> I was researching the failure on John Slades EC2 and found some
    > disturbing things.
    >
    > The input power filter uses a choke which is the only single failure
    > point in the EC2. The part was originally specified to be so over
    > rated such that failure could only be caused by physical damage to
    > the part. If an overload occurred sufficient to fail this part, the
    > circuit traces on the board would fail long before the part would.
    > This
    > was the rationale for the basic design approach. Don't want to get
    > into
    > a discussion of why separate chokes are not used.
    >
    > At some point the manufacturing facility substituted a different part
    > with same inductance but lower current rating. It was still over
   rated
    > and sufficient for any foreseeable situation so it was considered OK.
    >
    > Still later, the board maker substituted an even lower rated part
   that
    > looks almost identical to the previously substituted part. I was not
    > informed of this change. The unit will function normally with this
    > part but it has no extra margin for safety in the event of mis wire,
    > shorted output, etc. I was able to duplicate the failure John Slade
    > had
    > by shorting 1 or more ignition driver outputs to ground or 12V input
    > power. The original design intent was to allow this condition without
    > failure of the choke.
    >
    > Point of this message is to announce an AD (airworthiness
   directive) to
    > inspect and verify the type of choke used on your EC2. Attached to
    > this
    > message is a picture of the three types of chokes used. The left is
    > the
    > originally specified part. The center part is an acceptable
   substitute
    > part. The right hand part is the unacceptable choke. If you have this
    > part, do not fly the aircraft until it has been replaced. In addition
    > to the visual difference, you can determine which part by
   measuring the
    > resistance. The bad part has a resistance over 10 ohms. The correct
    > parts are much lower in resistance.
    >
    > We will replace the part for you for no charge except shipping
   cost as
    > specified in the warranty. This is a simple through-hole soldered
   part
    > that is relatively easy to replace. If you are qualified to replace
    > the
    > part yourself, we will send the correct part at no cost.
    >
    > Tracy Crook
    > Real World Solutions Inc.



   Tracy, for the record, I have the original choke. Jerry



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Tracy:   Where is this choke located? What do I need to do--do I pull
the cover off?  How do I  inspect my EC-2?  The picture shows which
choke(simply a resistor??) is correct, & which is wrong, but:  where do
I look; why measure their resistance if I can visually inspect?  If I
measure the resistance, must I disconnect any power source; what about
capacitors; diodes;retained charges; static electricity; etc... please
explain precisely to us non-EEs!
Tomorrow I am doing fast taxi testing;   maybe first flight.
                                                                  John
Andrich

Turbo-rotary Long-EZ

Camarillo, Ca