Definition
An instrument in the aircraft that records the total time the engine has been running, used for tracking maintenance intervals, rental billing, and logbook entries. It is typically activated by oil pressure once the engine starts, and runs continuously in real time until the engine is shut down.
Plain English
A small clock inside the aircraft that only ticks while the engine is running. It tells you how many hours the engine has been operating in total.
Context Anchor
You will see the Hobbs Meter on or near the instrument panel, and you may record its reading before and after a flight.
Derivation
Named after John W. Hobbs, the American inventor whose company developed the original elapsed-time meter in the 1930s. Knowing it is a brand-turned-generic name explains why the term is capitalized and why it does not describe what the meter does.
Why Pilots Care
Accurate engine time tracking determines maintenance schedules, prevents mechanical issues, and supports proper billing and logbook entries in rental aircraft.
Analogy
Think of it like a stopwatch built into the airplane. It does not measure distance; it measures how long its trigger has been on.
Intuition Check
A Hobbs Meter does not always mean “time in the air.” It means time recorded by that particular meter, based on how the aircraft is set up.
Example Sentence 1
Before taxiing, she noted the Hobbs meter reading so she could calculate the rental hours after the flight.
Example Sentence 2
Before approving the aircraft for the next flight, the mechanic reviewed the Hobbs meter to confirm the required inspection interval had not been exceeded.