Today's Message Index:
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1. 07:07 AM - Re: Article from AOPA on Glass EFIS failures (Mike)
2. 08:41 AM - Re: Article from AOPA on Glass EFIS failures (Robert L. Nuckolls, III)
3. 08:51 AM - Re: Article from AOPA on Glass EFIS failures (Robert L. Nuckolls, III)
4. 09:04 AM - Re: Article from AOPA on Glass EFIS failures (Robert L. Nuckolls, III)
5. 09:10 AM - Re: Article from AOPA on Glass EFIS failures (Robert L. Nuckolls, III)
6. 09:14 AM - Re: Article from AOPA on Glass EFIS failures (Robert L. Nuckolls, III)
7. 10:12 AM - Bose X Aviation Headset For Sale (Geico266)
Message 1
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Subject: | Article from AOPA on Glass EFIS failures |
I just want to add my 2 cents here. I have been flying the Airbus
319/320 for over 11 years and have not heard of a failure of all screens
at once. But I will add this, I have seen and heard of avionics
failures that were not suppose to happen and did. In every case that I
have heard of or been a part of they ALL have been due to changes during
modification or maintenance and not the original TC wiring. What I have
extrapolated from these anomalies is the oversight of system integrity
goes down considerably once the airplane leaves the factory.
Just my 2 cents,
Mike Larkin
<nuckolls.bob@cox.net>
At 08:56 AM 8/4/2008 -0700, you wrote:
>Article worth forwarding to this list from AOPA
>
>
>July 30, 2008 by Bruce Landsberg , AOPA Safety blog<?xml:namespace
prefix
>= o ns = "urn:schemas-microsoft-com:office:office" />
>The old joke about the fully automated airliner with no flight crew -
just
>an automated cabin announcement that misfires - seems prophetic with
last
>week's NTSB announcement about massive display failure on Airbus
aircraft.
>There were 49 failures on Airbus 319 and 320 aircraft including seven
>incidents where all six screens failed simultaneously. Didn't think
that
>was possible? Neither did the manufacturer, the FAA or the NTSB.
<snip>
>
>"One of the great mistakes is to judge policies and programs
> by their intentions rather than their results." -Milton Friedman
You betcha!
Has anyone found further discussions of these events on the Airbus?
I spent about 30 minutes searching the web . . . turned up a number
of items dealing with EFIS (or electrical system) failures on
various ATP class aircraft . . . but nothing that speaks to what
might be called an epidemic of failures aboard the Airbus.
I'm having trouble visualizing the lack of attention to system
design that produces gross failures of flight deck systems.
I cannot imagine folks who designed the A319/320 were so lacking
in due diligence.
How do these tales affect the OBAM aircraft community?
I'll suggest no more than ANY story of gross systems failure
aboard ANY vehicle. If it's important that failures do not
propagate across multiple systems, then it's generally not
difficult to make sure this doesn't happen.
I think I've mentioned this before . . . but if I were
building an airplane intended to spend a lot of time in
the clouds, I'd take advantage of the low cost, GPS aided
wing levelers and install TWO . . . each driven by its
own GPS engine (they're under $30 now). Further, I'd make
sure that each system was powered separately. If you have
even one of these devices working (along with alt and a/s)
there is nothing ATC asks you to do that cannot be
accomplished with no other instrumentation at all while
you maneuver to VMC somewhere.
As many of you have already decided, there are back-up
steam gages to your "non certified" glass displays.
We've discussed separation of duties between various energy
sources -AND- loads that are exceedingly useful when you
can't see the ground.
I'm still pained by narratives from incident investigations
where a single failure (perhaps combined with mis-positioning
of controls by crew) caused a cascade of failures or shutdowns
in otherwise perfectly good systems.
Z-14 is but one example of a way that one can build a firewall
between a catastrophic electrical event and the total suite
of necessary equipment items. Z-13/8 is a two-layer electrical
system that offers excellent robustness in the face of certain
failures.
There's a difference between how the TC side of the house
thinks and how we are permitted to think when it comes to
failure management. They bust their butts striving for
MTBF and reliability tree numbers that would make King
Midas envious. We're allowed to consider that EVERY part
in the system is going to quit at some point in time. If
it quits because we ignored simple preventative maintenance
duties and wore the thing out, then a pox on OUR house. If we
REALLY want it to work, it FAILS for unanticipated issues
and we didn't have a Plan-B . . . then it matters not
whether the thing had a 1,000 or 1,000,000 hour MTBF
number. Anyone who places any degree of faith in the
published reliability numbers for the purpose of keeping
his underwear dry has been poorly taught or wasn't paying
attention.
I don't intend to diminish the significance of anyone's
difficulties in the cockpit . . . especially those
responsible for hundreds of lives. I ride behind
a crew of those folks with some frequency. At the same
time, let us not assign significance to the miseries
handed down to our brothers by a regulatory
process that runs smoother on intentions than
upon cold logic. By virtue of understanding
you've acquired one can craft and meet design
goals that put you light-years away from the
probability of experiencing an electrical system
event that ruins your day.
