JPI EDM 900 Install in an M20J

[LANCECASPER]

On 3/25/2023 at 9:33 AM, 0TreeLemur said:

Tom, my question wasn't clear.   I had a JPI EDM900 in my C, so I know how those work.   My question is, if connected as shown with the JPI substituting for the analog fuel gauge, will the Low Fuel annunciator lights still work?

@Aerodon will have an answer to this

[jetdriven]

You're doing this right now with a 62 M20C we are going from all of that stuff to a single Garmin G.I.275

[jetdriven]

[Aerodon]

11 minutes ago, LANCECASPER said:

@Aerodon will have an answer to this

So the EDM's have the option to set up a warning on time and fuel quantity. So with the EDM830, the only way for this to work is to make sure you start with fuel quantity matching actual, and then the EDM will use fuel flow to calculate remaining fuel.

I believe the EDM900 uses 'actual fuel' for this calculation, but I am not certain. I believe you also get a 'fuel quantity mismatch' if the calculated quantity is not closely aligned with measured FQ. I asked JPI directly, but did not get a straight answer, they tend not to get drawn into any discussion on how things work, but seem to be briefed to refer you to the instructions.

I looked at the fuel gauge circuit and came to the conclusion there is no way to keep the analog signal to the annunciator panel to trigger the low fuel warning.

Aerodon

 

[0TreeLemur]

The rpm sensor JPI sent for the A3B6D (dual mag) consists of a wire with a plug at one end and a ring terminal (maybe 1/2" I.D.) on the other.   The instructions are unclear.  Obviously the plug connects to the JPI wiring harness.  Where does the ring get installed?  I assume on the magneto somewhere- but where?

[ArtVandelay]

The rpm sensor JPI sent for the A3B6D (dual mag) consists of a wire with a plug at one end and a ring terminal (maybe 1/2" I.D.) on the other.   The instructions are unclear.  Obviously the plug connects to the JPI wiring harness.  Where does the ring get installed?  I assume on the magneto somewhere- but where?

My JPI IM has diagrams for each magneto model showing connection point, page 30.

[0TreeLemur]

7 hours ago, ArtVandelay said:

My JPI IM has diagrams for each magneto model showing connection point, page 30.

Thanks Tom.  The IM is at the shop.  I scanned it but missed that figure.

Downloaded IM and see it.   -Fred

[RoundTwo]

On 3/28/2023 at 7:56 PM, Aerodon said:

So the EDM's have the option to set up a warning on time and fuel quantity. So with the EDM830, the only way for this to work is to make sure you start with fuel quantity matching actual, and then the EDM will use fuel flow to calculate remaining fuel.

I believe the EDM900 uses 'actual fuel' for this calculation, but I am not certain. I believe you also get a 'fuel quantity mismatch' if the calculated quantity is not closely aligned with measured FQ. I asked JPI directly, but did not get a straight answer, they tend not to get drawn into any discussion on how things work, but seem to be briefed to refer you to the instructions.

I looked at the fuel gauge circuit and came to the conclusion there is no way to keep the analog signal to the annunciator panel to trigger the low fuel warning.

Aerodon

 

I had the glare shield off my J today and see that 4 wires were cut off at the back. Also, 4 light bulbs were pulled out and electrical tape was placed across the alerts. Gone are low Left Fuel, Low Right Fuel, Hi/Lo volts and lo vacuum. All I have left is Gear Down, Gear Unsafe, Start Charge On (the one that won’t light up during testing, and Ram Air On.

[ArtVandelay]

I had the glare shield off my J today and see that 4 wires were cut off at the back. Also, 4 light bulbs were unsoldered and electrical tape was placed across the alerts. Gone are low Left Fuel, Low Right Fuel, Hi/Lo volts and lo vacuum.

Not sure why vacuum is gone, but 900 will handle voltage and fuel annunciations.
At some point you’ll only have gear annunciations left, and can get rid of the annunciator and just have a couple of warning lights.

[RoundTwo]

1 hour ago, ArtVandelay said:

Not sure why vacuum is gone, but 900 will handle voltage and fuel annunciations.
At some point you’ll only have gear annunciations left, and can get rid of the annunciator and just have a couple of warning lights.

I have no vacuum pump. But I still have RAM AIR  

[M20F]

On 3/10/2023 at 11:49 PM, jetdriven said:

Or, if you crawl underneath the copilot side and look out board of the heater box it's on top of that metal plate

I would just pull the cheek plates, oh wait :-)

[0TreeLemur]

On 3/28/2023 at 5:52 PM, as350 said:

I am about to embark on this same install in a '67 E. I have the 201 windshield so I expect it to be a royal PIA. I plan on removing an EDM-700, the 6-pack, tach/fuel press and MP gauge. It should be worth the hassle as the instrument panel will be much cleaner once completed. 

