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There are three components that define RISK. Most of your comments
address only 1 of those, the failure rate. Yes, it's a little tough to
nail the fail rate on the rotary engine. The other two components have
equal weight. What EFFECT the failed component will have on flight. How
likely to notice the defect before flight. It's not too difficult to
assess those two components accurately. So if we have the discipline to
use these methods, we've got most of the risk equation nailed. Therefore,
we don't have to be precise in defining the fail rate. We just have to do
our best to be moderately objective.
But you know what this is essentially about? If we use our natural method
of determining risk, we make substantial judgement errors. You know
what's worse, we don't have any feedback to tell us how wrong we are. We
tend to put more emphasis on items from recent memory, like anecdotes we
heard recently. We attach significance to emotional appeals. It's
difficult to realize these truths. The Japanese analyzed design judgement
errors, and found if they followed the FMEA approach, there were fewer
failures.
Here's an excellent example. I've seen people describe their reasoning
for going rotary. Often I would hear: "It only has three moving parts,
therefore it's safer". I suspect that 80% of you believed that. That is a
gross error in perspective. No maybe, it's a huge distortion. It's a
wonderful theory, it has a component of truth in it, but totally fails
the tests for significance. If a logical theory is not significant, you
dump the theory.
When you assess risk, at some point you have to look at the whole
picture. Converting a rotary engine is extremely risky because there are
so many creative activities you are doing. Each has many potential
oversights, so the oversights occur. You have lot's of evidence that
describes this. The ratio of dead sticks, the number of alarm conditions,
whatever you choose. But you need the courage to face the truth. It's not
easy.
Now if we can take VERY effective action on those risk items, then we
have a power plant that has some real potential. Many of it's failure
modes are gradual, thus reducing the EFFECT of the failure. Basically
giving us more time to land safely. In theory, the rotary is less prone
to torsional risks...although there are indications that too fails the
significance test. We get the satisfaction of being different and
thumbing our noses at nay sayers. We contribute to what can very likely
be a viable alternative that exceeds Lycoming performance on all levels.
So this guy that spent all those years looking into the root causes of
failures, hopes he'll eventually be able to explain these things well
enough, provide enough facts, that a life or two will be saved. I suppose
that sounds corny, but that's my view.
-al wick
On Mon, 06 Jun 2005 17:27:06 -0500 Jim Sower <canarder@frontiernet.net>
writes:
> <... in my book, redundancy is job one ...>
>
> The engine has demonstrated its ability to get you to the next
> airport
> without coolant or oil. Ignition and fuel are another matter. Dual
>
> EWPs might be necessary for TO and climb and redundant in cruise.
> Redundant oil pumps seem to me a whole lot more trouble than they're
>
> worth.
>
> As for CAS and the like, NAPA, dealerships etc. could provide the
> least
> UNreliable available as to what needs to be backed up and what
> doesn't. Might even discover that you need to back up the MAP
> sensor or
> something of the like before the CAS on account of they fail all the
>
> time. My point is: *who knows??*
>
> In my view, Al's discipline and methodology work beautifully in a
> factory where the same machines are doing the same thing hundreds of
>
> thousands of times a day. It works less well for say, cars because
> it's
> so much more difficult to gather accurate data. How you gonna
> determine
> how many of some component failed after how much use? Dealerships
> are a
> help - they track what failed and when - but the independent shops
> do
> not and I'm pretty sure they do the great bulk of the repair
> business.
> On top of not knowing with any degree of reliability what failed and
>
> when, we are totally clueless as to fleet mileage. Therefore MTBF
> is
> impossible to track unless you assume (remember that acronym) that
> the
> fraction of data gleaned from dealerships reflects the entire fleet
>
> accurately. Bit of a stretch IMO.
>
> So here we are examining airplanes. Homebuilts no less. How in
> hell on
> earth are you gonna' get data around failures? Al got his little
> slice
> off the Canard or Cozy list(s), but it was a *tiny* slice of reality
>
> submitted by volunteers. Just for openers, I'd have to question the
>
> *motives* of the guys who participated in his little study - and the
>
> guys who *didn't* as well. Beyond participants' agenda, the small
> size
> of the sample is troubling. If one could identify all of the
> suppliers
> of parts and components, one might estimate MTBF of this component
> relative to that component, but life expectancy in actual hours is
> still
> an impossible dream. Add to that the fact that Lycs on planes that
> fly
> all the time (like instruction, air freight, air taxi and the like)
>
> almost always make it to TBO while the same engines on privately
> owned,
> rarely flown planes almost never do. Quantify *that* Tarzan! Does
> that
> phenomenon apply to auto conversions too? Does it matter? Damned
> if I
> know.
>
> I may be mistaken here, but it seems to me that the very soul of
> Al's
> methodology is accurate data around the incidence of failures. He
> can
> speak to that better than I can, and I sure hope he does.
> Additionally,
> only he can speak to the degree to which data that is dirty and/or
> unreliable skews the results. Basically, it seems to me that Al is
>
> trying to quantify something that's qualitatively intuitive to
> everyone
> on the list. We can guess which components need attention and set
> rough
> priorities as to which ones to address first. The main issue is
> quantifying these occurrences failure. At this juncture Al simply
> does
> not have the data to do this with a lot better reliability than we
> could
> do with educated guesses. He needs a *lot* of *good* data IMO.
>
> I'm wondering if it's possible that he will ever get it ... Jim S.
>
> -------------------------------------------------
>
> Was said ...
> I see guys doubling up on water pumps (2 EWP in some cases) yet
> because
> there hasn't been a CAS failure (that we know of) they are not
> worried .
> If you want true redundancy, you must double up on the systems that
> have
> a possibility of killing you engine (and you,no matter how remote)
> The
> CAS failure could be between the ECU & the CAS due to our
> application.
> Not to be too critical, but I've seen some pretty scary (sloppy)
> installations. If you follow the certificated aircraft procedures as
> far
> as securing, protecting & routing wires, hoses, pipes & components
> you
> can be on your way to a safe installation.
> Georges B. (in my book, redundancy is job one)
>
> and ...
>
> I fail to see how installing another CAS will 'dramatically' reduce
> risk of all ECM causes.
>
> We have already said we have no history of failure of the CAS, how
> can
> installing another CAS (with no history of failure), 'dramatically'
> reduce the risk of failure?
>
> And how can installing another CAS have any influence on "the risk
> of
> all ECM causes" ?
>
> I also have great respect for redundant systems, but I cannot see
> your
> logic in this one. It is the 'dramatic reduction' that troubles me.
>
>
>
> >
> >
>
> >> Homepage: http://www.flyrotary.com/
> >> Archive: http://lancaironline.net/lists/flyrotary/List.html
>
>
-al wick
Artificial intelligence in cockpit, Cozy IV powered by stock Subaru 2.5
N9032U 200+ hours on engine/airframe from Portland, Oregon
Prop construct, Subaru install, Risk assessment, Glass panel design info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html
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