Maintenance and defects

An aircraft loses life on two fronts at once. The planned one: checks fall due as the hours pile up. The unplanned one: defects appear after flights, and a hard landing delivers them in bulk. Both cost money and downtime.

Scheduled checks

Checks are driven by the airframe's hours, not by the calendar: an aircraft parked in the hangar never gets any closer to one. The table gives the downtime each check costs and the interval after which it falls due again. Each check counts from the last time it was carried out — and from the last time any heavier check was: a C-check covers the A-check scope, a D-check covers both plus the engine inspection, so after a heavy check the lighter one starts its interval afresh. A second-hand aircraft counts from the hours it arrived with: buying it does not make it overdue on day one, and it does not reset wear either — the structure arrives already spent, and the listing says so.

Checks are paid for by the aircraft's maintenance fund. Every flight pays a maintenance reserve into it — the cost line you see in the flight report — and it builds up on the aircraft itself: a widebody's reserve will never be spent repairing a Cessna. Once an aircraft leaves the fleet — sold, returned off lease or repossessed over arrears — whatever is left in its fund comes back to your account as its own line. A check costs exactly what the aircraft pays in over that check's interval: the engine inspection takes half of those contributions, an A, C or D-check takes 12% each, and the rest is left for unplanned work. So an aircraft that has been flying honestly has already saved up for its own check by the time it falls due; anything short is topped up from the company account.

The hours in the table are real time the aircraft spends in maintenance, and it cannot fly during them. You can pull it out early for a surcharge, and the earlier you do, the steeper it gets: up to +20% of the work cost. To pull several aircraft out at once, use the Fleet tab: tick the aircraft in maintenance and a bar with the total fee and a single button appears at the bottom. There is no bulk discount — each aircraft pays on the same scale. Once the time is up, the aircraft is released on its own and for free. A hangar shortens the downtime: 15% per level, up to 45% at level three. What counts is the hangar at the airport where the work is done, not the one where the aircraft is based — order maintenance somewhere without a hangar and the downtime is the full one. The aircraft card shows both figures at once: the one in force, and struck through, what it would have been without the hangar.

Ordering a job is a single action. “Schedule” puts it in the aircraft’s queue: an idle aircraft standing at the maintenance centre airport goes in right away, a busy one as soon as it is free. An aircraft runs one job at a time; the rest wait their turn. Money is charged when the work begins, not when it is ordered, so the queue costs nothing while the aircraft keeps flying — and you can cancel it from the planned list. The one thing worth deciding up front is the airport. If the aircraft serves a route there, the queue waits for its normal arrival: no ferry is sent, and the planned list names the flight it will come in on. An empty ferry — at the airline’s expense, with the price shown to you right away — is only used when the aircraft would never get there on its own. The queue waits about a day; if the aircraft has not arrived by then, it is ferried. What the queue never does is take an aircraft out from under a signed commitment: if a charter programme leg or a crew-assigned contract is due and the aircraft could not make it back from the maintenance centre in time, the job waits — a customer flight missed costs more than maintenance postponed. An overdue check does not have to be ordered from the aircraft card: the fleet advisor on the Fleet tab names the check, and the button in its row puts that very job into the same queue, from the airport where the aircraft stands.

Why an aircraft is standing still is shown on its own card, on the “Dispatcher” tab. It holds the next twenty-four hours: who is holding the aircraft right now, what is ahead of it and until when — and beside that a list of claimants with the reason named: the maintenance queue, the AI fleet, a ferry. When a job refuses to start, an answer like “busy with flight SKA2261 until 17:13” sits where the question is asked, instead of having to be guessed from the aircraft not moving.

What a check restores: an A-check brings back the airframe’s surface condition, a C-check brings back that AND the structure, the engine inspection restores the engines, a cabin refurbishment restores the interior, and a D-check does all of it. The airframe carries TWO numbers, and that is the whole difference between a light check and a heavy one: an A-check costs four times less and grounds the aircraft six times shorter, but it never touches the primary structure. Landing gear inspection, avionics check, post-storage inspection and unscheduled work can no longer be ordered: they had no resource of their own, and buying them gave nothing. Defects are cleared by line maintenance — as a discounted batch — and by defect repair — one by one. Any scheduled check also clears the minor defects that have piled up — that work is already in the price. What the job you picked will do, and what it will NOT fix, is spelled out in the order dialog.

