if we are waiting.. I run it at idle.. about 800rpm... not to wait more than
3 minutes, if the glider is already on the runway.. if they are not pushing
out for another 5 minutes.. I shut down... issue with ground idle is more
fuel burn or fouled plugs if set full rich

No cowl flaps on the Pawnee.. it is wide open.. and we have a fixed pitch
propeller

Everything forward for take off, full throttle and full rich, we recommended
leaning for max RPM during the climb... in the summer we are leaning before
we get above pattern altitude, airport elevation is 2833MSL and ground temps
are will over 95F.. at tow release, I reduce power to 2200RPM, and nose over
to about 80-100knts (standard turns of course), which pushes the RPM back up
to redline, reduce power again to 2200rpm, which if in level flight would be
about 2000rpm. Power, flight path and speed are controlled in the descent to
reach the downwind at just above pattern altitude, no level off, reduce
power to about 1700rpm, below 80knts, flaps, and 60knots is normal on final
and about 1500rpm, if all the planning works out, we do not increase power
after it has been reduced.

Same idea as "Stage cooling" a high powered Bonanza or Turbo Seneca after
cruising at altitude for hours... so in essence.. we are following guidance
or procedures to avoid shock cooling the engine.

But back to the original post.. I don't think thermocouples and digital
microscopic readouts are needed in the airplane, need to get eyes outside,
make sure all engine baffles are in place and do what has worked for the
last 18 years.

BT

"Bill Daniels" wrote in message
...
What do you think of the idea of running the tug's engine at 1000 - 1200
RPM
while waiting on the ground for the next glider to get ready? What do
you
consider 'proper' leaning procedures?

BTW, I've read Kas Thomas's "Aircraft Engine Operating Guide" and Lycoming
white papers on the subject but it seems many tug operators come up with
their own techniques.

Automatic cowl flaps on tugs has always seemed like a good idea.

Bill Daniels

"BTIZ" wrote in message
news:SqL%d.73111$Tt.48796@fed1read05...
ahh.. the dreaded "shock cooling" problem for tow planes..
we have operated tow planes in the desert for 18 years with out a engine
problem that could be contributed to "shock cooling"... I agree, power
reduction and cooling of the engine is best for engine life... full power
climbs and "reduced" not idle power descents.. people worry about shock
cooling and then they slip it for 2000ft altitude loss to get down,
totally
disturbing the airflow through the engine..

more important is proper leaning procedures during full power climbs and
let
down procedures that don't stress the engine and foul the spark plugs..

BT

"dhaluza" wrote in message
oups.com...
Anyone interested in doing additional research on towplane engine
thermal stress may be interested in this 4 channel 24 bit USB
thermocouple datalogger for ony $395:

http://sine.ni.com/nips/cds/view/p/lang/en/nid/13880

It does need a host computer, so you would have to connect it to a
laptop PC. With it you could monitor CHT and EGT thermocouples with
very high precision.

I don't have any commercial interest in this, just ran across it and
thought I would pass it along.