Simple keep one mag On Fri, Jul 8, 2022 at 10:57 AM Dr. Feng Hsu via KRnet <krnet@list.krnet.org> wrote:
> Good morning all, > > I enjoyed reading all the excellent stories, failure event descriptions, > arguments of pros & cons and thoughts (from John, Chris and Luis etc.) > pertaining the debate of safety on dual mags, dual E-ignition or one meg > plus one E-ignition redundant aircraft engine systems.... Well, I am glad > to see this discussion actually got us into a classical technical debate on > pros & cons in safety between conventional engineering vs digital > engineering, which has been going on for several decades across all the so > called "high integrity and high reliability" industries, such as nuclear, > aerospace, chemical and medical ....A famous topic debate on this issue in > the aerospace or aviation industry for example is the debate on "flying by > wire"!! Frankly, I am on the camp of opposing the concept of "flying by > wire" within the safety/reliability & risk assessment academic community, > and this is simply because the folks who have been advocating the concept > of "flying by wire" are the "extremist" in engineering design... For the > same reason, I am a none believer of a truly autonomous and safe unmanned > cars & trucks or ground-based transportation system based on AI technology > due to theoretically obstacles or limitations in coding highly reliable and > safe software packages based on human brains. The chilling fact is that > over 75% catastrophic accidents from all high-integrity industries were > contributed by software and human errors combined! Guess what, the single > most "unreliable component" in our man-machine systems (such as aviation) > is the human brain itself! > > Obviously, my views on this topic is taking a balance between the two > approaches and avoid going for both extreme ends of the argument! In > other words, I believe an one mag (mechanical) plus one E-ignition > redundancy makes a lot of sense in risk reduction based on theorems & > reliability engineering principles. I understand what's in the mind of Luis > on dual "independent e-ignition" component and DC power channels... The > issue here is that the two e-ignition channels are not truly independent as > you would believed! Yes, it looks independent in a physical sense but it is > inherently connected or identical due to the design and manufacturing > processes! Although I have not done a model based risk assessment myself to > compare the trade-offs in risk & reliability of these two ignition > configurations, but I am confident (based on expert judgement) that a meg > plus e-ignition configuration would highly likely to be the winner in terms > of safety risk concerns... I am sure other people in the aviation industry > have done a rigorous model based risk assignment comparison on this matter. > > Just to offer some food for thoughts for folks here who might be > interested in this topic debate...! > > Best of luck! > > Dr. Hsu > > On Fri, Jul 8, 2022, 8:07 AM Luis Claudio via KRnet <krnet@list.krnet.org> > wrote: > >> I think these discussions are healthy and welcoming. I read them and go >> "hmmm" then I make my own decisions. I have been flying since 1966 when I >> took my first ride as a civil air patrol cadet in High School in a PA-22 >> 108HP. As a student at Embry-Riddle, I was an understudy of Dr. Richie >> (RIP) a true pioneer in failure analysis (FMEA) of everything >> aviation-related. I understand failure modes, and most importantly how >> to mitigate the risk for each independent system or collectively (through >> risk priority number= severity x occurrence x detection...) I am also >> very familiar with E-Mags and other electronic ignitions which is why after >> careful consideration I chose a dual SDS ignition system. It wasn't by >> "gosh or by golly" that I arrived at my conclusion. Considering that my >> initial choice of ignition system was a Dual Bendix D3000 mag with a single >> failure mode (the main coupling), I asked what else is out there... and >> here is what I considered >> >> 1. A dual mag setup such as the aforementioned dual mag - Four points, >> four capacitors, one coupling = Total 5 points of failure minimum >> 2. An independent mag with an electronic ignition driven by the timing >> gears - Minimum of four points of failure (points, capacitor, two couplings) >> 3. An "E-Mag like" with an electronic ignition driven by the timing gears >> - Engine couplings = two points of failure (minimum) >> 4. Two independent electronic ignitions with no mechanical moving parts - >> dual independent battery backups - Component failure >> 5. Just screw it and go sailing... >> >> My most predictable component failure is the spark plugs. So moving >> forward I then wrote a proactive maintenance schedule in my POH and >> annotated it in my conditional inspection form to reduce the risk of >> component failure. Additionally, during my selection process, I >> prioritized the failure modes of each system, mechanical and electronic... >> from highest RPN to lowest RPN noting that it’s worth emphasizing that it’s >> nearly impossible to address every potential failure. Instead, I focused on >> addressing the potential failures that would most jeopardize the safe >> outcome of my flights and I chose from analysis and not from bells and >> whistles... just my rambling thoughts here trying to justify that $50K I >> spent on getting educated at Embry-Riddle back in the day... keep building >> >> Luis R Claudio, KR2S N8981S >> On Friday, July 8, 2022 at 06:23:13 AM CDT, victor taylor via KRnet < >> krnet@list.krnet.org> wrote: >> >> >> To answer Chris yes I do have a flying KR2 with a single electronic >> ignition though I was actually talking to Dan Diehl yesterday about adding >> a magneto for a backup. >> I do