Today's Message Index:
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1. 05:18 AM - Re: Redundant Fuel pump wiring, 914 Rotax (Robert L. Nuckolls, III)
2. 05:34 AM - Oops, hit send too soon (Robert L. Nuckolls, III)
3. 10:27 AM - Re: Redundant Fuel pump wiring, 914 Rotax (user9253)
Message 1
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| Subject: | Re: Redundant Fuel pump wiring, 914 Rotax |
At 08:36 PM 1/21/2013, you wrote:
>
>Bob,
>
>I'm not familiar with the term "golden suite" in this context. A
>quick dfn please.
Collection of elegant solutions. Every
new product is fraught with birthing
pains and it seems that they number
in proportion to the square of the
complexity.
If the design/manufacturing/marketing
team can refrain from radical tangents
in a product's evolution, it has a chance
of maturing into a golden suite of
elegant solutions. Airplanes like the
J3, BE36, C172, C185, C208, RVs,
Ezs, Kitfox, come to mind just to name
a few. Yeah, you can fiddle with engines
and avionics but the core strengths
require no further attention . . .
the design goal has been satisfied.
When any of those airplanes presents with
a problem, it's almost a sure bet that
the problem is rooted in behaviors of
the users, a departure from "been there,
done that" as opposed to a design deficiency.
Bob . . .
Message 2
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| Subject: | Oops, hit send too soon |
At 08:36 PM 1/21/2013, you wrote:
>
>Bob,
>
>I'm not familiar with the term "golden suite" in this context. A
>quick dfn please.
Collection of elegant solutions. Every
new product is fraught with birthing
pains and it seems that they number
in proportion to the square of the
complexity.
If the design/manufacturing/marketing
team can refrain from radical tangents
in a product's evolution, it has a chance
of maturing into a golden suite of
elegant solutions. Airplanes like the
J3, BE36, C172, C185, C208, RVs,
Ezs, Kitfox, come to mind just to name
a few. Yeah, you can fiddle with engines
and avionics but the core strengths
require no further attention . . .
the design goal has been satisfied.
When any of those airplanes presents with
a problem, it's almost a sure bet that
the problem is rooted in behaviors of
the users, a departure from "been there,
done that" as opposed to a design deficiency.
In the context of policy and procedure, there's
a school of thought that suggests you can
write down a set of rules, get them blessed,
and declare them the official path to Nirvana.
i.e. the Golden Suite of ideas. Individuals
who put a lot of faith in such rules are seldom
beneficiaries of the school of: Understand
the customer's wants. Deliver to those wants
with reliability, warranty and incremental
improvement. Failure to deliver offers risk
that the customer takes their business elsewhere.
Hawker-Beechcraft expended $millions$ in
achieving and maintaining ISO standards
for the generation of policies and procedures.
But after all the dust settled and we were
'holy watered' . . . nothing changed except
that it got more expensive to do the best
we knew how to do.
I.e., words in books do not motivate suppliers
of goods ands services to improve on
the best they know how to do. Smiling
customers waving credit cards are 1000
time more incentive than a row of P&P books
on the shelves.
Bob . . .
Message 3
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| Subject: | Re: Redundant Fuel pump wiring, 914 Rotax |
> 2) Have the primary pump connected directly off of the B+ line at the capacitor,
with 5A slow-blow breaker protection.
Although physically apart, the main power bus and the capacitor in Z-16 are electrically
the same. I would wire the fuel pump using the least amount of wire
to minimize weight and complexity.
> 3) Breaking the B+ line for charging control and OV protection (instead of breaking
a field wire).
I would like to see the source of this. Something has been lost in translation.
The Rotax dynamo field consists of permanent magnets, not wires. Locating
the alternator relay as shown in Z-16 has advantages over moving it to the rectified
output side of the voltage regulator. AC current is easier to switch than
DC and a faulty regulator will have its power source removed. The O.V. relay
will function in either location, before or after the regulator. But I see
no advantage to modifying Z-16.
Connecting one fuel pump to the Main Power Bus and the other fuel pump to the battery
(or E-Bus) will eliminate common failure points.
> d) If I can use a self-reset breaker at the large capacitor to protect the fuel
pump wiring, then there is no way for the pilot to accidentally (or intentionally)
kill power to the main fuel pump. (I think this is a good thing?)
I think that the pilot should have control of the fuel pumps. Fuel pumps need
to be shut off in case of engine fire.
> Where having only one battery, a battery connection failure could kill both fuel
pumps in any other wiring method.
Why? I disagree.
> What happens if there is a failure at (or very near) the battery (hot or ground)
making an open circuit. This disconnect from the alternator seems likely to
trip the crowbar, thus eliminating the charging circuit too, drops the battery
and charging contactors open with no means to re-energize the OV relay.
Disconnecting the battery will not cause an over-voltage condition. This can be
tested by jumpering the alternator half of the master switch. Then with the
engine running, turn the master switch on and off.
The Rotax alternator is highly unlikely to fail. It has no moving parts except
for magnets that are part of the flywheel. If the flywheel stops turning, the
pilot has bigger problems. The Rotax alternator has no brushes or diodes.
There is not much to go wrong with stationary coils of wire. The rectifier /
regulator IS failure prone and should be provided with dedicated cooling air.
Joe
--------
Joe Gores
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http://forums.matronics.com/viewtopic.php?p=392884#392884
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