When we are pursuing a problem like Johns, we are eager to find
the cause. It's a great relief when we do. We say "Eureka!". We did it!
We did it! This sense of relief is a root cause for failure. We are so eager
to get the problem off our back, that we don't take the next step....
Yes, I know you firmly believe this connector was the problem. But if
you can force yourself to pretend it WASN'T, then you can do this:
Is the cause logical? Like is that really the wire that causes that
effect? If I remove that wire, does it have the same effect? What if I have
two things causing the same thing? By pretending that really wasn't the
cause, then you will do some more testing, looking around. Looking for
similar connector issues, stuff like that.
Now I have to admit, this really does sound like he found the cause.
But I've seen this scenario so often. So you use the disciplines I suggest
to reduce your risk. Logical cause? Can I make it recur?
Repeat after me: "Al Wick is an idiot". "Al will jump to conclusions".
If you believe that, then you start finding ways to prove your
theory with facts instead of just accepting your first conclusion.
My best asset is that I know I'm an idiot.
Yeah, yeah, I know, you guys already knew I was.
We had a perfect example of this on Cozy list couple weeks ago. Subaru
engine slipped 2 teeth on timing belt. Would no longer start. Keith talked
to expert and the guy said:"You know, the engine normally is never rotated
backwards. But you've been pushing your new prop backwards recently
(installing new prop). I think you relaxed the belt tensioner when going
backwards and caused it to skip tooth." So Keith said" Yes, all of that's
true. That has to be it."
But then one of the guys looked into it, guess what? The direction the
belt slipped is the opposite of that theory. That could not have caused it.
The lesson? Prove all aspects of the theory are logical. Prove that all
the various facts support the theory. Find a way to convert
your theory to facts!
Oh, by the way, if you look at my analysis of my engine risks....you
will notice that timing belt is the highest risk item on this engine. So we
have exposed another root cause for his problem. He didn't focus on the
leading cause for all engine failures. When we reviewed some facts he had,
we found conclusive evidence he had loose belt from day one! It was
installed wrong.
Regarding CAS risk. It's not just crank angle sensor that is the risk
item. Going to redundancy with the CAS will dramatically reduce risk of all
ECM causes. Like this connector risk. I'm not always proponent of
redundancy, but with my limited info on this item, I SUSPECT it's
significant, positive step.
-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
On Sun, 5 Jun 2005 21:44:00 -0400 "Tracy Crook" <
lors01@msn.com> writes:
Ahh.. Music to my ears John : )
And this brings up the subject of risk (rotary &
otherwise) that Al W. (and every other builder I know) is concerned
with. I agree with Al W. that getting to the major causes of
failures is a (hell, THE) key issue. That is why I have not spent
much time on the crank angle sensor single point failure question. I
have never seen or heard of a confirmed Mazda 13B CAS failure. Can
it happen? Of course. I am in the process of developing a dual
CAS for the Renesis CAS but it is not a 'front burner'
project.
I'm reading between the lines of Al's posts but it seems that
he is emphasizing the importance of leaving the engine as un-touched as
possible. I once wrote an article for Light Plane World (EAA's
ultralight magazine back in the late 80's) and advocated the same thing
after noting that many Rotax failures occurred soon after the owner
opened up the engine for maintenance. Decarboning the piston ring
grooves was important but many builders were causing more problems than
they fixed when they went inside so I recommended some products and
procedures that would do the job without opening the
engine.
That was the basic gist anyway but I eventually decided
this was not a reasonable approach for builders who planned on installing
an alternative engine in 200 mph category airplanes. There were
simply far too many areas where things could go wrong in this
process. The root cause of the problems had to be
identified. One of the names I gave to the cause is a
term I recently used on this list - Shopcraft (or lack of).
This referred to the ability to identify the quality or suitability of
virtually everything that goes into the plane. Yes, I know this is a
generality of the highest order but if we are to get to the root
cause of failures in the field of alternative aircraft engines, this level
of abstraction is required.
It has been suggested that a collection of 'best practices'
might be a solution. This may help but it is not a solution.
There is an unlimited number of potential problem areas so a list of
them could never be compiled. So, how do you learn to
recognize what is or is not a 'good thing'? I'm getting so
frustrated just trying to describe the problem that there may not be a
solution, at least not one that can be spelled out in something like
an email message. Damn, now I can't even criticize
Al W. for not spelling it out.
The best I can do for now is to emphasize two things.
Pay attention to every detail and admit to yourself when you don't have
the ability to execute something well. Another version of
these rules was given to me long ago:
1. Rules are for those who are not smart enough to make
up their own. (Author unknown)
2. A man's got to know his own limitations.
(Dirty Harry)
3. Always follow BOTH rules 1 & 2.
Small details like the problem of soldering thermocouple wire
to a connector that Al Gietzen mentioned can be critically
important. He was able to recognize the problem (he made a lousy
solder joint) and devise a solution (acid flux) even though it violated
one of the cardinal rules of electrical wiring. He recognized that
too and took the steps necessary to achieve satisfactory results (knowing
when to make up his own rules).
Out of time, I'll stop blathering now.
Tracy
Subject: [FlyRotary] EC2 problems - solved
Tracy
and others.
Following more than 12 months of battling with EC2
issues I'm pretty sure it's Eureka day!
After
rewiring and testing for almost 4 weeks I plugged the EC2 in last night,
and got exactly the same symptoms as before. NOP flashing indicating no
communication. I took the EC2 to Buly's plane and tried it in his
installation. Same NOP, so I was thinking I'd fried it again. Before
sending it back yet again I decided to install it my plane one more time
and see if there was a spark.
To my
amazement it worked. No NOP, and I could bring up the EC2 data. The only
thing that changed overnight was that I moved the cable to unplug it. I
climbed in the back and found that I could make the NOP flash, or stop
flashing, by moving the cable. I haven't taken the connector apart
yet, but I'm expecting to find a broken wire inside the insulation,
probably near a solder joint at the pin. Whenever I bent the
connector outward for testing it made contact. When I bent it back to
plug it in, contact was lost.
Bingo!
John
Just guessing, but maybe the new
EC2 can't communicate with a pre-autotune EM2 like Buly's.
???