PA28-180D Hobbs Meter Not Working

Koby Sronce

Koby Sronce

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Ksronce
Hey guys Im kinda new to the GA world and I'm looking for a little advice/help to save some pennies.

We recently just purchased a 1969 PA-28-180D Cherokee. It runs great but, like anything this old, it has it's problems. One of the first things I noticed is the hobbs meter not working correctly, it only read 3 hours on a 5.5 hour flight back to Texas.I have to go off the tach and im basically shorting myself time because of this. I know flight schools have them tied into the Battery to start cycling when the battery is turned on, Im not necessarily concerned about doing that as I crank the engine 20 seconds after flipping the master. My question is, Is there an oil pressure switch behind the hobbs that needs replaced with the Hobbs?

My father is a 35 year A/P IA for American Airlines so any maintenance can be done by him, he just isn't proficient in GA airplanes like he thought.


Any replies would be greatly appreciated.
 
mark it non-op and get on with your life.

Tach X 1.2 is generally accepted. Or you can log by the big hand and little on the thing on your wrist. Or any other timer you may possess.

Hobbs is for billing... Elapsed time is for logging.

[And now you'll get a few dozen contradicting opinions]
 
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I generally give myself tach + .3 for logging purposes. I was only ever taught to log with hobbs so that's what I know how to do.
 
Your airplane, the hobbs is wasted space in the panel. Maintenance and such goes on tach time. For logging your flight hours, use your watch.
 
Koby Sronce said:
I generally give myself tach + .3 for logging purposes. I was only ever taught to log with hobbs so that's what I know how to do.
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A Hobbs Meter is nothing more than an elapsed time meter. And elapsed time is nothing more than End Time minus Start Time. And those are easily measured using a watch or your phone.
 
SkyDog58 said:
A Hobbs Meter is nothing more than an elapsed time meter. And elapsed time is nothing more than End Time minus Start Time. And those are easily measured using a watch or your phone.
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So do I "start" the meter from the time I step into my plane, turn the master/engine on, or become airborne? Dumb Question but I wanna make sure I do it correctly.
 
Koby Sronce said:
So do I "start" the meter from the time I step into my plane, turn the master/engine on, or become airborne? Dumb Question but I wanna make sure I do it correctly.
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A Hobbs normally works off of oil pressure but some are off the master and some off a gear squat switch. I normally go with engine start to engine shutdown if the plane doesn’t have a Hobbs.
 
Seems OP might be better off with Tach * 1.2 until the tach breaks.
 
Koby Sronce said:
So do I "start" the meter from the time I step into my plane, turn the master/engine on, or become airborne? Dumb Question but I wanna make sure I do it correctly.
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From the time the aircraft moves under its own power for the purpose of flight until it comes to rest after landing.
 
Thanks for the replies. Saved me $70 on a hobbs meter.
 
dmspilot said:
From the time the aircraft moves under its own power for the purpose of flight until it comes to rest after landing.
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And for me, that begins on the take off roll. I know others log it as soon as the plane moves - but I take issue with that, because you could taxi around the airport for 12 hours, fly once around the pattern and log it as 12 hours of flight time.

My flight timer on the MVP 50 start at something like 2000 RPM (which I only attain on the takeoff roll) and it stops at under 500RPM, which only happens when I kill the mixture.
 
Koby Sronce said:
Thanks for the replies. Saved me $70 on a hobbs meter.
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Before it comes back to bite you, make sure there was no previous maintenance performed based on the hobbs time like an AD. I would verify aircraft total time now and make an entry just to be sure.
 
Hobbs meters are usually reliable things. You put 10-30V on them and they count up. The first thing I'd look at is what is it connected to. There's no standard for this.

The rules for PILOT TIME say you log from when the aircraft first moves on it's own for purposes of flight until it comes to rest. In practice, the FAA will buy any reasonable estimation of that (hobbs time, FBO rental receipts, tach time with reasonable conversion factors, etc...).

The rules for TIME IN SERVICE (that is time for maintenance purposes) are when the aircraft is FLYING (off the ground). Some planes like mine have the hobbs on the gear switch (best approximation in my estimation). Again the FAA takes either a recording tach or a hobbs connected to whatever or any other reasonable and consistent measurement of the time.
 
I don't have a Hobbs meter in my aircraft, nor did I have one in the last. If we had to measure hours we just used the tachometer.
 
In Canada we must track Air Time and Flight Time. AIr Time is the time the wheels are off the ground, and is the time counted against the airframe, engine and prop. Flight Time is engine start to engine shutdown, and is what is usually billed to a renter and is also what counts toward the pilot's total time.
 
