Three Defects, One Certificate of Release: Radar, an Overdue AD and Pitot Heat
A Dornier 228 of a regional operator is at a line station with five sectors planned. The technical log shows: (i) weather radar inoperative, deferred 7 days ago under MEL item 34-41, category C (10 calendar days), the MEL being DGCA-approved and part of the operations manual; (ii) a DGCA-issued airworthiness directive requiring a flap actuator inspection every 300 flight hours, last done at 4,200 hours, aircraft now at 4,505 hours; (iii) No. 2 pitot heater failed, found at the walk-around and entered by the pilot 20 minutes ago. The route and destination forecast gives moderate icing between FL090 and FL130 and rain at destination. The AME has already signed a Certificate of Release to Service covering the radar deferral, says the AD 'can be caught up at base tonight', and offers to 'add a note' about the pitot. The certificate of airworthiness runs until next March. Forty passengers are checked in and the next available aircraft is tomorrow afternoon.
1. For each of the three items, can the aircraft be dispatched, and under what conditions?
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Radar. Possibly. A category C MEL item allows deferral within the stated interval, and 7 of 10 days are used, so the time is not the problem. The conditions attached to the MEL item are: whether the intended route or operations specification requires radar, and whether the dispatch is limited to day/VFR or airspace where radar is not needed. With the aircraft already in IMC and icing forecast, the MEL conditions must be read before accepting it.
Overdue AD. No. An airworthiness directive is mandatory and cannot be deferred by MEL. The inspection is due every 300 hours; at 4,505 hours against a last inspection at 4,200 hours, the aircraft is 5 hours past a hard limit. 'Catching it up at base tonight' means operating five sectors in known non-compliance with a DGCA directive: the aircraft is not airworthy and no CRS can make it so.
Pitot heat. No. A failed pitot heater with moderate icing forecast on the route is a no-go. Even where an MEL entry tolerates an inoperative heater, the usual conditions exclude flight into known or forecast icing, and the flight cannot be planned away from that forecast here.
The honest conclusion is that one item stops the dispatch outright and a second stops it under this forecast; the radar is the only genuinely deferrable item and only within its MEL conditions.
2. What is the standing of the Certificate of Release to Service and the AME's assurances, and who decides?
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The CRS certifies that the maintenance listed on it has been carried out and that the aircraft is, at that moment, airworthy in respect of that work. It does not certify items not yet entered, and it cannot cure an overdue AD. Two things follow:
- A CRS signed before the pitot heater entry does not cover the pitot heater. 'Adding a note' about it is not maintenance certification, and an MEL deferral requires the proper procedure, the correct MEL entry and the appropriate certification.
- A CRS does not override a hard-time AD. No engineer can certify compliance that does not exist.
The commander's pre-flight checks should cover: the tech log and all open entries, the deferred defect list against the approved MEL for this type and serial number, AD and life-limited component status, and confirmation that the CRS post-dates the work. The AME is the certifying person for what he signs; the commander is the person who accepts the aircraft for flight, and that decision cannot be delegated to the AME or directed by the station manager. The captain's authority to refuse an aircraft is not qualified by passenger numbers.
3. If the aircraft has to be moved to base for rectification, what mechanism applies and what limitations?
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An aircraft that does not meet its airworthiness requirements may be positioned only under a specific DGCA authorisation - a special flight permit/ferry authorisation obtained through the operator's continuing airworthiness management organisation, with the defect list and the proposed flight conditions attached.
Typical limitations and what they mean here:
- No passengers, and usually no cargo for remuneration; the purpose is positioning for maintenance, so the forty checked-in passengers are irrelevant to the legality of the move.
- Defined route, altitude and conditions, often day/VFR only, and a crew acceptable to DGCA.
- A statement of what makes the flight safe despite the defect. That is where this aircraft struggles: the overdue AD can in principle be covered by a permit, but dispatching into forecast icing with a failed pitot heater is a separate hazard that the permit does not remove.
The alternative - send the engineer to the station, or wait for parts - is usually cheaper than a permit that may not be granted, and puts no pressure on the flight crew. The commander's refusal should be recorded in the tech log so the reason for the delay is documented.