FADEC Anomaly

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GimpyPilot
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FADEC Anomaly

Post by GimpyPilot »

Hi Gang,

As shared a couple of days ago, I sold my XL-2 on Friday. In my seven years with the airplane, I had only two FADEC related squawks, both related to fouled fuel injectors. The injector was ultimately replaced, and the problem resolved.

On the way out of KVNY on Friday afternoon, the new owner experienced a similar issue, and landed again after climbing to 3,000 feet or so. An extended full power run-up did not duplicate the issue though I observed an intermittent FADEC Caution before he shut down after landing. We hustled to clean the injectors, (though without a solenoid because both of by spare solenoid are enroute to the new owner, via FedEx along with all of my diagnostic equipment.) We also replaced the #4 spark plug wire that appeared to have slight damage to the insulation. The airplane was test flown on Saturday morning and the problem seemed to have been resolved.

The new owner launched and flew from KVNY to KPHX without issue. The bird was running well. After an hour on the ground, he launched for KELP and apparently the problem was back again. He began getting the flickering FADEC caution at power levels of anything over 55%. He chose to continue, (about three hours), and was able to complete the leg by managing power. The next leg was KELP to KABI, (again about three hours), and the trip was uneventful. No FADEC issues; and no engine anomalies. Next was KABI to KSHV, and the problem was back again. From KSHV to KBHM was without issue, then on to JZP, where the problem came back, though he was able to clear it by cycling the FADECs this time.

The new owner is a warrior! Having hand flown an XL-2 from SoCal all the way to central Georgia in a little more than 36 hours,but he is exhausted. That said, I really would like to help him figure this out. His experience is that the problem seems to occur consistently on every other flight. I've never heard of such a thing, but the owner did point out that on Boeing FADEC systems there is a master/slave relationship between FADECs, and they are designed to "swap roles" with every cycle. This is not something I've heard of with the TCM/Aerosance system, but the consistent pattern is curious. (The new owner is an airline pilot, which is why he is aware of the Boeing systems. He is going out on a trip soon, so he won't be able to resume diagnostics for several days. All of my accumulated spares, (which include both wiring harnesses, several injectors, and a couple of FADECs, along with PowerLink laptop and cables), will arrive at their new home on Thursday, which should help. I've given him contacts of a factory A&P plus one at TCM, and I suspect that he already has what he needs to resolve the issue. Our transaction was otherwise flawless, and I enjoyed passing the torch.

I would love to help figure this one out. I have not experienced this issue, nor have I heard of a similar one in my seven years here...

If the collective braintrust has any experience or ideas, please speak up.


Thanks,
-Michael
Last edited by GimpyPilot on Tue Aug 25, 2020 4:05 pm, edited 1 time in total.

tafisama
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Re: FADEC Anomaly

Post by tafisama »

I am in now in the same shoes having Fadec warnings because of Fuel pressure issues.Today I had intended to fly over 200NM but had to turn back after 10mins.The engine was definitely running lean and pressure indicated 0psi on the VM1000.I manually selected BPS to on but the engine nearly quit making me quiclkly return it to Auto and pressure went up to 24psi and it improved running.I had to reduce rpm back to 2350rpm.Just about to get to circuit pressure dropped to 12psi.I was high enough to be able to glide onto the runway.As soon as I touched down Fuel pressure shot up to 34psi at idle which is where it normally is.I put the switch on off and taxied to the apron on the mechanical pump still it maintained 34psi.My Lame suggested something is wrong with the pressure compensating system on the mechanical pump.Later I went up to do some circuits and what I observed is on the ground the system runs very well with pressure reaching 43psi at 2400rpm.On climb between 500-650ft AGL the Fadec Caution comes on and on reaching circuit height when I powered back to 2350rpm the lights go off.This happened for the 3 circuits I did.At 2350rpm it was showing 115knts IAS.

N645XL
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Re: FADEC Anomaly

Post by N645XL »

Michael - I mulled over your post overnight. I should keep my printed schematics at the house so I don’t have to guess at the System diagram. I’m curious if FADEC A is turned off will the engine continue running. Sounds like it may not be a safe test unless the anomalous behavior can be replicated on the ground. If the engine dies it could be isolated to the EBAT side of things. Again, just guessing not having my book handy.

