Hi Paul-

  We've run into a puzzler with our EC2 setup & since Tracy is away on a
  vacation for a few weeks, I thought I'd throw it out here & see if anyone
  has any bright ideas.

  The suggested wiring setup for the EC2 has switches that allow injector
  banks (primary or secondary) to be disabled in flight should one of the
  injectors fail.  The pilot rolls the dice and arbitrarily switches off
  one of the banks -- either the engine smooths out, or the engine goes out.
  Keep trying until one figures out the position for smooth running.

  I changed this to instead wire it to a single switch (pri-both-sec).
  Figured its easier to reverse the position of a single switch if the engine
  stops, vs messing with 2 switches.

  Here's the conundrum.  As part of our runup, it sure would be nice to
  confirm each bank of injectors is working by going from both to pri, and
  then from both to sec.  Seems like this ought to work too.  But, when we
  try
  this, what happens is:

      both to pri = engine continues running just fine.
      both to sec = engine dies.

  Before anyone leaps up with "Staging" as the answer, we have tried this at
  widely varied rpms -- from idle to WOT.  Always the same results.

  Sooo... in the absence of Tracy, anyone have any bright ideas??

  ** One possible reason.  In the manual, Tracy calls for the cold start
  terminal to be tied to ground when either of the injectors is switched off.
  The manual indicates this is supposed to double the flow rate of the
  remaining injectors to compensate for the missing pair.  I did not wire it
  this way (didn't have a 3-pole swich).  Have I just answered my own
  question??  I was expecting to find the engine rpms reduce (since there is
  no doubling) but not just die.

  Thanks everyone--

  Mark (Rocky Mtn High)


For those interested, I rewired the injector switches to match the drawing
in Tracy's manual and the system now continues to run regardless of failing
either the primary or secondary injector banks.  Clearly, grounding the cold
start line at the same time as failing an injecor banmk is necessary to
allow the EC2 to continue functioning using the remaining injector bank.

I had a conversation with Bob White regarding the loss of his rotary powered
BD4, and he was able to get back to the airport because of the injector
switches (although the photos look like he didn't quite make it to the
runway proper, unless it is a grass runway).

Mark (Rocky Mtn High)


There was a very nice paved runway there.  I bounced around on it for a
while before driving out into the weeds.  Mainly I made some bad
decisions after the initial problem which was stalling the plane way
too high on landing. As it turns out, Paul was there the next day and
helped me find some of the missing prop blades that had broken off and
ended up in a field next to the airport.

Mark, I know it was quite an effort to get two switches in there, but I
think you're better off in the long run.

Bob W.