Hi Guys,
I have question for the case when we could not identify the cause.
Even though we could not identify the detail of the cause and/or in the situation we have system failure without message, can we apply MEL which is for one higher assembly/system?
Example:
Ex.1) If we have trouble in APU, but could not find the troubled parts, can we apply MEL itself for entire EPU?
Ex. 2) If we have trouble in AIR PACK, but without associated message, can we deactivate the PACK, and apply MEL for entire pack itself?
If you have some published guide line (aircraft manufacturer and/or your authority) for such cases, please give me the link for my understanding.