Mark, what model MT prop/diameter and controller did you install and do
you
 remember the cost or did it produce selective amnesia?

 Also, some folks report their MT electric control system has a
significant
 lag period between input and pitch change, especially in pattern, etc,
 although the last time I flew one with a rotary engine I don't remember
it
 being that bad.  You?


 Steve Beckham

Steve,

It has been years since I ordered my M/T prop.  I would have to dig out
the
paperwork to find the model no.  It was a 76" as is recommended by
Lancair.
I bought it through Jim Ayers who was doing a group buy, so I got a pretty
good price (relatively speaking).

I normally fly it with a combination of pitch and throttle, unless on long
x-country flights.  Then I normally fly WOT at 1700 prop rpm.  This gives
me
around 5200 rpm on the engine and 158-160 TAS with a fuel burn of 11.3
gph.
If I need to go faster, I change to 1900 prop rpm.  If I really want to go
fast (190 TAS), and burn lots of fuel (20+ gph), I go to 2100-2200 prop
rpm
with WOT.  I don't fly like this very often, but its nice to have options.

You're correct in that the electric controller is slow (slower than a
hydraulic), but you get used to it.  The method I've developed for landing
is this... a few miles out from the airport I adjust the prop to 1900,
wait
for the engine to speed up and settle in to the new rpm, then switch the
prop controller from AUTO to MANUAL and then fly it like a fixed pitch
from
there all the way to touchdown, adjusting speed with the throttle.  At
this
setting the 20b has plenty of power to do a go-around if needed.

My takeoff setting is 2200 prop rpm.  With slippage, I'll see 7200 rpm
initially and then after a few hundred feet of ground roll it will bite
and
rpm will drop down to about 6800.  (Because of this, I bring the power in
slowly, unlike a Cessna 152/172). This airplane really accelerates and
requires a bunch of right rudder to keep it on the centerline.  When clear
of the 50ft. obstacle, I start dialing the prop back slowly until I
finally
reach my cruise setting of 1700/5200 rpm.  Last flight I saw 1600-1700 fpm
climb rate.  Not too bad for a 2100 lb. 4-place airplane running an auto
conversion.  I hope to see 2000 fpm climb rate once I get my new p-port
engine done.  ;-0

Mark S.



--------------------------------------------------------------------------------

Very good information Mark.  Once we got the power up on even the two rotor
engine years ago we found that some sort of adjustable pitch propeller was
essential for realizing the full efficiencies and potential of the engine.
You could fly and fly well with a fixed pitch prop but there were very large
compromises. The deal-breaker for most folks with the MT and other prop
options at this point appear to be primarily cost.  And prop tip velocity
and efficiency is limited to some degree by the inherently thicker tip.

Steve Beckham

I remember the time to climb contest at Sun & Fun and you guys changed the prop for the time to climb contest :)

As I recall your rotary powered RV airplane running NOS with Allan Tolle flying set the all time un official record from a dead stop to 3000 feet in less than one minute. Of course most of your competitors were using NOS as well. I keep forgetting. Was that an RV4 or RV3?

Paul Lamar