Well, as a former reliability expert, I can give you the text book answer:
- Reliability is risk management;
- The universally accepted method of managing that risk is what gives
birth to aircraft safety standards;
- The authorities (like ICAO) are supposed to define what is your
acceptable level of risk for the activity (roughly, basically, deaths per
X flight hours).
- At designer level, you then find what is likely to cause these risks,
and define "unwanted events" (example: power loss, flight controls
failure, etc.)
- If failure of one component that is likely to cause an unwanted event is
so unlikely that it is less than the acceptable risk level, then you don't
have to do anything about it. You assess that by estimating the
probability of failure (occurrence) and its consequences (severity), to
define the level of CRITICITY. A part can be non critical because it is so
unlikely to fail, or because .. If it is not the case, then you have to
improve the reliability. You have many ways to do that, (can be better
technology, better part design, monitoring, maintenance, you name it.). Of
course, one method is redundancy. It is seldom the correct answer, but it
is generally the easiest, and that's why it is so popular in aviation.
Now, this is the rule for expensive designs (airliners, jet fighters,
nuclear power plants, space shuttles or whatever). In general aviation,
the trouble is it is not affordable to calculate exactly all the risks
attached to all the parts and equipment. So, we apply a rule of thumb,
which is: no single failure may lead to an unwanted event. That is what
you do with your ignition or fuel system.
But we also apply criticity, through return of experience of 100 years of
designing and flying. We know that single engine is an acceptable
solution, so we don't make the engine redundant. But we make the engine's
most critical components redundant. The ignition, but not the carb...
Likewise, we know that control cables are unlikely to fail, provided you
rig them properly and inspect them regularly, so we don't make them
redundant either.
In my opinion, the statistics of engine failure in aviation are an
absolute shame, and the ignition is the main culprit. So, I go for a
better technology, and ultimately, as soon as it will become practical, I
will go for an engine technology without ignition: the Diesel engine.
Serge Vidal
KR2 "Kilimanjaro Cloud"
Paris, France
"Mark Jones" <mjo...@muellersales.com>
Envoyé par : krnet-boun...@mylist.net
2005-09-13 19:33
Veuillez répondre à KRnet
Remis le : 2005-09-13 19:37
Pour : "KRnet" <kr...@mylist.net>
cc : (ccc : Serge VIDAL/DNSA/SAGEM)
Objet : RE: Réf. : KR> RE: Dual Ignition Systems, it Saved My Bacon -
CORRECTION
I have never said it was a better system and do not advocate that it is.
It was my personal decision to use a points distributor with two sets of
independent points for it's simplicity and reliability. Now mind you, a
wire broke not the distributor system. Mags have been proven too, so it is
your choice. I also personally think that anyone who flies without
redundant systems is asking to have Daisy's growing over them. Every
critical electrical and fuel system in my plane is redundant. Why would
you not have back up systems?
Mark Jones (N886MJ)
Wales, WI
Visit my web site: http://mywebpage.netscape.com/n886mj
Email: flyk...@wi.rr.com
-----Original Message-----
From: krnet-boun...@mylist.net [mailto:krnet-boun...@mylist.net]On
Behalf Of Serge VIDAL
Sent: Tuesday, September 13, 2005 12:11 PM
To: KRnet
Subject: Réf. : KR> RE: Dual Ignition Systems, it Saved My Bacon -
CORRECTION
I remember having been flamed out once when I expressed my lack of
confidence in the magnetos, and stated that my system consisted of two
totally independent solid state ignition systems. The question was: "if
your system is so much better than the good o'l magnetos, then why ya
making it redundant?"
Originally, I decided for redundancy because I wanted to make the
certification people happy, but thinking of it, redundancy is also an
answer to real life problems in aviation: bad luck, and failure to notice
trouble in the making.
Serge Vidal
KR2 "Kilimanjaro Cloud"
Paris, France
"Mark Jones" <mjo...@muellersales.com>
Envoyé par : krnet-boun...@mylist.net
2005-09-13 17:00
Veuillez répondre à KRnet
Remis le : 2005-09-13 16:56
Pour : "Corvair engines for homebuilt aircraft"
<corvaircr...@mylist.net>, "KR
Net (E-mail)" <kr...@mylist.net>
cc : (ccc : Serge VIDAL/DNSA/SAGEM)
Objet : KR> RE: Dual Ignition Systems, it Saved My Bacon -
CORRECTION
John,
You are absolutely correct. What am I thinking and I am surprised my
hand was not called on this sooner. The wire that actually broke was the
coil primary circuit wire to the points. It broke where it connects to
the post on the coil and not the condenser wire. My mistake in
describing the problem. Regardless, dual ignition ran independently of
each other is the way to go. If you were to run them both together and
one failed, you would never know it and then later on if the other one
failed you would be without a back up. When ran independently, they can
each be tested prior to flight and you will know both are working. Sorry
for the mix up in my analysis report and thanks for opening my eyes.
Mark Jones (N886MJ)
Wales, WI
Visit my web site: http://mywebpage.netscape.com/n886mj
Email: flyk...@wi.rr.com
-----Original Message-----
From: corvaircraft-boun...@mylist.net
[mailto:corvaircraft-boun...@mylist.net]On Behalf Of John Brannen
Sent: Tuesday, September 13, 2005 9:13 AM
To: Corvair engines for homebuilt aircraft
Subject: Re: CorvAircraft> Dual Ignition Systems, it Saved My Bacon
Mark,
Congrats on getting her down safely.
One question though. If it was the condenser wire, how do you have it
connected? Every condenser install I have seen would only result in the
points burning faster if you lost the condenser. I would have guessed
you would get errant firing before complete ignition loss.
John B.
Mark Jones <flyk...@wi.rr.com> wrote:
I pulled my cowl look for the problem and found that the condenser wire
had
broken at the coil. A pair of wire strippers and a wrench and two
minutes
later the problem was fixed.
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