Tach time

[Dickard]

OK, I give up.  I can't figure out how to get the tach time on my JPI EDM 900. Nor can my A&P.  The instructions in the manual don't work.  Am I holding my mouth wrong?  Do, I need to stand on one leg and pat my stomach?  What's the trick?

[smwash02]

If any warnings or questions are on the bottom blue bar it won't work, clear those out first, then hold the two middle buttons down. It'll switch to a black screen with the tach and hobbs times in the middle.

[Marauder]

OK, I give up.  I can't figure out how to get the tach time on my JPI EDM 900. Nor can my A&P.  The instructions in the manual don't work.  Am I holding my mouth wrong?  Do, I need to stand on one leg and pat my stomach?  What's the trick?

The new firmware displays the tach time on the main screen. Mine is in landscape mode and it appears in the lower left corner.

Older firmware, I think it was seen by pressing the 2 (LF) and 3 (Dim) button together. It first shows the Hobbs value and then hitting next button, I think that takes you to the tach time.


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[Greg Ellis]

4 hours ago, Marauder said:

Older firmware, I think it was seen by pressing the 2 (LF) and 3 (Dim) button together. It first shows the Hobbs value and then hitting next button, I think that takes you to the tach time.
 

You are correct that on the older firmware pressing the LF and Dim buttons together will show the Hobbs and also the Tach time on the same page (at least on mine).  Hitting the next button takes you to a different page showing firmware revisions, etc....

[Marauder]

You are correct that on the older firmware pressing the LF and Dim buttons together will show the Hobbs and also the Tach time on the same page (at least on mine).  Hitting the next button takes you to a different page showing firmware revisions, etc....

Thanks for confirming. I may be getting older but it is good to see I don’t have any holes in my marbles sack yet.


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[Pinecone]

Do Mooney even have tach time?

My 252 only has a Hobbs, that supposedly is connected to an airspeed switch

[jaylw314]

3 hours ago, Pinecone said:

Do Mooney even have tach time?

My 252 only has a Hobbs, that supposedly is connected to an airspeed switch

Interesting question, the basic VFR requirements are just for a tachometer, not a tach counter.  Is one or the other required in the maintenance rules?

[kortopates]

4 hours ago, Pinecone said:

Do Mooney even have tach time?

My 252 only has a Hobbs, that supposedly is connected to an airspeed switch

Actually if we're talking about the factory installed system, its an "Hour Meter" and its connected to the tach (Not airspeed switch) and records time based on and RPM at about 2550 from memory. So at idle, of around 1000 rpm, its only adding time at 40% of elapsed.

Hobbs meters are added when someone has their plane on a leaseback or a flight school, which log 1:1 for engine running time.

Edited August 18, 2022 by kortopates

[carusoam]

Mooneys and tach time…

In a more general sense…

It very much depends on the year and model of the Mooney…

Older Mooneys have the tach that counts engine revolutions… and translates that number as hours… of course, it is accurate at only one rpm… that rpm is often noted in the paperwork for the airframe… and the case of the tach itself…

A few Mooneys have installed an air switch out on the wing… to power a separate engine time clock…

 

More modern Mooneys…. Have a paragraph in their POH on how their hour meter works, often starts counting based on oil pressure…

If you haven’t seen your hour meter… look on the back wall of the baggage compartment….

Mooney started hiding the hours so it wasn’t bothersome to the pilot on every flight, for every minute….   
 

PP thoughts only, not a mechanic…

Best regards,

-a-

[EricJ]

6 hours ago, Pinecone said:

Do Mooney even have tach time?

My 252 only has a Hobbs, that supposedly is connected to an airspeed switch

Is that what your mechanic uses for recording maintenance times?

 

[Pinecone]

2 hours ago, EricJ said:

Is that what your mechanic uses for recording maintenance times?

 

I don't know.  I just picked up the airplane last weekend.

86 252.  The meter is on the right side of the console above the mesh pocket.  It is a Hobbs type meter.  There is no meter on the tach.

It doesn't count engine run or electrical time.  It counts less than those. 

[EricJ]

Just now, Pinecone said:

I don't know.  I just picked up the airplane last weekend.

86 252.  The meter is on the right side of the console above the mesh pocket.  It is a Hobbs type meter.  There is no meter on the tach.

It doesn't count engine run or electrical time.  It counts less than those. 

It might be worth asking your A&P/IA what they expect or want to use going  forward, and looking at how the maintenance has been recorded historically.   It's not anything urgent, obviously, but it may help things going forward.

