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



As per the KISS requirement, p-port rotor motor. You could use the Holley 2
barrel carb. Beef up the tail as Paul mentions for the instance when something
distracts you and VNE gets exceeded. I have noted in life-- shit happens. More
power is always better and the throttle can always be pulled back to control
the speed. Climb and take off would be good. By the time you get there with
the install a source for an axial flow turbine for power recovery may be
figured out for better economy. The engines qualify like the old Timex watch
ads; take a licking and keep on ticking.

Dale Davies


I beefed up the elevators on my plane by using .005 thicker than stock skins
on the elevators.  I also used the extruded trailing edges so my elevators
have a 1" longer cord than stock.  There was a problem with skins cracking
on RV-4s at the aft end of the skin stiffeners, so I think my mods probably
addressed the problem.  Hope to have my plane back in the air by the new
year, I'm foaming up the underside and will be e-glassing the new air scoop
for the heat exchangers.  No fun working in a 36 degree hangar, but I gotta
get back up in the air.


Brian Trubee



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