The scenario
A Lycoming O-360 installation needs the HOBBS hour meter to run only when oil pressure is present and after a 5-second start delay to avoid recording engine start cranking.
What is in this drawing
Read the decisions behind it.
01
Power feeds through a 1 A breaker to protect the HOBBS meter circuit.
02
An oil pressure switch enables the relay coil, so the meter only runs with engine oil pressure.
03
A 5 s time delay relay prevents the HOBBS meter from logging the start sequence.
Use when wiring a HOBBS meter in small aircraft with battery, oil pressure switch, breaker, and start delay.
More like this