<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.

 

-al wick

 

 

----- Original Message -----

From: Tracy

To: Rotary motors in aircraft

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.

Tracy Crook 

Sent from my iPad

On Sep 3, 2011, at 9:08 AM, "Bobby J. Hughes" <bhughes@qnsi.net> wrote:

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. 

Bobby

Sent from my iPad

On Sep 3, 2011, at 10:20 AM, "Ed Anderson" <eanderson@carolina.rr.com> wrote:

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.

 

Ed

From: Bobby J. Hughes

Sent: Saturday, September 03, 2011 9:43 AM

To: Rotary motors in aircraft

Subject: [FlyRotary] Re: The good news and the bad news......

Bill,

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. 

Bobby

Sent from my iPad

On Sep 2, 2011, at 11:54 PM, "Bill Eslick" <wgeslick@gmail.com> wrote:

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