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PeytonM

JPI FuelScan 450 erratic: ISSUE RESOLVED

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I have seen a few of these installed, and what does work on NPT threads is Permatex Aviation sealer. It is non-hardening, and it does dissolve in fuel so it doesn’t find its way to some critical component and cause  problems.

Teflon tape is a big offender in this regard, it somehow finds its way into a fuel injector or into a main bearing passage, starving or for oil for oil, or the vacuum pump causing failure, either way it’s gotten a few people killed. If it doesn’t get you the first time, then shreds of it remain behind after reassembly the second time and that’s when it gets you, but either way the stuff is a time bomb. 

 

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I did the following experiment today. At cruise with the JPI 450 jumping wildly, I gradually reduced speed. At around 120KIAS, the JPI started reading correctly! I brought the power back up and the JPI started jumping around like Jack Flash around 130KIAS. I also noticed when I slowed for approach to landing, it read correctly. 
I guess it’s a loose connection. 

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2 hours ago, PeytonM said:

I did the following experiment today. At cruise with the JPI 450 jumping wildly, I gradually reduced speed. At around 120KIAS, the JPI started reading correctly! I brought the power back up and the JPI started jumping around like Jack Flash around 130KIAS. I also noticed when I slowed for approach to landing, it read correctly. 
I guess it’s a loose connection. 

From your description, it sounds more like it is fuel flow related which would implicate the transducer.

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In my experiment above, after I slowed the airplane, the fuel flow decreased as you would expect and the readings stabilized in the 8-9 GPH. I then applied WOT; the fuel flow immediately increased to the expected flow, and the JPI reading was stable.  As the plane accelerated through 130KIAS, the JPI reading became erratic again. 

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Bearing or the "feathers" on the transducer rotating part gets into a harmonic at a specific rotation speed / fuel flow?  I mean, it is the only mechanical part...

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RESOLVED: after replacing the transducer, shaking down the wiring, our last resort was that the instrument itself was the problem.

JPI provided a loaner FS450 instrument, and we installed that Wednesday. I flew Thursday and the readings were perfectly stable; problem solved!  JPI will repair my instrument for flat $100.  Thank you to Tim and JPI staff for their patience and support.

I especially want to thank David (sabremech) for the hours he put into this project. 

BTW, the software now reports %horsepower (??) on the FS450 during its read-out sequence.  My 19 yo FS450 did not offer that, and frankly, I’d like to turn it off.  Any ideas?

Also, JPI checked out my old transducer, and it’s fine (of course), so I also have an extra transducer. 

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Interesting Pirep, Peyton.

See If there is an updated manual to go with the new software that comes with the instrument...

JPI may have a few things that can be toggled on/off in a set-up menu... somewhere...

%hp is really good for LOP... while LOP... not so accurate for ROP...

Best regards,

-a-

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JPI found a bad connector on the instrument; it’s on it’s way back to me.
 

Fortunately, my own instrument does not have software with “%horsepower,” so I won’t need to worry about that. (I was seeing 81%H at 6000ft,  8°C, 24x24, 10.8 GPH on the Loaner FS450; I don’t think that’s possible.)

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JPI found a bad connector on the instrument; it’s on it’s way back to me.
 
Fortunately, my own instrument does not have software with “%horsepower,” so I won’t need to worry about that. (I was seeing 81%H at 6000ft,  8°C, 24x24, 10.8 GPH on the Loaner FS450; I don’t think that’s possible.)

There’s a HP constant (conversion factor) that needs to be set.

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Great follow-up, Peyton!

Thanks for posting the detail.

Best regards,

-a-

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