Hobbs

Let'sgoflying!

Let'sgoflying!

Touchdown! Greaser!
Joined
Feb 23, 2005
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Location
west Texas
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Display name:
Dave Taylor
I have a digital/electronic Hobbs meter that will only display anything when the engine is running.
So, you don't hop up on the wing to see when the next oil change is due.
You can't turn on the master and avionics power hoping to see the current hours.
You have to fire up the engine!

Could there be a small battery inside that needs changing?
Could it have been connected incorrectly?

I will try to get the model for you.
 
Tach is usually used for maintenance purposes like 100 hour inspections. Should be able to see that on the tach/RPM gauge.

Hobbs generally used for rental charges.

What airplane?
 
He is saying it won’t even display unless the engine is running. Not just the master switch on.
 
He is saying he uses hobbs for maintenance tracking. Mark said he should use Tach for that. I agree with Mark.
 
Getting sidetracked on unimportant minutiae when we don't know anything helpful to say; it's a recognized specialty.
 
Put a switch in to close the circuit in place of the oil pressure switch or what ever you have for a run circuit. Shut the switch off and all works as advertised. A lot of work for something you could log at shutdown of every flight. Just saying..
 
Write your time down at the end of each flight before shutting down....
 
Other than just preference, is it an actual problem?
You can see the tach for the hour readings needed (desired). ?
just curious
 
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My Hobbs meter is connected to the oil pressure switch which only works when the engine is running, but it isn't digital.
 
Here it is with the engine running.
When the engine is off but all the electrics are on, it is blank.
Anyone recognize the brand/model?

hobbs.jpg
 
Looks like it might be a Honeywell 98000 series or similar. See here. Not sure if it's intended for aircraft use and if it is probably not intended to be used off an oil pressure switch but straight off the master instead. I'd replace it.
 
Tach mx
Hobbs log it
 
Let'sgoflying! said:
Here it is with the engine running.
Click to expand...
Trace the wires and see if an inductive meter (wrapped on spark plug lead) or connected to alternator /volt regulator. If a dc meter, might be able to rewire to batt. If inductive no option.
 
definitely not wrapped on a spark plug wire; might call skydog's link tomorrow to see about replacing one that is on with master switch
 
Let'sgoflying! said:
definitely not wrapped on a spark plug wire; might call skydog's link tomorrow to see about replacing one that is on with master switch
Click to expand...

That would require rewiring. Maybe best to replace with the traditional analog type but leave it hooked up the way it is. Then it will still only run with the engine but you can read it without power.
 
Let'sgoflying! said:
definitely not wrapped on a spark plug wire;
Click to expand...
A guess, but it's probably wired to the charging sjde of the electrical bus. A simple swap of the power lead to the switched side of the battery should give you displayed hours but add unnecessary time without a oil pressure switch. FYI, had previous customer with inductive type who got in habit of including hobbs time in pilot log after each flight. Might work for you.
 
Those meters come one of two ways. One has an internal lithium battery so the display stays on. The other kind uses the same voltage that it's using to trigger the timer to power the display.

The FAA accepts just about anything to measure time in service as long as it's consistent. I've got a Hobbs on the landing gear which is probably the best approximation of what the FAA calls "time in service." My plane has no recording tachometer (and neither does the Bonanza the old engine instruments came out of).
 
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