As stated in 66.A.30(e), for mechanics having a military background and seeking a Part-66 licence, the objective is to ensure adequate understanding of the civil aircraft maintenance environment, not only because of possible different aircraft technologies, but also because of practices linked to the civil environment.
Not only the technology or systems of the civil aircraft might differ from the military aircraft version configuration (e.g. no video entertainment system; no sliding chutes; different fuel or electrical systems) but the experience gained in the military environment might also significantly differ from the scope of work of the civil maintenance organisation, its procedures and policies (e.g. use and meaning of the certificate of release to service - EASA Form 1, standard parts, store and tools procedures, use of the maintenance documentation such as ADs, SB, SIL…, quality and safety management system; human factor aspects, continuing airworthiness record systems…).
In addition the interaction with the customers (i.e. the airliners) induces new practices such as use of the aircraft technical log book, MEL, aircraft defect rectification and deferment of items; use of customer documentation (e.g. MPD, MRB, SRM, IPC); interaction with the crew; how to behave with the passengers; special procedure such as (re)fuelling, de-icing /anti-icing; communication with the tower or moving on the apron.
Finally, the requirements for the continuing airworthiness of the aircraft might significantly evolve in the civil environment. To name a few, the following items can be reminded: ADs, SBs, operational directives, EASA requirements; records and archives; repairs and modifications (use of data, EASA/FAA rules; dual-release); special inspections (e.g. CPCP, EWIS); approved maintenance programme and its effectiveness / reliability; occurrence reporting; understanding of MSG-3 methods …
The military regulations widely differ from country to country, with certain countries having military rules similar to the EU ones, while others have very different rules. The 12-month additional civil maintenance experience average (as per AMC 66.A.30(e)), has been agreed by the Member States and accepted as a standard way to demonstrate compliance with the rule to achieve mutual recognition and adequate degree of standardisation.