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Posted for erosiak@postoffice.pacbell.net:
Tom, I believe what you are referring to is running a engine with a constant speed
prop over square (i.e. 26" MP- 2400 RPM). I still remember my first check out in a
then high performance aircraft a Beech Deb (yes I am admitting my age here). My
instructor was very clear that BAD things would happen if I ever ran more RPM's
than manifold pressure. In fact, he scared the hell out of me at the time stating
I could blow off a cylinder. That's true too, if you try a go around with the prop
back. But we have since learned that holding a bit more MP than RPM's moves the
piston rings out a bit and thereby wears the cylinders more evenly. The Cessna
Pilot's Association is the source of my enlightenment on this several years ago
(we owned a T210).
One more thing. If you haven't flown the constant speed aircraft you fly with an
instructor, and practiced engine out (idle) maneuvers you should. Peter Stiles,
Lancair's chief pilot (he wasn't then.....you still the only pilot Peter?) put me
through a great check out in my ES (TSIO-550, four blade MT). We saw 1500 ft a
minute down at idle which lowered to approximately 670 ft p/m down with the prop
back. Call it 700 to round it off. That is at 100 knots indicated. He pulled the
engine (to idle) in the pattern for me too, twice, and while I was nervous it
showed me I could make it (1500' patterns) from abeam the numbers and at about
7/8's through down wind at Bend, Oregon.
I think the best insurance we can buy is flying regularly, with a professional
attitude, and practicing with a qualified instructor at least once a year.
Ed Rosiak
ES N350EL
Tom Gourley wrote:
I'm certainly no expert on this subject, but I seem to recall an article that
also said the prop driving the engine is not a good thing. I believe the
explanation was that when this happens the pressure in the crankcase will be
higher than the pressure in the combustion chambers of the cylinders --
something that does not happen under normal operation of an aircraft engine.
(Car engines do this all the time but are designed for it.) If I'm
remembering the article correctly, in some cases this has been known to induce
ring flutter, which apparently is not good. As for de-tuning, I'm not sure
what the A&P was referring to.
Tom Gourley
tom.gourley@verizon.net
L2K #122
Banks, OR
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