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<< Lancair Builders' Mail List >>
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To Bill, N7WB:
After the first couple hunred hours on my 235 with fixed pitch wood props (I
tried two different makes) I switched to a MT electric CS unit. I wouldn't
trade it for anything!
Here are just some of the reasons:
1. To get a reasonable cruise prop, the pitch was so high (about 74 -78", if
I remember) the best sea-level take-off RPM I ever saw with my Lyc O-235-L2C
with the hi-compression pistons, was no more than 2350. I had more than my
share of rejected take-offs in situations where I needed everthing I could
get for take-off (high, hot and heavy). Obviously, the low RPM didn't allow
the engine to produce enough HP at the time where it was needed most (HP
[approx.] = Torque x RPM / 5200 ), resulting in some very "exciting"
situations, but situations I would rather not have experienced!
2. Even with the relatively high pitch, to use the airframe's speed range, I
needed to cruise at 2600+ RPM while I prefer to cruise at around 2500. A
small gripe maybe, but a consideration, nonetheless.
3. Last, but not least, I had two wood props (from the same manufacturer)
fail in use! One developed a 6 - 7 inch radial crack about 8 inches in from
one tip, and it's replacement shed most of the rear lamination after just a
few hours of use. Fortunately, it happened just as I was about to rotate for
take-off and I aborted with nothing worse than needing clean shorts!
The MT prop allows my engine to develop just under max RPM (my engine is
placarded for 2800 max continuous and I get right at 2750 for take-off - I
have an electronic tach with digital read-out so these numbers are quite
accurate).Take-offs that were a real struggle with the wood props are now
typically non-events. The only caveat with the MT electric prop is that the
pitch change mechanism is a highly geared, small electric motor (most likely
to keep the weight down) and as such, the prop reacts a bit slower than
we're used to with a hydraulic prop. As a result, one has to be gentle with
the throttle when bringing the power in, particularly on T &G's and
go-arounds to keep from over-speeding the prop and engine. No big deal, you
just have to take an extra couple of seconds when going to full throttle -
it's easy to get used to.
The hub and prop combination is somewhat heavier than the extension and wood
prop - I think the paper work says the MT for the 235 weighs in around 27
pounds. My weight and balance is still acceptable without moving anything
else around in the airplane. I do notice using a bit more nose-up trim on
landing, of course, but the airplane is closer to mid-CG when I have a
passenger and some luggage aboard.
Hope this answers some of the questions posed. I think it's worth it if you
can go this way.
I'm at the Coeur d'Alene airport and a member of the Spokane EAA chapter. If
you get over this way, stop in if you need more information.
Dan Schaefer
Early LNC2 N235SP
Phone: 208-762-1104
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LML website: http://www.olsusa.com/Users/Mkaye/maillist.html
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Please send your photos and drawings to marvkaye@olsusa.com.
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