There is some truth in many stories, but with any
turbocharged aircraft engine, allowing the temperatures and
clearances to normalize is critical. A turbo may be at
70,000-100,000 RPM, at 1400 degrees on one end of the shaft
and just a few hundred on the other. The cylinder heads may
be at 375-425 degrees and when you cut the power to idle the
heads shock cool, the turbo cools and that includes the
housing which can shrink faster than the impeller. The next
thing is that the housing and impeller make contact and
grind away. The turbo may spin for some time after
shutdown, without any engine oil pressure or flow. If the
pilot lands on the far side of the airport or stops on the
ramp/taxiway to allow the turbo to spin down and more
importantly cool, the oil will flow and cool the turbo
bearings and the oil won't fail (coke) extending the turbo
life. From 40-to 30 inches you can move the throttle
smoothly, but I would never go below 20 inches in-flight and
then not until I'd flown a minute at 25 inches. I used the
cowl flaps to keep the engine warm on approach and opened
them for all ground and T..O/climb operations. I used full
rich in the climb and I made sure to observe the TIT limits
as well as oil and cylinder temps.
I rarely flew any single airplane more than a dozen times,
but I saw many airplanes that were flown thousands of hours
by one pilot.

One thing about the Duke, I always made a modified soft
field take-off, using full back elevator until I got to
about 50 kts, then I'd fly the nose down to prevent a
premature take-off. The Duke sits with a negative angle of
attack and the engines will drive the nose down unless the
pilot lightens the load on the nose wheel. Take-off
performance is much improved with this technique.


--
James H. Macklin
ATP,CFI,A&P

--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.
some support
http://www.usdoj.gov/olc/secondamendment2.htm



wrote in message
ups.com...
| The Dukes that I saw, that were flown by civilian
trained pilots usually flew pretty trouble free to TBO.
|
|
| Another BS hangar myth destroyed. I've heard the same of
the Cessna 421
| from a few guys who've owned/flown them. Most of what I'd
heard
| previously about that type was the turbo'd & geared Contis
were a
| complete pain in the arse and would never make TBO without
new jugs or
| worse. I guess ya gotta question just how qualified
somebody is when
| they start talking trash about airplanes & engines, huh?
|
| Thanks,
| Wooly
|