Pawnee Cooldown Procedures

We have acquired a 260 hp Pawnee for a towplane and was wondering what
others are doing for cool down after the sailplane releases...


Thanks,

Tim Hanke
Adirondack Soaring Group
Saratoga Springs, NY

The following has worked at Skylark North in Tehachapi for around 30
years and was policy at Estrella when Horvath owned it:

Upon release, smoothly increase airspeed to around rough air redline
(120 mph, 100 kts indicated) while smoothly reducng power to remain at
about 2400 RPM. Rich Benbrook, one of my mentors and chief pilot at
Skylark for many years stated it succinctly: "Make the engine sound
the same going down as it did going up". This power setting is held
until in the pattern where the power is slowly reduced, the goal being
to be at flight idle and 70 mph over the fence. I also never get out
of dead-stick glide range of the airport.

If you are in a hurry to get down, roll in full back trim and maintain
whatever bank angle that gives you around 120 mph. This is a lot of
g's to pull all day but it is effective.

The engines at Skylark routinely make TBO and they experience no
cracked cylinders or other problems. We had a 260 hp Pawnee with CS
prop which added the complexity of managing the prop. We slowly
reduced pitch while reducing the throttle. CS props are not worth the
workload, cost or maintenaance issues, IMO.

Many schemes have been tested and ultimately abandoned for this KISS
procedure that works.

On Sep 17, 5:59 am, Tim Hanke wrote:
We have acquired a 260 hp Pawnee for a towplane and was wondering what
others are doing for cool down after the sailplane releases...

Thanks,

Tim Hanke
Adirondack Soaring Group
Saratoga Springs, NY

I believe the Lycoming guidance is to cool down no faster than 50
degrees a minute (CHT). To accomplish this, after release we continue
to fly straight and level for one minute, reducing power to just keep
the RPM at or below red line. Then we start a decent at 100-120 mph
reducing power gradually until we enter the pattern. This allows us
to cool down at about 25 degrees a minute. Works for us. No cracked
cylinder heads.

Olin Kane
Durango Soaring Club
Durango, CO

On Sep 17, 4:59 am, Tim Hanke wrote:
We have acquired a 260 hp Pawnee for a towplane and was wondering what
others are doing for cool down after the sailplane releases...S

Thanks,

Tim Hanke
Adirondack Soaring Group
Saratoga Springs, NY

Once the glider releases and I'm in my left turn I lower full flaps
and reduce power SLOWLY to 2400 RPM and begin to lean. Then during
the decesnt hold about 100-110 while making a series of steep S-Turns
to keep the rate of decent high at the relatively low airspeed. Also
during the decent I reduce power about 100RPM every minute untill
reaching 1900-2000 RPM. Things usually work out to 1900 RPM just as I
enter the pattern and I can adjust from there. The key to the whole
process is Flaps & S-turns = high rate of decent/higher power
settings, at a relatively low airspeed. I'm curious what the
operators with AgWagons are doing to keep thier Continental's warm as
they seem to be not quite as tolerant? Anyone know?

This technique of increasing airspeed and reducing
throttle to maintain a constant RPM (noise) and safe
cooling is the simplest and in my opinion works on
all tugs.
Robins, Rallyes, Supermunks, Pawnees all come down
fast at about ~ 110kt using this method and if you
plan your profile properly you should hit downwind
at about 500ft, the speed will fall into the flap range
and the first time you need to touch the throttle will
be around the turn onto finals.

KISS indeed

Gav





At 15:00 17 September 2007, wrote:
The following has worked at Skylark North in Tehachapi
for around 30
years and was policy at Estrella when Horvath owned
it:

Upon release, smoothly increase airspeed to around
rough air redline
(120 mph, 100 kts indicated) while smoothly reducng
power to remain at
about 2400 RPM. Rich Benbrook, one of my mentors and
chief pilot at
Skylark for many years stated it succinctly: 'Make
the engine sound
the same going down as it did going up'. This power
setting is held
until in the pattern where the power is slowly reduced,
the goal being
to be at flight idle and 70 mph over the fence. I
also never get out
of dead-stick glide range of the airport.

If you are in a hurry to get down, roll in full back
trim and maintain
whatever bank angle that gives you around 120 mph.
This is a lot of
g's to pull all day but it is effective.

The engines at Skylark routinely make TBO and they
experience no
cracked cylinders or other problems. We had a 260
hp Pawnee with CS
prop which added the complexity of managing the prop.
We slowly
reduced pitch while reducing the throttle. CS props
are not worth the
workload, cost or maintenaance issues, IMO.

Many schemes have been tested and ultimately abandoned
for this KISS
procedure that works.

Gav:

You can add Super Cubs and AgWagons to that list.

0-540 Lychoming engines are incredibly tough and durable but the one
way I have seen cylinders crack is by excessive leaning.

On Sep 20, 8:17 am, " wrote:
Gav:

You can add Super Cubs and AgWagons to that list.

0-540 Lychoming engines are incredibly tough and durable but the one
way I have seen cylinders crack is by excessive leaning.

