"Richard M. Martin" wrote:
There has been lots of e-mail lately about the pro and cons of enlarging
the
trailing spark plug hole in rotary engines for aircraft use. I just
received this attachment from Hayes Rotary Engineering with their views.
Richard
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R.E. Enlarging Trailing Spark Plug Hole
I have 27 years experience working with the rotary engine, including full
dynometer facilities in
-house. I am the largest remanufacturing facility for rotary engines in
the United States.
I have worked with NASA, US Energy Dept., US Coast Guard. I develop
single rotary applications
for pumps and generators and I have worked extensively in alternate fuel
for the rotary engine
which includes natural gas. Over the past two decades for experimental
aircraft only, I have
successfully opened up the trailing spark plug hole to allow for a TRUE
dual ignition system.
Dr. Michael Seals of Western Washington University, who heads up the
Vehicle Research Development
Program for the last three decades and myself collaborated and developed
the best running and
reliability redundancies of a TRUE dual ignition for experimental
aircraft. We have built over
100 engines with this modification. We have disassembled and inspected
engines after actual
aircraft usage and found no cracks in the spark plug holes, no
pre-ignition, nor destruction of
rotor housings.
Our findings were conclusive that there is certainly additional blow by
when the trailing spark
plug hole is enlarged, specifically at idle and low speeds.
Understandably aircraft application
does not rely on idle and low speeds for extended periods of time. Dr.
Michael Seals and myself
did not find any pre-ignition conditions when ran at higher Rpm's. After
two decades of building
experimental aircraft engine we have not seen any destruction to a rotor
housing.
The importance of this procedure is to have TRUE dual ignition systems,
allowing for enough
engine power if either the ignitions were to fail to be able to land the
vehicle safely.
Dr. Michael Seals and myself would recommend that if there is any concerns
about enlarging the
trailing spark plug hole, we suggest to have a switch that if primary
(leading) ignition were to
fail you can turn on the trailing ignition.
Without enlarging the trailing hole there will likely not be enough power
to land the aircraft
safely. We are troubled with the idea of someone using dual ignition on
the leading plugs only.
If a spark plug fouls then there is no TRUE dual ignition.
Thank you
Dennis Hayes
Owner - Hayes Rotary Engin