The Hobbs meter measures either the time the engine has been running, or the master has been on, or something like that, but it wouldn't really make much of a difference.  Anyways, the Hobbs will read total time, so I double check the time on the Hobbs as one of my first preflight items, then I check the Hobbs again after I've landed, parked and shut-down, and then I find the difference between the two times to get the total time (duration of the flight).  The Hobbs meter reads every tenth of an hour, so your reading off the Hobbs will be accurate down to each tenth of an hour, and the time I read off the Hobbs is the time I use in my logbook.  Is that what you were wondering?

Hobbs meters generally have an oil pressure switch... that way if you leave your master on overnight you dont have 18 hours on the plane when you open shop the next day... you just have a dead battery.

The hobbs will start turning the moment you see an oil pressure indication.

6 minutes = one tenth of an hour since there are 60 minutes in an hour, so if you fly for 42 minutes you log 0.7 hours since thats what the hobbs meter would say.

if your hobbs meter says 1.3 then you flew for one hour and 18 minutes.

the decimal place on the hobs meter is always multiplied times 6

757200ba wrote on May 15^th, 2007 at 10:48pm:



How was the time noted in your log book prior to solo? I've never heard of anything other than tenths being used.

As for knowing what your total time is, when bragging  to friends: round it up to the nearest 1/2 hour.    

I too have never heard of anyone refering to hours and minutes.  And also, always use the Hobbs, even if it is more expensive.

Plus, if you have questions regarding how to log time, it is spelled out pretty simply in the FARs.

also good to know is if the hour meter is a total time or tach time type of meter

as I learned about in school the total time meter is running anytime the engine is running as stated in previous responses.

The tach time type of meter on the other hand will start running when the engine rpm is above normal idle speed.

correct me if I'm wrong, but that's what I was taught..

For purposes of logging flight hours, the Hobbs is used. Anyone who's ever learned to taxi even the most forgiving airplane knows that they deserve to log that time towards their total flight experience, so it doesn't matter that the engine is near idle and you're still on the ground...

The tach meter, as you might suspect, is meant for logging engine hours... although I do know that sometimes (in a flying club situation, for example), the tach hours are used for billing for hourly use of the plane.