Ed Anderson wrote:
Hi Paul,
You may want to pass this on to the list in the interest of safety.
I am happy to report another Rotary Glider event (not me this time {:>))
turned out
safely. The builder/pilot found himself in his GlaStar with an engine that
would not
respond to throttle advances and by sticking to the fundamentals (fly the
aircraft) made a safe engine-out landing at a nearby airport.
The diagnosis turned out to be the infamous resistor in the base of the
leading Mazda Ignition module. As Tracy Crook points out in his conversion
manual and has mentioned several times in forums, this resistor is likely
to fail in
aircraft use. He had one fail, I personally had one fail and this is at
least the third one to fail I am aware of. If you are using Tracy's EFI
then you simply
fly home on the trailing ignition (you do check both before take off don't
you?).
However, if you are using or thinking about using an after market EFI, they
all require a trigger signal to drive the fuel injection circuit. I
initially used an aftermarket unit by name of HALTECH and this more recent
event uses the Holly Throttle body injector system (two large injectors in
the throttle body). The trigger signal is normally taken from the ignition
system and I drove mine from the negative side of the leading ignition
module successfully for approx 40 hours. Fortunately, I was on the ground
doing a run up when the engine died. The leading coil was not functioning
and the light bulb lit up - with no lead ignition module I had no injection
trigger signal so even thought my trailing coil was still providing spark -
I was injecting no fuel. The same thing happend in this event with the
Holly Throttle Body injection unit.
The problem is the 0.3 ohm resistor in the base of the leading ignition
module is apparently inadequate to handle the continous high rpm ignition
load hour after hour. It appears to overheat and open up. The fix is to
install a resistor with a higher wattage rating. I use a 10Watt resistor
situated on the outside of the case( not enough room in the case for the
larger wattaged size) and Tracy recommends a 25watt capacity. I might
suggest wiring two ten watt sizes in parallel for the additional redundancy.
I modified mine and now have 140 hours on it with no further problem, I
suggest you do the same BEFORE you fly. If, however, you are using either
ignition module to provide an external trigger signal to an aftermarket fuel
injection system
then I very strongly suggest that you also rig a SPDT (or use one side of a
DPDT
which ever you might have - it can be a miniture toggle switch) so that you
can select either ignition module to drive you fuel injector by the flick of
a switch. I used the yellow wire (the Tachometer) lead from the trailing
coil and the negative (black wire ) as my two sources with the switch wired
so that in the up position it uses the main source and down the emergency
source.
My HALTECH eventually died (again, fortunately on the ground) and I was
happy to switch to Tracy's EC2 unit with its redundancy and robustness and
so no longer need an external injector trigger source. Again if you have
Tracy's Fuel Injection Units then I recommend you modify the resistor in the
leading ignition module, but of course you do not need
to concern youself with an external injector signal.
As an aside, the Holly unit apparently has some sort of "Limp Home" mode as
even without the injector signal from the ignition unit the unit would
apparently just dump fuel into the manifold and enable the engine to run
(very rough) up to 3400 rpm then it would stop injecting fuel. 3400 rpm in
an automobile will probably get you home, but is not adequate for many
airborne
operations.
Flying experimental aircraft, powered by experimental engine installations
by experimental pilots occassionally reminds us of the aviation priority
three - Aviate, Navigate and Communicate. If you don't pay adequate
attention to the first, you won't be around to worry about the other two.
FWIW.
Ed Anderson
Matthews, NC
RV-6A N494BW
eanderson@carolina.rr.com
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