AeroElectric-List Digest Archive

Tue 08/05/08


Total Messages Posted: 7



Today's Message Index:
----------------------
 
     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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    Time: 07:07:06 AM PST US
    From: "Mike" <mlas@cox.net>
    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


    Message 2


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    Time: 08:41:36 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net>
    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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    Time: 08:51:55 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net>
    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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    Time: 09:04:45 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net>
    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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    Time: 09:10:29 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net>
    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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    Time: 09:14:35 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net>
    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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    Time: 10:12:40 AM PST US
    Subject: Bose X Aviation Headset For Sale
    From: "Geico266" <Geico266@aol.com>
    I have a nice Bose X for sale on e-Bay http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&ih=020&sspagename=STRK%3AMESE%3AIT&viewitem=&item=300247651009&rd=1 Read this topic online here: http://forums.matronics.com/viewtopic.php?p=196670#196670




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