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Matt Dralle
Site Admin
Joined: 08 Nov 2005
Posts: 25704
Location: Livermore CA USA
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 Posted: Sun Jun 20, 2010 8:02 pm Post subject: Update On RV-8 Princeton Fuel Probe Installation... |
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Fellow RV'rs,
I am elated to report that last week I decided to try recalibrating the Princeton fuel level probes in my RV-8 one last time before I began the arduous task of replacing them with resistive float senders. I started with the right tank and drained all of the fuel out, then entered calibration mode by applying power to the unit with the button pressed. I then pressed the button once to indicate the "empty" set point, then added exactly 5.5 Gallons, pressed the button, etc., etc., until I'd added 21 gallons. During the whole process, the various LED flashing patterns correctly matched the documented sequences based on the stage of calibration. With a full tank, I went out and flew a little over two hours at about 10 gallons per hour. During the flight, I carefully compared the Priceton readings with the turbine fuel flow "fuel used" indicator which has proven to be exceptionally accurate. As expected, the Pricetons reported "Full" for the first 6 gallons or so because of the dihedral in the wing tank and the fact that the probe is mounted at the root. Again, as expected, abruptly the fuel level went from 21 to 15 gallons after about 6 gallons of burn (or there abouts - sometimes both tanks seem to drop to around 18 then back up to 21 during this first 6 gallons). From 15 to about 2 gallons, the Priceton's reported a fuel level within 1 gallon of the flow meter's fuel used indicator! Yahoo. I then repeated the whole calibration procedure exactly as before but this time on the left tank and then went out and repeated the comparison tests above on the left tank. I am even happier to report that again the calibration of the left fuel level tracked the fuel flow meter's used amount within 1 gallon after the initial drop from 21 to 15 gallons after 6 gallons of burn. I flew to about 4-5 gallons remaining on the left and right sides tonight as reported by the fuel level meters and noted that the fuel flow meter's fuel remaining coincided with a reported remaining of 10.3 gallons. I topped off both tan!
ks and n
oted that both tanks then reported 21 gallons as expected.
So why didn't the first and second calibration attempts take? Who knows. All that matters at this point is that they are both working and are exceptionally accurate in the 15-0 gallon range which is where it counts. Oh, and that I don't have to replace the probes! Yahoo.
Best regards,
Matt Dralle
RV-8 #82880 N998RV
http://www.mattsrv8.com - Matt's RV-8 Construction Blog
http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
Status: Enjoying The Fruits of 2500 Hours of Labor!
| | - The Matronics RV8-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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Matt Dralle
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rv8builder
Joined: 02 Jan 2009
Posts: 56
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| Posted: Mon Jun 21, 2010 2:44 am Post subject: Update On RV-8 Princeton Fuel Probe Installation... |
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Oh, the travails of airplanes! Go Figure!
do not archive,
Dale
On Mon, Jun 21, 2010 at 12:00 AM, Matt Dralle <dralle(at)matronics.com> wrote:
| Quote: |
Fellow RV'rs,
I am elated to report that last week I decided to try recalibrating the Princeton fuel level probes in my RV-8 one last time before I began the arduous task of replacing them with resistive float senders. I started with the right tank and drained all of the fuel out, then entered calibration mode by applying power to the unit with the button pressed. I then pressed the button once to indicate the "empty" set point, then added exactly 5.5 Gallons, pressed the button, etc., etc., until I'd added 21 gallons. During the whole process, the various LED flashing patterns correctly matched the documented sequences based on the stage of calibration. With a full tank, I went out and flew a little over two hours at about 10 gallons per hour. During the flight, I carefully compared the Priceton readings with the turbine fuel flow "fuel used" indicator which has proven to be exceptionally accurate. As expected, the Pricetons reported "Full" for the first 6 gallons or so because of !