Say it again, bro Grubb, "STAY IN DEAD STICK GLIDING RANGE OF THE
AIRPORT!"
The engine won't run on air or water. If it quits, or runs rough,
don't try to fix it in the air. Pick a landing spot first.
That spot will be very nearly 45 degrees down with the prop turning.
Most pilots don't know how to land off-field, so they will get up-
tight and either land long or short if its not their own airport.

I speak from painful experience,,, 3 different "good pilots" put down
3 Pawnees with heavy damage to the aircraft. Two out of gas, one with
water in the fuel...didn't check after refueling. One landed on a
road, signs tore the wings off.
The second one landed on the airport but stalled it high, almost high
enough to start a spin. Totaled.
The one with water was at 9,000 ft and tried to fix the rough running
engine by switching mags and pumping the throttle. It blew up and
caught fire. He landed in a field, hit a sprinkler line. A farmer
nearby had a fire extinguisher and put out the fire. It was contained
in front of the FIREWALL. Everything had to be replaced and a wing
major repair.
He overshot his landing.
In summary, Pilots are taught to pre-flight their planes, but often
don't. Most are taught how to talk on the radio, but not taught how to
land offf field.
Fred

"fred" wrote in message
ps.com...
On Sep 20, 8:17 am, " wrote:
Gav:

You can add Super Cubs and AgWagons to that list.

0-540 Lychoming engines are incredibly tough and durable but the one
way I have seen cylinders crack is by excessive leaning.

Say it again, bro Grubb, "STAY IN DEAD STICK GLIDING RANGE OF THE
AIRPORT!"
The engine won't run on air or water. If it quits, or runs rough,
don't try to fix it in the air. Pick a landing spot first.
That spot will be very nearly 45 degrees down with the prop turning.
Most pilots don't know how to land off-field, so they will get up-
tight and either land long or short if its not their own airport.

I speak from painful experience,,, 3 different "good pilots" put down
3 Pawnees with heavy damage to the aircraft. Two out of gas, one with
water in the fuel...didn't check after refueling. One landed on a
road, signs tore the wings off.
The second one landed on the airport but stalled it high, almost high
enough to start a spin. Totaled.
The one with water was at 9,000 ft and tried to fix the rough running
engine by switching mags and pumping the throttle. It blew up and
caught fire. He landed in a field, hit a sprinkler line. A farmer
nearby had a fire extinguisher and put out the fire. It was contained
in front of the FIREWALL. Everything had to be replaced and a wing
major repair.
He overshot his landing.
In summary, Pilots are taught to pre-flight their planes, but often
don't. Most are taught how to talk on the radio, but not taught how to
land offf field.
Fred


I've heard these stories from all around the country. We probably don't
hear about those that make good dead stick landings.

One of our local tuggies managed his "Out-of-Gas Adventure" with the local
FSDO director in the glider he was towing.

It reminds me that no one has crashed a winch.

Bill D

Bill Daniels wrote:
It reminds me that no one has crashed a winch.

Perhaps, but I was recently standing near a winch that nearly did, as a
result of inadequate wheel chocks and no tie downs. The winch ended up
about 10 feet away from where it started...

Marc

We have a PA-25-235, Lycoming O-540 with fixed pitch prop. At the last
rebuild we used the STC and pumped it up to 250HP. We tow from apx 3000MSL
airport on 110F days with no problems. In the winter (40-50F) we start
leaning just above pattern altitude. In the summer.. about 500ft AGL.

Technique, When the RPM starts to drop during the climb, lean to get the RPM
rise and leave it, your climbing so you will get richer with more altitude,
then lean again. Full power climbs. At release, Left turn and nose over to
about 80-100, depending on turbulence, and reduce power to maintain 2400rpm,
don't touch the mixture. Faster airspeed, no load on the prop, rpms
increase, slow reductions in power setting, 2200, 2000, 1800, etc into the
traffic pattern, plan the pattern so as to not have to level off and
increase power to maintain altitude. I normally enter the downwind at 1000ft
and may be down to 500ft when I turn a close in base leg, power back to
about 1500 rpm, airspeed slowing (nose attitude change) to 70 and 60 on
final. I don't touch the mixture until the next take off, or full power if a
go around is needed.

Other techniques include rolling to steep bank, and pulling G while
maintaining airspeed with nose on the horizon (rudder) control. Can get
descent rates of over 2000fpm, it helps coming down from a high tow while
maintaining cooling.

Others on their warm up flight will determine the mixture position to get
max rpm in level flight at normal release altitudes. Using the same leaning
technique in the climb, but will reset the mixture to the predetermined
position for the descent and using the "staged cooling" process. Again,
planning the descent into the traffic pattern to not have to level off on
downwind, a continuous descent to earth.

BT


"Tim Hanke" wrote in message
ups.com...
We have acquired a 260 hp Pawnee for a towplane and was wondering what
others are doing for cool down after the sailplane releases...


Thanks,

Tim Hanke
Adirondack Soaring Group
Saratoga Springs, NY