Fuel transfer breaker popping

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Fuel transfer breaker popping

Post by doclink »

I have a new 2021 DA40NG with 80 hrs on it. I put fuel transfer pump on during 75% cruise and the breaker popped. I shut it off, reset the breaker and it worked fine. I was charging an iPad with USB at the time and thought that might have been an issue.
Since that time it has happened 3 more times, all without anything charging. The plane was at southtec for service bulletin and they couldn't duplicate the problem.
Any ideas?
Thanks-
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Boatguy
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Re: Fuel transfer breaker popping

Post by Boatguy »

Each time it happens you reset the breaker and then it works fine?

Presumably Southtec tested on the ground so that suggests there is some interaction with the electrical system when in flight.

Electric motors draw lots of current on startup so it could be an issue with the motor, or it could be a defective breaker. The least expensive place to start is replacing the circuit breaker.

Please continue to post on this.
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Re: Fuel transfer breaker popping

Post by doclink »

I reset it previously and it usually worked fine. When leaving southtec for Atlanta, it popped 2x, than worked the third time.
I heard back from southtec and Diamond said it might be a bad fuel pump and it could be replaced under warranty, i just have to get it back up there again.
I'll post updates when they are available.
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Re: Fuel transfer breaker popping

Post by Donkadillapig »

I'm a rookie owner of a '21 NG myself but I did have one thought.... are you running the pump when there is actually fuel to transfer? Per other threads here, you need about 45-50 mins of flight/consumption from full for the pump to reliably stay on and do it's job, otherwise it "blipping". That to me could cus a breaker issue ... maybe??

See, Russ's (Boatguy) handy dandy table....
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Re: Fuel transfer breaker popping

Post by Donkadillapig »

Has anyone else seen this in an NG?
We had it on a night flight, low feeezing level around 4-5,000 ft OAT 0c
The breaker popped, and again on reset. We left it out and completed our leg.
Once on the ground with OAT at 9c it reset and worked fine.
My CFII who is also an A&P wondered if it were jet fuel gelling in the transfer pump causing it to overload. I have no additives in my fuel currently.
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Re: Fuel transfer breaker popping

Post by chili4way »

Find an FBO that has pre-mix Jet-A with PRIST (Phillips 66 FBOs typically have this) and see if that makes a difference. In theory, the fuel recirculation system should keep the fuel in the tanks warm enough to avoid problems. The idea that the temperature issue is inside the transfer pump itself is an interesting theory. If you're running at low power/fuel burn in cold temperatures and the time between transfers is long, I suppose this could happen. Otherwise, replacing the circuit breaker or the transfer pump seem the likely solution.
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Re: Fuel transfer breaker popping

Post by Donkadillapig »

So sure enough, this happened in air again at temps well above freezing.... on my way to SouthTec in NC LOL
They confirmed that no it shouldn't be doing that.... (and that there's really no way fuel would gel in the Transfer pump at minus temps anyway!)
They are going to investigate.

Which puts it right back on topic with Robert's original post.
Slight scope creep, but for any NG owners, I had a rattle in a brake caliper at taxi speeds, nothing huge just annoying. SouthTec confirmed that this is sadly "normal" for recent NGs after a bit of brake wear and they've seen a bunch like this despite the caliper being secured correctly.

A very enlightening visit to the shop yesterday :)
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Re: Fuel transfer breaker popping

Post by doclink »

I have an appointment next Friday with southtec to replace the fuel transfer pump. They spoke to factory and the thought was I may have a bad transfer pump. I was flying yesterday locally, popped twice and third time it stayed on. I'll keep you posted.
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Re: Fuel transfer breaker popping

Post by krellis »

Don’t really know anything about the fuel transfer system on a diesel DA40, but as a retired airline pilot I must express some amount of concern about the multiple resets of a circuit breaker on a fuel pump.

If there is something unique about how this system is designed and the checklist specifically approves it, then ok. Otherwise, you may want to stop resetting this popped CB.

Just an opinion…
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Re: Fuel transfer breaker popping

Post by Donkadillapig »

Keith you are of course absolutely correct... I personally tried one or two resets and called it a day... a fuel pump is the last thing we want "burning out" lol
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