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Z-14 implementation

 
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foghorn757(at)gmail.com
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PostPosted: Sun Feb 02, 2020 12:10 pm    Post subject: Z-14 implementation Reply with quote

Here is what I’m working on for my SDS powered RV8. This is a work in progress. I’m not sure about the diodes to the ENG BUS since I can control power through the switches from the BATT BUSs one at a time. The main ALT is a PP 60A internally regulated, until it fails, then I’m going to switch to a B&C externally regulated ALT. For now I’m going to give the PP and VPX the opportunity to run the show.
Ok I’m here to learn so help me get smarter.
Jeff Parker

Quote:
On 2Feb, 2020, at 13:45, Krea Ellis <krea.ellis(at)gmail.com (krea.ellis(at)gmail.com)> wrote:
Clearly, my emails are getting through even though I get a reply from the server that they are being rejected.
Thanks for all the valuable information and thoughtful responses.

You're not going to be comfortable with your system until you're comfortable with it. But it might be worth stepping back and looking 'big picture' for a bit. Checking every detail should happen, but sometimes our initial premise may need re-evaluation. There are one or two of my basic premises I'm currently rethinking a bit.... Charlie

Agreed and I am stepping back and working hard to overcome the concerns about multiple redundancies. Years of flying big iron I guess and a fear about new ground (at least for me) with SDS.

How would that happen? EVERY branch feeder in Z-14 is QUAD sourced until some component fails in flight (an exceedingly rare event). Two distribution busses (main and aux) remain at least DUAL sourced and sometimes TRIPLE sourced depending on nature of failure. Complete loss of power on either bus just doesn't happen . . . Z-12 (revised) is another solid option where a single bus is TRIPLE fed and no less than DUAL fed after loss of a single component.

I need to keep things in perspective. In 1000 hours of GA flying and multiple thousands of large airplanes, any electrical problems I have had have been totally controllable and I have never had total electrical failure - although there are plenty of anecdotal stories of that happening. So the risk is probably very small.

I guess things are quad sourced if you assume you can close the cross tie contactor. I was hoping to do that only for start and only in a dire emergency in flight. But if the only source of power to the injectors has failed, not much to lose by closing the cross tie and hope it powers up. Screens in front are backed up by an IBBS battery and the G5 has an internal battery, so we can keep the shiny side up no matter if we are a glider.

Can you suggest that SDS contact me with a goal of collaborating on a unified approach to minimizing risks?

I will absolutely do that a greatly appreciate your willingness to help me (and others) through this.

I am coming to the conclusion quickly that a single injector bus fed by one of the two battery busses and with a good battery and an externally regulated alternator is probably the best compromise of simplicity and reliability. I’d still like to consider a slightly more redundant approach too.

Krea


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nuckolls.bob(at)aeroelect
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PostPosted: Sun Feb 02, 2020 12:18 pm    Post subject: Z-14 implementation Reply with quote

Quote:

I guess things are quad sourced if you assume you can close the cross tie contactor. I was hoping to do that only for start and only in a dire emergency in flight.

The whole reason for the cross-feed contactor
is to PREVENT a 'dire emergency' . . . not
react to one.

If system components never failed, FBOs would
be out of business. Tires and batteries wear
out. Radios go belly up.

Quote:
But if the only source of power to the injectors has failed, not much to lose by closing the
cross tie and hope it powers up.

Okay, failure of WHAT component would prompt closing
the cross-tie? Will failure of that component result
in instant loss of engine?

Quote:
Screens in front are backed up by an IBBS battery and the G5 has an internal battery,
so we can keep the shiny side up no matter if we are a glider.

Batteries which, in my never humble opinion,
only add cost of ownership and offer little
benefit in terms of mission reliability.

If one of these batteries is ever called
upon to do it's job, it's because you
probably DO HAVE a real EMERGENCY borne
of poor design and/or craftsmanship.

Quote:
Can you suggest that SDS contact me with a
goal of collaborating on a unified approach
to minimizing risks?

I will absolutely do that a greatly appreciate your willingness to help me (and others) through this.

I am coming to the conclusion quickly that a single injector bus fed by one of the two battery busses and with a good battery and an externally regulated alternator is probably the best compromise of simplicity and reliability. I’d still like to consider a slightly more redundant approach too.

Define 'slightly' and articulate the
sequence of failure events that would
bring that benefit into play.

This is what failure mode effects analysis
is all about. You need to have confidence
in your minimally configured, well considered
constellation of airframe systems. Otherwise,
the benefit of a 'slightly more redundant'
feature is reduced to the same utility
as carrying a rabbit's foot.

What you're going through here is equivalent
to a process I've participated in dozens of
times. They're called Preliminary and Critical
Design Reviews. I've stood in front of a
Power Point screen many times in a room full
of Navy engineers, technicians, pilots and
program managers along with other members
of my project group.

In my later years, I 'ran the gauntlet'
and sold the idea(s) most of the time.
On occasion, I took some hits. But in
any case, the process was invaluable
in that it prevented bad ideas from
going to production.

I suggest that what we're doing here
has the same goals. Another goal is to
eliminate the word 'emergency' from the
lexicon of electrics-speak . . . we're
just not going to have one.



Bob . . .


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