[Pinecone]

Yeah, I have to check the last log entries to see what was used.

But it seems to be the only meter.

[Dickard]

My A&P has tried to get it off the EDM, but hasn't figured it out either.  Hobbs time is for pilot logbooks.  Tach time is for engine log books.  Right?

[PT20J]

5 hours ago, Dickard said:

My A&P has tried to get it off the EDM, but hasn't figured it out either.  Hobbs time is for pilot logbooks.  Tach time is for engine log books.  Right?

Sort of. FAR Part 1 defines pilot time as

Pilot time that commences when an aircraft moves under its own power for the purpose of flight and ends when the aircraft comes to rest after landing.

And time in service as

Time in service, with respect to maintenance time records, means the time from the moment an aircraft leaves the surface of the earth until it touches it at the next point of landing. 

Usually tach time is used for maintenance log entries since most airplanes lack a way to record flight time, and renters pay Hobbs time since it usually records whenever the engine is running and is thus the greater of the two measurements.

Skip

[Floyd]

My JPI900 is a bit difficult to get to the tach/hobbs page.  I have the best luck getting there by pushing and holding the bottom button a fraction second before the top button.

[carusoam]

@Dickard…

See if Floyd has your answer above…

Go MS!

-a-

[Pinecone]

OK, the Hobbs meter in my plane does not track engine run time.  So I think my transition CFI is correct, that it runs off an airspeed switch (maybe the gear one).

And the logs seemed to be based on the time in the Hobbs meter.

Since there is no hour meter in the tach, what else would you do?

 

 

 

[carusoam]

PC,
Airspeed switch can handle it… often triggers near 65kias…  matched somewhat to Vr and lower than Vx…

Oil pressure switches are common…

Modern POHs have a small paragraph that describes all the instruments… and the engine timer should be listed with a sentence of what it reads and how…

Some older planes added an airspeed switch, but gear up light is also a good resource with no added drag… 

PP thoughts only, best regards,

-a-

[Pinecone]

I just checked again, but nothing about the hour meter.

Not sure if it works off the gear up switch or the airspeed switch for the gear.

I guess I could go fly around for a while with the gear down and see if the time registers.

 

[PT20J]

If you have a factory BDI electric tach, Mooney used a special Hobbs meter that records tach time from an output on the tach. I believe it reads 1:1 at 2500 rpm but I’ve never seen that documented. 

If it is an air Hobbs, connection to the gear is unlikely because that would not match the definition in the FAR since the gear is usually lowered well before landing. Usually, there is an air switch under the wing. The airspeed safety switch has two microswitches. One is used to prevent gear retraction at low airspeed and the other can be used for a flight timer. 

Skip

[Jim Peace]

I have the JPI900 in portrait view. About 4.5 years old. 
Would I be able to update the firmware and have tach time in view 100% of the time?

Would love to have a clock with seconds as well just like the 930  

 

[Pinecone]

3 hours ago, PT20J said:

If you have a factory BDI electric tach, Mooney used a special Hobbs meter that records tach time from an output on the tach. I believe it reads 1:1 at 2500 rpm but I’ve never seen that documented. 

If it is an air Hobbs, connection to the gear is unlikely because that would not match the definition in the FAR since the gear is usually lowered well before landing. Usually, there is an air switch under the wing. The airspeed safety switch has two microswitches. One is used to prevent gear retraction at low airspeed and the other can be used for a flight timer. 

Skip

 

Ah, this makes sense.  So it is reading tach time.  But on a Hobbes meter.

 

Although I have never heard of a variable Hobbs meter.  I thought they on or off only.  Learn something every day.

 

[kortopates]

6 hours ago, Pinecone said:

 

Ah, this makes sense.  So it is reading tach time.  But on a Hobbes meter.

 

Although I have never heard of a variable Hobbs meter.  I thought they on or off only.  Learn something every day.

 

Technically its not a Hobbs meter, hobbs are only on of off as you say. It just looks similar to one. If you review your documentation, its referred to as the "Hour Meter", if you look at your schematic it shows its wired directly to your tach. Perhaps the thing confusing is that tach hours are not contained on the tach meter but show in this separate "hour meter" on the right side of the pedestal. But its essentially a normal "tach" split into two different displays; probably due to the small size. 

[Pinecone]

OK, it LOOKS like a Hobbs meter.

My POH does not mention it, that I can find.  And it not shown on the schematic.

Where would I find that it is wired to the tach?