Quieting a Pawnee

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My club is about to acquire a 250 HP Pawnee with no muffler and a 7 ft
climb pitch prop. We are anticipating some noise issues. I have seen
Pawnees in the UK with mufflers and four bladed (Hoffmann?) props and
which were eerily quiet.

Anyone know what these mods cost, in performance and money?

Richard Kellerman

[Frank Whiteley]

On Jan 24, 11:42 am, wrote:
> My club is about to acquire a 250 HP Pawnee with no muffler and a 7 ft
> climb pitch prop. We are anticipating some noise issues. I have seen
> Pawnees in the UK with mufflers and four bladed (Hoffmann?) props and
> which were eerily quiet.
>
> Anyone know what these mods cost, in performance and money?
>
> Richard Kellerman

Call Mile High Gliding. Not sure if there's a 250hp pitch
http://www.milehighgliding.com/common/propposter.doc

[Ian]

On 24 Jan, 17:42, wrote:
> My club is about to acquire a 250 HP Pawnee with no muffler and a 7 ft
> climb pitch prop. We are anticipating some noise issues. I have seen
> Pawnees in the UK with mufflers and four bladed (Hoffmann?) props and
> which were eerily quiet.
>
> Anyone know what these mods cost, in performance and money?

Borders GC has a small Pawnee which came with 150bhp engine, 4-bladed
prop and silencer. Yes, stunningly quiet - you could barely hear it as
it passed with a tow. The downside was that it couldn't pull the skin
off a rice pudding - fine for single seaters but could be a little
worrying with two seaters. It later acquired a two bladed prop and
160bhp (no STC for the full 180bhp in the UK) and lost the silencer.
Significantly better, but still not stunning for two-seaters. And I do
think the BGA should have acquired it and kept it hushed for use at
sites thinking of aerotowing and needing local permission.

I had a tow behind a Rotax Falke earlier this month. That was about
the same as the hushed Pawnee.

Ian

[Bill Daniels]

"Ian" > wrote in message
...
> On 24 Jan, 17:42, wrote:
>> My club is about to acquire a 250 HP Pawnee with no muffler and a 7 ft
>> climb pitch prop. We are anticipating some noise issues. I have seen
>> Pawnees in the UK with mufflers and four bladed (Hoffmann?) props and
>> which were eerily quiet.
>>
>> Anyone know what these mods cost, in performance and money?
>
> Borders GC has a small Pawnee which came with 150bhp engine, 4-bladed
> prop and silencer. Yes, stunningly quiet - you could barely hear it as
> it passed with a tow. The downside was that it couldn't pull the skin
> off a rice pudding - fine for single seaters but could be a little
> worrying with two seaters. It later acquired a two bladed prop and
> 160bhp (no STC for the full 180bhp in the UK) and lost the silencer.
> Significantly better, but still not stunning for two-seaters. And I do
> think the BGA should have acquired it and kept it hushed for use at
> sites thinking of aerotowing and needing local permission.
>
> I had a tow behind a Rotax Falke earlier this month. That was about
> the same as the hushed Pawnee.
>
> Ian

Well, just as a counterpoint. The soaring Society of Boulder, CO operates a
235HP Pawnee with the 4-blade Hoffmann prop and mufflers and it is very
quiet. However, it tows heavy 2-seaters just fine with density altitudes of
well over 10,000 feet at takeoff. Tows frequently reach over 12,000 feet
MSL. SSB also operates a 180HP Supercub which also tows well though not
quite like the Pawnee.

I think towing with a touring motorglider would not be a good idea at this
altitude unless somehow the 80HP Rotax could be replaced with say, 135HP.

Bill Daniels

Bill Daniels

[David Campbell]

Thanks, Frank.

Clicking our thumbnail Ad at the Lower Right Hand corner of www.ssa.org
will take you directly to our product information page. We hold the
FAA STC and dealer authorization from Hoffmann Propeller GmbH & Co.
KG.

Mile High Gliding, Inc.
Boulder, CO

[BT]

that's the difference between 150-160-180HP and 235-250HP

We towed with a 180HP Scout, not good out here in the summer 100F plus temps
at a field elevation of 2800MSL.
250HP Pawnee is much nicer, especially with a heavy Janus C with two up in
tow.

Tow a few 1-26s or L-33s, don't even notice them, even the 2-33, and then
latch onto the Janus... you know you've hooked onto some MASS behind you.

We are in the middle of the desert, we run 250HP on straight pipes and
standard prop.. noise is not an issue.

BT

"Ian" > wrote in message
...
> On 24 Jan, 17:42, wrote:
>> My club is about to acquire a 250 HP Pawnee with no muffler and a 7 ft
>> climb pitch prop. We are anticipating some noise issues. I have seen
>> Pawnees in the UK with mufflers and four bladed (Hoffmann?) props and
>> which were eerily quiet.
>>
>> Anyone know what these mods cost, in performance and money?
>
> Borders GC has a small Pawnee which came with 150bhp engine, 4-bladed
> prop and silencer. Yes, stunningly quiet - you could barely hear it as
> it passed with a tow. The downside was that it couldn't pull the skin
> off a rice pudding - fine for single seaters but could be a little
> worrying with two seaters. It later acquired a two bladed prop and
> 160bhp (no STC for the full 180bhp in the UK) and lost the silencer.
> Significantly better, but still not stunning for two-seaters. And I do
> think the BGA should have acquired it and kept it hushed for use at
> sites thinking of aerotowing and needing local permission.
>
> I had a tow behind a Rotax Falke earlier this month. That was about
> the same as the hushed Pawnee.
>
> Ian

[Peter Thomas]

The Black Mountains Gliding Club, Wales, UK have been
operating a 235 pawnee with a hoffman 4 blade prop
and gozzmogoli muffler for at least 15 years that i
know of. I seem to remember someone saying it lost
a few HP, but it will regularly haul a k21, Duo discus,
open Jantar, Nimbus 2 off a 350 yard downhill sloping
grass field as long as the ground is not to wet

The field is 900ft amsl

www.blackmountainsgliding.co.uk/ email the club, they
should be able to put you in touch with someone with
some more information, I dont do things with engines

Pete

At 17:48 24 January 2008,
wrote:
>My club is about to acquire a 250 HP Pawnee with no
>muffler and a 7 ft
>climb pitch prop. We are anticipating some noise issues.
> I have seen
>Pawnees in the UK with mufflers and four bladed (Hoffmann?)
>props and
>which were eerily quiet.
>
>Anyone know what these mods cost, in performance and
>money?
>
>Richard Kellerman
>