You'll like it.  Getting rid of those legacy gauges really frees up a lot of panel space.   Having all the engine/fuel data in one display greatly improves in flight troubleshooting in case of a roughness or heaven forbid, engine stoppage.

[carusoam]

Let’s see if @Jeev is around…

He runs Wolf Aviation and has been a great resource for JPI answers….

Jeev also flew a Mooney for a long time….

Best regards,

-a-

[RoundTwo]

On 3/10/2023 at 11:26 PM, 0TreeLemur said:

Tomorrow I'm taking our J model to my A&P to install a JPI EDM900 and a few other things to clean up the panel.  He's not installed one in a J.   I installed one in our C model, under the supervision of a A&P who has since flown west.

First question:  Where is the current shunt installed in an '83 J?   

Thanks,

Fred 

You’ve probably figured this out by now, but here is a picture of the top of the shunt in the vertical position behind the CB panel from an 88 J.

[RoundTwo]

On 3/28/2023 at 7:56 PM, Aerodon said:

I believe the EDM900 uses 'actual fuel' for this calculation, but I am not certain. I believe you also get a 'fuel quantity mismatch' if the calculated quantity is not closely aligned with measured FQ. I asked JPI directly, but did not get a straight answer, they tend not to get drawn into any discussion on how things work, but seem to be briefed to refer you to the instructions.

Since you’re prompted for REFUEL? at every power up, testing for a mismatch alert will be really easy to do. Now I’m curious what it will do when I tell it the tanks are full but the gauges say otherwise, and vice versa.

[RoundTwo]

13 hours ago, 0TreeLemur said:

You'll like it.  Getting rid of those legacy gauges really frees up a lot of panel space.   Having all the engine/fuel data in one display greatly improves in flight troubleshooting in case of a roughness or heaven forbid, engine stoppage.

This is all true, but there is some luxury in having the analog fuel gauges front and center, in your line of sight, and an illuminating warning in your peripheral vision. With my 900 down and low, the information must be intentionally retrieved because it is out of sight otherwise. And, the display is much smaller too.

[Aerodon]

5 hours ago, RoundTwo said:

You’ve probably figured this out by now, but here is a picture of the top of the shunt in the vertical position behind the CB panel from an 88 J.

 

That's like my 1986 M20K.  The top shunt is a massive 50mV / 210A for the overall LOAD to the busbar.  There are two more 50mV/ 70A shunts for each alternator directly below that.  So if you install an EDM900, you have some decisions to make, you can order your EDM900 with 2 shunts, one for each alternator output.  Then you either have to remove the third shunt, or find another way of displaying the overall load (another instrument?).  The EDM900 is not certified for replacing an ammeter, so you need to check carefully with your IA on how you are going to handle this.

Aerodon

 

[Aerodon]

5 hours ago, RoundTwo said:

Since you’re prompted for REFUEL? at every power up, testing for a mismatch alert will be really easy to do. Now I’m curious what it will do when I tell it the tanks are full but the gauges say otherwise, and vice versa.

Yes, at the start is easy, but as you use fuel there is a calculated fuel remaining and a measured fuel quantity.  If there is a mismatch, one of them is wrong.  If you started with the incorrect amount, it's easy to 'add/subtract fuel', even in flight.  If you fuel flow is wrong (bad transducer or bad K factor), that can also be easily fixed.

Now if your fuel tank calibration is incorrect, the calibration points can be adjusted.  But you need to fully understand what you are doing, and start with a good set of data.

I'm not there yet, but I do plan on following the correct procedure for draining and calibrating the tanks.  And once I have full confidence in the fuel flow / fuel remaining calculations, if I get errors in the fuel measured, I will easily be able to make fine adjustments.

One more thing to take note of - in a Mooney it is quite easy to start with as much as 5G 'extra' fuel, depending upon whether you fill to the bottom of the filler neck to the top - an immediate mismatch error.  And this might not lead to a mismatch error because the transducers show full either way.  

Arodon

 

 

[0TreeLemur]

5 hours ago, RoundTwo said:

With my 900 down and low, the information must be intentionally retrieved because it is out of sight otherwise. And, the display is much smaller too.

That's where the remote alarm light comes in.   The IM says that if the EDM display is more than some number of inches from the center of the AI, you must install the RAL in the instrument panel near the AI with a post or other light shining on its "ENGINE" placard.  When one of the fuel gauges gets down to a limit, it will illuminate the RAL, and the main display will show "LOW FUEL" in big font.

In flight having the wing-top sight fuel gauges provides a tie-breaking vote for how much fuel is in each tank in the case of a disagreement between the fuel senders and the fuel totalizer estimated fuel remaining, provided you've got more than 8-10 gals in each side.

[0TreeLemur]

49 minutes ago, Aerodon said:

 The EDM900 is not certified for replacing an ammeter, so you need to check carefully with your IA on how you are going to handle this.

