Air Operations
Operator responsibilities and the MEL
Air operations in the EU are governed by Regulation (EU) No 965/2012 with its annexes: Part-ORO (organisation requirements common to operators), Part-CAT (commercial air transport), Part-SPA (specific approvals such as PBN, RVSM, ETOPS, low-visibility operations) and Parts NCC, NCO and SPO for non-commercial and specialised operations.
Key concept: the operator holds the responsibility and the AOC. Maintenance may be contracted to a Part-145 or Part-CAO, but responsibility for the aircraft's condition stays with the operator, who must ensure continuing airworthiness is managed under contract.
The MEL is derived from the manufacturer's MMEL, tailored to the operator's aircraft and approved by the competent authority (ORO.MLR). Flight crew use it to dispatch with defects deferred under stated conditions and time limits. The CDL covers missing external items. Defects are recorded in the technical log, and the commander accepts the aircraft for the flight.
Traps: treating the MEL as a maintenance document or as a way to defer anything not listed; confusing MEL approval (authority) with maintenance approval (Part-145); mixing up the MEL with the maintenance programme, which schedules inspections. Another trap is forgetting that specific approvals must appear on the operator's approval, not just in the OM.
Rule of thumb: MEL = dispatch; maintenance programme = scheduled work; AD = mandatory.
Worked example: a generator fails at an outstation. If the MEL allows dispatch using the remaining generator with the stated conditions, the commander may dispatch with the defect deferred; the defect is logged and must be rectified within the MEL interval.