An overdue check grounds the aircraft. While the interval still has life in it the call is yours: you may do a check that is coming due, or fly it out. Once the interval is exceeded the aircraft is no longer airworthy — it cannot be booked, put under a charter contract or taken on the flight of the day, and an AI crew will not take it either. Airworthiness is asked once more at departure: the tracker checks the aircraft when it starts recording the flight, so a booking made before the check ran out will not take off. A recording already in progress is never cut off — an aircraft in the air flies on. The refusal names that very check rather than saying "maintenance required": the refusal, the letter and the fleet list all carry the same job name. Getting it to a shop still works: the maintenance queue delivers the aircraft as usual — on its own route if it flies there, by ferry if it does not. If your airline has a base mechanic, he is the backstop: an overdue check nobody ordered he books himself — not for free, but out of the aircraft maintenance fund and the company account, and the aircraft goes down for its full downtime. He books at most one job per hour per mechanic, overdue ones first. By default that is all he takes, but the Hubs and bases page lets you change it: with planning ahead allowed he also takes a check marked "due soon", sending the aircraft to the hangar before it gets grounded. That permission is asked separately for a reason: an aircraft that was still flying and earning goes down earlier, and the company pays for it. If neither the account nor the fund can pay, the job is not booked, the aircraft stays grounded, and a letter says so. The mechanic watches more than the schedule: an aircraft with a badly spent component he also sends in — under the same planning-ahead permission, with the job that actually restores that component. And an aircraft worn so far that it is no longer allowed to fly he sends in regardless of the switch and without asking: that state never clears on its own, so there is nothing to wait for.

A D-check has something no other job removes — teardown findings. The longer an aircraft flies without a D-check, the more hidden damage builds up in its primary structure, skin, wiring and wing tanks: the first finding appears once 40% of the D-check interval is used, the next ones at 55, 70 and 85%. Each adds 0.5% to the fuel cost of every flight, shown as its own line in the flight breakdown. Only a D-check clears them (for a personal aircraft, the owner service): an A-check, a C-check, the base mechanic and defect repair never reach them. Which findings the aircraft already has, and how many hours remain to the next one, is shown on the aircraft page in the D-check row.

What actually wears out

• Engines — about 0.5% per flight hour, so a full life lasts around two hundred hours. It is the fastest wear in the game, which is why the engine inspection falls due more often than the other checks. Worn engines also cost more to run: every flight adds a surcharge to its fuel bill, growing as condition drops — up to 10% for an aircraft right at the airworthiness limit. The flight report shows it as its own line, with the percentage named. The surcharge does not pay for the inspection, and it is not meant to: it prices the delay, while the 25% limit is what makes the inspection unavoidable.
• The cabin — about 0.3% per takeoff-and-landing cycle. It ages faster on short flights than on long ones. It is the one wear figure a passenger literally sits in, and they pay for it: a worn cabin brings in less ticket revenue — up to 6% less at its worst. The flight report explains the shortfall in its own callout, with the percentage and the amount. A shabby cabin does not stop you flying: it does not ground the aircraft, it lowers the price. A cabin refurbishment restores it in full, and a D-check does so along the way.
• The airframe, surface condition — from hours flown and from the way you land. Restored by an A-check.
• The airframe, structure — fatigue of the primary structure. It counts CYCLES rather than hours: roughly 0.11% per take-off and landing, plus a large bite for a rough landing (2%) and a very large one for a heavy landing (6%). About a quarter of it goes over one C-check interval. The direct consequence: two aircraft with identical hours wear differently — the one flying one-hour legs loses structure three times faster than the one flying three-hour legs. Only a C-check or a D-check brings it back. On a used aircraft part of that life is spent before you even buy it, and the listing says so up front.

Defects

• Wear defects — small and near enough unavoidable: a hydraulic seep, engine vibration, a dead display. They trickle in after flights and simply with time.
• After a hard landing (roughly 600–1000 fpm) — one or two more serious items: brake overheat, a leaking strut, wrinkled skin.
• After a heavy landing (beyond 1000 fpm) — a critical defect, and the aircraft stays on the ground until it is repaired.

Repairs are paid for, priced by the defect itself and by the value of the aircraft. When small stuff piles up, close it in one go: “Snag rectification” clears every wear defect at once with a 20% discount.

A repair is work, not a purchase: the aircraft goes on the ground and returns to service when the job is done. A minor defect takes about an hour, a moderate one three, a serious one eight, a critical one a full day. “Fix all” opens a single repair for the whole log — noticeably faster than the same defects one after another, though each is still paid for in full. As with any maintenance task, you can take the aircraft back early for an expedite fee.

Every aircraft keeps a maintenance history: all jobs in order, with the date, the airframe hours at completion, the downtime, the cost and who ordered the work — a person or the automated fleet. It opens as a tab on the aircraft card and answers what the condition figures cannot: whether the aircraft went in early or late, and what it cost the airline.

A personal hangar aircraft is simpler: there are no check tiers. Its card has a single «Service the aircraft» button — an hour of work, after which the airframe, primary structure, engines and cabin are back at 100%, accumulated wear snags are cleared, and every scheduled-check countdown starts over. The price is fixed and does not depend on the aircraft type; the aircraft's own maintenance fund, built up from your charters, pays first, and the rest comes from your personal account. Repairing individual snags works as it does for an airline, and hard-landing damage is still not covered by servicing — only a targeted repair closes it.