Glossary
Tach Time
Definition
Engine time measured by the tachometer, calibrated so one tach hour equals one hour at cruise RPM (typically 2,400 RPM). At idle, the tach accumulates slower than real time. At full power, slightly faster.
Why It Matters
Most flight schools use tach time for maintenance intervals because it more closely represents actual engine wear than Hobbs time. A typical training flight accumulates 10-15% less tach time than Hobbs time due to ground operations at low RPM.