Towplane cooldown experiments?

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.

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.

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.

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.

There was an interesting article in the GASCO newsletter, Spring 2003.
Experiments were led in Lasham, with good results.
I have lost the english language original document, but I still have
an Italian translation.
What follows is an automatic translation back to english... Sorry!

Aldo Cernezzi



The English club of Lasham, with beyond thousand associates, is sure
the place where the greater amount of aerial towings is carried out.
The fleet includes six towings. In the four-year period of
observation, they have been completed 60,000 operations of towing of
gliders, it installs 8 new motors to you, and 28 substitutions of
cylinders have become necessary very, for some cracks tied obviously
to the thermal shocks. We remember that the operating life of a
Lycoming motor (the most diffused, give beyond 70 years, with variable
powers between the 150 and 260 HP) is equal to 2000 hours, that they
are equivalent to approximately 12.000 climbs until 700 meters, more
or less to all throttle, continuations from one fast reduction with
gas parzializzato in the attempt to reduce the thermal shocks. No
motor can be happy of a similar treatment. The first symptoms of the
cracks are the power decrease, perceived from the trainatore pilot in
the comparisons of it accustoms them quotas escape from the field, and
the less "round" noise. The cure is normally that one to make to
audit (weldings) heads and cylinders, or to acquire motors and/or
cylinders ricondiziona you. A palliative. In order to study the
problem seriously, an appropriate system of recording of the
temperature of ognuna of the single heads has been installed on an
aircraft, and a.termine of the period of test all give have been
analyze to you to you. Result: normal probes CHT have excessive
inertia and they do not show the real situation of the motor. The
posterior cylinders catch up the greater temperatures, of
approximately 15 °C higher. But above all, the operation to all
throttle carried to worrisome temperatures, from which too much comes
down quickly already with one modest parzializzazione of the gas; an
increase of the flight speed does not make that to get worse the
already critical picture. The Lycoming prescribes a rate of the not
advanced maximum cooling to 28 °C to the minute.

Solution
Executing several test second various procedures, has been able to
delineate one different operating modality: to the term of the climb
to full power with approximately 2550 rpm (and released the glider),
one reduces with calm and progressivity the gas in the period of ten
second ones, without to increase the speed and maintaining the
altitude or still climbing of some meter, with the motor that comes
down to 2400 rpm. In the next ten seconds, again rpm come reduced to
2300, and while the descent can be begun. Maintaining the 2300 turns,
and increasing the speed until to 110 kts , the temperature comes down
within some ten of second under the 200 °C, outside from the danger
threshold, and the airplane can be lead to the ground in the preferred
way. It seems also better to avoid the reconditioned motors , only
choosing new replacement parts of factory. With this new procedure,
the damages to the motors have been reduced drastically, and only very
rarely it must be proceeded to substitutions of parts before the
expiration of the TBO, than indeed often it has been extended until
beyond 2600 hours

If you wanted the English original, this article by
Phil Phillips of Lasham
was also in the August-September 2003 Sailplane & Gliding.
Back issues
available for sale via the contacts at www.gliding.co.uk

Helen
Editor, S&G

aAt 13:30 22 March 2005, Cernauta wrote:
There was an interesting article