Dear Mr. Richter,
The Agency is of the opinion that a "supported location" is a location where all the resources necessary for maintenance (as described in the MOE) are available (facilities, tooling, materials, staff, etc.).
As a consequence, a line station could be considered unsupported if Part-66 certifying staff is not available, in which case, the commander may release the maintenance described in their authorisation.
However, special care has to be taken as to the meaning of "Part-66 certifying staff is not available". Although it could be possible to say that the Part-66 certifying staff is not available, for example, if the maintenance takes place outside the times where the presence of Part-66 certifying staff has been agreed or when the Part-66 certifying staff has been unexpectedly sent to support an AOG situation at another location (in accordance with approved procedures), this should not be the case where the Part-66 certifying staff is present at the line station maintaining one aircraft and they cannot attend at that very moment an additional aircraft requiring maintenance.
This means that it is essential to clearly define in the MOE, to the satisfaction of the competent authority, the operating conditions of the line stations.
This is particularly important for the purpose of defining which locations need to be supported, the amount of Part-66 certifying staff required and when these staff should be available.
In addition, the Agency considers crucial that special care is given to ensure compliance with the existing requirements in order to issue the commander authorisation (defined procedures, practical training, duration of the authorisation, etc.) and to ensure that the scope of work authorised to the commander is in line with AMC 145.A.30(j)4.
I hope, this information clarifies the situation.
Ludwig Heßler
Airworthiness Expert
European Union Aviation Safety Agency
