GM4 MMEL.145(c)
Justification of MMEL items
ED Decision 2020/012/R
QUALITATIVE SAFETY ASSESSMENT – ITEMS
INVOLVED IN NON-NORMAL AND EMERGENCY PROCEDURES
(a) When the item is necessary for the crew to perform an existing non-normal or emergency procedure, the consequences of its unavailability should be evaluated, taking into account the potentially worsening of the severity of the in-flight failure condition.
(b) Items which are powered by an emergency bus or equivalent and required to accomplish an emergency procedure are normally not allowed.
(c) Relief may be granted for items that are powered by an emergency bus, provided that the applicant demonstrates by flight test, analysis, or a combination of both, that the MMEL relief neither affects the successful intended completion and the outcome of the procedure, nor increases the complexity of the procedure for the crew.
(d) Emergency procedures are aircraft-specific, for example, some procedures may direct the pilot to physically turn the emergency power switch to the ON position when a complete electrical failure occurs in flight. One consequence of the selection of the emergency power switch to ON can be that the only communications system available is the number one system, and the only navigational system available is the number one system. That configuration must not allow operations with the number one radio system on the MEL. However, other aircraft may be designed with an electrical system that will automatically select any available electrical power supply during an electrical abnormality. For such a design, it would not be appropriate to limit the radio relief to just the number two radio system, since both radios are able to be powered under any circumstances.
Issue No: MMEL/2
EASA MMEL guidance requires safety assessments for inoperative equipment impacting emergency procedures. Items crucial for these procedures are typically disallowed, especially if emergency bus powered. Exceptions require proof that the MMEL relief doesn't hinder procedure success or increase crew workload. Aircraft-specific electrical system designs influence permissible relief.
* Summary by Aviation.Bot - Always consult the original document for the most accurate information.
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