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< It must have been
intermittent because the engine still ran fine for the most part – just a little
rough every now and again
This is a great example from the real
world. If you had multitooth crank trigger, and measured the integrity of the
CAS, Joe would have known LONG before failure that the sensor was bad. Most
sensors don't just stop, they have partial failures first.
If you are walking along the road,
want to cross. You use your ear sensor, compare to history. You hear the
clicking of tires and change in pitch of car approaching from behind you. You
verify with second sensor, your eyes. Compare both to history again. Car is too
close to be able to cross safely. We are "smart" because we constantly use
multiple sensors, compare them to history.
-al wick
----- Original Message -----
Sent: Tuesday, September 13, 2011 1:32
PM
Subject: [FlyRotary] Re: The good news
and the bad news......
Al,
Good
points Al. I found an old post from Joe Hull regarding an interment CAS issue.
I think Joe gave up after a spark plug failure that damaged his apex seals in
flight.
Bobby
“I
know I’ve taken a little flack for my MicroTech computer…but on the plus side
it did tell me a couple of months ago that I had a “bad Crank Sensor”.
Of course, it turned out to be a bad connector - the Mazda factory pig
tail coming out of the sensor had a bad connection in the plug. It must
have been intermittent because the engine still ran fine for the most part –
just a little rough every now and again.”
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Al
Wick
Sent: Tuesday, September 13, 2011 11:32 AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: The good news and the
bad news......
<An open CAS would cause instant shutdown
The Oem guys have
such a brilliant solution for this. They know from history that sensors
occasionally fail. So they plan on it. Every revolution they count the number
of pulses they saw from the CAS. So normally they see 16 pulses, with 2
breaks. The toothed wheel is missing teeth at two different spots. One area
missing 3 teeth, one missing 4 teeth. So when they see TDC, they say "Hey,
how'd the sensor do last revolution? Did we get 16 total pulses? Did we see
both a 3 tooth break and a 4 tooth break? No? Ok, then let's use the
backup sensor and turn on the fault lamp.
They also measure
the integrity of the backup sensor. Pretty simple really, it's just software
calculations. Comparing to history. The other cool thing, once you develop
this logic, you have it forever. Every future pilot has a ton of extra safety
if he needs it. They do this with all critical sensors. Oh, yeah. The other
cool thing is that the engine takes longer to start. So the user doesn't just
get fault light, they also get poor starting feedback. It's just so brilliant.
There's another
important lesson here: The KISS concept. So often true, but every once in a
while it's a big mistake. Not a good idea to blindly adopt a philosophy.
Depends on the details. Two CAS sensors are much safer if you compare readings
to history, make a decision.
----- Original
Message -----
Sent: Saturday,
September 10, 2011 7:09 AM
Subject: [FlyRotary] Re:
The good news and the bad news......
I agree that it sounds like electrons Bobby. An
open CAS would cause instant shutdown but I've never heard of a Mazda CAS
going bad. Have had reports of bad Subaru
CAS's.
BTW, apologies for the confusion about your fuel system.
I was confusing you with Sam Hoskins who also had a recent power
failure. His sounded like fuel system problem but no further word from
him.
What was the system voltage during run up? At what
voltage does the EC2 shutdown? Not a likely
candidate.
What happens when the CAS circuit goes open? Does the
EC2 stop firing?
Will a exhaust blockage of ?% stop the engine
completely? Steve's testing showed a partial blockage has a major effect
on power. Bill's muffler had to be full of crud for that much to end up
back in the engine. If the HP2 lower cone was partly intact and came loose
then a major blockage is very possible. It would trap all the little
pieces that had been collecting in the muffler. My first HP had large
chunks of cone still intact along with all the little pieces. My second HP
seemed more intact when my incident occurred. Meaning less large chunks
appeared to be loose but plenty of the small crud. The outlet cone was
loose but more intact. I had hoped that moving the second muffler to the
belly would extend it's life but it didn't. In fact it may be more
dangerous since the small pieces can't be discharged as easily. My under
cowl muffler was mounted at a downward angle. Belly mount is almost
flat.
I agree Ed that electrons seem to be the most logical
cause but may be impossible to validate.
We
still don't know (and may never),the causes, but Sam's and Bills
incidents based on initial information would appear to me to be two
different causes.
Sam's engine kept
running - although sputtering and producing no power - this to me
sounds like a fuel related problem (possibly vapor lock, possibly
something else - could be muffler blockage). Bill's on the other
hand quit suddenly and without any warning - that to me sounds more like
an electrical problem - either the firing pulses to the injector stopped
or the spark stopped.
If I
were Bill, I would use the EC2's diagnostic modes to check out each
circuit - if one doesn't check out then that is probably the
answer. If both check OK then more head
scratching.
Sent: Saturday,
September 03, 2011 9:43 AM
Subject: [FlyRotary]
Re: The good news and the bad
news......
