Today's Message Index:
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1. 08:56 AM - Re: Re: AeroElectric-List Digest: 1 Msgs - 11/11/23 (Robert L. Nuckolls, III)
2. 08:59 AM - Re: Fuse Upstream of Breaker (Robert L. Nuckolls, III)
3. 09:30 AM - Re: Fuse Upstream of Breaker (Robert L. Nuckolls, III)
4. 01:09 PM - Re: Fuse Upstream of Breaker (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: AeroElectric-List Digest: 1 Msgs - 11/11/23 |
At 09:05 PM 11/12/2023, you wrote:
>Different topic:=C2 Are Lithium ion batteries
>affected by low ambient temperature like, or any
>where close to, what lead acid batteries suffer down around zero F and
below?
>. . . Just wondering if electric powered cars
>and trucks will be seriously affected this winter up north.
Performance of every battery technology
is influenced by temperature of its
chemistry.
Here is one of many resources on the
topic:
https://batteryfinds.com/what-do-you-think-of-lifepo4-temperature-range/
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: | Re: Fuse Upstream of Breaker |
At 11:49 AM 11/13/2023, you wrote:
>Listers,
>
>I want to put a 5 amp breaker in the regulator circuit in a airplane
>that has a 12-fuse distribution panel. The breaker would be mounted
>in the instrument panel which is about 2-3 feet away from the fuse panel.
Per Charlie's suggestion and configurations
depicted in ALL the Z-figures, fusible linked
extension of the bus to the remote breaker
is recommended.
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 3
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| Subject: | Re: Fuse Upstream of Breaker |
>
>I am looking at BobN's analysis of a fatal accident in a
>Experimental with an electrically-dependent engine where the
>electrical system had fuses up-stream/in-series with breakers. (PDF attached)
>
>IIRC, the system suffered a ground fault in one of the ignition
>modules which was supposed to be protected by a 5A circuit
>breaker. The breaker is down-stream from 2 fuses. The failure
>occurred because BOTH up-stream fuses blew before the 5A breaker. I
>don't know what the values of the up-stream fuses were.
This was not a fatal accident although very
expensive with some victims suffering enduring
effects of their injuries.
Suggest you study the analysis of that accident
more carefully. Deliverables produced for my
client in this analysis are available at:
http://aeroelectric.com/Reference_Docs/Accidents/N811HB_Feb2008_LA-IVp/
In particular, check out the demonstrated
performance of the system AS INSTALLED on
the aircraft:
http://aeroelectric.com/Reference_Docs/Accidents/N811HB_Feb2008_LA-IVp/02_N811HB_Configuration.mp4
This project was burdened with many 'slices of swiss cheese',
errors in judgement that set the stage for this accident.
The most significant features of this system were:
(1) Bus tie contactor featured in Z-14 was replaced with
a DIODE and breaker. The diode injected a fixed voltage
drop between main and aux busses of approximately
0.7 volts.
(2) For reasons not clear to me, it was deemed useful
to bring power sources for BOTH flight critical systems
TOGETHER into a single point of failure.
(3) Lack of failure mode effects analysis supported
by LOADS data for the ignition system.
The diode voltage drop and mis-configuration of
the ignition power feeders caused a single fuse
to be burdened with the draw for BOTH ignition
systems. This combined with the fact that max
draw was transient . . . take off and initial
climb-out with prop set for full increase.
These events were only once-per flight cycle
and limited to perhaps 60 seconds per event.
Not severe enough to pop the fuse on any one
event but EACH event abused the fuse causing
its I(squared)T fusing value to steadily
erode.
The main fuse went first leaving the aux fuse
to soldier on for some number of flight cycles
but it too eventually succumbed to the
abuse.
There was no gross fault condition causing the
fuses to open; rather a combination of design
decisions which produced a system that WAS
GOING TO FAIL.
Had the system been configured in the spirit
and intent of Z-14 as published,
http://aeroelectric.com/Reference_Docs/Accidents/N811HB_Feb2008_LA-IVp/04_Z14_Hypothesis.mp4
those ignition breakers and common, dual-feed
ignition bus would NOT have been installed
and just perhaps, that airplane and those people
would still be whole today.
I'll never forget my first view of the sketches
for the system as-installed on HB811. My
client spread them out on his desk and I
could see immediately why this engine quit
on 'short final to the rocks'.
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 4
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| Subject: | Re: Fuse Upstream of Breaker |
> The main fuse went first leaving the aux fuse
> to soldier on for some number of flight cycles
> but it too eventually succumbed to the
> abuse.
This is what FMEA is all about. Here was an
opportunity for a latent failure to go
un-annunciated and impossible to
detect in a pre-flight procedure. Interestingly
also, even if the fuses had been fitted with
LED indicators, it is unlikely that the
failed fuse would have 'indicated' anything.
Voltage across open fuse too low.
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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