The short answer
Track your aircraft as a set of components: the airframe, each engine, and each propeller, because each has its own hours, overhaul life (TBO), and ADs. The airframe carries total time; an engine carries time since major overhaul (SMOH), which is usually far lower because it's been overhauled or replaced. Tracking each component on its own clock is the only way intervals and remaining life stay accurate, especially on a twin with two of everything.
Why one number isn't enough
“Aircraft total time” tells you almost nothing about when the next big maintenance event is due, because the parts that drive those events have their own histories:
- The airframe accrues total time from new.
- The engine is tracked on time since major overhaul (SMOH); it may have been overhauled or swapped, so its clock is independent.
- The propeller has its own time and overhaul interval.
- A 6,000-hour airframe can be flying behind a 600-hour engine; only per-component tracking captures that.
Single-engine vs twin
On a single, you're tracking one engine and one prop against the airframe. On a twin, everything doubles:
- Two engines, each accruing its own time and each with its own overhaul schedule and ADs.
- Often two propellers, likewise tracked independently.
- The two engines rarely match (different SMOH, different remaining life), so they can't share a clock.
How to track component times
- 1
Model the aircraft by component.
Airframe, one or two engines, and propeller(s), each as its own item.
- 2
Record current time and SMOH.
Capture each component's hours, and time since overhaul where it applies.
- 3
Attach intervals, ADs, and TBO.
Hang each component's maintenance schedule and overhaul life off the component itself.
- 4
Update from logged hours.
As you log flight time, each component's remaining life and next-due roll forward automatically.
How Maggneto handles it
Maggneto lets you model the aircraft the way it's actually built: airframe, one or two engines, props and accessories, each with its own time, status, and history. Engine times feed oil tracking and maintenance scheduling per engine, so a twin is tracked as two distinct powerplants rather than one blurred average. You can add and adjust components as the aircraft changes.
Track every clock on your aircraft
See how Maggneto's component tracking models your airframe, engines, and props as real components, each with its own hours, overhaul life, and maintenance history.
Frequently asked questions
What does SMOH mean?
SMOH stands for 'since major overhaul', the time accumulated on an engine since its last major overhaul. It's tracked separately from the airframe's total time because the engine may have been overhauled or replaced during the aircraft's life.
Why track engine and propeller time separately from the airframe?
Each component has its own maintenance intervals and overhaul life (TBO), and components get overhauled or replaced at different points. An airframe might have 6,000 hours total while its engine has only 600 hours since overhaul. Tracking each on its own clock is the only way the intervals stay accurate.
How do I track components on a twin?
A twin-engine aircraft has two engines (and often two propellers), each accruing its own time and each with its own overhaul schedule and ADs. Track each engine and prop as a separate component with its own hours and history.
What is TBO?
TBO is 'time between overhauls', the manufacturer's recommended operating time before an engine (or prop) is overhauled. Comparing time since overhaul against TBO tells you how much life remains before the next major event.