HOBBS hourmeter

[shumway76]

Any idea what HOBBS stand for? Or is Hobbs just a trade name?

My guess - Hours On Board Before Start?

[India Four Two]

The Hobbs brand is well known worldwide for the development of quality electro-mechanical products. The invention of the first electrically wound automobile clock in 1938 created what is now known as Honeywell Hobbs. John Weston Hobbs was the inventor that cultivated this electrically-wound vehicle clock into a company that has over the years expanded to include hour meters, pressure and vacuum switches, halogen lamps, transmission shifters, and other custom electro-mechanical products.http://stevenengineering.com/Tech_Support/PDFs/31HOURMETER.pdf

While searching for the answer, I came across this very nice description of the practical implications of a Hobbs meter:
When oil pressure rises beyond some predetermined minimum value—usually about 10 pounds per square inch absolute—the switch contacts close, the circuit is completed, and at that point, your wallet becomes eligible for a new weight-and-balance.

[TheOddOne]

A friend of mine describes it as the damage meter, because of the distress it inflicts upon your bank balance.

TOO

[PA28181]

In the same category as "The sperm of the Devil" a mischevious piece of kit designed to extract more cash than you think.........

Putting the levity aside, the assumption they all work on oil pressure at To/cruise revs is not correct. I know many that start as soon as the master is on, they are an abomination that encourages bad practice, If they were all pressure activated I could live with that.

[Tinstaafl]

How a recording meter, such as ones from Hobbs/VDO /others, is activated can vary. Common switches include oil pressure, master, weight-on-wheels/oleo extension, gear up, and airspeed. Of them all, I prefer airspeed followed by oleo as the most representative of time-in-sevice for maintenance tracking.

How an owner charges for the use of the plane is up to the owner. It could match time-in-service but could equally be block time, tacho time, per mile, or even the number of clouds in the sky.

[skyhighfallguy]

I knew of one plane, a twin...it had the hobbsmeter on one of the two engines.

We always shut that one down to practice our single engine work, using our wristwatch for logbook time, hobbs time for billing.

AND THEN we figured out, you could just pull the oil pressure circuit breaker and turn the hobbs off, again using your wristwatch for logbook time.

But you always worried if you would lose oil pressure.

But then again, I might just be making this all up and you should never try it in real life!

[9 lives]

The Hobbs meter is an entirely electric thing. It can therefore be powered directly with a chosen electrical circuit, or it can be switched by the switch of the installer's choice (like oil pressure).

[sharpend]

Yes, indeed in a Pup I know it starts reading on battery on. So the owner makes quite a good profit if, like me, you do your walk-round with the battery on and/or leave the battery on when refuelling (silly boy!). I once ran up over an hour on the Hobbs for a 15 minute flight!

[India Four Two]

Yes, indeed in a Pup I know it starts reading on battery on.

Now there's a good case for flying non-radio! ;)

[Jan Olieslagers]

leave the battery on when refuelling On top of being silly, that is contrary to most POH recommended procedures AND to common sense. Which is not to say it never happened on me...

[sharpend]

Jan, have you ever done anything wrong? If you have not, then you are new to flying. But then you plead guilty also :)

I am quite aware that leaving the battery on whilst refuelling is wrong. Hence my comment 'Silly boy' :)