Hobbs

[Tip]

So, while updating my Skyviews, my Hobbs increased 3/10. Is that how it should work? Master switch was on, engine was not.

[Garrett Gee]

13 minutes ago, Tip said:

So, while updating my Skyviews, my Hobbs increased 3/10. Is that how it should work? Master switch was on, engine was not.

Can't speak to your airplane, but my hobbs is tied to the generator breaker.  If the generator breaker is on, even without the engine running, my hobbs will run.  Was the generator breaker pushed in by chance?

[Anticept]

Even if the hobbs runs, it's not time added to the airplane. If you want, you can make a note in the logs that during an update the hobbs meter rolled three tenths if you're using hobbs to track total time.

14 CFR 1.1 says that time in service only counts when the aircraft leaves the ground to the time it touches back down, so hobbs meters are kind of a silly meter to use anyways, I'd rather use flight timers. Both the D series and skyview have flight timers in them.

[Tip]

Thank guys, the generator switch probably was on. I’ll check on that today?

[Warmi]

8 hours ago, Anticept said:

Even if the hobbs runs, it's not time added to the airplane. If you want, you can make a note in the logs that during an update the hobbs meter rolled three tenths if you're using hobbs to track total time.

14 CFR 1.1 says that time in service only counts when the aircraft leaves the ground to the time it touches back down, so hobbs meters are kind of a silly meter to use anyways, I'd rather use flight timers. Both the D series and skyview have flight timers in them.

Does it matter what it says ? Everybody reports their plane time from looking at the Hobbs so it always pretty much includes ground time.

[Anticept]

Warmi:

There is no FAA rule that requires you to use a meter to record time in service. You could use a notepad to do it.

I have seen logbook inspection entries that show just hobbs in them, which isn't legal, it has to say time in service. I can't remwmber if it's an AC or FAA interpretation that states that just reporting meter readings is insufficient.

I don't like using hobbs because it adds a lot of extra hours to an airplane that aren't actually hours TIS. That's all.

[Roger Lee]

Hobbs should not run unless the oil pressure is 15 psi or higher. The Tach will run with just power on in many planes and a tach doesn't record actual time. It is influenced by engine rpm. It's usually around 10% off. This is why Rotax wants you to use only the hobb's. It should be only real engine run time.

[Anticept]

You can still maintain the engine to hobbs time. I'm just not going to put hours on my airframe that aren't real hours because an engine company wants to do things differently. While I never intend to sell my airplane, why devalue it on purpose?

Tach is supposed to be set to cruise RPM, but since it's not a required reg anywhere, nobody does. Most people are probably unaware that you can configure the cruise RPM in Dynon units, unlike round gauges which has to be set by an instrument shop (if they even have that adjustment).

Flight timer on Dynon units is the closest thing to the TIS definition in the regulations.

Some aircraft use squat switches, others have a pressure sensor hooked into the pitot line that triggers at a certain airspeed for TIS.

[Roger Lee]

Hobbs time reflects true engine run time regardless of it on the ground or in the air. This is what Rotax cares about,, engine run time and since hobb's is more accurate on engine run time vs the tach for the huge majority of owners this is where they (Rotax) drew the line in the sand.

You could use either in the overall scheme of things, but hobb's just records a truer run time. Just because you're on the ground doesn't mean you don't accumulate a lot of time and it doesn't show how hard or abused the engine was run. So the MFG just draws that line in the sand for engine run time.

[Anticept]

Right, which is why I say, you can still maintain it to hobbs regardless of how you record your airplane's TIS. Nothing says you can't record airplane TIS differently from engine TIS as long as you can defend your position that you're not running afoul of the 1.1 definition.

I'm just not going to record my airplane's TIS using hobbs just because the engine manufacturer wants to use it. That's just silly.

I have forked this thread over to

 

[Tip]

14 hours ago, garrettgee2001 said:

Can't speak to your airplane, but my hobbs is tied to the generator breaker.  If the generator breaker is on, even without the engine running, my hobbs will run.  Was the generator breaker pushed in by chance?

Garrett is correct. If my generator breaker is in, the hobbs is ticking. I like Roger’s statement about 15 psi, but that’s not how mine is wired. So, if the Gen breaker is left on by mistake, time will accumulate until the bay is dead.

[Roger Lee]

Hi Tip,

If you have a panel tach then it does run when the power is on (usually).

Most use the Hobbs in the Dynon 120. It has the option for either.

[Tip]

2 hours ago, Roger Lee said:

Hi Tip,

If you have a panel tach then it does run when the power is on (usually).

Most use the Hobbs in the Dynon 120. It has the option for either.

 

[Tip]

I have dual Skyviews

[Roger Lee]

1 hour ago, Tip said:

I have dual Skyviews

Then you can pick tach or hobb's. I make sure all my clients are on hobb's as Rotax recommends. 

[tevbax]

So fun fact, this just happened to me the other day. Went for a Young Eagles flight, turned the plane off COMPLETELY, then flipped the master to get the hobbs time. I must have left it on, as when I went to move the plane, it had accumulated .9 hrs. I looked into the EMS manual, and it states it only accumulates time when the engine is above 15 psi of oil pressure. 

Im baffeled. 

[Roger Lee]

The manual may have said that, but they may not have installed it like that. Manuals don't always keep up with changes. FD made tons of changes with hundreds of aircraft, but those changes never made the manuals. They may have run out of a part or found a better way, but it doesn't seem like many people maintain up to date manuals.