DA40D/Thielert 2.0/ECU Fail A&B/Fuelpressure out of range

[Hawker]

Hello,

we faced ECUA&B failure followed by oscillating power between 35% and 70%. Constant speed held revs. constant.

we have been told that this is a typical DA40D problem when fuelline gets air bubbles in due to low fuel. Although fuel level was always over 5 gallons. There is no advice in POH?

Any comments on this?

TXS!

[cfiguy]

I've only seen the fuel pressure out of range occur in a DA42 when the high pressure fuel pump was replaced (under warranty). It appeared that the new replacement pump was the culprit. The high pressure pump was replaced and the problem went away.

In the DA42, there is a checklist item for concurrent ECU A & B failure. It involves reducing the power to idle, then slowly increasing power to see if there is surging or roughness. You can repeat this a second time and if there is continued surging/roughness, the checklist says to adjust the power lever to no more than 1975 RPM and land as soon as possible. Since I've never laid eyes on a DA40D let alone flown one, I can't say what might be in the AFM.

I saw the surging power condition once in a DA42NG due to a turbo boost valve failure on the left engine. Luckily we had lots of altitude (though we were IMC at the time) and were only a few miles from an airport on an approach. We broke out of the clouds, landed without incident, and proceeded to do the ECU swap and test. The left engine would not go above 40% power during the ECU test and we assumed something really bad had happened. The mechanic found the vacuum line for the boost valve had come loose and it was a very inexpensive repair.

You may have issues with your high pressure fuel pump or with your turbo boost valve or something else. I'm not a mechanic, but I would think an authorized mechanic would connect a laptop to the ECU, pull the codes, and diagnose the problem.

My $0.02 ...

John

[Steve D]

I had a similar problem on a 2.0 that reported ECU A & B failures. The AMO couldn't find the problem and ultimately it led to an EFATO on a subsequent test flight. The cause was a blocked micro filter on the fuel pressure sensor in the common rail. Simple thing to check out before looking for more expensive problems.