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Did You Install a Hobbs Meter?

rockitdoc

Well Known Member
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Just wondering if this is something I should add to my panel. Tach gets pretty close to Hobbs, anyway. Pluses, minuses?

Scott
 
Why........?

Aircraft logbooks - Tacho minus 10%

Personal logbook - Tacho plus 10%

Quite straightforward.
 
I have the Hobbs meter on the panel. Easy to see and record flight time without having to have the EFIS on or doing the necessary buttonology to find the screen with the information.
My Skyview TACH hours is somewhere around 840 hours, and the Hobbs is at 1036. The Hourmeter on the Skyview is roughly the same -- within a few hours of the mechanical Hobbs. The Hobbs meter runs when the oil pressure switch closes, and the master is on.
 
No.

Maintenance events are typically tracked by tach time.

Seems to me that unless it's rental or flight school plane, a separate hobbs isn't very useful and isn't worth my precious panel space.
 
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Why........?

Aircraft logbooks - Tacho minus 10%

Personal logbook - Tacho plus 10%

Quite straightforward.

Aircraft logbooks should be Tach time. Not anything less than tach.. maybe you were thinking you can use Hobbs and minus 10%.

I agree you can log tach + some percentage..
 
Yes.

Even though my engine monitor has a Hobbs function I chose to install a mechanical Hobbs ($15 -- I think for boats).

When doing a software change to my engine monitor I would have to remember to record Hobbs time before upgrade and set it after the upgrade.

I consider a mechanical Hobbs controlled by oil pressure switch a very reliable way to keep track of engine time.

Engine monitor also has a Flight Time function (minutes) that starts and stops at 30 mph airspeed, which I use for my Pilots log book.

In my case, during Phase I a very significan difference between the two, due to static ground engine runs and taxi times along with relatively short flights. I think I reached 40 hours on the Hobbs with less than 30 hours in the air. More than 50 hours on the Hobbs before the required 40 hours Phase I time was reached.

Finn
 
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I use the digital meter inside the Dynon HDX. One less oil line to worry about.

Me too. I just take a picture of the display before shutting down the engine each flight and then every so often go through the photo storage folder on my phone and transcribe Hobbs and Tach to a Notes folder along with date and flight info. Then periodically I go through the Notes folder and update my paper logbook. I use Hobbs for logbook time and Tach for maintenance time. Hobbs comes on with Master, Tach starts with 900 RPM or something like that.
 

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The terms "tach" and "Hobbs" are meaningless unless you know what's triggering them. In the old, rental days it could significantly alter what you paid for a clock hour of flight time. Hobbs could be triggered by the master or master plus oil pressure or something else like an airspeed switch. Big differences. Tach time was typically a recording mechanical tach calibrated to a particular RPM but maybe not your cruising RPM nor even the right one for that plane. In the experimental world I'd argue that the difference is meaningless for maintenance. Pick one and adjust your actions accordingly.
 
I put in an old fashion hobbs meter that is started by an air switch off the pitot effectively measuring air time. Air time is used in Canada for logs and maintenance. I love the fact that I can look at the hobbs at anytime to know total time without firing up the avionics.
 
NO

It’s in my Dynon. I also take a pix of my EMS after I shut down. This gives me Tach & Hobbs. Plus my fuel balance so I can plan for fuel delivery. No writing down info or trying to remember. And no panel space for the antique meter.
Today’s picture after flight up to KFFC and ACS.
 

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I am simple so use one number for everything. I have a Hobbs meter connected to an oil pressure sensor and use it for my pilot log book and maintenance logs. I don’t need to do any mandatory hourly, like 100 hour, aircraft maintenance and is anyway based on my discretion except the Condition inspection which is calendar. Plus Hobbs is more conservative than tach time.
 
Hobbs, Tach and Prop Time

I track three times in my aircraft logbooks. Hobbs - based on oil pressure switch; Tach - starts when RPM > 800RPM and recorded by the EIS/EFIS; and prop time - since the aircraft will have its third propeller when I pick it up in January/February from Myers Aviation.

Tach and Hobbs time do vary a little (the difference now is still less than ten hours). The aircraft had its second prop strike last summer at Airventure after striking an unmarked concrete abutment in the grass with the nose gear and nosed over into the grass, digging a trench, while taxiing to parking. The aircraft and engine had a total of 540 hours on it at that time while the prop only 380 hours. The first prop strike occurred when the original owner had trouble landing in 2014 - again at Airventure. At that time the aircraft, engine and original prop had around 160 hours.

The insurance company wanted to know engine hours and prop hours to adjust for “wear and tear” which impacted how much of the propeller cost and potential engine repair cost would be paid by me. Having this type of detailed information in my logs helped keep my cost share down. Insurance companies pay for “damage costs”, owners pay for “wear and tear” costs with that determined by recorded time in your logs vs TBO. The more detailed your logs are the better you can differentiate between damage and wear and tear costs apportioning.

I personally use Hobbs for maintenance times since it’s the most conservative in my case. My personal flight log book also use’s Hobbs - when I can remember to record it!