contract work for Velocity Aircraft as a pilot. We love electronic >> ignitions and put them on every airplane. They are the way to go and in the >> past have gone 100% electronic ignition but over time have had enough >> failures that we went back to having one mag. I also test fly new airplanes >> for M-Square who builds the Zenith CH-750 SLSA. I actually have had two >> electronic ignition failures with brand new aircraft there in the last >> couple of years. M-Square is still committed to 100% electronic at this >> point. Just to be clear I’m not knocking electronic ignitions nor their >> reliability. If you have dual electronic ignitions though you likely are >> relying on the same electrical system to run both systems. Up until four >> months ago I had never had a magneto failure in my 40 years of flying but >> recently I lost a magneto while ferrying a Grumman AA1A. Fortunately the >> other one got me to the nearest airport where a safe landing was made. >> There is a reason why aircraft manufacturers such as Velocity have reversed >> their positions on going 100% electronic. And that reason is failures in >> the past and accidents such as the one in Kissimmee. >> When Teladyne Continental first built their full FADEC engine system it >> kept experiencing total ignition failures in flight. After over a year of >> flight testing with multiple in flight failures yet not a single one in the >> test cell they finally got to the bottom of it. The problems was found to >> be the frequency that the US government uses to communicate with submarines >> was interfering with the FADAC system. The fix was simple by shielding the >> system. >> One of the functions of this group is to make the KR’s safer. That’s done >> by discussions and experience. Mostly bad experiences and I’ve personally >> had those bad experiences as a professional test pilot. All of us in this >> group look at canopy latches a little closer today than we did a year ago. >> Controls have gotten balanced, fifth bearings have been added to engines, >> fuel tanks are being moved to the wings etc. You would think that over the >> years we’ve fixed every possible failure point. Have we? >> It’s our duty in this group to be devils advocate at times and to point >> out past failures of similar systems. >> >> Victor >> >> > On Jul 8, 2022, at 00:24, John Gotschall via KRnet < >> krnet@list.krnet.org> wrote: >> > >> > >> > Hi all, >> > >> > Quite a bit of commentary about risk, system failure etc. >> > >> > So I am convinced everything will fail sooner than later. I make my >> living on failing machines, so I may appear a pessimist about machines, or >> an optimist about future employment fixing them. On the upside there is so >> much failed stuff I get paid more than just several times every day since >> 1988 to set those broken machines straight. >> > >> > I find it particularly interesting to see the failures that come in >> groups or waves. I experienced such an odd failure scenerio in aviation >> recently. >> > >> > I bought an experimental flying boat, a volmer home built, OMG, what a >> pretty unit! And a blast to fly! A cub can't touch a volmer for fun. >> Sadly I broke that and am still working to fix it. >> > >> > Anyway there is an annual seaplane fly in at NW Idaho, and I and a >> friend went in the volmer. What a blast! the mountain crossing, middle of >> nowhere overnight camping, etc. However the alternator quit near Idaho and >> we made our way there and home by never turning on the battery switch the >> whole time, except to run the starter motor, and then to cross under the >> Seattle class B. Needed adsb working for that. >> > >> > I found the High current alternator output wire had failed by vibration >> fatigue and had simply broken off that big alternator output post. Simple >> to fix, and I replaced the entire wire with welding cable, better for >> vibration. No big deal. >> > >> > Then I broke the Volmer (another story), and needed another flying boat >> so bought a lake LA-4. We found it in Arkansas and flew it home to the >> Seattle area. >> > >> > The same seaplane fly in came up in Idaho this year, and we went again >> this time in the lake. A complete blast for all the same reasons, but on >> the way home the alternator quit outputting current! This time the plane >> has heavy electrical laods that quickly consumed and flattened the battery >> in short order (less than 40 minutes) on the final leg home. instead of >> panic we just turned west to get out from under the class B, shut all the >> electrical off and used the hand hydraulic backup pump to operate the gear >> and flaps. Made the uneventful landing at home in the backyard and went >> digging for the fault. >> > >> > Dang if it wasn't the SAME DAMN WIRE that broke in the Volmer! On the >> second occurrence of the same trip. Except this time the wire pulled out of >> a bad crimp rather than broke off. Pulled out of a bad crimp on a >> certified factory built plane. hmmm. >> > >> > Well, both the Volmer and the Lake are dual mag lycomings. An o290 and >> o360. >> > >> > So I will say mags are a great choice, from experience. In both cases >> mags brought us all the way home. My kr has one mag and one electric >> ignition. It'll probably make it home without an electrical system. >> > >> > cheers! >> > >> > >> > jg >> > >> > >> > >> > -- >> > KRnet mailing list >> > KRnet@list.krnet.org >> > https://list.krnet.org/mailman/listinfo/krnet >> >> >> -- >> KRnet mailing list >> KRnet@list.krnet.org >> https://list.krnet.org/mailman/listinfo/krnet >> -- >> KRnet mailing list >> KRnet@list.krnet.org >> https://list.krnet.org/mailman/listinfo/krnet >> > -- > KRnet mailing list > KRnet@list.krnet.org > https://list.krnet.org/mailman/listinfo/krnet >
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