Calculating total airframe time when Hobbs is hooked to master

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k9medic

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ATP-H, CMEL, CSEL, CFI/CFII Airplanes and Helicopters
During our last (which was also our first) annual, we identified that the hobbs meter was attached to the battery master switch and starts to tick away when the master is turned on. This obviously is an issue since that "logs" time.

We us the tach for our times normally so the Hobbs meter is not much of an issue. How would you account for the difference in time if we were to sell the airplane? Just get a new meter and stat from zero with it wired correctly?
 
I would do nothing. The Hobbs meter doesn’t match the tach in every airplane I’ve ever seen with a Hobbs meter.

The buyer doesn’t give a **** about the Hobbs time. Track the engine and airframe time using tach time.
 
I wouldn't account for it at all. Hobbs never equals tach. Assuming a standard light GA airplane here, the tach meter should be used for all aircraft maintenance and AD compliance, etc.
 
Think of the Hobbs as the fare meter on a taxi and the tachometer as the odometer.:)
 
k9medic said:
How would you account for the difference in time if we were to sell the airplane?
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Your aircraft time-in-service (total time) is a separate record in the logbook and the only one required. How you count that time could be through your tach, hobbs, watch, or any time keeping device. Simply verify your current TIS and when you rewire the hobbs make an entry with all your current time keeping values plus your current TIS. This will give you a bench mark to the TIS in case the tach/hobbs goes inop. Technically TIS is defined as the time from the moment an aircraft leaves the surface of the earth until it touches it at the next point of landing.
 
Is the Hobbs time higher than TTAF? If it is and you think it's going to affect your sale price then put a new Hobbs meter in it.
 
Im using tach time for tracking time for overhaul,and airframe total time.Hobbs time records the battery being activated. Tach time is usually hundreds of hours less than Hobbs.
 
A friend just sold two late model airplanes, both with a Hobbs meter connected to the master switch. Both airplanes were very low time and there was a 100+ hour difference between tach and hobbs time on both of them. The times were never questioned by the buyer. My point here is that I think you're making a problem out of nothing.

Also, there is no right or wrong way to wire a hobbs meter. Some airplanes have them wired off the master, others off of an oil pressure switch, and a few also use a gear position switch or weight on wheels switch so that the time spent in the air could be recorded. Most of the late model airplanes ive been around seem to come on when the master switch is turned on.
 
asicer said:
Sounds like a good excuse to go NORDO.
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The same could be said for any electric powered recording device, assuming you’re paying for aircraft use based it. If not, I cant see why it would matter much what number is on it. :)
 
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