How significant is a simple aircraft equipment/computer reset ? Why reset has become a part of certain AMM (Aircraft Maintenance Manual) procedures ?
✔Though AMM may not tell you, it’s a ‘Reset’, its instructions to ‘Switch OFF/ON’ or ‘Pulling a CB(Circuit Breaker)’ is a form of system reset apart from electrical equipment safety aspect of it.
✔The System reset is often needed to clear faults recorded by systems before or even possibly during maintenance.
✔Some systems use fault latching mechanisms, i.e. ,once a fault has been registered, it gets latched. Now the input system (Computer) will be considered unavailable for the user system (Computer), untill a reset.
✔Failing to follow AMM fully & neglecting the ‘Reset’ step had forced an Airbus aircraft to undergo ‘Alternate Flight control law’ in the past.
✔The Event:
👉During flight, due to ADR-1 (Air Data Reference) fault, the ELAC (Elevator and Aileron Computer) latched the ADR#1 (failed unit) & used ADR-2 & -3 data.
👉Upon landing, ADIRU-1 was swapped with -3, to place ADIRU-3 under MEL & the aircraft departed with out a ELAC & SEC ‘Reset’.
👉Now ELAC read both ADR-1 & -3 as INOP, due to latched memory. Without ADR-1 or -3, only ADR-2 was treated available & Flight Alternate Law applied.
Author – Tanmay Palei
Sr. Aircraft Structure Engineer
Linkedin- https://www.linkedin.com/in/tanmay-palei/