Bob . . .
7/22/2008 4:05 PM
7/22/2008 4:05 PM
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Subject: | Article from AOPA on Glass EFIS failures |
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: Article from AOPA on Glass EFIS failures |
At 04:18 PM 8/4/2008 -0500, you wrote:
>Bob, et al, Here's one possibility for failure while still on the ground,
>an open or leaky canopy on a night of intense ground fog that lets the
>whole aircraft cold soak and become coated with water.
>Happened on my truck (an electrically dependant 2006 Toyota Tacoma Pre
>Runner) which has eight on board computers. I left the windows down all
>night and came out the next morning to find the interior soaked.
>The engine started normally, but almost immediately the dash began to
>light up like the proverbial Christmas tree. The stability control system,
>ABS system, the electric limited slip differential, and the service engine
>warning lamps were all lit. Brakes worked, as did the FBW throttle,
>although applying the brakes caused the left turn signal to light, so I
>continued on my way. After my first stop the lights were out after start
>up, then came back on a mile or so down the road. After my second stop the
>lights were out after start up and stayed out, although applying the
>brakes still caused the left turn signal to light. It was on this leg of
>the trip that I learned that actuating the left turn signal caused the
>cruise control to turn off. Once we were well into the heat of the Kansas
>day, all the symptoms went away.
>I've put the truck through some pretty wild weather on many cross country
>drives to both coasts and never saw any problems like this, but one good
>soaking of the interior sure made for an interesting morning.
Condensation and hygroscopic behavior of normally
insulating materials is a sleeping misery that
we 'normally' discover during qualification. DO-160
calls for testing under conditions of severe humidity.
But as you've experienced, there are occasions WWAAaaay
out on the end of the bell-curve that can lead to new
and unpleasant discoveries.
An airplane (or any other vehicle) that sits outside
gets to test all the points on the bell curve. Most
folks never get past 99.9; some folks get there but
one time. One of the slippery challenges of engineering
is to anticipate and make rational plans to deal with
99.9th percentile events without stacking a lot
of "worry expense" on the product.
Bob . . .
Message 4
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Subject: | Re: Article from AOPA on Glass EFIS failures |
At 01:55 AM 8/5/2008 +0000, you wrote:
><http://online.wsj.com/article/SB121684995725478651.html?mod=googlenews_wsj>http://online.wsj.com/article/SB121684995725478651.html?mod=googlenews_wsj
Hmmm . . . funny thing about those search engines. Another search today
on "airbus" and "failures" didn't turn up items on the EFIS failures
but plenty of other stuff. In particular, you may run across some stories
about one Joe Mangan. I'll leave it up to the List readers to research
and draw their own conclusions.
As I suggested earlier, all this kerfuffle has very little if anything
to do with our airplanes.
Bob . . .
Message 5
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Subject: | Re: Article from AOPA on Glass EFIS failures |
At 10:14 PM 8/4/2008 -0400, you wrote:
>This sort of thing is why my EFIS-equipped RV-10 (with electronic
>ignition) is built with backup mechanical altimeter and airspeed, a vacuum
>powered artificial horizon, and an old fashioned mag to back up the
>electronic ignition. That's the most diverse approach to redundancy I
>could get for my experimental aircraft.
>
>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), but it's pretty unlikely to take out the vacuum pump or the
>mag at the same time.
The reliability gurus have long suggested that
"twin" systems are not as confidence building as
"alternative" designs.
As you've cited, it's unlikely that products of
disparate but functionally interchangeable systems
yield the highest probability for at least one
system staying awake if one of them goes to sleep.
This goes to the idea that identical systems can
simultaneously suffer the same failure mode. When I
propose a micro to do control, the companion
monitor processor is a different device with
code produced on a different tool. Folks flying
a Dynon to back up a Blue Mountain are not only
saving some $ but are taking advantage of the
separation of failure modes in disparate designs.
Bob . . .
Message 6
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Subject: | Article from AOPA on Glass EFIS failures |
At 07:00 AM 8/5/2008 -0700, you wrote:
>
>I just want to add my 2 cents here. I have been flying the Airbus
>319/320 for over 11 years and have not heard of a failure of all screens
>at once. But I will add this, I have seen and heard of avionics
>failures that were not suppose to happen and did. In every case that I
>have heard of or been a part of they ALL have been due to changes during
>modification or maintenance and not the original TC wiring. What I have
>extrapolated from these anomalies is the oversight of system integrity
>goes down considerably once the airplane leaves the factory.
>
>Just my 2 cents,
>
>Mike Larkin
Thanks for your contribution. It's always useful to hear from
someone who has been-there, done-that.
I'm not suggesting that the stories be totally discounted
but given the scientific acumen of those who write for
the popular press, a rational skepticism as to severity
of the problem is called for.
Bob . . .
Message 7
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Subject: | Bose X Aviation Headset For Sale |
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Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=196670#196670
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