Is the ESS Bus Switch Required?

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LCBlue
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Is the ESS Bus Switch Required?

Post by LCBlue »

Hello everyone,

We have a 2007 DA40 and the other night I was demo’ing the use of the ESS Bus switch and when we turned it ON, nothing happened (it has previously worked). We will obviously get this corrected ASAP, but I’m trying to determine if the aircraft should be immediately grounded or not.

When I look in the POH the “kinds of operation” table lists “Essential Bus” for Night VFR flights. Does this mean the switch or just that the aircraft have an essential bus?

I’m inclined to allow the aircraft to continue to be operated (mostly by me) with pilot understanding of how to manually shed load if needed until it is repaired (my guess is its just a switch issue). My logic is as follows but I’m open to counterpoints or if I’m missing something:

The ESS Bus switch is listed as OAM (optional equipment). I feel that it is a quick way to load shed in the event of an alternator failure but it is not the only way to load shed and the same thing can be accomplished manually by pulling appropriate CB’s. In fact, many GA aircraft do not have an essential bus switch and you have no choice but to load shed manually.

What are your thoughts on this?

Thanks everyone!
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Rich
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Re: Is the ESS Bus Switch Required?

Post by Rich »

I agree with you completely. It would seem to be a quick way to shed predetermined load. I'm not sure I want to shed load as dictated by the essential bus in any case.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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Boatguy
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Re: Is the ESS Bus Switch Required?

Post by Boatguy »

I interpret that as being that the items on the ES are operational. Since the switch disables other items, I don't think there is an airworthiness issue flying with an inoperative ESS switch.

FWIW, there is no entry regarding the ESS in the DA40NG AFM KOEL.
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Rich
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Re: Is the ESS Bus Switch Required?

Post by Rich »

One suggestion: Check that the breaker labelled "Master Control" is not tripped. I believe this would act to keep the essential tie relay from isolating.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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