P.S. Just got my tear down inspection report on my engine from Poplar Grove. It basically said I had a “pristine” engine with only normal wear indicated. My cost share is less than $2,800 plus some additional cylinder valve guide work I’m having done with new rings and honing. I requested they do this for preventive maintenance purposes since everything is already torn down.

Prop replacement cost share is basically computed as (prop time/TBO x cost of a prop overhaul), thankfully not the cost of a new propeller. Therefore again the lower the actual documented prop time - the lower my cost share.
 
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I bought my plane just about 12 years ago, and the panel had an EI Super Clock and an EI Tach/RPM, with tach time.

I don't recall if I ever even looked at the "hobbs" time on the Super Clock until this same subject came up on VAF maybe 6 months ago.

For flight time I look at the 496 every once in awhile.

The insurance company wanted to know engine hours and prop hours to adjust for “wear and tear” which impacted how much of the propeller cost and potential engine repair cost would be paid by me. Having this type of detailed information in my logs helped keep my cost share down. Insurance companies pay for “damage costs”, owners pay for “wear and tear” costs with that determined by recorded time in your logs vs TBO. The more detailed your logs are the better you can differentiate between damage and wear and tear costs apportioning.
Interesting. My plane had a prop strike 12 years ago (I wasn't PIC) and there were no such insurance "wear and tear" calculations. They paid for the prop overhaul and engine tear down inspection, less the deductible. Period. Prop had ~350 hours on it.
 
Just wondering if this is something I should add to my panel. Tach gets pretty close to Hobbs, anyway. Pluses, minuses?

Scott

It's very inexpensive. Easy to install. But I do not plan to put it on the panel.
I'm building a tip up 7A and it will be on the sub panel visible when the canopy is up.
 
Even though my engine monitor has a Hobbs function I chose to install a mechanical Hobbs ($15 -- I think for boats).

When doing a software change to my engine monitor I would have to remember to record Hobbs time before upgrade and set it after the upgrade.

I consider a mechanical Hobbs controlled by oil pressure switch a very reliable way to keep track of engine time.

Engine monitor also has a Flight Time function (minutes) that starts and stops at 30 mph airspeed, which I use for my Pilots log book.

In my case, during Phase I a very significan difference between the two, due to static ground engine runs and taxi times along with relatively short flights. I think I reached 40 hours on the Hobbs with less than 30 hours in the air. More than 50 hours on the Hobbs before the required 40 hours Phase I time was reached.

Finn

Using the engine monitor time that starts at 30mph, you are robbing yourself of loggable flight time. When you rented a plane, you are paying for (and logging) all time since engine start, including taxi out and taxi in until shutdown. You are PIC and responsible for the aircraft anytime the engine is running. In the airline word, they log out Block Time from the moment the door is closed and brakes released, until we open the door at the gate with the brake set. You should consider using the mechanical Hobbs time off the oil pressure for logbook time, then the tach time for maintenance, which is adjusted for rpm.
 
The terms "tach" and "Hobbs" are meaningless unless you know what's triggering them. In the old, rental days it could significantly alter what you paid for a clock hour of flight time. Hobbs could be triggered by the master or master plus oil pressure or something else like an airspeed switch. Big differences. Tach time was typically a recording mechanical tach calibrated to a particular RPM but maybe not your cruising RPM nor even the right one for that plane. In the experimental world I'd argue that the difference is meaningless for maintenance. Pick one and adjust your actions accordingly.

Bingo !

A basic Hobbs starts destroying your engine and airframe time from putting the master switch on.

The Tacho is tuned to certain revs and will really only read from application of take off power until landing - that is what the engine manufacturers call 'flight time'

Thus, as a easy peasy calculation +10% and - 10% suits the average carry on.

So...

Let's go forward to a modern aeroplane, a Pilatus PC-12. You can sit on the ground with the engine idling for 20 mins - nowt, nada, nothing on the Hobbs. Give it the beans and go flying - the Hobbs comes alive. !


Guys....... Chill - come off the spectrum and realise that a minute or two here or there matters not a jot.

What you decide to do is up to you, I am with this guy..... Keep it simple :D
 
Bingo !

A basic Hobbs starts destroying your engine and airframe time from putting the master switch on.

The Tacho is tuned to certain revs and will really only read from application of take off power until landing - that is what the engine manufacturers call 'flight time'

Thus, as a easy peasy calculation +10% and - 10% suits the average carry on.

So...

Let's go forward to a modern aeroplane, a Pilatus PC-12. You can sit on the ground with the engine idling for 20 mins - nowt, nada, nothing on the Hobbs. Give it the beans and go flying - the Hobbs comes alive. !


Guys....... Chill - come off the spectrum and realise that a minute or two here or there matters not a jot.

What you decide to do is up to you, I am with this guy..... Keep it simple :D

Tach minus 10% for what? For maintenance? That doesn’t make any sense.. tach time is already adjusted for maintenance time.. you have 2000 hours on the tach, that’s the time on the engine. You don’t minus 10% off that..
 
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