Hobbs

On Mon, 2 Jul 2007 16:35:20 -0400, "Peter R."
wrote in :

I was taught that all the newer model C172s' Hobbs are wired to the
master,

Usually there's an oil pressure switch in series with the Hobbs meter,
so that it is only energized when the engine is running. I have no
idea if that is true of the newer aircraft, but it should be.

"Orval Fairbairn" wrote in message
news

Sometimes, unscrupulous owners will wire the Hobbs to the master switch,
so you get charges whenever the MS is ON.


It's not unscrupulous if you know about it up front.

Unscrupulous is when you go to rent a U-haul truck for $19.99 a day, but
they consider a day to be the calender day(s) you use it. Pick it up at 8:30
Friday night, drop it off at 8:00 Saturday night, and that's 2 days. The
best one was when they said the would charge me a $50 cancellation fee. I
drove down, picked up the keys, and returned the truck thirty seconds later.
cost me $19.99 for the 'day'.

On Jul 3, 2:53 am, Airbus wrote:
I have seen dozens of Hobbs meters fail (they are used on plently of
devices, other than airplanes) but never in they way you suggest.

This was on an Arrow, and that is what I thought as to how it would
fail.. Interesting about being wired to the master...
I just recently started renting this Arrow, so I'll keep a closer
watch on the Hobbs and tach now.

I suppose that we can all dream for a slower hobbs

A couple of months ago, the C172N I was renting had a Hobbs that was still
running even after the master was *off*. I joked with the FBO owner that
they were figuring out a new scheme to make money with the planes stuck on
the ramp.




"Larry R" wrote in message
ps.com...
Ok, I am *almost* embarrased to ask this question, but here goes. Do
Hobbs meters ever "go bad"? No, this isn't a joke!

I recently took a flight from KLOU-KWWD-KLOU. It was IFR and I wrote
down my off and land times, which coorespond with the FlightTracking
times within a couple of minutes.

The hobbs time was 10.7. The flight time was 9.6. Not whining here,
but it was a little hard to believe that I had over an hour of taxi/
start time on this!

Just wondering..

--Man would that be some kind of AD-- LOL!

I have seen dozens of Hobbs meters fail (they are used on plently of
devices, other than airplanes) but never in they way you suggest. As
others here have mentioned, their failure mode is that they just stop.
Frequently it's a mechanical (gear-drive) failure, and you can see the
meter "trying" to advance, but it doesn't. These are
escapement-controlled devices (like mechanical watches) so a considerable
speed error would be unexpected. They are esay to misread though (grin).



In article om,
says...


Ok, I am *almost* embarrased to ask this question, but here goes. Do
Hobbs meters ever "go bad"? No, this isn't a joke!

I recently took a flight from KLOU-KWWD-KLOU. It was IFR and I wrote
down my off and land times, which coorespond with the FlightTracking
times within a couple of minutes.

The hobbs time was 10.7. The flight time was 9.6. Not whining here,
but it was a little hard to believe that I had over an hour of taxi/
start time on this!

Just wondering..

--Man would that be some kind of AD-- LOL!

Peter R. wrote:
On 7/2/2007 3:31:14 PM, Orval Fairbairn wrote:

Sometimes, unscrupulous owners will wire the Hobbs to the master switch,
so you get charges whenever the MS is ON.


Isn't that true for the Hobbs installed by the aircraft manufacturer in newer
aircraft? I was taught that all the newer model C172s' Hobbs are wired to the
master, which results in about a 20% greater difference between their
readings and the tach.

Bonanza's don't even have recording tachs anymore. All they have is the
hobbs. My plane is similar, but it's on the gear so I don't pay for taxi.

wrote:
Larry R wrote:
Ok, I am *almost* embarrased to ask this question, but here goes. Do
Hobbs meters ever "go bad"? No, this isn't a joke!

Everything eventually "goes bad", just some things sooner than others.

A Hobbs meter is a mechanical counter with gears, bearings, a motor,
etc. so yeah, it can go bad.

I've seen more tach's fail than hobbs. A hobbs is much simpler.

Peter Clark wrote:
On Mon, 02 Jul 2007 18:53:49 -0000, Larry R
The hobbs time was 10.7. The flight time was 9.6. Not whining here,
but it was a little hard to believe that I had over an hour of taxi/
start time on this!

In my experience, usually they just stop. What kind of aircraft is
this?

The student's greatest fear: a runaway hobbs!
When given a choice which instrument to smash in an emergency, most
students choose the hobbs meter.

-Rod Machado

Orval Fairbairn wrote:

Sometimes, unscrupulous owners will wire the Hobbs to the master switch,
so you get charges whenever the MS is ON.

My Hobbs is on the master, but the airplane has never been rented.

On 7/3/2007 6:50:49 AM, Ron Natalie wrote:

Bonanza's don't even have recording tachs anymore. All they have is the
hobbs. My plane is similar, but it's on the gear so I don't pay for taxi.

Interesting. So Hobbs time is what gets logged in the aircraft/engine
logbooks?

--
Peter