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Ceengland
Joined: 11 Oct 2020
Posts: 381
Location: MS
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 Posted: Thu Jun 08, 2023 7:10 am Post subject: Z101 switch state question: engine and main bus shutdown |
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On 6/8/2023 9:26 AM, jcohen(at)post.com wrote:
| Quote: |
I am implementing Z101 on my electrically dependent RV7 with a Lycoming IO360 engine, SDS EFII. I have a very basic question regarding operating states and switches. It may be stupid, so help me out. Here goes....
1. To shut the engine down, I was assuming I would turn the engine bus alt feed relay to off, then turn the master to off and the engine stops. But, wouldn't the primary alternator still keep supplying power to the engine bus and main bus, even without the battery in the loop, as it can supply power to energize its own field once running, without the master switch? So in effect nothing appears to happen?
2. IF #1 above is correct, should the best procedure for engine shutdown be turn off both electric fuel pumps first, and/or turn off both Ignition Coils (Top and Bottom), then turn off the engine bus alt feed switch and the Master switch to OFF?
3. And how do I turn off the main bus in flight but keep the engine running? If I am correct, turning the master off doesn’t de-power the main bus. Should the emergency procedure to get the main bus off in-flight for Z101, e.g. an electrical fire but keep the engine running, is to pull the alternator field circuit breaker along with the Master switch to off?
I am probably confused; most of this question centers on: Why couldn’t the primary alternator keep working even with the master off and battery out of the loop? Not sure I like the idea of having the main bus stay alive even when the master is off with the engine running.
--------
Jeff
This is from just a quick look, but a few thoughts.
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Turning off the master switch shuts down the primary alternator via the
2nd set of contacts in the master switch, which interrupts power to the
regulator.
For shutting the engine down, do you not have switches for each of the
controllers within the SDS system? The ideal situation IMO is to have
a pair of switches that have the same effect as a pair of mag switches,
and have the aircraft electrical bus(es) switched independently of the
engine bus, so that in stressful situations, our training will allow us
to react the same way we did with traditional engines/mags/carbs.
I never did a deep dive into the Z101 drawing because I'd already
finalized my architecture, but looking at it now, I would question the
choice to put the aux alt control on the aux bus, especially when
running an automotive style injection system with its high current
demand. My choice was to place the aux alternator output and control on
the engine bus, so that the entire airframe can be made 'cold' without
affecting the engine and its electrical power source; as close as
possible to traditional systems.
As I said, this was a quick look, so I may have missed some stuff.
Charlie
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Charlie |
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cluros(at)gmail.com
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| Posted: Thu Jun 08, 2023 7:20 am Post subject: Z101 switch state question: engine and main bus shutdown |
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Last time I worked on an EFII engine you had to shut down the whole system at once. Shutting down just the ignition or just the fuel lead to a very rough shutdown.
On Thu, Jun 8, 2023 at 8:12 AM Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)>
On 6/8/2023 9:26 AM, jcohen(at)post.com (jcohen(at)post.com) wrote:
> --> AeroElectric-List message posted by: "jcohen(at)post.com (jcohen(at)post.com)" <jcohen(at)post.com (jcohen(at)post.com)>
>
> I am implementing Z101 on my electrically dependent RV7 with a Lycoming IO360 engine, SDS EFII. I have a very basic question regarding operating states and switches. It may be stupid, so help me out. Here goes....
>
>
> 1. To shut the engine down, I was assuming I would turn the engine bus alt feed relay to off, then turn the master to off and the engine stops. But, wouldn't the primary alternator still keep supplying power to the engine bus and main bus, even without the battery in the loop, as it can supply power to energize its own field once running, without the master switch? So in effect nothing appears to happen?
> 2. IF #1 above is correct, should the best procedure for engine shutdown be turn off both electric fuel pumps first, and/or turn off both Ignition Coils (Top and Bottom), then turn off the engine bus alt feed switch and the Master switch to OFF?
> 3. And how do I turn off the main bus in flight but keep the engine running? If I am correct, turning the master off doesn’t de-power the main bus. Should the emergency procedure to get the main bus off in-flight for Z101, e.g. an electrical fire but keep the engine running, is to pull the alternator field circuit breaker along with the Master switch to off?
>
> I am probably confused; most of this question centers on: Why couldn’t the primary alternator keep working even with the master off and battery out of the loop? Not sure I like the idea of having the main bus stay alive even when the master is off with the engine running.
>
> --------
> Jeff
>
>
This is from just a quick look, but a few thoughts.
Turning off the master switch shuts down the primary alternator via the
2nd set of contacts in the master switch, which interrupts power to the
regulator.
For shutting the engine down, do you not have switches for each of the
controllers within the SDS system? The ideal situation IMO is to have
a pair of switches that have the same effect as a pair of mag switches,
and have the aircraft electrical bus(es) switched independently of the
engine bus, so that in stressful situations, our training will allow us
to react the same way we did with traditional engines/mags/carbs.
I never did a deep dive into the Z101 drawing because I'd already
finalized my architecture, but looking at it now, I would question the
choice to put the aux alt control on the aux bus, especially when
running an automotive style injection system with its high current
demand. My choice was to place the aux alternator output and control on
the engine bus, so that the entire airframe can be made 'cold' without
affecting the engine and its electrical power source; as close as
possible to traditional systems.
As I said, this was a quick look, so I may have missed some stuff.
Charlie
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jcohen@post.com
Joined: 10 Mar 2022
Posts: 17
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| Posted: Thu Jun 08, 2023 7:43 am Post subject: Re: Z101 switch state question: engine and main bus shutdow |
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Thanks for the replies I now understand the primary regulator is off when the master is in the BAT or OFF position, thank you.
The aux alt control in z101 is placed on the battery bus, so I can shutdown the main bus, the entire airframe goes cold, as you said, without shutting down the engine.
I actually power my main EFIS display off of the engine bus as well, so I can still get engine info / attitude info when the engine is running, even with all other stuff cold. That is the only item that is not essential to the engine that I placed on the engine bus, to keep engine bus current loads to a minimum if only running on the third electrical source, (I.e. battery only). Plus this way, if I lose my pri alternator, I am only time limited by fuel on using my primary EFIS, not battery power.
I believe I can do a normal engine shutdown by turning the aux alternator switch OFF, then master switch and engine bus Alt feed switch to OFF simultaneously; that will cut both feeds and both alternator power sources together, shutting the engine CPU off. Just like an automotive shutdown.
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user9253
Joined: 28 Mar 2008
Posts: 1913
Location: Riley TWP Michigan
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| Posted: Thu Jun 08, 2023 10:44 am Post subject: Z-101 Suggestion |
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Looking at Z-101, The aux alternator control is not on the aux bus, but gets
powered by the battery bus as jcohen stated. However the aux alternator
and aux bus are both controlled by one switch (separate halves of a double
pole switch). Evidently the thinking is that if the primary alternator fails, then
the pilot will want both the aux bus and the aux alternator turned on.
Having one double pole switch control both functions eliminates one switch
on the panel. However, what if there is smoke in the cockpit from a
suspected electrical failure. Wouldn't the pilot want to shut off both the
battery contactor and the aux bus relay? But what if he wants the aux
alternator to keep running to power the engine bus? In an emergency, the
pilot's brain quits working. And so the simpler, the better. The pilot won't
remember if the switch needs to be in the middle or fully up. I suggest two
independent switches, one for aux alternator and one for aux bus.
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