Sorry ,I may not be communicating clearly in English; it could be a language issue on my part. What I am trying to say is that, in an aircraft, no system should fail to the point where almost nothing is left—there must always be something to back it up.(Navigation …) I think you understand what I mean.
In other words, when a system fails, there should be another system that can perform the same or a similar function. For example, when the ADIRU fails, there is the SAARU that can still provide limited functionality. But if there is no SAARU, and the ADIRU fails, then there should be another system to provide backup,(Navigation ,Initial&air data ….not back ADIRU up directly )such as GPS.
If I explain it in simple terms, I would call this a “backup.” However, you might say that GPS is not actually a backup for the ADIRU.
For example, if the light bulb in your house fails, but you have a flashlight, that is what I am trying to convey.
Another example: if you are a police officer and you have a gun, you also carry a knife as a backup. The knife cannot replace the gun or perform the same function as the gun, but it is still there as an alternative. That is what I am trying to say.
Or I have to say “redundancy “ instead of “back up”.
Last edited by Noknoipobin; 16th January 2026 at 01:21.