Boeing 787 aircraft must be restarted every 51 days to avoid displaying misleading data. After a while, the Boeing operating system no longer filters out stale data, which can eventually cause the network switches to fail.
According to the European Aviation Safety Agency’s airworthiness directive, the control system component that is supposed to counter steal data stops after being switched on continuously for 51 days. The agency does not write why this is happening. This error can lead to undetected or unannounced error messages and the failure of network switches of the aircraft’s common data network, CDN for short.
A lot of critical data is communicated via this CDN, such as altitude, speed, orientation and engine information. Failure of the steel data monitoring function can lead to erroneous, critical flight data being communicated to pilots without their knowledge. This limits the pilots’ ability to safely control and land the aircraft. The American aviation service FAA therefore recommends that the Boeing 787 aircraft be completely shut down and restarted every 51 days.
According to The Register, the CDN network is an Ethernet-based network with stricter security requirements. The British news site has spoken to pilots who say the problems mentioned don’t necessarily have to lead to catastrophic accidents. For example, the aircraft have back-up panels to show the speed and altitude. The pilots do indicate that such problems are never good and can make certain emergency situations more difficult.
This is not the first time that Boeing 787 aircraft have had to be rebooted to avoid problems. In 2015 there was a warning about a bug that could cause all electricity in the plane to go out. When this happens, the aircraft may become uncontrollable. To prevent this, the planes had to be restarted once every 248 days. Presumably this had to do with a 32bit integer overflow.
In the past, the Airbus A350 aircraft also had a similar problem of reboot cycle. A reboot then had to take place every 149 hours, otherwise a loss of communication between certain avionics systems could occur. This problem was solved more than 2.5 years ago with the introduction of new software.