True.  This raises three options:

1)  put JPI shunt in series with factory shunt for redundant ammeter.

2)  put JPI shunt between alternator and bus for "Load Meter" configuration.

3) leave JPI shunt out altogether.  (I'm leaning towards this option).  Can display of current be disabled in the JPI?

What do most people do?

Q: why did they not certify it as primary for V, A?   It seems that those are some of the most reliable measurements to make!

[EricJ]

2 hours ago, Aerodon said:

The EDM900 is not certified for replacing an ammeter, so you need to check carefully with your IA on how you are going to handle this.

I don't think that's really true.   While the EDM900 says it isn't "primary" for volts or amps, there aren't any limitations or required markings in my POH for either of those, and I think the regs mostly just say you should have an ammeter (I'm guessing CAR3 says that, I didn't look).   So I suspect there's not a "primary" indicator for those, just an instrument.   I don't think I've seen many, if any, installations of EDMs where the janky old ammeters were retained, and most airplanes don't have voltage indicators, anyway.

All of the old instruments (except my recording tach) got ditched when my EDM was installed by my ridiculously-anal avionics shop (the reason I got my A&P).   I think if it was an issue you'd see more airplanes with the old instruments retained.   As it is, that's seldom done.

[ArtVandelay]

 
The EDM900 is not certified for replacing an ammeter, so you need to check carefully with your IA on how you are going to handle this.

I don’t think that’s true, you’re probably referring to this language:
“The functions of Volts, Amps, and Horse Power were tested to DO-160D and DO-178B, but not TSO’d since no TSO exist for these functions.”

That doesn’t mean is not certified, just that there was no TSO standard for that function.

[carusoam]

Watch theory…

A man with two fuel level sensors on one tank… never really knows how much fuel is really in there….  

Fuel floats definitely bump the ceiling before the fuel stops getting filled…

on the longer tanks… two float sensors is definitely better than one.

 

My O’s fuel level sensors are not very precise…. So, its Fuel totalizer has that job…

Trouble can occur when the fuel totalizer doesn’t get reset properly…

This gives a similar mismatch in data challenge…

 

Where the calibrated Fuel Level sensor is king!

Followed by their Low Level lights calibration… is nice to know is working and properly calibrated…

Don’t run out of fuel…

Best regards,

-a-

[RoundTwo]

On 4/2/2023 at 1:10 PM, 0TreeLemur said:

That's where the remote alarm light comes in.   The IM says that if the EDM display is more than some number of inches from the center of the AI, you must install the RAL in the instrument panel near the AI with a post or other light shining on its "ENGINE" placard.  When one of the fuel gauges gets down to a limit, it will illuminate the RAL, and the main display will show "LOW FUEL" in big font.

In flight having the wing-top sight fuel gauges provides a tie-breaking vote for how much fuel is in each tank in the case of a disagreement between the fuel senders and the fuel totalizer estimated fuel remaining, provided you've got more than 8-10 gals in each side.

Yeah, about that RAL… mine has numerous issues.

1) It doesn’t self test red/yellow at start-up.

2) Low Oil P at low rpm shows yellow and since Oil P is primary, I believe it should be red.

3) When my alternator has tripped offline, I get no lamp when I think I should see yellow because amps isn’t primary.

I called JPI and spoke to one of their techs who wasn’t very aware of how the light was supposed to work. He was going to call me back after doing some research, but never did. Maybe today. 

[Fly Boomer]

1 hour ago, RoundTwo said:

Yeah, about that RAL… mine has numerous issues.

1) It doesn’t self test red/yellow at start-up.

2) Low Oil P at low rpm shows yellow and since Oil P is primary, I believe it should be red.

3) When my alternator has tripped offline, I get no lamp when I think I should see yellow because amps isn’t primary.

I called JPI and spoke to one of their techs who wasn’t very aware of how the light was supposed to work. He was going to call me back after doing some research, but never did. Maybe today. 

I know it's a lot of work, and pretty frustrating, but I encourage you to hold their feet to the fire.  As I read about issues like this with various aviation systems, it seems like they fall into one of three categories:

1.  The vendor didn't design the item in the best way, but
        a.  is ready, willing, and able to correct the problem or
        b.  is unable, unwilling, or not interested in correcting the problem

2.  The item was installed in such a manner that sort of performs its intended function, but not in the manner it was designed

3.  The vendor built an excellent product and the installer was as thorough as possible, but the setup keeps the product from performing as we would wish

Trying to weed through all those gates can be a tortuous and time consuming ordeal.  On this forum, it's always risky to point out that a beloved mechanic or product appears to fall short, but I would say that the aftermarket Garmin autopilot most of our birds are eligible for is one such product.  And apparently no one knows which category it's in.  And therefore can't provide an answer.

Okay, that turned into a rant -- I need more coffee.