Outstation Defect, an Overdue Airworthiness Directive and Three Booked Sectors
You are flying the company's Part 135 BN-2B Islander, P2-ABC, based at Telefomin for a week of charters. On Tuesday morning the technical log shows: (1) the left engine-driven vacuum pump was deferred under MEL item 24-3, category C with a ten-day limit, and today is day 9; (2) the aircraft has flown 98.5 h since its last periodic inspection, due at 100 h; (3) an airworthiness directive requiring oil-filter inspection at 50-hour intervals was last accomplished 60 h ago; (4) the maintenance release was signed three days ago and two sectors have been flown since. The nearest approved maintenance organisation is at Mount Hagen, 1.1 flight hours away. Three sectors totalling 2.5 h are booked today, all within the valley network. The maintenance controller says by phone: 'The MEL covers the vacuum pump and the service bulletin is only a recommendation - do the two short sectors and bring her to Hagen tomorrow.'
1. Assess each of the four items in the technical log and decide whether any of today's sectors can legally be flown.
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Take the items one at a time, because each has a different legal character.
1. Deferred vacuum pump. An MEL deferral is a legitimate airworthiness tool. Category C with a ten-day limit is still valid on day 9, so this item alone does not ground the aircraft - but it must be rectified before the limit expires, and the deferral must be recorded correctly against the item in the technical log, including the placard and any operating restriction (typically day VFR only for a vacuum-driven instrument).
2. Periodic inspection. 98.5 h against a 100 h limit leaves 1.5 h. Today's programme of 2.5 h exceeds that, so the aircraft cannot complete even the booked sectors, let alone the positioning to Hagen at 1.1 h plus the inspection. The remaining 1.5 h is enough to reach Hagen - that is the key operational fact.
3. The airworthiness directive. The maintenance controller's characterisation is the error to catch. The interval is mandated by an AD, not by the manufacturer's service bulletin. ADs are mandatory under CASR Part 39 and cannot be deferred by an MEL, by commercial pressure or by a controller's phone call. At 60 h against a 50 h repeat, the aircraft is out of compliance. It is unairworthy for normal flight until the inspection is done, subject only to an approved special flight permit.
4. Maintenance release. It covers the aircraft for the flights made; whether it remains valid depends on the AD status, not the signature date.
Conclusion. The answer to today's programme is no. The aircraft may be positioned to Hagen only under an approved special flight permit; it may not carry passengers.
2. What is the special flight/ferry permit mechanism, who authorises it, and on what terms would you expect it to be issued? Can a verbal assurance from the maintenance controller substitute for it?
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A special flight permit (sometimes called a ferry permit) is a flight authorisation issued under CASR Part 21 by the Director of Civil Aviation, or by a delegate with the appropriate authorisation, permitting flight of an aircraft that does not currently meet its type certificate, AD or maintenance requirements, for a defined purpose.
Permitted purposes are narrow: flying to a location where maintenance or repair can be accomplished, evacuating an aircraft from a location where it cannot be maintained, or similar limited purposes. Commercial carriage of passengers or freight is not among them.
Typical conditions you would expect to see on the permit: the specific defect and the specific flight or flights authorised; no passengers and no freight other than necessary crew and equipment; day VFR only; a defined route and maximum flight time; operating limitations (for example, no flight into known icing, no night flying, restricted speed or altitude); a validity period; and the signature and date of the issuing officer.
Paperwork. The permit must be carried on board, referenced in the maintenance release and technical log, and the operator's exposition must be complied with. On arrival the AMO records the discrepancy, the permit, and the rectification, and issues a new maintenance release before further flight.
Is a verbal assurance enough? No. The permit is a document; an engineer's or controller's opinion does not create it, and the pilot remains responsible for verifying that the flight he is about to make is authorised. In practice you should telephone the authority yourself if the paperwork is not in your hands, and note the reference number in the technical log. Flying on a verbal assurance leaves both the pilot and the operator exposed to enforcement action and, if anything goes wrong, leaves the insurer with a straightforward defence.
3. The inspection is done at Mount Hagen. What must be in the maintenance release and aircraft records before passengers are carried again, and how does that differ for the AD compared with the periodic inspection?
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There are two distinct records with different content, and the pilot should check both.
Maintenance release. Issued by appropriately rated certifying staff under CASR Part 43 after the work. It must certify that the maintenance has been carried out in accordance with the rules and the approved maintenance programme, and identify the work. Before you sign for the aircraft you verify that the release covers the periodic inspection, the AD inspection, and the clearing of the MEL item, and that the mass and balance and any equipment changes are reflected in the aircraft records.
Airworthiness directive record. AD compliance is recorded separately and must be traceable: the AD number and revision, the method of compliance, the date and hours/cycles at which the inspection was done, and the next due point. This is what an auditor looks for first, because it proves a continuing airworthiness obligation, not just a one-off task. If the AD is repetitive, the 50-hour next-due must be entered into the maintenance programme or tracking system so the next occurrence cannot be missed.
Periodic inspection. Recorded as a scheduled maintenance event against the hour-based programme: entry, date, hours, signature, and the next due at 200 h (or as programmed).
MEL. The deferral is closed out with a rectification entry, and the placard removed. If the repair cannot be done, the MEL cannot simply be re-deferred beyond the category limit - the aircraft becomes unserviceable.
Pilot's final check. Release present and current, AD status current, MEL clear or validly deferred, weight and balance updated, and the aircraft log journey entries made before the first passenger boards.