“Rebooting servers at work is something I do quite frequently. Never thought that would extend to aircraft.”
It does, indeed, in the Challenger 300, which is highly automated with over 120 microprocessors involved. Essentially, virtually everything electronic in the 300 is connected to virtually everything else electronic in the 300, which creates the opportunity for problems to cascade from system to system.
In this case, the problem was driven by the fact that the rudder limiter relies on airspeed data from the air data computers (ADC) fed to it through the horizontal stab trim electronic control unit (HSTECU). Since the right ADC was only detecting about 4 knots of airspeed through the seams of the right primary pitot-static tube cover, and the left ADC was sensing over 90 knots, a miscompare state was created during the first takeoff attempt and the fault sent to other boxes in the airplane, including the HSTECU. Once a fault latches in the HSTECU, it can only be cleared by a complete electrical power-down including disconnecting the batteries for a minimum of five minutes and perhaps as much as thirty minutes. And that’s why a RUDDER LIMITER FAULT advisory in the Crew Alerting System (CAS) can indicate problems with the primary pitch trim and autopilot as well as the rudder limiter. Hence, an unextinguished RUDDER LIMITER FAULT is a “NO GO” item, and also why CL300 crews are required to check that GO/NO GO list for any unextinguished CAS message on the ground before attempting a takeoff even if they’ve already done the steps for that condition in the Quick Response Handbook but the message remains.
This message is entirely my own and does not reflect that of any other organization or agency.