Today's Message Index:
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1. 10:45 AM - Re: Fusible Link for Lightspeed Ignition (Robert L. Nuckolls, III)
2. 11:00 AM - Speaking of Lessons Learned (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Fusible Link for Lightspeed Ignition |
At 01:04 PM 3/28/2023, you wrote:
>I am using dual lightspeed ignitions on my project. Lightspeed's
>instructions specify using 18ga shielded wire, the shield used as
>the ground return and wiring directly from the battery to a 7.5 amp
>panel circuit breaker. I want to use a fusible links to protect the
>wires from the battteries to the circuit breaker. I acquired 14
>gauge shielded wire. My plan was to separate the conductor from the
>shield, use an 18ga conductor for the fusible link and solder an 18
>ga ground lead to the shield. The problem I am having is separating
>the center wire from the shield. I end up breaking 30 to 50% of the
>tiny shield strands while separating the center conductor. The
>resulting connection is less than ideal both electrically and
>security wise. I'm thinking a better method would be to roll shield
>back over the outer insulation and use a solder sleeve with an 18ga
>pigtail. I have made a couple practice connections and they seem
>very secure, especially when the whole joint is reinforced with some
>additional heat shrink. Does this seem like an okay approach? It's a
>very important termination.
I've had numerous conversations with Klaus about
his power delivery suggestions over the years . . .
the last being while witnessing some tests on
his product during an inquiry as to cause of
a LA-IV crash out in CA.
https://tinyurl.com/52kbwra8
This case was intently interested in the
performance of those 'very important terminations'.
The engine died in an approach to landing
and ended up on the rocks. Both fuses feeding
the pair of ignition systems were open.
As it turns out, the system was DESIGNED
to fail as explained in analysis documentation.
The project also showed lapses in
choice of materials and fabrication
processes.
Which brings me to this assertion: Failure
of your ignition system(s) will most
likely be a product of poor design and/or
installation error. The accident cited
above was a demonstration of BOTH of
these effects.
Klaus' recommendations are not 'wrong' . . .
just unnecessary . . . and they ignore
a century of lessons learned in the design
and fabrication of reliable aircraft
systems.
Others have cited some of my writings
on the topic of Lightspeed systems. But
in a nutshell, the use of shielded wire
connected directly to battery(ies) driving
panel mounted breakers is both unnecessary
and contrary to a 747-load of lessons
learned.
Those ignition systems will draw no more
than 2.5A at red-line rpm. Each one would
run happily fed by 5A fuse (from either a
hot battery or multi-path fed engine bus)
and 20AWG wire (for mechanical robustness,
not current draw). You have TWO systems,
each of which will run the engine. They
are pre-flight tested. If some failure takes
out a fuse (or opens a breaker), being able
to restore the power path is of exceedingly
low value . . . it will just re-open due
to the fault that caused the first event.
You can confidently skip the shielded wire
and crew-monitored circuit protection
while exploiting benefits of legacy-
proven design and fabrication techniques.
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 2
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| Subject: | Speaking of Lessons Learned |
Electrical 'bonding' of components in aircraft
is accomplished for some combination of three
requirements (1) reliable connection of a
device to power ground, (2) mitigation of
radio frequency interference and/or (3)
managing the effects of electro-static
discharge (ESD).
Here's a good example of failure to manage
ESD back before we'd been schooled in
'lessons learned' . . . 1929
https://youtu.be/LR02blpCJMk
Some pretty cool detective work here . . .
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
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