Engine Load indication incorrect at higher altitudes

[baldesk]

Has anyone observed an incorrect engine load % reading at higher altitudes for the DA42-VI? I experienced this several times on a long cross country at or above FL150. Specifically the L/R load indicated, as well as the fuel in GPH, were asymmetrical (e.g. Left 87% and 8.0 GPH ; Right 79% and 7.1 GPH) yet was RPM was symmetric at 2040. In all cases, pulling the throttles back and then moving to 75% rectifyed the discrepancies.

Thanks in advance for your input.

[ultraturtle]

I observe an opposite load % discrepancy in my -VI at altitude. I have air conditioning installed, and the book (Ops Supplement S07, 5.3.10) states "The Cruise Speed with the Recirculating Air - Cabin Cooling System switched OFF is reduced by 2 %." I interpret this to mean that there is always less motive power available from the left engine at any given RPM. I have always had the left engine load lag, with the RPM similar to the right at the same throttle position while climbing through the mid teens, and assumed it was due to the idle drag of the additional alternator on the left engine (the air conditioning having been turned off long before).

Oddly, and much like you, I have been able to largely rectify the difference by pulling power to well below 75%, then restoring it, but the left load % has never fully caught up with the right load % at the same RPM at altitudes in the mid teens and above when advancing both throttles to achieve anything much above 75%.

[CFIDave]

The differences you see in L vs. R engine loads (and fuel consumption) at the same RPM are likely due to variation in prop governor operation between engines; sometimes one engine governor will lag behind the other as power is increased. As noted, this can sometimes be fixed by temporarily throttling back and then increasing power back to 75% or whatever your desired cruise loading is. In my experience this can happen at lower as well as higher altitudes.

I doubt the RACC (especially when turned OFF) has anything to do with the difference. The exception is when sitting on the ground at idle with air conditioning ON you can see 2% more load needed on the left engine to maintain idle RPM.

[ultraturtle]

At FL180 I've seen as much as 8% less load on the left than the right at firewall power, RPMs roughly matched, even after throttling back then restoring full throttle.

At 75%, however, they are evenly matched. That's my preferred cruise power, so I'm not too concerned. For me, it's only an issue in the climb.

[baldesk]

Thanks all. Happy to hear there is no major concern and that others are seeing the same behavior.

[ememic99]

Thanks all. Happy to hear there is no major concern and that others are seeing the same behavior.

Which doesn’t mean that’s ok.