Originally Posted by
PilotBrandon07
Hobbs time and Tach time usually both start moving at engine start. The difference is Hobbs is electrical and Tach runs off engine RPM. Tachs are set to work accurately at a certain power setting. If the Tach is accurate at 2400 RPM, then if u run the engine at 2200 RPM one hour of hobbs time would not equal one hour or tach time (it would be like .8 or .9. not a math wiz so dont know the exact). This becomes very evident in multi training when ur hobbs time is one hour and ur tach time is .5. I'd like to think i didnt spend 30 minutes with the master on but the engines not turning
Different Hobbs meters are wired differently. Some start when master is turned on, some start with oil pressure and master, some are wired to a strut switch for weight on wheels. Generally only a FBO trying to maximize revenue has it wired only to the master switch.
Joe