Glossary
Time in Service
Definition
Per FAR 1.1, the time from the moment an aircraft leaves the surface of the earth until it touches the surface again. This is the official reference for 100-hour inspection intervals.
Why It Matters
Time in service is technically neither Hobbs time nor tach time — it's actual flight time. In practice, most schools use tach time as the closest practical approximation because it's recorded on every flight.