Hobbs Meter Wiring

[avi8tor50]

Have a 85094 Hobbs meter. Supposed to wire it to the ignition (keyed). Diagram does not specify which terminal of the ignition to connect to.
Any help is appreciated.

Peter K
9A

[L.Adamson]

Originally Posted by avi8tor50

Have a 85094 Hobbs meter. Supposed to wire it to the ignition (keyed). Diagram does not specify which terminal of the ignition to connect to.
Any help is appreciated.

Most builders connect the Hobbs to an oil pressure switch, so it only counts time when the engine is running.

L.Adamson -- RV6A

[SportAvServ]

If your using a key mag/on off switch, there will be a "B" or battery connection which gets power when you turn the master on. You can run a wire from there or from the main buss. The other wire goes to the pressure switch usually on the firewall, all the switch does is ground the hobbs when there is a couple of pounds of oil pressure. Because of the high failure rate of an expensive switch, I prefer to have 2 toggle switches for the mags, put a lock on the canopy and you can get a throttle lock if you prefer.

[Jeff R]

Just asking, but why do homebuilders install a Hobbs? I wasn't planning on it since I haven't seen a need for on, but since a number of people do install them, I was just wondering why.

[az_gila]

Originally Posted by SportAvServ

If your using a key mag/on off switch, there will be a "B" or battery connection which gets power when you turn the master on. You can run a wire from there or from the main buss. The other wire goes to the pressure switch usually on the firewall, all the switch does is ground the hobbs when there is a couple of pounds of oil pressure. Because of the high failure rate of an expensive switch, I prefer to have 2 toggle switches for the mags, put a lock on the canopy and you can get a throttle lock if you prefer.

...you work on a certified plane.

They are usually wired so that the power for the hobbs comes directly off the battery through a seperate fuse/breaker (not accessible in the cockpit) and is always live.

I guess folks used to switch off the master while flying to save billing hours...

This wiring counts engine run hours even if the master is off... ...unlike the circuitry described above.

[az_gila]

Originally Posted by Jeff R

Just asking, but why do homebuilders install a Hobbs? I wasn't planning on it since I haven't seen a need for on, but since a number of people do install them, I was just wondering why.

...it's usually a built-in function on EFIS/EMS units.

[Jeff R]

I guess you can legally log a little more time, too, when using a Hobbs - or its EFIS equivalent.

[gasman]

Originally Posted by Jeff R

Just asking, but why do homebuilders install a Hobbs? I wasn't planning on it since I haven't seen a need for on, but since a number of people do install them, I was just wondering why.

A hobbs meter can give you a history of your aircraft. It will run for thousands of hours, and be there when you remove and install things in the panel that alse read time. They are cheap, lite, and don't take up much space. It is not an item that needs to be mounted in the panel. You can mount it in the floor (seat) pan, or in the glove box.

The hobbs meter is an industry standered for time in service...........

[RV8N]

Originally Posted by az_gila

...it's usually a built-in function on EFIS/EMS units.

I don't know how the EFIS counts but the VM1000 only tracks time over 1500 RPM. I currently have around 250 hours on my -8 and the VM1000 only shows around 180 hours. That's a big reason why I installed a hobbs.

Also, the VM1000 only displays engine time prior to engine start-up. I don't know of a way to look at it in flight. I usually use the hobbs to track how long my local flight has been. Just glance over at it.

Karl

[az_gila]

Originally Posted by RV8N

I don't know how the EFIS counts but the VM1000 only tracks time over 1500 RPM. I currently have around 250 hours on my -8 and the VM1000 only shows around 180 hours. That's a big reason why I installed a hobbs.

Also, the VM1000 only displays engine time prior to engine start-up. I don't know of a way to look at it in flight. I usually use the hobbs to track how long my local flight has been. Just glance over at it.

Karl

...modern EFIS/EMS units.

The VM1000 was one of the first "out of the gate" integrated large screen EMS devices and probably does not have all of the features we are use to seeing on the more recent units...