Boeing 787s Must Be Turned Off and On Every 51 Days To Prevent “Misleading Data” Being Shown To Pilots
The Register (UK) | Apr 2, 2020 | Gareth CorfieldThe US Federal Aviation Administration has ordered Boeing 787 operators to switch their aircraft off and on every 51 days to prevent what it called “several potentially catastrophic failure scenarios” – including the crashing of onboard network switches.
The airworthiness directive, due to be enforced from later this month, orders airlines to power-cycle their B787s before the aircraft reaches the specified days of continuous power-on operation.
The power cycling is needed to prevent stale data from populating the aircraft’s systems, a problem that has occurred on different 787 systems in the past.
According to the directive itself, if the aircraft is powered on for more than 51 days this can lead to “display of misleading data” to the pilots, with that data including airspeed, attitude, altitude and engine operating indications. On top of all that, the stall warning horn and overspeed horn also stop working.
Um… so that would be bad, right?
One [airline pilot] told us: “Loss of airspeed data combined with engine instrument malfunctions isn’t unheard of,” adding that there wasn’t really enough information in the doc to decide whether or not the described failure would be truly catastrophic. Besides, he said, the backup speed and attitude instruments are – for obvious reasons – completely separate from the main displays.
Not sure I like that guy.
Another mused that loss of engine indications would make it harder to adopt the fallback drill of setting a known pitch and engine power setting that guarantees safe straight-and-level flight while the pilots consult checklists and manuals to find a fix.
Ambivalent about that guy.
A third commented, tongue firmly in cheek: “Anything like that with the aircraft is unhealthy!”
I like that guy.
A previous software bug forced airlines to power down their 787s every 248 days for fear that electrical generators could shut down in flight.
Airbus suffers from similar issues with its A350, with a relatively recent but since-patched bug forcing power cycles every 149 hours.
Staleness Persists
Persistent or unfiltered stale data is a known 787 problem. In 2014 a Japan Airlines 787 caught fire because of the (entirely separate, and since fixed) lithium-ion battery problem. Investigators realised the black boxes had been recording false information, hampering their task, because they were falsely accepting stale old data as up-to-the-second real inputs.
More seriously, another 787 stale data problem in years gone by saw superseded backup flight plans persisting in standby navigation computers, and activating occasionally. Activation caused the autopilot to wrongly decide it was halfway through flying a previous journey – and manoeuvre to regain the “correct” flight path. Another symptom was for the flight management system to simply go blank and freeze . . .
Even coders should learn to code.
Not surprising really and coders for the nav and control componants are not entirely to blame here (though the ‘new kids’ are used to so much power in the systems they do get sloppy).
All computer systems need a ‘flush reset’ occasionally to clear old memory buffers and to clear registers. The fact that these are not scheduled regularly in such a critical application environment is a lack of technical knowledge and/or lack of consideration for such things. Get an old dog IT systems guy on board, or a competent systems engineer in the mix and this would not be news but standard operating procedure.
I run old software on obsolete hardware.A regular 6-month PM reset is helpful in ‘gremlin prevention’, and I do this on a system that may just drop a position outside the 10th decimal place occasionally, not drop to the ground from 30K feet.
Sorry for the rant but this hits home.
Now back to the funny….Frnak?…Anyone? Basil or Basil?
One of the comments on this article at https://www.freerepublic.com/focus/f-chat/3831010/posts: