Dale
does your decent method work well for not shock cooling the engine?

Dale wrote:

In article ,



I fly turbo-charged 206 hauling skydivers so I make lots of descents.
The drill we use is to reach jump altitude at least a minute before the
jumpers exit to give us time to ease the power back and start cooling
the engine. We're at 13000 and pulling 30 inches with 2600RPM. I
reduce MAP to 27 inches (about 1" every 20-30 seconds or so), then
slowly reduce RPM (which will also cause a reduction in MP) until
getting 2100 RPM set. Then it's a further throttle reduction to 17-18"
MP where I lean for 6-8 GPH (setting up for the descent). If I timed it
right it's time to open the door, reduce power to 10-11" MP and lets the
folks out..as soon as they're gone close the door, power back up to 18"
and maintain the 18" throughout the descent, monitoring fuel-flow to
keep EGT up while maintaining top of the green or even into the yellow.
This gives descent rates of 2500-3500fpm...sometimes a little more if
you want to work at it.

We've been flying the turbo 206 a couple of years now with no engine
problems...our other 206 has been operated for about 6000 hours as a
jump plane and the engine goes to TBO or beyond.

Your idea of reducing RPM is the way to go if you need a rapid descent.
It allows you to keep the engine working to maintain some heat. Your
descents will be made from cruise flight and the engine will not be as
hot as after just making a best rate climb to 13K so there will be less
change in engine temp during the descent. For a cruise descent I'd just
push the nose over for the descent needed and reduce power to maintain a
safe airspeed. ALL power changes should be made smoothly.

Thermal cycles are certainly stressful for an engine but frankly, IMO
shock-cooling is BS. Much more damage is done by not allowing the
engine to come up to temp before applying power.....thermal stress
happens both ways. G

--
Dale L. Falk

There is nothing - absolutely nothing - half so much worth doing
as simply messing around with airplanes.

http://home.gci.net/~sncdfalk/flying.html