Money
Engine reserve
Money set aside per flying hour to fund the engine's eventual overhaul, so the cost lands on the hours that caused it.
In practice
The engine wears per hour, so fair groups fund it per hour: overhaul cost divided by TBO, charged on every flight, accumulating in a dedicated fund. Done right, overhaul day arrives with the money already in the bank and no capital call. Done late, the required per-hour rate climbs because fewer hours remain to spread the shortfall across. Prop and avionics reserves follow the same logic with smaller numbers.
Get started
See it with your own aircraft.
Add your aircraft and your rates, then see the schedule, the squawks, and the ledger all work off one record. No card required.