Today's Message Index:
----------------------
1. 06:43 AM - B-lead protection (Allan Aaron)
2. 07:49 AM - Re: B-lead protection (Robert L. Nuckolls, III)
3. 01:11 PM - Re: B-lead protection (Robert L. Nuckolls, III)
4. 01:45 PM - Re: FAR 23 and airplanes of any stripe (John Loram)
5. 02:25 PM - Re: FAR 23 and airplanes of any stripe (Robert L. Nuckolls, III)
6. 03:53 PM - Navman Fuel Flow Meter (Joel Ventura)
Message 1
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| Subject: | B-lead protection |
I'm finishing the wiring in my safari helicopter and need some advice re B-lead
ANL or fuse. I'm using the skytec starter with built in solenoid with about
3 feet of number 2 wire going from the starter to the master contactor. I'm using
a tractor style push-button starter switch and an externally regulated 40a
alternator. Since I have no external starter contactor, do I need to run the
B-lead from the alternator via a fuse to the master contactor or can I run it
the much shorter length between the alternator and starter? If the former, I
could mount the ANL holder on the firewall but I would have three fat wires (starter,
B-lead and main bus) bolted to the master contactor. If I can just connect
the alternator to the starter lead I can use an inline fuse holder. My questions
are:
1. Where do I put the B-lead and fuse/ANL?
2. What size wire for the B-lead?
3. What size fuse/ANL?
4. Do I need to put a diode across the starter button and if so, which one and
in what direction?
Thanks!
Allan
Message 2
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| Subject: | Re: B-lead protection |
At 08:42 AM 7/31/2013, you wrote:
>
>
>I'm finishing the wiring in my safari helicopter and need some
>advice re B-lead ANL or fuse. I'm using the skytec starter with
>built in solenoid with about 3 feet of number 2 wire going from the
>starter to the master contactor.
#2 is possibly overkill, #4 would certainly suffice
for your battery/starter wiring.
>Since I have no external starter contactor, do I need to run the B-lead
>from the alternator via a fuse to the master contactor or can I run it
>the much shorter length between the alternator and starter?
Take it to the starter.
>1. Where do I put the B-lead and fuse/ANL?
As close as practical to the starter but if
the fuse ends up in the middle of the wire run,
it's no big deal.
>2. What size wire for the B-lead?
8AWG is fine for 40A alternator.
>3. What size fuse/ANL?
I see Walmart is offering this fuse
in a 30A, which is plenty robust for
your alternator.
http://tinyurl.com/l6qbxsc
This is a miniature fuse for which you
can fabricate your own holder from a piece
of phenolic and some screws, nuts and washers
from the hardware store.
>4. Do I need to put a diode across the starter button
>and if so, which one and in what direction?
Not ACROSS the button but from contactor side
of button to ground. Cathode connected to pushbutton,
anode to ground. Any of the 1N5400 series diodes
from Radio Shack are find. See:
http://tinyurl.com/l65nqnw
There was an AD issued against the ACS key-switch
some years back that put a diode across the switch . . .
completely ineffective.
http://tinyurl.com/l6qbxsc
Diode needs to wire across
the solenoid coil either at the switch as described
or on the contactor (probably not as convenient but
if you can put it there, that's good too.)
Bob . . .
Message 3
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| Subject: | Re: B-lead protection |
>
>2. What size wire for the B-lead?
>3. What size fuse/ANL?
Here's a 40A MIDI style stocked by Digikey
http://tinyurl.com/mpudgxu
and a holder like this
Emacs!
To mount it can be found here . . .
http://tinyurl.com/kcbyc79
Bob . . .
Message 4
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| Subject: | FAR 23 and airplanes of any stripe |
Where would I find the FAA definition of "circuit essential to flight
safety"?
Thanks, -john-
(get'n close to inspection)
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: Monday, July 29, 2013 8:43 PM
Subject: AeroElectric-List: FAR 23 and airplanes of any stripe
.
Sec. 23.1357 Circuit protective devices.
.
(b) A protective device for a circuit essential to flight safety may not be
used to protect any other circuit. .
Bob . . .
Message 5
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| Subject: | FAR 23 and airplanes of any stripe |
At 03:45 PM 7/31/2013, you wrote:
>Where would I find the FAA definition of "circuit essential to flight safety"?
There is no such definition that I know of. It's one
of those catch-all phrases that will be addressed
by the certification test plan for each airplane.
I wrote the cert test plan for the GP-180's electrical
system. We took each paragraph of the applicable FARS
and spoke to how requirements of that paragraph were
to be addressed. It's been almost 30 years but as I
recall, there were no circuits (or associated protective
devices) that were essential to flight safety. In
other words, any single circuit who's failure would
put the airframe at risk had (1) immediate notification
to crew that a failure had occurred and (2) a back-up
plan for that condition.
The idea that being able to reset a breaker for some
circuit that put the airplane at risk simply wasn't
a consideration. If a breaker trips, that system
is off line for the duration of the flight and
prudent design called for making such circuits
un-essential for comfortable termination of the
flight.
Failure tolerant design drives risks to insignificant
probability without having to prove 10-to-the-
minus-9 failure rates . . . the probability of
dual failures for 10-to-the-minus-4, 5 or 6
rates within an operating window of a single
tank of fuel is exceedingly small. Hence the
statement for identifying "circuits essential to
flight safety" have been moot for decades. Well
crafted machines have no such circuits.
Bob . . .
Message 6
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| Subject: | Navman Fuel Flow Meter |
This is a post I made on one of the canard lists a couple months ago. I
got no response
there, so I thought someone here might have some information. First a
little background.
A member of that canard list posted a Navman fuel flow meter for sale on
the list,
and a well respected member of that list condemned the use of that flow
meter in aircraft
because it uses a plastic housing in its flow transducer, and at least
one pilot was killed
when that housing failed, feeding large amounts of fuel to an inflight fire.
=======================================================
First I want to thank Marc for his strong condemnation of the Navman
Fuel Flow Meter. (I started to say "vociferous condemnation" but I am
not sure I know what that means.) That enabled me to buy a used one
very inexpensively. I bought it primarily for automotive and motorcycle
fuel flow testing, and it may see limited aviation use in testing fuel
flow to large model airplane engines. (Some model airplane engines use
alcohol and nitro-methane fuels; do any of you know if the Navman sensor
will be damaged by those kinds of fuels?)
However, one of you got my attention by mentioning that the Navman
electronics can be used with other manufacturer's transducers, so at
least part of the Navman may eventually get into my LongEz. If it
happens, this is a long way off, but I have a few questions related to
that topic I would like to ask while this is all fresh in the collective
canard-aviators consciousness:
1. Most flow transducers use small "turbines". Since all the fuel
flows through the transducer, do these turbine sensors have a failure
mode that can block the fuel flow, for example if the turbine seizes, or
can enough fuel still get through for me to limp to an airport?
2. Which transducers would you recommend? Are there any metal housing
turbine type automotive transducers that you consider acceptable? The
one in my car works very well.
3. There is an extra calibration procedure in the Navman manual for use
with their sensor (pour a know amount of fuel through the transducer,
and tell the electronics what that was). I assume I would follow the
same procedure to calibrate any other transducer I hook up to it. Is
that correct, or is there anything else I would have to do?
4. What pins correspond to what function in the Navman connector? I
obviously need that information to hook up the Navman electronics to
someone else's transducer. I am sure I could figure that out with a
volt meter and a scope too, but is there any other modification necessary?
5. Is there anything else I have missed?
Thanks for your help. --Joel
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