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Thread: RV7A fuel tank calibration

  1. #1

    RV7A fuel tank calibration

    This is for an RV7A, no tail wheel so left and right columns should be identical. AFS3500EE

    Following the manual, I calibrated my left (#1) tank using 5 calibration points. 0, 1/4, 1/2, 3/4, full. 21 gallons per side. total 42.

    I started with a bone dry tank on the left. Scrolled down to the tank calibration data table, hit copy left column, zero row, then hit copy right column, save.

    Added 5 gallons exactly, scrolled down to next row. Hit copy left then hit copy right, etc for 10, 15 and 21 gallon (I changed the 20 to 21)

    The tank appears full as it is, but the AD numbers are not linear. I assumed I did something wrong so on the right tank (#2) I again started with an empty tank. Same settings as above. Scrolled down to tank calibration data table, hit copy left column then changed the right column with the knob to match the left, hit save. I did the same when adding 5, 10, 15, and almost 21. Then save. The tank reads 2.5 gallons and all the ad numbers both columns are roughly the same showing 867.

    Clearly I did the right tank wrong. Was I correct for the left tank even if the ad numbers were not linear when increasing fuel by 5 gallon increments?
    Last edited by timotb; 04-19-2014 at 04:06 PM.

  2. #2
    The numbers will not be linear because of the tank shape and float arm, if they were linear you would only need two points empty and full.

    Email a picture of your tank calibration values to info@advanced-flight-systems.com
    Rob Hickman
    Advanced Flight Systems Inc.

  3. #3
    So can I can assume I did tank 1 (Left) correctly?

  4. #4
    Email me the tank calibration numbers, info@Advanced-flight-systems.com
    Rob Hickman
    Advanced Flight Systems Inc.

  5. #5
    Last I left off on this frustrating issue, I sent a pic of the tank calibration numbers and they were all the same on each side around 800 or 900. I've been playing around with this on and off for a few months changing the calibration point from 5 ( 0, 1/4, 1/2, 3/4, full) to 10 points for every 2 gallons. Both sides. Always the same calibration numbers when I fill, copy and save at each stop.

    Tested the wire and grounding to AD values on the EFIS and got in the neighborhood of 2700 or 3700 (dont remember which) with the main wire at the float sensor disconnected. Shows zero when that same wire is grounded to the frame. Both sides. I am told this is normal. So can we assume wiring is correct?

    That leaves a float sensor not moving freely, as suggested by tech. I drained the right tank and accessed the float, saw that it was moving freely but did not check for AD value changes. This might be a place to start again.

    After changing the calibration points from 5 to 10, the tank indication shows full bars but in red regardless of fuel level consistently for the last few weeks.

    I can send new tank calibration numbers if you'd like.

  6. #6
    I can't help you solve this unless I can see your current calibration numbers, post them here, send a picture or call me from the plane.
    Rob Hickman
    Advanced Flight Systems Inc.

  7. #7
    Hi Rob. We spoke about this issue by phone maybe a week ago. You suggested to put a meter on the sensor float and check for Ohms to be between 40-240 as the arm moved. Also you raised the question of the bent sensor arm. It should be bent at 90 degrees according the RV7 DWG 16a. I note the plan suggested the arm swing should be about 3" This was my first order of construction after the empennage so I dont remember exactly what I did except that they were assembled in the wing cradles.

    Today I was able to free the Left tank sensor from the small mounting hole, attach a meter and move the float manually and see a change in Ohms. Next I re-attached the sensor to the tank, kept the meter attached and noted Ohms change as fuel was added to this 21 gallon tank. Empty was 249, 12 gallons was 154, and above 20 gallons it showed 89 Ohms. If the float is moving, and I get a change in Ohms as the tank is filled, I'm not sure why my AD numbers don't change when attached to the EFIS. The first time I calibrated this wing using 5 points I got a good number spread but haven't been able to repeat that with 11 calibration points.

    Not expecting any serious comments here. I plan to keep trying. It is possible the bend is not correct.
    Last edited by timotb; 07-24-2014 at 07:30 PM.

  8. #8
    Advanced Flight Systems Shawn McGinnis's Avatar
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    Quote Originally Posted by timotb View Post
    Empty was 249, 12 gallons was 154, and above 20 gallons it showed 89 Ohms.
    Since you are noting the resistive change on the float now reconnect the harness to the EFIS and try a voltage measurement between the orange / brown (tank 1) line that is connected the the float and airframe ground (preferably closer to the EFIS ground.)
    Shawn McGinnis

    Advanced Flight Systems
    support@advanced-flight-systems.com

  9. #9
    Today, (before seeing your post Shawn) I calibrated the left tank from empty to full as I done several times before. The difference today is I manually set each value to zero before filling then hitting the copy button. Previously, I tried to copy over old data and got all same numbers. Next, set the tanks to "fill all" and went for a flight just under an hour. EFIS said total gallons burned was 7.2. Filled it afterwards to 7.4. Close enough for me to say it's working after this single test.

    Next I'll do the right tank.

    Thanks...
    Last edited by timotb; 08-01-2014 at 02:07 PM.

  10. #10
    Advanced Flight Systems Shawn McGinnis's Avatar
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    Could you post or email a picture of your tank calibration numbers for verification.
    Shawn McGinnis

    Advanced Flight Systems
    support@advanced-flight-systems.com

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