I am finally, after 10 years of false starts, soon to begin construction of
an RV9A.  Even though it is rather soon in the process, I have been
struggling with engine selection.  Over the years I have been considering
the Mazda Rotary as the number one choice on my list.  I have had experience
with a shock cooling situation in the past that helped me make the Rotary
decision.  I do not want to spend the money for an "old" technology engine
that very well may fail me and or cost me even more down the road fro
mandated factory error repairs.  Besides, I am one who believes completely
in the KISS principle.

My question to all and you Paul is this... Since Van's limits the 9A
to 160HP, what engine series would you recommend I begin searching for and
what problem might I run into with this engine during conversion?


Tom H

I think Van has engine weight more in mind than HP.
He assumes you are going to use an AC engine.

He also feels his biz is less threatened if somebody buys the engine from
him and assembles the aircraft exactly like an Ikea furniture kit
and exactly according to the instructions.

Tab A in slot B :) IMHO that amounts to a ploy to get around
the certified aircraft cost and rules. That is also why the
EAA no longer mentions the word "experimental".

Lets us say for the moment you decide to put in a 250 HP rotary
in that weighs the same as a 165 HP Lyc.

What is the downside?

None!

You don't have to use more than 165 HP.

The 165 HP NA Lyc engine becomes 115 HP over 12,000 feet.
The 250 HP NA rotary engine becomes 175 HP over 12,000 feet.
Flat rating without a turbo.

Van's airplanes have strict VNE's. Bad things happen when the VNE is significantly
exceeded. Tails have fluttered and come off. The 9A tail has probably been
improved over the earlier models. Never the less don't exceed the VNE.

It is true. People have gone faster in various competitions with Van's airplanes
than the VNE but they have beefed up the tails in most cases. IMHO I suspect
part of the problem is the vibration characteristic of the aircraft piston engine.
I know engine vibration enters into the equation for flutter. The rotary is much
smoother.

Another factor, for some strange reason, is composite designs
do not seem to have this VNE/tail-flutter problem. IMHO I suspect this is due to
the higher damping characteristics of composites over metal. Carbon fiber movable
control surfaces would have a better stiffness to weight ratio and require less
balance weight. On the other hand there are more RV's out there.

Paul Lamar


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