Ireland’s four Pilatus PC-12s have been on the ground for about eight weeks. The Defence Forces bought the Swiss single-engine aircraft in 2020 for close to Euro 50m. They were meant to be the useful aeroplanes for surveillance, light cargo, staff movements, air-ambulance sectors across the Irish Sea. A Defence Forces spokesman told that aeronautical engineers, in a routine review, found a small number of scheduled tasks sitting on the fleet’s maintenance-tracking software at a different interval from the timing Pilatus requires. Flying stopped while that mismatch is unwound. No return date has been given. No final cost has been published. The pause is described as precautionary. It is also a professional act. Someone had to look at a screen, look at a manufacturer’s page, and decide that four serviceable-looking aeroplanes should not fly.
An engineer’s ordinary work is to keep the hull available. That means doing the inspection when the hours, the cycles or the calendar demand it and recording the work so the next person can trust the record and signing a release only when the two agree. Digital tracking was sold as the memory of a small fleet. When the software says a task is still ahead and the manufacturer says it should already have been done, the engineer is no longer filing. He is deciding whether an aeroplane that looks ready is legally ready.
The reasons he applies are not mysterious. First, the document. The manufacturer’s maintenance programme, accepted by the military airworthiness authority, is the standard. Software is a tool for following it, not a substitute for it. Second, traceability. If a later inspector, a board or a crash inquiry asks when a filter was changed, the answer must be the same in the computer and in the manual. Third, the nature of the error. A 'very small number' of items, in the spokesman’s phrase, is not a comfort. Interval errors compound. A task deferred on the screen can remain past the point at which corrosion, a life-limited part or a calibration would have been caught. Fourth, the use of the type. These PC-12s carry patients and do surveillance. The public consequence of a wrong interval is not a delayed holiday. Fifth, the absence of a workaround that is itself legal. An engineer can sometimes inspect, repair and restore a line on the same day. He cannot invent an interval that Pilatus did not write.
Pressure arrives from the other direction. An air-ambulance request does not wait for a software house to patch a database. A squadron short of hours wants metal on the line. Ministers notice grounded fleets. Commercial shops that maintain other people’s jets feel the same squeeze as profit an aircraft on the ground will be invoiced. The skill is to use every lawful means to keep the engine and the airframe earning even like cannibalise a parked hull, work the night, fly a mechanic with a part, argue for a justified extension where the book allows one. The duty, when the book and the screen still disagree is to stop. Grounding four aircraft looks bureaucratic from the car park. Inside the hangar it is a signature that may have to be explained to a court.
Baldonnel will put the PC-12s back on the line when the tracking system and Pilatus agree. Until then the unused hours are the price of a doubt taken seriously. The unrecorded part of both stories is the person who decided that a full hangar was safer than a full flying programme. Availability is a virtue. A false release is not.