nuckolls.bob(at)aeroelect
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 Posted: Sat Dec 24, 2016 5:56 am Post subject: IBBS battery with B and C alternators? |
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At 05:24 PM 12/23/2016, you wrote:
| Quote: | --> AeroElectric-List message posted by: Alec Myers <alec(at)alecmyers.com>
The only contactor failure I've had is when it welded itself shut, due to a short in the starter motor. It's quite unusual not being able to turn off the aircraft..
On 23Dec2016, at 7:12 PM, user9253 <fransew(at)gmail.com> wrote:
--> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com>
> If you're going to that much trouble why not just have two independently switched contactors?
There is not much trouble, same number of components either way. The relay has the advantage of less current, less weight, less cost, and less space. I am not necessarily recommending this circuit. Just offering it for others who want redundancy.
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Contactor failure (or failure of the
control wiring/swtich to a contactor
is rare. Figure Z-13/8 was designed
so that ENDURANCE mode flight was not
only possible with the contactor
deliberately opened to reduce en
route energy demands.
Have you done a load analysis of your
proposed installation? Have you selected
a system architecture? I'm betting
that with a little pre-planning and
adjustment of architecture, a Plan-B
can be identified for every single-
failure event but without adding a lot
of weight, cost-of-ownership and system
complexity.
Electrical system failures as root or
even contributing cause for a bad day
in the cockpit are exceedingly rare.
Most bad days in the cockpit arise
from poor pilot preparedness for steering
around the many inevitable pot-holes
in their flying experience.
I'll suggest a review of the Z-figures,
accompanying notes and supporting narratives
in the 'Connection would be useful.
Particularly the chapter on system reliability
(where 'system' includes prop-to-tailcone
environs and all components in between).
If you don't have a paper copy of the
'Connection, you can download a .pdf at
http://www.aeroelectric.com/Book/AEC_R12A.pdf
I've been out of pocket for the last few
days . . .had a melt-down of my office
computer. Just got a re-build up and running
late yesterday. Leaving for Wichita today
for Christmas celebrations. Be back on
line late Sunday. In the mean time, let's
see if we can figure out why Z-13/8 WILL NOT
serve to PLAN for any real risks to the
enjoyment of your airplane.
Lets do failure mode effects analysis to
your proposed system with a goal of keeping
ANY and ALL single failures from creating
an EMERGENCY . . . the goal is to upgrade
a component because you're tired of replacing
it . . . not because it damned near got you
killed. FMEA is the easy, light, most economical
way to craft an electrical system and mitigate
any worries associated with flying it.
Merry Christmas folks! See you in a few
days.
Bob . . .
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