also insist the audio issues are not 787-specific.
The EAFR’s audio function records digital “audio packets” received from a network, a source says. And while the system can attenuate recordings to make them more audible, it cannot amplify the recordings.
The EAFR also records analog audio from the cockpit area microphone, but crew conversations cannot be well heard on some aircraft types, the source adds.
Goglia agrees. Some pilots talk softly, while some mumble, he says.
Also, new aircraft types can make noises engineers did not expect as components like the cockpit microphone – typically mounted above and behind the pilots – settle, he says.
“We have seen that before. As the airplane gets into service, there might be some new noises, as things start to wear together,” says Goglia.
Though such issues might not be new to the 787, the NTSB has recommended that the Federal Aviation Administration examine the stale data issue and require Boeing to improve the quality of the voice recording system.
It also urges the FAA to consider publishing guidance for cockpit voice recorders.
But Goglia thinks attention shed by the NTSB’s report has likely already led engineers to begin designing improvements.
“Once you identify it as a problem, it will get fixed,” he says. “Engineers can’t live knowing something they did was not right.“
Source: Cirium Dashboard