"GeorgeB" wrote

I'd certainly like for a citation on that one. While neither a pilot
or a builder, I follow the Sonex site; their plane with the Jab 3300,
at WOT, greatly exceeds limits.

You are right on that, I believe. At one time it was stated as WOT.

As they understand it, the rule is
"Maximum speed in level flight with maximum continuous power (Vh) of
not more than 120 kts (138 mph) CAS under standard atmospheric
conditions at sea level." The word "continuous" is in there ... the
3300 Jabiru is specified at 2750 RPM max continuous which keeps things
legal. Many of the owners report significantly higher capability ...
and maximum RPM is specified, IIRC, at 3300.

I think you have the key here, when you say the Jab engine is rated for 2700
continuous. (by the manufacturer) That is in line with other direct drive
RPMs. The higher RPM's can be done with that engine, but just like the
other major direct drive makers, you can not run them for long at those
speeds, without some consequences.

If you took a Lycoming, and said you were going to limit it for continuous
operation at 2,000 RPM, that would not fly for the sport plane restrictions.
They (the FAA) all know that this engine can run much faster than that, with
no harm. So you are told to try again; no dice.

It seems if you have a homebrew engine, you have an advantage, because you
are the one that will set the continuous operating RPM's. That is my take,
anyway.

Sorry about the WOT bit. Best be having the WOT close to the continuous
RPM, if you want to have a chance of passing, IMHO.

A lot of these things are unknown, since the envelope has not yet been
pushed, and case precedents have not been established, yet. We will have to
wait and see how much they will let us get away with. g
--
Jim in NC