Most private owners track maintenance time for engine and airframe purposes using straight tach hours, no conversion. I use my watch or the panel clock for hours logging.
 
flyingron said:
When given a choice of an instrument to break in an emergency, most students chose the hobbs meter.
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I wouldn't limit that to students. It is the most expensive instrument in the panel of our club planes. It costs me money every time it increments 1/10 of an hour. If anything else breaks, I just record it in the log and call the maintenance officer for that plane. :D
 
Jeff Oslick said:
Most private owners track maintenance time for engine and airframe purposes using straight tach hours, no conversion. I use my watch or the panel clock for hours logging.
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Unless they fly a Twin...
 
Jeff Oslick said:
1) Most private owners don't own a twin.
2) Why would a twin owner not use tach time to track maintenance on each engine?
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1) Lots of private owners have twins.
2) Most twins have a single tach for both engines (two needles), and as such don't have "tach time" since the dual tachs typically don't have a meter in them. So, most twin owners are stuck with hobbs time for tracking.
 
bradg33 said:
1) Lots of private owners have twins.
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I said "Most" private owners. Only about 10% of piston aircraft are twins; therefore, my statement stands. You could have just added information to the thread, such as "FYI, twins don't typically have recording tachs", instead of being needlessly argumentative.
 
You haven’t read the “What can I log” threads? You can write whatever you want in your log book. ;)
 
bradg33 said:
1) Lots of private owners have twins.
2) Most twins have a single tach for both engines (two needles), and as such don't have "tach time" since the dual tachs typically don't have a meter in them. So, most twin owners are stuck with hobbs time for tracking.
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And besides, using a hobbs on the squat switch gives a smaller number (but legally the most accurate). Gets you more time on 100 hours or any other time limited thing.
 
On Barons I've flown, it's been connected to gear retraction...if you flew around with the gear down, the Hobbs didn't run.
 
So without a HOBBS meter, how do you know what your Aircraft Total Time is? I always thought the Hobbs was also used to AFTT.
 
Lachlan said:
I thought real pilots don’t log flight time after the check ride?
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I haven't logged much of my later time in my Skyhawk. If I can find the airplane logs I may add in those hours, though I don't need time.
Our flight school Hobbs started the second you flipped the master ...
 
jd21476 said:
So without a HOBBS meter, how do you know what your Aircraft Total Time is? I always thought the Hobbs was also used to AFTT.
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AFTT is air time, not flight time. Air time is, basically, time in the air, though the takeoff roll time is often included. A Hobbs is usually fired by an oil pressure switch that turns the Hobbs on once the engine starts, and that number is used for billing purposes. A Hobbs is not a legal requirement, but tracking the air time is. One uses a watch for that.

The Hobbs is fed from the battery through a low-amp fuse, like 1/4 amp or so, to the oil pressure switch and then to the meter. Those that are fired by the master might be off the bus through a small fuse. In many cases, the Hobbs quits when the fuse blows or gets corroded with age. Corrosion is common with most, as they're often mounted right next to the battery and are suffering the vapors that come from the battery during charge. The clock fuse will be right next to it.
 
jd21476 said:
So without a HOBBS meter, how do you know what your Aircraft Total Time is? I always thought the Hobbs was also used to AFTT.
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Depends on the plane. Most light aircraft use a recording tach however. Very few use the hobbs, the later Bos (and my Navion) were an exception. They use a Hobbs on the gear switch (which gives the best definition of time in service by the rulebook definition).
 
Dan Thomas said:
AFTT is air time, not flight time. Air time is, basically, time in the air, though the takeoff roll time is often included. A Hobbs is usually fired by an oil pressure switch that turns the Hobbs on once the engine starts, and that number is used for billing purposes. A Hobbs is not a legal requirement, but tracking the air time is.
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TIme in service is the time the aircraft is off the ground by definition.
A Hobbs runs by whatever is powering it, I've seen them connected to masters, to oil pressure switches, to gear switches, to the heater switch, etc...
One uses a watch for that.[
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I've never seen anybody use a watch for time in service and have my doubts that the FAA would be too happy with that.[/QUOTE]
 
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flyingron said:
I've never seen anybody use a watch for time in service and have my doubts that the FAA would be too happy with that.
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In Canada it's perfectly OK. What does one do when the airplane has no electrical system and no recording tach, as with a lot of old Cubs and Champs?

Edit: Unlike the US, in Canada we have a Journey Log, required by regulation, and the times are recorded in it.
 
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