GimpyPilot
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Re: FADEC Anomaly

Post by GimpyPilot »

Hi Bob,

Thanks. My diagrams are enroute to Georgia via via FedEx ground, for the new owner. You make an interesting point regarding the FADEC power cycle. If you happen to visit your diagrams, your input would be appreciated.

-Michael

GimpyPilot
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Re: FADEC Anomaly

Post by GimpyPilot »

tafisama wrote:
Tue Aug 25, 2020 11:46 am
I am in now in the same shoes having Fadec warnings because of Fuel pressure issues...
Tafisama,

Your issue sounds unrelated to the one being experienced with N605XL. Do you have a data card in the EDI? If so, that data may be helpful.

For reference, in flight fuel pressure at 60% power was 58 PSI.

-Michael

N645XL
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Re: FADEC Anomaly

Post by N645XL »

Michael - I did grab my maintenance manual since I needed to update my AFM for the new Aspen Pro Max. My comment above is still applicable but looking at the schematics and Mx Manual 135A-970-100 there are a multitude of connections that could cause an intermittent FADEC caution. I’d probably start with a system diagnostic run and hopefully get it at a time with the intermittent fault present. If nothing’s apparent my next step would be checking the EBAT installation to include opening the 10 amp fuse holder and checking it for corrosion, etc. That said I recently repaired a non-aircraft equipment failure where the 10 amp fuse DID NOT blow but the element broke where it was formerly fastened to the end-cap. So the fuse looked new but failed a continuity test. A broken fuse element making intermittent contact with aircraft vibration is possible but IMHO unlikely. Something to consider.

Additionally there are a multitude of connections on the HSA box behind the instrument panel which could be reset in case there’s some galvanic corrosion creeping into the pin connections.

Without seeing it that’s about all I can offer right now.
Bob

GimpyPilot
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Re: FADEC Anomaly

Post by GimpyPilot »

Thanks Bob. The pilot/owner is here, and reading. I'll let him review your analysis directly, and remain available to help.

FlyGuyBry737
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Re: FADEC Anomaly

Post by FlyGuyBry737 »

Hey all. Thanks to everyone who has chimed in with suggestions. Michael did his usual, thorough job of recounting what I experienced enroute to Atlanta. On one of the longer legs over relatively hospitable terrain, I took the opportunity to troubleshoot the issue in greater detail. The problem persisted while operating on both FADECS, only on FADEC A, only on B, and with the ignition in L, R and Both. It happened in WOT and at power settings less than WOT. It also persisted regardless of boost pump position. The only anomaly noted on the VM was a cycling of the RPM needle and a noticeable change in the pitch of the engine noise of a few hundred RPM at times (noted at throttle positions just below WOT). It was definitely a chicken/egg situation where I couldn’t tell which came first, the light or the drop in RPM. It happened on a cold engine (first flight of the day) and it happened after a three hour flight and some time on the ramp in the Phoenix sun. About the only things that I could find that were repeatable were the frequency; every other flight, and that a reduction to ~55% power caused the FADEC Caution light to extinguish. FedEx will be dropping of the diagnostic computer on a Thursday and I hope to perform a download this weekend. Hopefully then I will know more, but in the meantime, any suggestions are welcomed.

—Bryan

N645XL
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Re: FADEC Anomaly

Post by N645XL »

I hate to suggest it but it sounds reminiscent of some early-on engine RPM sensors that failed. I believe there are two sensors. If one starts providing erroneous data the computers get confused which causes uncommanded engine RPM variations. Someone several years ago did a detailed post of the data you might find on the engine memory card detailing how to troubleshoot a failing sensor. Good luck.

Supplemental: I suspect (per the maintenance manual) the engine speed Sensor was giving the engine computer an over speed warning and the computer was going into over speed protection mode which I think would account for your symptoms. What doesn’t fit with what I read is the every other flight. That’s a head scratcher.

Omerrett
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Re: FADEC Anomaly

Post by Omerrett »

I just got a fadec caution Yellow light a few times. All engine parameters seemed in spec and would come on and go away.
Now it has done it a few more times and looks like I’m losing egt signal on cylinder 1 which then prompts the caution light. All temps seem fine end engine runs smooth(suspect wire or probe failure since the engine doesn’t change at all when reading goes to zero, also the cht stays steady). Are the egt probes easily changeable or are they integrated into the fadec wire harness?
Thanks

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