Electrical Load Shedding - How?

Hi All,

I’ve hear mention of the SR20’s ability to allow the pilot to shed non-essential electrical loads easily due the the bus layout.

I recently got a copy of the Pilot’s Handbook and although it mentions this feature, it doesn’t say how to do it. The electrical diagram doesn’t help much in this area either (at least for me).

Two questions for current owners:

  1. Is there a more detailed systems discription provided to new owners aside from the POH?

  2. How is the load shedding accomplished?

  3. Is this sort of thing covered in the pilot fam course?

Thanks!

Joe

I’ve hear mention of the SR20’s ability to allow the pilot to shed non-essential electrical loads easily due the the bus layout.

I recently got a copy of the Pilot’s Handbook and although it mentions this feature, it doesn’t say how to do it. The electrical diagram doesn’t help much in this area either (at least for me).

Two questions for current owners:

  1. Is there a more detailed systems discription provided to new owners aside from the POH?
  1. How is the load shedding accomplished?

It is my understanding from a brief review of the POH that there are several electrical busses (3?) which are labelled ‘essential’ or ‘non-essential’. You can pull the master breaker for the non-essential busses thereby reducing the overall load.

  1. Is this sort of thing covered in the pilot fam course?

I talked to Jeff Van West @ Wings aloft and while not specifically asking that question, he indicated that they thoroughly go through the plane’s systems and failure modes.

When you do figure out how to pull a circuit breaker for the non-essential bus make sure you know what you have lost. According to Figure 7-1 on Page 7-38 (Reissue A) you will lose pitot heat and flaps among other less essential things. You might want to know that you don’t have flaps before you are on final and pitot heat could be vital.

Hi All,

I’ve hear mention of the SR20’s ability to allow the pilot to shed non-essential electrical loads easily due the the bus layout.

I recently got a copy of the Pilot’s Handbook and although it mentions this feature, it doesn’t say how to do it. The electrical diagram doesn’t help much in this area either (at least for me).

Two questions for current owners:

  1. Is there a more detailed systems discription provided to new owners aside from the POH?
  1. How is the load shedding accomplished?
  1. Is this sort of thing covered in the pilot fam course?

Thanks!

Joe

I’ve hear mention of the SR20’s ability to allow the pilot to shed non-essential electrical loads easily due the the bus layout.

I recently got a copy of the Pilot’s Handbook and although it mentions this feature, it doesn’t say how to do it. The electrical diagram doesn’t help much in this area either (at least for me).

Two questions for current owners:

  1. Is there a more detailed systems discription provided to new owners aside from the POH?
  1. How is the load shedding accomplished?

It is my understanding from a brief review of the POH that there are several electrical busses (3?) which are labelled ‘essential’ or ‘non-essential’. You can pull the master breaker for the non-essential busses thereby reducing the overall load.

  1. Is this sort of thing covered in the pilot fam course?

I talked to Jeff Van West @ Wings aloft and while not specifically asking that question, he indicated that they thoroughly go through the plane’s systems and failure modes.

Having nothing better to do, I took a very close look at the POH recently (the A revision) and in the course of passing on the things I found (most of which had already been fixed) the doc guy mentioned that there had been considerable confusion about the load shedding stuff, and that section was being rewritten. I vaguely recall that the prototype had a switch on the panel bolster, but this doesn’t exist in the production model. Instead, there’s a non-essential bus breaker that you can pull that turns off all of the non-essential stuff (study the electrical diagram carefully…)

When you do figure out how to pull a circuit breaker for the non-essential bus make sure you know what you have lost. According to Figure 7-1 on Page 7-38 (Reissue A) you will lose pitot heat and flaps among other less essential things. You might want to know that you don’t have flaps before you are on final and pitot heat could be vital.

My understanding is that the revised POH will say to pull the nonessential avionics bus as the first move.

You can always take the time to pull individual items beyond that if you have the time and inclination.

Hi Dave,

I realize, of course, that pulling individual CB’s is always an option. But Cirrus seems to make a specific point that a more user-friendly type of load-shedding capability has been built in. I just can’t figure out what they mean by that, and the POH is of little help in that regard.

As to pulling individual CB’s, I seem to remember from my demo ride that the CB panel was in a relatively awkward position and not easy to read without some possibly vertigo-inducing body-twisting head-down work. To be fair, though, I didn’t specifically try it. (It may be easier than it would appear.)

BTW, I think a detailed drawing of the actual CB panel would be a valuable addition to the POH.

Joe

For the Cirrus doc folks: See what having an enthusiastic following with time on their hands leads to? Pick, pick, pick!

My understanding is that the revised POH will say to pull the nonessential avionics bus as the first move.

You can always take the time to pull individual items beyond that if you have the time and inclination.

Joe - TheCB’s are easy to pull. You just put your head between you legs and read the labels. A flashlight is useful. Also, count down the list before you pull - depending on the angle at which you are looking at them the labels don’t always line up with the appropriate circuit breakers. Handling the CB problem is especially dificult for those of us with reading glasses, bifocals etc. because the viewing distance is not always right for whatever glasses you are wearing. I think a good CB chart available in the cockpit would be essential because in a real emergency you may have to work by feel, count and pull. Ideally you will put on the autopilot and work out the problem at your leisure. - Jim DeVries

Hi Dave,

I realize, of course, that pulling individual CB’s is always an option. But Cirrus seems to make a specific point that a more user-friendly type of load-shedding capability has been built in. I just can’t figure out what they mean by that, and the POH is of little help in that regard.

As to pulling individual CB’s, I seem to remember from my demo ride that the CB panel was in a relatively awkward position and not easy to read without some possibly vertigo-inducing body-twisting head-down work. To be fair, though, I didn’t specifically try it. (It may be easier than it would appear.)

BTW, I think a detailed drawing of the actual CB panel would be a valuable addition to the POH.

Joe

For the Cirrus doc folks: See what having an enthusiastic following with time on their hands leads to? Pick, pick, pick!

My understanding is that the revised POH will say to pull the nonessential avionics bus as the first move.

You can always take the time to pull individual items beyond that if you have the time and inclination.

Hi Jim,

Thanks for confirming my suspicions about the CB panel.

Ideally you will put on the autopilot and work out the problem at your leisure

Then again, the A/P is one of the loads you might need to shed. (It’s on a non-essential bus, as I remember…)

Joe