"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