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       #1  

    Fuel Quantity Indicator- Phenom 100

    We got a right fuel quantity indicator fault with a red line cross through the indicator where the number would be.
    initially, working with Embraer, they identified the fuel computer as culprit.
    However, after a delay of a week, on replacing the computer, we would get the indicator to show the fuel quantity but only for a minute or so, before reverting to the red cross there.
    The shop and Embraer now think it’s the fuel probe that’s faulty.
    I asked them to put back the old fuel computer since it appears that was not the problem. However, I am told that since changing the computer resulted in a change to fuel quant being visible for a minute or so, they say the bad probe may have damaged the computer and they don’t want to take a chance on old, perhaps corrupted computer messing things up after changing the fuel probe!?
    How would the computer mess up a new probe?
    Anyone had this or similar issue?
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    #2  
    Having same issue on 2010 P100 now: CMC shows efcu fault -- do not see harness or probe fault codes. Installed new efcu but yellow x still over left fuel quantity. Was told to check g1000 OEM Diagnostics A/C System Status for fuel tank probe capacitance values -- mine showed N/A for all Left Tank probes. Was then told to check wiring harness & fuel probes. Doing that now. FYI: another phenom had this problem last year & it turned out to be bad wiring harness inside the wing -- brass ferrule worked loose and no longer crimped to the wire was enough to cause the wire harness to fail.
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    #3  
    In a more mechanical day, there was a component which enabled the technician to measure and adjust the harness ohm reading from the probe(s) to the indicator. An incorrect resistance didn't result in a fault, but a higher or lower reading on the fuel quantity indicator than actual fuel in the tank(s). This adjustment wasn't the most user friendly. It was a "trial and error" process to get the the measurement within an acceptable window of resistance. And was an art to get the reading exactly in the middle of this acceptable window.

    Today a computer measures this signal or resistance across the probes and harness to determine fuel quantity. An out of limits signal latches a fault. Troubleshooting is to determine which component is at fault and replace it. But what if two probes and the harness are barely within limits? Could the combined resistance be far enough from nominal to generate a fault by the computer at certain extremes in flight? It might explain why your technician says, a harness or probe was replaced, extinguishing the fault in a heated hangar at nearly sea level. But the fault returns shortly thereafter resulting in another parts change; and then another parts change. When there's no available adjustment, is an individual part change or the final part changed actually the fix?
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       #4  
    They replaced the fuel computer. Did not fix the problem. Next, they replaced the right fuel probe and that, at least for now resulted in right fuel quantity being shown.

    we also had SWPS HTR FAIL. However, they could not reproduce it.
    When the GPU was disconnected after engine start, the CAS came on. It appears that the LEFT AOA unit is faulty. Awaiting replacement and will report anything exciting.

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