I'm sorry to here about the damage but glad you
weren't injured. I don't know at what percentage of exhaust blockage the
engine would stop running. Also no reports on the condition of Sam's HP2
muffler. Three aircraft experiencing very similar problems this year is
too many. If you have leading / trailing plugs and primary /
secondary injectors on separate power feeds then it should have kept
running. That leaves fuel delivery (vapor lock), CAS circuit, Controller
power, A side computer issue or muffler? I believe Sam did switch
controllers during his incident. I didn't and had plenty of time to do
so. It's now the second item in my emergency
flow.
One common item can be eliminated be removing any
muffler that has packing. Especially Hushpower 2 since they are common
to all three incidents. I'm assuming Sam's muffler also had loose
internals.
I
have been holding up reporting this until all the facts are in, but
that might never happen, so here we go.
Good
news: No injuries.
Bad news: I have some
work to do.
Photos at: http://www.tiny9.com/u/2101
On
August 16th at 10 AM, I lined up for takeoff at my home airport (3600'
paved) into a 5 knot headwind. I had just finished changing the
oil and filter and plugs. Run-up was fine, so off I went.
Approximately mid-field, and a couple of hundred feet in the air, it
suddenly and without any warning became very silent.
Hit the
big switch which puts direct battery power to everything engine, but
no noise. No more time. At this point flying the machine
becomes THE priority. Dropped the nose and was amazed to see a
little bit of runway under the nose! I had fully expected to
land in trees, houses or the river, so I dove what seemed like
straight down to capture as much runway as possible while (somehow)
holding the electric flap switch long enough to get full flaps
(noticed this later). Pulled probably my best round-out ever -
no bounce. Brakes to max and tail up for weight. I think
my sub-concious put it all the way on the nose to try to prevent going
through the fence and down the hill. Wheel skid starts about 200
feet from the stopping point. Skid marks from the wheel pants,
cowling and prop run about the last 50 feet. It stopped nose
down just off the end. The tail was still over pavement.
Pushed the slider canopy UPHILL, stepped out and down. Noticed
that I was not even scared by the whole event.
Interesting. Never even considered trying to turn around.
Pre-thinking that non-option apparently paid off.
More
good news. No FAA or NTSB as it was a non-reportable
incident. Didn't even bend the gear legs. Also, my
neighbor crashed in a Challenger about 10 minutes earlier at the city
airport about 10 miles away. The police and rescue types were
headed that way (they had injuries) and were not interested in my
minor mishap.
As for the engine. When we got it back to
the hangar, the prop would turn only haltingly. You could feel
grinding going on inside. First try at turning had it come up
hard and stop. More fooling with it and it gradually came looser
and would turn. Really looked like something came loose in
there. Pulled a plug from each rotor and did a compression
test. Rotor 1 was 80-80-80. Rotor 2 was 2-2-2. More
proof that something had come loose. With that evidence, the
insurance company allowed me to remove the engine for
inspection. What I found was a pile of ground up ceramic
junk. All the seals were still fine. Lots of time went in
to finding where that stuff came from. Went through every inch
of the induction system. Finally Jason Hutchison (my other
on-airport rotary guy) broke the code. While the RV was standing
on it's nose, this crap from my burned-out Hushpower II ran back up
the manifold and in the exhaust port. That is what was
grinding. Crap. Now the entire thing is off the firewall
including the engine mount. All the wiring is disconnected (did
not find anything loose or missing). I spent the morning looking
under the panel for any loose or broken wiring, but found none.
When I get the EC-2 out, Jason wants to plug it into his plane and
we'll do the plugs and injectors test. If that checks out,
Tracy, it is coming to you for a good look. I don't know what
else to check. The engine quit just like somebody reached over
and turned off the ignition. No stumble, no hiccup, just instant
silence. I honestly do not know if the prop was turning or
not. I suspect not, due to the silence and the fact that one
blade is untouched.
As you can see from the photos, there was
something going on with Rotor 1. Wear is apparent down stream
from the plug holes and all 3 apex seals are starting to chip in the
center. There is quite a lot of carbon also on the rotors after
170 hours.
Going forward, I have decided to look at resale
value for if/when my RV-12 days arrive. This means putting a
(gasp) IO-360 on it. The rotary has given me a safe 10-year run
(til now, of course), so I have no regrets, but this is an opportunity
to make some changes, and parts are already on the way. I will
still be hanging out at the engine tent at S-n-F and wherever else
gatherings happen. Hope to be flying by the first of next
year....
I'm sure some of you will have suggestions about what
might have gone wrong, and I welcome any kind of speculation, but bear
in mind I am just looking at a pile of parts and wires at this
point. Both fuel pumps were on, tanks were over half full, crank
angle sensor worked fine.
Guess it's obvious that I now have a
RD-1A, EC-2, EFI Monitor (Ed's), Felix 68/72 and Props Inc 68/72
wood props and LOTS of engine parts (my whole 14-year stash)
available! And priced to sell!
Bill Eslick
RV-6 13B/NA EC-2
RD-1A
750 Hours
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