Mailing List Message #65381
From: David Leonard <>
Subject: Re: [FlyRotary] Re: Mufflers
Date: Wed, 20 Nov 2019 08:22:34 -0800
To: Rotary motors in aircraft <>
I am really glad you brought up the Mistral incident, as I have been meaning to mention it too.  For what it's worth, my experience with mufflers confirms what many other have said.  The exhaust environment in rotary aircraft is very extreme and component  failure can be catastrophic.  I have tried several types of high end packing, and nothing survives more than a few hours.  300 series stainless tolerates the heat, but any welds on thin stainless have limited life.  I would be very suspicious of anything with complex innards like the Aero Turbine 2525.  Doing what Jeff Whaley did by adding perforations should be a must-do in my opinion.

Dave Leonard

On Wed, Nov 20, 2019 at 5:59 AM Marcus Wiese <> wrote:
Just remember the Mistral muffler event. The muffler caused the Piper Arrow  (?) with their rotary to crash after the internals blocked the outlet and led to power loss. It may have partially led to their withdrawal from the engine/PSRU market. To all our loss.

Sent from my iPad

On Nov 20, 2019, at 12:28 AM, Matt Boiteau <> wrote:

This is the Aero Exhaust 2525XL diagram. I have one, but left it in Canada. Will bring it back with me in Jan to try at taming the exhaust again.

- Matt Boiteau

On 2019-11-19 3:23:50 PM, Charlie England <> wrote:

On Mon, Nov 18, 2019 at 11:57 PM Andrew Martin <> wrote:

Kelly, I would if I had some, really did not expect it to work as I deviated from the design a bit. Will be back at airport on weekend to take photo, too late for construction photo. But nothing to it.

I read about the idea by Gary Schwarz in this thread, post #7 , post #58 for his testing and post #142 sums up his findings.
Someone on here may know him as he was doing it for a rotary. Mine is much shorter than his drawing below due to space constraints but the theory works.
edit: Ahh!!! deleted his picture as too big to post. it is in his post #7 mentioned above though.

That looks a lot like a simplified version (one less turn) of a standard automotive muffler.
The Aeroturbine tries to achieve similar effect (without the flow reversals) by using venturi effect to suck part of the exhaust around and then back into the central tube.


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