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Tony Cann
Joined: 10 Jan 2006
Posts: 3
Location: Fair Oaks, CA
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 Posted: Tue Jan 27, 2009 3:48 am Post subject: Bob Nuckolls's Z-14 with dual Lightspeed iii |
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>Time:
07:01:35 AM PST US
>From:
"Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>
>Subject:
Re: Bob Nuckolls's Z-14 with dual Lightspeed iii | Quote: | | > and SD-8> > > At 02:12 PM 1/25/2009, you wrote:> >> >Busy building an RV-8 with dual LS Plasma III (crank sensor) and > >would appreciate some input on Z 14 changes required for my set-up.> |
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mlas(at)cox.net
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| Posted: Tue Jan 27, 2009 5:02 am Post subject: Bob Nuckolls's Z-14 with dual Lightspeed iii |
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Tony,
I have a dual Light Speed system and I used the Z-14 very close to the way it was written. The changes I made: I followed Light Speed's recommendation of using a dedicated CB wired directly from the battery. And due to the 5 screen EFIS system with multiple gyros and air data computers I also incorporated a dual avionics bus with it own transfers and cross ties. What changes are you looking to make.
Mike
On Jan 27, 2009, at 4:44 AM, Tony Cann wrote:
| Quote: | >Time:
07:01:35 AM PST US
>From:
"Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>
>Subject:
Re: Bob Nuckolls's Z-14 with dual Lightspeed iii
| Quote: | | > and SD-8> > > At 02:12 PM 1/25/2009, you wrote:> >> >Busy building an RV-8 with dual LS Plasma III (crank sensor) and > >would appreciate some input on Z 14 changes required for my set-up.> |
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nuckolls.bob(at)aeroelect
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| Posted: Tue Jan 27, 2009 12:03 pm Post subject: Bob Nuckolls's Z-14 with dual Lightspeed III |
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| Quote: | | Quote: | I don’t understand the
downside of Z-14:
[/b] |
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Let's study the upside first. What is the mission profile
for your airplane? Under what conditions of failure (study
the effects for failure of each and every component) would
you find the specifics of Z-14 useful in crafting a Plan-B?
Z-14 was crafted for a Lancair IVP builder who planned
to use the airplane for business travel. I.e., be at important
locations at appropriate times. He was an accomplished pilot
with a lot of IFR (Pacific N.W. where there's LOTS of IMC
that does not involve either ice or convective conditions).
It was my advice and his intent that both sides of the
panel be capable of comfortably completing anticipated
flight scenarios. This means that 1/2 of the ship's
IFR goodies were powered from the main bus, 1/2 from
the aux bus. This airplane also has a large engine but
there was value in having small as practical batteries.
Hence, the cross-feed feature for cranking the engine.
Now, this system is not cheap, it's not light, it's not
simple in comparison to other options like Z-11 through
Z-13. It adds to cost of acquisition, fabrication, maintenance
and loss of performance for payloads.
| Quote: | | Quote: | - If you replace the
single big battery with two smaller ones, [/b] the weight increase shouldn’t be much.
Cranking power combined[/b] should be similar.
[/b] |
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Yes.
| Quote: | | Quote: | - Does the SD-20
produce power at idle speeds (on the ground or in descent),
[/b] |
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Not much at idle, less than rated in descent. The SD-8 is even
worse.
| Quote: | | Quote: | [/b] or would the two busses need to be tied until
airborne?
[/b] |
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Depends on aux bus loads . . . have you done a load
analysis for the proposed system?
| Quote: | | Quote: | - the weight of the
extra battery cables seems to be the major weight increase
[/b] |
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You've used "shouldn't be much" and "major" to describe some discussions on weight. It would be useful to speak
to exact numbers and them compare them to your design
goals. It's pointless for us to discuss anything in terms
of weight savings without first having your personal
design goals in mind.
| Quote: | | Quote: | - switchology
doesn’t seem that complicated:
[/b] |
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Again, non quantified.
| Quote: | | Quote: | -
turn both alternators (and buses) on prior to start[/b] - If you replace the
single big battery with two smaller ones, [/b] |
0
| Quote: | - If you replace the
single big battery with two smaller ones, [/b] |
1
| Quote: | - If you replace the
single big battery with two smaller ones, [/b] |
2
| Quote: | - If you replace the
single big battery with two smaller ones, [/b] |
3 |
The only airplanes I'm aware of that need a starter
for airborne restart are the canard pushers. Every
airplane I've flown will not cease wind-milling
during fuel starvation or ignition failure events.
The idea of crafting mission requirements is key
here. I'm reminded of what must be millions of "automobile
emergency kits" sold in stores that contain band-aids,
antiseptic, tourniquet, scissors, burn ointment
and snake-bite kit. Oh yeah, a couple of flares
perhaps a warning reflector is a good thing to have
too.
Had one of those in the first car I ever owned
(1941 Pontiac 6-cyl Coupe). It was still in the
car when I junked it after being rear-ended. 50
years and about a 600K+ miles later, I've never
since missed NOT having one in my car.
So the real answers to your questions should begin
with a study of value and need that is exchanged
for cost of ownership and loss of payload. Bottom
line is that you're going to wire the airplane
any way you wish . . . not the way I or anyone
else wishes. So OUR task is to encourage you
to do the failure mode effects analysis on your
proposed system in situations that describe
how your airplane will be used.
Every part/feature LEFT OFF can only be
improvements in cost of ownership and increased
performance. Keep in mind that the incidence of
electrical system failure precipitating a bad
day in the cockpit (or arrival with the ground)
is exceedingly rare. Unless you plan to spend
a lot of time boring holes in clouds, then
your most reliable back up system looks like this:
http://www.aeroelectric.com/Pictures/Misc/Failure_Tolerance.pdf
Now, assuming you have a similar suite of goodies
in your flight bag, start with Z-11 and consider
how your airplane is to be used. What are the
effects for loss of ANY single component (includes
complex accessories like radios, instruments, etc).
If loss of any single component raises concerns
for breaking a sweat, then what needs to be
added to your electrical system to offer a
Plan-b mitigation of that failure? Finally, assuming
that you do not plan to have a vacuum pump, then
consider a $400/4-pound penalty for plugging the vacuum
pump pad with an SD-8. How does 8A of unlimited
power affect your Plan-b for any failures identified earlier?
If I were building an airplane today, Z-13/8 would
be the architecture of choice. Since MY planned
use of instruments is to poke through cloud
layers and to navigate the Ohio summer haze, I
wouldn't need more than the traditional full
and partial panel compliments of goodies. Further,
I would have a GPS aided wing-leveler that does
not depend on any other accessory for data.
I respectfully suggest that a Z-13/8 architecture
and totally independent GPS aided wing leveler
is a protection against sweaty terminations of flight
that exceeds capability of the vast majority of
S.E. aircraft. I'll further suggest that an upgrade to Z-14
should be driven by an unusual set of mission requirements.
Finally, if you DO find a failure condition that begs
for such an upgrade, please make us all aware of it.
Bob . . . [quote][b]
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