Ten Days, Two Defects and a C-Check
SkyRegional operates four A320s under an AOC; its MEL, derived from the MMEL, is approved by the competent authority and its continuing airworthiness is managed by a Part-CAMO. On Monday at 08:10 at a line station the crew reports that the No. 2 air-conditioning pack trips closed shortly after selection. The MEL entry for PACK 2 is Category C, rectification interval 10 days, with an operational (O) procedure requiring Pack 1 to be serviceable and the flight to be conducted at or below a stated cabin altitude limit. The same aircraft already carries a deferred item raised on Friday: a Category D item with a 120-day interval. The aircraft is due at the operator's base for a C-check in 15 days. The station holds no pack spares. The next flight departs in three hours with 174 passengers, and line maintenance there is contracted to a Part-145 organisation.
1. Is the aircraft dispatchable, and what has to happen before the next departure?
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Potentially yes, but only by working through the MEL entry and the operator's procedures, not by decision of the crew or the station alone.
Checks required:
- Applicability: does the MEL entry match this aircraft's configuration and the actual failure mode (pack trip vs. pack valve vs. controller)? The MEL covers the listed defect, not a diagnosis.
- Conditions: the (O) procedure must be capable of being met on the planned route and altitude profile, and the (M) maintenance procedure must be accomplished and recorded.
- Multiple defects: the MEL preamble rules on combinations of deferred items and on whether items interact. Two items in unrelated systems are usually acceptable; the CAMO must confirm, because the combination is a continuing-airworthiness decision, not a line decision.
- Records: the defect, the MEL reference, the category, the date/time it started, and the planned rectification date go into the technical log, and the commander must be made aware of the deferred item and its operational consequences.
- Control: the CAMO must schedule rectification inside the interval, with a spares/planning action now - not when the interval is nearly up.
The Part-145 at the station accomplishes and certifies the (M) actions; it does not decide whether the aircraft may be dispatched.
2. The PACK 2 interval would expire while the aircraft is away from a station with pack capability, and the CAMO proposes to 'carry the item over' for three more days so it reaches the C-check. Is that acceptable, and what would make it acceptable?
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No. A rectification interval in an approved MEL cannot be extended by the operator or the CAMO as a planning convenience.
- The MEL and its intervals are part of the approved document; the operator must rectify within the interval, and any extension is a change to the approved document that requires the competent authority's approval under the applicable air-operations rule (ORO.MLR.105) and the authority's MEL procedure. It is exceptional, documented, and granted for a defined period - not a routine scheduling tool.
- The forthcoming C-check is not a justification: the aircraft must be brought into compliance, or taken out of service, before the interval expires.
What makes it work: either move the aircraft to a station with pack capability within the interval and rectify; or make a formal, evidenced request to the authority in advance (with the aircraft's location, the operational need, any additional restrictions proposed) and obtain written approval; or ground the aircraft. If approval is granted, the CAMO records it, revises the due date in its planning system, and informs the operator's operations and the crew. If the interval expires without rectification and without approval, the aircraft has been operated outside its approved MEL and that is a reportable occurrence requiring notification to the authority.
3. At the station the Part-145 finds the pack bay has additional cracking not covered by the MEL. Outline the responsibilities of the operator, the CAMO and the Part-145 from that point.
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The MEL cannot absorb a defect it does not list. Once cracking is found beyond the MEL entry, the aircraft is not dispatchable until the defect is rectified to approved data or the CAMO obtains an approved alternative.
Part-145 (station): stops the release, records the finding precisely, assesses against the approved data (SRM/AMM) whether it can be rectified within its approval and capability, quarantines the aircraft from release, and reports back to the CAMO in writing. It certifies only the work it does; it does not 'manage' the aircraft's status.
CAMO: owns the airworthiness decision - authorises any repair (major repair needs Part-21 design approval), plans the rectification, updates the deferred-defect list and maintenance programme records, and evaluates whether the aircraft remains compliant with the rest of its due list. It also decides on the ferry/repositioning question with the operator and the authority.
Operator: owns the commercial and operational consequences - cancellation, re-routing, passenger handling - and holds the AOC and the MEL approval. It must not instruct that the aircraft be dispatched.
Any airworthiness-relevant finding goes into the occurrence-reporting process, with the authority informed as required.