Tach Hour Billing

A tach hour is tied to engine RPM rather than elapsed time. The meter is calibrated to read 1.0 after one hour at cruise RPM, but in the pattern or during climbs it advances more slowly. A typical training flight accumulates fewer tach hours than Hobbs hours.

So if two schools both charge $150/hr but one uses Hobbs and one uses tach, the tach school is cheaper in practice. We apply a 0.8 conversion factor to tach rates when estimating PPL costs, meaning $150/tach-hr is treated as roughly $120 in Hobbs-equivalent cost.

Tach billing shows up most often at flying clubs and smaller independent schools. Hobbs billing is the norm everywhere else.