Hi Tim,
Isn't it wonderful how stories get twisted around as they fly from list to list. Obviously this particular twisted story relates to my recent experience, so let's dilute the fun a little by adding some truth.

So he was flying along when his engine started crapping out.
Actually I was in the pattern at my home field flight testing some minor modifications. The engine began to run rough above about 4600rpm. Below 4600, which is more than enough to maintain level flight, it ran perfectly. I circled the field for a few minutes to try to diagnose the problem by switching redundant coils, injectors, ECUs, fuel pumps and batteries, checking fuel pressures and adjusting mixture. Nothing changed so I made a normal landing (at my home field).

I have the details correct
You don't

he fired his plane up after cool down. It sounded ok, so he proceeded to depart. Fortunately he lucked out again. His engine crapped out on takeoff run. He finally had to push it off the runway.
Yes, I waited for the engine to cool down, then (after returning from a business trip a few days later) tried another runup with no intention of taking off. The runup was normal, so I did I high speed taxi run on the runway to try to replicate the problem. I was successful. The problem worsened as I pulled off the runway. This time max rpm was around 1100. Not enough to propel the plane so, yes. I pushed the plane 100' back to my hangar.

2) Making assumptions when diagnosing fault. No doubt this failure could
be difficult to diagnose. But we all have tendency to jump to
conclusions, hope for the best, etc. We are all influenced the most
recent discussions. We are at strange airport and want to get back home.
No assumptions were made. It was considered a possibility that the coils might be the problem since similar symptoms had been experienced by another flyer. Unlike other possible causes, coils take a while to obtain, so a spare set was ordered while I was out of town IN CASE they were at issue. This way they would be at hand if needed. As it happens, they weren't. The decision to order new coils was simply one of logistics.

4) Using marginal components. If he wasn't using known marginal coils, he
would not have jumped to that false conclusion.
The LS1 coils have an excellent reputation, with only one reported failure on an aircraft of which I'm aware. I have 2 coils per rotor with switching to defeat each set in turn during runup. The engine runs well with either set  switched off.

While we're speaking of assumptions, making them in third hand reports of a fault and subsequent fix, while entertaining,  is totally counterproductive with respect to learning from others mistakes.

The truth is that the rotary has two crank angle sensors, and ran smoothly with what may have been an intermittent fault on one sensor. The RTV was, in fact, used to seal the end of the connector and was well away from the soldered connection. I suspect either a bad solder joint or insufficient strain relief as the probable causes.

John Slade

PS Feel free to post "The rest of the story" back to wherever the rumor mongers lurk

Timothy Peters wrote:

All,

 

I'm going to risk the wrath of the anti-cross posters and post here what I read on one of the Fly Subaru lists.  I was hoping someone else here might have caught it and raised the issue with the group, but I haven't seen anything yet. (Although I do run perpetually 2 days behind.)  It was weighing too heavily on my mind to let it pass.

 

It may help to know that I have not made a final decision about what type of engine I am going to use, so I monitor several different mailing lists...  John Slade has told me I don't even need to worry about an engine until I get an airframe built... or even decide which airframe to build. ;-)

 

I'm primarily looking at the Cozy IV and the design changes I'm considering involve engine type.  I will be deciding on an engine before building. 

 

So far I'm thinking Bruce T. built 13B turbo-equalized with RWS redrive and EC2.  (I'm also kicking around a H6 turbo Subie engine).

 

But this raises a question about fault tolerance, specifically how non-OEM engine controllers handle such things as a failed crank sensor. 

 

I did get irritated with the rounds of self congratulatory rhetoric and Darwin jokes that passed back and forth after this post.  One following post even boasted that, unlike this silly bloke, he used bullet proof GM coils.  To his credit, the original poster did return that the suspected failed coils were GM coils.

 

Well, time to separate the facts from the hot air...  where do we stand with sensor faults and how do they affect the RWS controller verses an OEM controller?

 

Couple weeks ago one of the guys had ignition failure on his conversion.
There were so many contributing causes, so much to be learned by his
experience. Fortunately he and his plane survived, although we should all
pretend it didn't turn out so well.

I've been harping a few years now on the need for the custom ignition
systems to handle sensor faults better. This failure would have been
lower risk if he had such a system. So he was flying along when his
engine started crapping out. Wisely he took precautionary landing.
Recently there were newsgroup discussions about a certain brand of coil
giving out from heat. So he assumed that was what he was experiencing. If
I have the details correct, he fired his plane up after cool down. It
sounded ok, so he proceeded to depart. Fortunately he lucked out again.
His engine crapped out on takeoff run. He finally had to push it off the
runway.

The direct cause? He lost his crank sensor. The wire connector was
corroded. Reportedly he adapted OEM plug to the sensor and used RTV as a
strain relief. I never knew this but I'm told RTV cures using a chemical
that can corrode electrical contacts. Coupled with the fact that he flies
in corrosive part of country (humid Florida).

So here are all the causes. I attach significance to them all. Many of
them we are all vulnerable to.

1) Custom wiring of critical component using unproven method (RTV). He
had good intentions, but inadvertently caused a problem. This is very
common failure scenario. All custom work is high risk.

2) Making assumptions when diagnosing fault. No doubt this failure could
be difficult to diagnose. But we all have tendency to jump to
conclusions, hope for the best, etc. We are all influenced the most
recent discussions. We are at strange airport and want to get back home.

3) Use of unintelligent custom ignition system. Your car in this scenario
would have immediately turned on the check engine light and the code for
"bad crank sensor" would be sent. This ignition system boasts dual
computer and all that, yet is vulnerable to crank sensor. I sure want to
encourage these suppliers to improve fault handling.

4) Using marginal components. If he wasn't using known marginal coils, he
would not have jumped to that false conclusion.

5) No discussion of contributing causes. We don't learn from these
situations if we don't pursue the other causes.

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

From: Russell Duffy

To: Rotary motors in aircraft

Sent: Monday, June 05, 2006 9:22 PM

Subject: [FlyRotary] Re: Shoe Goo Research, Was Re: Protecting splices

 DAMHIKT.
>
>
OK, I give up.  What does it mean? :)

Don't Ask Me How I Know This

 

Pretty soon, "acronym" will be an official language, without any words :-)

 

BTW, a belated congrats to Jason on his first flight, Joe on his continued testing, and a big thanks to John for getting the hell out of my state :-)

 

Cheers,

Rusty (Kolb on Ebay as I type)

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