I have been thinking a little harder about the issues Al has raised and I
have to admit that this discussion has been a good thing for me.  I
decided that redundancy could be more of a problem then a solution. I just
shaved 1500 dollars from my budget!

The rest of my email rambles a bit but if you are without anything useful
to do you can continue reading.  No one in my family cares to listen to me
talk about my plane and I am without anything better to do between
meetings here at work.

 I had planned on an EC-2 as a my primary engine management system plus a
DIY management system (a megasquirt derivative) as a backup to the EC-2.
I was primarily concerned with the single crank angle sensor issue, it
just seemed a bit sketchy to me.  I thought hard about redundant crank
angle sensors and I had the details worked out so that I would have two.

Last weekend while I was clekoing and drilling up a storm I considered why
dual CASs were so important to me, the obvious answer: "If the control
unit does not know where the e-shaft is relative to TDC you are without
spark and fuel."  I suppose GA aircraft all have dual magnetos and the
fuel delivery is not tied to either.  It must be a fundamental
requirement, hell I have not been flying that long and I have had a
magneto fail, so I know it is a good thing.   On the other hand I have
never had an engine management system fail in one of my cars even though I
must have driven a  million miles in cars that used them.  I work in an
office these days, I asked my co-workers if their cars had ever stopped
while driving for a reason other then running out of gas, or a dead
battery, none had.

The vehicle that has the hardest life in our family is a 1999 Dodge Grand
Caravan ES,   I have six children, four are old enough to drive and the
van is the kid’s daily driver.  It has a little more then 100,000 miles on
the clock,  60,000 of those saw them as the primary drivers, the service
history follows:
oil changed about every 8,000
transmission changed oil three times
coolant changed once
2 drive belts
1 tensioner
3 air filters
8 sets of brakes (6 front 2 rear)
four sets of tires (3 X 4 summer,  1 X 4 winter)
Replaced AC pipe chaffed where it penetrates the floor at the rear
Replaced all of the ball joints and rubber mounts in the front end to
bring back the “new car feel” at 70,000 miles.

That is the total service history, it runs like a top, does not use any
oil, I have never touched the engine or accessories.

When I think back 20 years ago to my early days as an apprentice at a
dealership I remember working on a few carbureted cars with mechanical
fuel pumps, and points in the distributors, none of the mechanics wanted
to work on them so they went to me the apprentice.  They were pretty
simple, but they did have their share of troubles.  Every garage had a tow
truck 30 years ago, and you use to see them on the road dragging around
cars that had stopped running; I don’t think many garages have tow trucks
any more and most of the wreckers I see are cleaning up after an accident.

I recall reading about a fellow who presented at Oshkosh one year in the
Alternative Engine forum.  I think that he had a Subaru engine in a Kit
Fox.  He was questioned about his lack of redundant ignition and he
replied “redundant reshmundant how often have you heard of an electronic
ignition failing."  I think that he had about 600 hours on his
installation at the time…  I hope he is still flying.

-- Ian