Today's Message Index:
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1. 01:00 PM - Re: Should a tripped circuit breaker be reset in flight? (Robert L. Nuckolls, III)
2. 03:26 PM - Re: Should a tripped circuit breaker be reset in flight? (Bill Watson)
3. 04:44 PM - AN 3087-8 Connector (H.Marvin Haught)
Message 1
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| Subject: | Re: Should a tripped circuit breaker be reset |
in flight?
Bill "happily flying with a fully equipped kitchen and sink" Watson
Addendum: One other thing that breakers can do for you is to
visually indicate what circuit popped. LED equipped blade fuses can
do the same and do it quite well. My fuse panels are installed in
the passenger seat foot well and have transparent panels. While not
easily reached by the pilot in flight, they are easily
visible. Combined with a panel diagram (or transparent panel
labeling) it is easy to see what fuse is popped.
Are there fuses that could be popped and go unnoticed
during preflight? I.e. is there potential for latent
failure that goes unnoticed beyond preflight?
The only fuse that ever popped in flight was for the strobe
unit. The fix was to replace the unit with one that didn't require a
power run from the rear mounted battery, forward to the on/off
switch, and back to the rear mounted strobe unit. Now there is an
unreachable inline fuse between the battery and the strobe unit. The
on/off switch controls the unit via some sort of relay.
Bill, Thanks for sharing your observations and deductions from
lessons learned. I am curious as to your load distribution
configuration that drove the 'fuse pulling' incident. Z-14
offers some pretty robust engine driven power sourcing
supported by two batteries. What are your battery sizes
and which one is 'critical'?
I've always encouraged builders not to revert to circuit
breakers as either the normal on/off ops of an accessory
(like the breaker-switches in Bonanzas and Barons),
or as a prophylactic against an FMEA deduced situation
requiring shutdown of select appliances.
If there's ever a reason to shut a thing off, providing
a switch to do the job makes the most sense. Putting
an crew-operable breaker on the panel for that purpose
MOVES a chunk of your bus structure onto the panel.
An attractive feature of the fuse-blocks is organization
of the bus structure in tidy, off-panel chunks.
The notion of adding switch based on an FMEA-driven
requirement seems elegant way to go while keeping
distribution busses off the panel.
Yeah, those pesky strobes . . . Gray beards here on the
List will recall a rash of incidents cited by readers
experiencing one or more failures of switches on their
strobe systems.
http://tinyurl.com/2a2qqp
There was also a rash of failed fast-on terminals with
the predominant failure being an under crimped wire.
Seems that many of the modern strobes use constant power
energy sources to the tubes. I.e., while 'rated' at 7-8
amps or so at 14.5 volts, they would draw half again more
during battery-only and during cranking transients. So
strobes that are left ON to warn outsiders of a 'powerd-
up' aircraft tend to stress the supply feeder hardware
more than the legacy strobes which in fact, would draw
less current at lower voltages.
No doubt, advancements in LED offerings will make even
this little design quirk a thing of the past . . .
Bob . . .
Message 2
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| Subject: | Re: Should a tripped circuit breaker be reset |
in flight?
On 10/12/2014 3:58 PM, Robert L. Nuckolls, III wrote:
>
> Bill "happily flying with a fully equipped kitchen and sink" Watson
>
> Addendum: One other thing that breakers can do for you is to visually
> indicate what circuit popped. LED equipped blade fuses can do the
> same and do it quite well. My fuse panels are installed in the
> passenger seat foot well and have transparent panels. While not
> easily reached by the pilot in flight, they are easily visible.
> Combined with a panel diagram (or transparent panel labeling) it is
> easy to see what fuse is popped.
>
> Are there fuses that could be popped and go unnoticed
> during preflight? I.e. is there potential for latent
> failure that goes unnoticed beyond preflight?
>
I don't think so. I must admit that checking the fuse panel for a
popped fuse, i.e. a red LED, is not part of my preflight checklist.
However, experience indicates that it catches my eye nonetheless, just
like any other red light in the aircraft. I think I'm going to add it
to my checklist anyway.
> Bill, Thanks for sharing your observations and deductions from
> lessons learned. I am curious as to your load distribution
> configuration that drove the 'fuse pulling' incident. Z-14
> offers some pretty robust engine driven power sourcing
> supported by two batteries. What are your battery sizes
> and which one is 'critical'?
>
It is very robust. I have (2) PC680s. Either will start the engine
under normal conditions but you pointed out that using both for start
will extend their life a bit and running them unlinked together during
flight should be SOP.
It has taken some 'tuning' to get to the point where I am no longer
concerned about a 'critical' battery. Nor do I feel the need to add (3)
on/off switches for the (3) EFIS units though I continue to wish they
had an integrated on/off function.
Before my 'tuning', the battery that doesn't run the (3) EFISs was
critical. That is, I depend on it being fully charged and in good shape
so that it is capable of starting the engine without being linked to the
other battery. If the EFIS battery is discharged by pre-start flight
planning activity, a linked start would force a re-boot of my EFISs and
sometimes the G430. To avoid that, I would do the start using only the
critical battery. In cold temps with a cold engine and a less than
fully charged and healthy critical battery, a single battery start may
not be possible (IO540 with a Skytech LS starter) . It happened.
The 'tuning' involved several changes:
1. The GRT units had an always-on clock circuit. One or two units;
perhaps no problem. Three units slowly degraded my battery. The
clock circuit is no longer needed since the GRTs now pickup the time
from the GPS signal so they were eliminated.
2. I added TCW Technologies Intelligent Power Stabilizer to the EFIS
and G430 circuits. This has completely eliminated reboots during
linked engine starts.
3. The above items allow me to always start with both batteries linked
and then operate them unlinked... all with confidence and
consistency. I've even gone back to turning on the strobes before
starts.
As always, thanks for your insights.
Message 3
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| Subject: | AN 3087-8 Connector |
What is the proper way to install an AN 3087-8 Connector on a 5 wire cable? Can
the connector be removed and reused? I've got to replace the power cable on
my Tig welder.
M. Haught
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