Pawnee PA-25 for Towing
Michael Exner
have considerable experience with the PA-18-180, but little with the
Pawnees. We operate from a 5000 ft field and tow to 8-10,000 ft msl fairly
often. Would appreciate feedback from community on buying experience,
converting from agricultural use, and actual towing experience. Some
specific questions:
1. Engine? 235 vs. 250 vs. 260HP?
2. Prop? Fixed vs. CS?
3. Airframe? B vs. C vs. D model?
4. Center vs. wing fuel tanks?
5. Factory vs. Hutch metal wings?
6. Best wing spar AD solution?
7. Real cost to buy (purchase + deferred ag use maintenance)?
8. total operating cost per hour?; per round trip tow?
9. performance compared to PA-18-180 or Scout?
10.Pilot training & checkout issues?
Thanks, Mike
303-817-2097
VNE
sea level, they do great. More power, more better, faster turn around.
235 fixed pitch pulls a full G103 at around 300 fpm at this density alt.
At sea level, more like 800-1000fpm I think. The 235 fixed gets pretty
weak above 8K or so.
2. Constant speed prop is obviously better,, fixed pitch will work.
Most with the constant speed pull it back on takeoff anyway for noise
consideration
4. Wing tanks are preferred by the pilot for reduced risk of burning to
death in the event of a crash.
10. Easy to fly by anyone with tailwheel time. Issues are,, single seat
socheckout is solo (no big deal) and
the slopeing nose is worth knowing about. (again, no big deal)
Great towplanes unless you just gotta have a training wheel under the
nose.
Cut out and remove the whole hopper to lighten it.
less...@aol.com
Mike, I fly two Pawnee's from a grass strip that is at about 300' MSL,
thus I cannot address many of your performance concerns. I will give
you my opinion of the Pawnee as a tow plane. One of the Pawnee's is a
180 HP with factory wing. The other Pawnee is a 235 HP with Hutch
wing. The 180 HP Pawnee works very well for us for all but the
heaviest ships and burns almost half the fuel of the 235 per tow (per
20 tows the 235 uses 40 gal, the 180 uses 25 gal). The 235 has much
better cycle times. The climb rate is of course better, but the Hutch
wing also allows a better descent profile. The high lift Hutch wing is
also high drag at the upper airspeeds. We fly our descents at 5 to 10
mph below the yellow arc. This is about 15 mph faster on the Hutch
wing. The Hutch wing requires very good airspeed control during
landing or it will float, and float, and float...
IMHO, Once you have towed with a Pawnee, you will never want to tow
with anything else (well, at least not a non-ag plane). The Pawnee was
designed as a working plane. It has very good flight characteristics,
visibility, and performance.
As far as pilot training goes, we make sure out tow pilots are
proficient in just about any other tailwheel airplane. The more
demanding the airplane the better, but just about any other tailwheel
airplane is more demanding than the Pawnee. Once we have confirmed
they can fly a tailwheel airplane, we give them a ground briefing and
tell them to go fly a little. In each of the two planes, we have them
go to altitude and do stalls and basic air work then 5 takeoffs and
landings. Of course we cannot do tow pilot signoffs in the Pawnee, but
we have other towplanes available for that purpose.
--
Les Sparks
less...@aol.com
http://members.aol.com/lessparks/
http://members.aol.com/woodglider/
Sent via Deja.com http://www.deja.com/
Before you buy.
Michael
> Our club is considering the purchase of a Pawnee for a second towplane.
We
> have considerable experience with the PA-18-180, but little with the
> Pawnees. We operate from a 5000 ft field and tow to 8-10,000 ft msl
fairly
> often. Would appreciate feedback from community on buying experience,
> converting from agricultural use, and actual towing experience. Some
> specific questions:
>
> 1. Engine? 235 vs. 250 vs. 260HP?
More power is better. My towing experience is roughly at sea level
out of a 3200ft obstructed strip and I find that when the density altitude
hits 2000 or so, pulling a glass two-seater out gets exciting with a
180 hp. The 235 is very comfortable - plenty of excess performance.
I would guess that if you are doing OK with the PA-18-180, you
should do just fine with a PA-25-235.
> 2. Prop? Fixed vs. CS?
Sort of pointless to go CS. Just put a climb prop (maybe a seaplane
prop) on it and pitch for maximum allowable static RPM. Won't cruise
for beans but you'll bet 90% of the takeoff performance and 95% of
the climb performance of a CS prop. Do you really want the
maintenance headaches of constant speed? With the faster glass
ships you really won't be able to tow slow enough to take advantage
of CS, and with the lighter slower ships you won't need it.
> 4. Center vs. wing fuel tanks?
Nice thing about the center tank is the fuel gauge. Be aware that
it's repeatable but not accurate. Wing tanks are safer in a crash.
> 5. Factory vs. Hutch metal wings?
I prefer the way the metal flies on landing - lots of low speed lift,
less critical on the flare, easier to land. But remember - if you
ding it, fixing it is expensive. Fabric patches are cheap and
easy.
> 9. performance compared to PA-18-180 or Scout?
Even a 180 hp Pawnee outperforms a 180 hp Scout hands down.
The 180 hp Pawnee is merely marginal, but the 180 hp Scout is
downright scary when towing a heavy two-seater in the heat of the
Texas summer.
> 10.Pilot training & checkout issues?
None worth mentioning. We consider 250TT and 25 tailwheel
to be enough. I started with just the absolute minimum tailwheel
time and found it to be the easiest possible tailwheel to fly. It's
far easier than the Cub, Champ and likely anything else people
are likely to have experience in. An hour of airwork and landings
and even a minimally competent tailwheel pilot is ready to tow
in it. Remember, it's built for ag work and is designed to be
flown by tired pilots - something you really get to appreciate.
Michael
Olivier Plaut
My club has a PA-18-180 and a Pawnee D 235, operating at 2200' elevation. The
RWY is 2600' long, so this a critical point on hot summer days.
The key-point is noise. We had an excellent metal fixed-pich 2-blades prop on
the 235 HP, but we had to change it to a 4-blades and to put a muffler on the
exhaust. This reduced performance. This winter, the 235HP comes to 2000 hours
and we are changing it to a 250HP with CS. One of the reasons is that the 250
will better accomodate a non-leaded fuel, when 100LL will not be available
(and unleaded is far cheaper in Europe: for 100LL we pay almost for a liter
what you're paying for a USGAL!!).
The noise is again the critical point: actually, the engine is a 260HP running
at 2700 RPM, but this makes it very noisy. To use it, you have to be sure that
EVERY pilot will reduce RPM just after clearing obstacles, and this is
difficult to make sure in a club. So we choose to 'reduce' it to a 250HP
running at 2525 RPM with a 3-blades CS prop.
Wing tanks are safer, but the capacity is the same as in the super Cub, with 6
cyl instead of 4! Endurance is not large. We don't tow over 90 minutes before
refueling.
The Pawnee is THE towing plane and once you work with it you'll never want to
go back to the Cub...
Olivier