Emergency Procedure.....High Current vs Alternator Amps

[Arman]

Hi.
Can anyone please explain the difference between High Current and Alternator Amps of DA 40 NG?

Both occurs due to alternator output in upper red range or above 70A. However, in the checklist of High Current, the Essential Bus needs to be switch ON, which is not there in case of Alternator Amps.

Does it require to switch on the Ess Bus in case of High Current?
TIA

[Boatguy]

Both describe the same underlying problem (too high current) and the same solution (reduce electrical consumption). One says "reduce electrical load", the other says to switch on the Essential Bus which will have the effect of reducing the electrical load.

The DA40NG AFM is a patchwork of 20yrs of pages refering MAMs, OAMs, and EASA to Transport Canada accommodations. Same problem, same solution, poor documentation.

The important take away is that to total current draw is too high, but not enough on any individual circuit to pop a circuit breaker. On my NG the Main Bus is on a 60a circuit. The only way to get > 70a is for the Main Bus to be pulling high 50's and the ECU's to be drawing 10-15a so that the total is > 70a which means the alternator will be getting very hot very fast.

You don't want the alternator to die or the Main Bus breaker to pop because then you have a complete power shutdown of everything except the ECU's controlling the engine and you're immediately running on backup instruments (after you switch them on to power up the AI). If you did pop the Main Bus breaker, I think the correct solution would be to switch ON the Essential Bus, thus reducing the potential load (no PFD, only one GIA, etc.), then restoring the Main Bus power breaker. And as the AFM suggests, landing as soon as possible.

Sorry for the long winded explanation, the short answer is in the first paragraph!

[Arman]

Hi Russ,
Thanks a lot for the response. The explanation was really helpful.
Safe landings.