Today's Message Index:
----------------------
1. 07:54 AM - P-Mag Overvoltage (Jeff Page)
2. 10:39 AM - Re: Article from AOPA on Glass EFIS failures (Hinde, Frank George (Corvallis))
3. 11:03 AM - Re: P-Mag Overvoltage (Robert L. Nuckolls, III)
4. 05:25 PM - Re: Article from AOPA on Glass EFIS failures (Ernest Christley)
Message 1
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Subject: | P-Mag Overvoltage |
> The reliability gurus have long suggested that
> "twin" systems are not as confidence building as
> "alternative" designs.
This is the most reliable strategy.
However, I am considering installing two P-Mags (or one P and one E).
This provides variable spark timing to both plugs, which should result
in improved engine performance.
With internal power generation, the P-Mags should be very reliable.
The only common failure mode I can think of is an overvoltage event
that damages the electronics in both P-Mags.
Do you know enough about the product design to comment on the
robustness of these products to a major overvoltage event ? Is there
a switching regulator that can handle almost anything ?
Thanks,
Jeff Page
Dream Aircraft Tundra #10
Message 2
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Subject: | Article from AOPA on Glass EFIS failures |
Ahh yes...As I tell my engineers who want every cool gadget going on their sysytems..."Every
component is an expensive point of failure"
Of course our systems are bolted to the ground in a wafer fab...God help them if
any of them tried to construct an IFR homebuilt..:)
Frank
Electrically dependant IFR RV7a
Do not archive
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L. Nuckolls, III
Sent: Tuesday, August 05, 2008 8:36 AM
Subject: RE: AeroElectric-List: Article from AOPA on Glass EFIS failures
--> <nuckolls.bob@cox.net>
At 09:40 PM 8/4/2008 -0500, you wrote:
> >>An unanticipated event may be able to take out even a well designed
> electrical bus that has passed multiple peer reviews (Diamond twin
> star, for example), <<
>
> Ah... what makes you assume it passed multiple peer reviews ?
>
> By whom? When ?
Exactly . . . and then you have "executive decision" to
contend with. I'm seriously considering bowing out of a
program wherein we walked in with a proposal for a
"been there, done that, best-we-know-how-to-do" product.
Various "forces" were applied to the design by both
supplier sales ("the customer is always right") and
buyer's engineering ("that's the way we used to do it
and I don't want to do something I don't understand").
The first article delivered was a super pain in the
arse. We're starting to stack band-aids on to fix the
problems . . . which is slowly creeping the design
toward the original proposal. I'd like to rip it all
out and start over but it's beginning to look like
the system will go to qualification with a pile of
band-aids in place as opposed to backing up and
doing it right.
If left unchanged the parts count will be too high,
the customer service technicians will curse "those
idiot engineers" and cost of ownership will be
unnecessarily high. One would like to believe that
these situations don't happen a Boeing, Airbus,
et. als. but I wouldn't bet on it!
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 3
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Subject: | Re: P-Mag Overvoltage |
At 10:46 AM 8/6/2008 -0400, you wrote:
>
>> The reliability gurus have long suggested that
>> "twin" systems are not as confidence building as
>> "alternative" designs.
>
>This is the most reliable strategy.
>However, I am considering installing two P-Mags (or one P and one E).
>This provides variable spark timing to both plugs, which should result
>in improved engine performance.
Agreed . . . and better starting and longer life on
plugs.
>With internal power generation, the P-Mags should be very reliable.
Agreed
>The only common failure mode I can think of is an overvoltage event
>that damages the electronics in both P-Mags.
>
>Do you know enough about the product design to comment on the
>robustness of these products to a major overvoltage event ? Is there
>a switching regulator that can handle almost anything ?
I'll have to talk to Tom and Brad . . . my short
visit with them last year left me with an impression
of much smarter-than-average-bears. I'd like to believe
their product is equal to or better than DO-160 qualification
recommendations for aircraft.
Of course, you could call them too!
I've copied them on this message and expect an answer
to your concern will be forthcoming.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 4
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Subject: | Re: Article from AOPA on Glass EFIS failures |
Hinde, Frank George (Corvallis) wrote:
>
> Ahh yes...As I tell my engineers who want every cool gadget going on their sysytems..."Every
component is an expensive point of failure"
>
>
It's not a disease in the high-tech industry. It's a pandemic. You ask
for a simple function to do a specific simple job. You get back several
thousand lines of code with a dozen optional parameters and a slew of
hidden side effects (for the uninitiated: unrelated things are changing
that you don't expect).
Software is a funny thing in that it is very easy to change. This leads
to a mentality of "throw it at the wall, and let's keep what sticks". I
don't know the veracity of the reports about all the displays going out
on the airliners, but my experience tells me that it is very likely.
I've seen code be approved by "professionals" that wouldn't pass muster
in a freshman college class, and the argument is always that "we don't
have time to fix it". If it passes QA (that also doesn't have time to
fix anything), then it is shipped.
Proper software engineering requires the same sort of methodical,
tedious system review and modularity that we expect to put in our
electrical design. In the end, that is exactly what it is, a lot of
tiny electrical switches going off all over the place. The fault
scenarios are often difficult to identify. Even people who should know
better often forget this.
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