Recording counters, and why they can't go backwards
How aircraft counters are recorded, why a reading cannot decrease, and how to fix a genuine mistake.
Last reviewed
Aircraft counters are recorded at flight close-out and only ever move forward. A new reading must be at least the last one held, because hours and cycles do not decrease in real life, and a counter that could go backwards would quietly corrupt the maintenance forecast.
How a counter is recorded
Each aircraft holds its counters with their source, block, airborne, Hobbs, tacho and cycles as your school uses them. When you close a flight out, you enter the new reading and FlyerOS checks it against the last one. A reading lower than the last is refused, so a mistyped digit is caught at the desk.
Fixing a genuine mistake
Sometimes a reading really was entered wrong. You do not overwrite it silently. A correction is recorded as a correction, carrying who made it and why, so the original stands beside it and the maintenance forecast is rebuilt from the corrected figure. The history stays intact.
Why this matters
The next maintenance due date is calculated from these counters at your real rate of flying. If a counter drifts from the aircraft's log, everything downstream drifts with it, the due list, the schedule blocks, the airworthiness picture. Keeping counters honest is what lets the schedule respect maintenance without anyone reconciling spreadsheets.