the dihedral in the wing tank and the fact that the probe is mounted at the root. Again, as expected, abruptly the fuel level went from 21 to 15 gallons after about 6 gallons of burn (or there abouts - sometimes both tanks seem to drop to around 18 then back up to 21 during this first 6 gallons). From 15 to about 2 gallons, the Priceton's reported a fuel level within 1 gallon of the flow meter's fuel used indicator! Yahoo. I then repeated the whole calibration procedure exactly as before but this time on the left tank and then went out and repeated the comparison tests above on the left tank. I am even happier to report that again the calibration of the left fuel level tracked the fuel flow meter's used amount within 1 gallon after the initial drop from 21 to 15 gallons after 6 gallons of burn. I flew to about 4-5 gallons remaining on the left and right sides tonight as reported by the fuel level meters and noted that the fuel flow meter's fuel remaining coincided wit!
h a reported remaining of 10.3 gallons. I topped off both tan!
ks and n
oted that both tanks then reported 21 gallons as expected.
So why didn't the first and second calibration attempts take? Who knows. All that matters at this point is that they are both working and are exceptionally accurate in the 15-0 gallon range which is where it counts. Oh, and that I don't have to replace the probes! Yahoo.
Best regards,
Matt Dralle
RV-8 #82880 N998RV
http://www.mattsrv8.com - Matt's RV-8 Construction Blog
http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
Status: Enjoying The Fruits of 2500 Hours of Labor!
|
| | - The Matronics RV8-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV8-List |
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Dale |
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Matt Dralle
Site Admin
Joined: 08 Nov 2005
Posts: 25704
Location: Livermore CA USA
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| Posted: Sat Jul 03, 2010 9:02 am Post subject: Update On RV-8 Princeton Fuel Probe Installation... |
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At 05:40 PM 6/28/2010 Monday, you wrote:
| Quote: |
On 06/21/2010 12:00 AM, Matt Dralle wrote:
>All that
>matters at this point is that they are both working and are exceptionally accurate in
>the 15-0 gallon range which is where it counts.
...and you just *might* owe Princeton an apology for what I *seem* to remember as some pretty heavy bad-mouthing in your last few posts. But w/o actually going back into the archives, I may be wrong...
Regards, J.
Sonex #325 C-FJNJ, Jabiru 3300a, Prince P-Tip, Aerocarb
restoring the Johnston Special
http://cleco.ca
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I might have been a little rough on Princeton initially, but considering how annoyed I was at that prospect of having to replace them, I think I held back pretty well: 
Reference:
http://forums.matronics.com/viewtopic.php?t=69954 and
http://forums.matronics.com/viewtopic.php?t=69999 and
http://forums.matronics.com/viewtopic.php?t=71281
Just having to remove them to adjust the probe tip so that it wasn't touching the bottom of the tank was a major ordeal. Since in a QB you can see into the tank when installing them, they should be pre-bent to make sure they don't touch or have an insulative piece of plastic on the tip.
And why the first three calibrations didn't take is completely baffling. I almost didn't try to calibrate again for the forth time, but I was just so demoralized at having to remove them and try to fit floats in, that I just gave the calibration one more try. Whew, glad I did.
Anyway, I wanted to clear the air and that's why I posted my extended pirep on the successful calibration finally. I sent the same report to Princeton, GRT, and the GRT-EFIS forum as well.
I've got about 20 hours on them now since the successful calibration. They remain about as accurate as I reported. They still give kind of wonky readings when the tanks are full sometimes. The lower the fuel level, the more accurate they seem to be. That being said, based on comparisons with the FuelChec DX flow meter, I wouldn't trust the level probes more than about +- 1.5 gallons or so (within 3 gallons of actual). But, that's good enough I suppose. I still rely on the flow meter's fuel "remanding" mostly as it has proved to be reliable to within .5 gallons or better.
BTW, the FuelChec DX has a really cool feature called the "Switch Tanks" warning. You set it to the amount of fuel burn you want to keep your tank levels balanced. For example, I have mine sent to 3 gallons. Every three gallons of fuel burn, the FuelChec flashes a warning indicating its time to switch tanks. I've found this really keeps the fuel balanced across the tanks. Its also an excellent reminder every 20 minutes or so to check the fuel levels.
Matt Dralle
RV-8 #82880 N998RV
http://www.mattsrv8.com - Matt's RV-8 Construction Log
http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
Status: Enjoying The Fruits of 2500 Hours of Labor...
| | - The Matronics RV8-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV8-List |
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Matt Dralle
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