Alan Tolle wrote:

Response to Peter Cowan/Lexi Cameron:

I am concerned about the problem of aft center of gravity because a number
of my RV series aircraft building friends have perished in stall/spin
accidents directly attributable to this condition.

The RV series aircraft are good candidates for rotary engine conversions,
but consider two points.  First, both  the -4 and -6 were designed around
the Lycoming 0320 engine.  Installing a lighter weight engine moves the CG
aft.

Second, think through your statement about the propeller again.  The
propeller on the aircraft stays in the same place, and I am presuming the
use of the standard cowl.   The weight of the rotary engine conversion is in
the engine itself, not in the gear box bolted to it. Therefore a long gear
box moves the engine weight aft, which moves the center of gravity of the
aircraft aft.

Both the RV-4 and -6 are well known to be aft CG sensitive when loaded.   An
intelligent builder will do all he can to keep the weight forward.  An
intelligent pilot will do the full load calculation before he launches, and
will know that the CG moves aft as the fuel burns off.

Certainly aft CG aircraft can fly.  They can also bite.

I think you misunderstand the term "performance" as it relates to an
aircraft.  You note that you fly a McCauly constant speed propeller.  When
you go to wide open throttle for a take off at sea level, what percentage of
rated horsepower do you expect  your engine to produce?  100%, isn't it?  We
are not talking about racing here, just a simple take off.  How well do you
think your aircraft would take off or perform if you replaced your Lycoming
or Continental with an engine capable of operating at only 75% of its rated
horsepower at sea level due to, for example, over heating problems at 100%?

Some of us really believe that the rotary engine is a viable replacement for
Lycomings and Continentals.  But the rotary will never make it if the rotary
can't produce power just like the engine it is replacing --- 100% every
time, all of the time, at sea level.   A few of us (I don't think I am the
only one)  are working to reach that goal.  The race track is the best place
available to test progress.   I do not consider myself a racer.  I do
consider myself an engine developer and tester.

I have no problem with the people who just want to get out there and fly.  I
enjoy that too.

Amen Allan.

Paul

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