flyrotary@lancaironline.net Mailing List Archive

I agree completely, especially about the EGT.

Don't use off the shelf mufflers, designed for piston engine applications. Call Racing Beat or one of the other rotary tuners and buy one of their mufflers specifically intended for rotary racing applications. You don't need inconel, but you can't just grab any old muffler, even a stainless one, and expect it to not fall apart.

I really recommend anyone using a rotary engine in an aircraft to join the RX-7 forums and see what they are doing. There are some things you can do in a car that you can't get away with in an aircraft, but if they can't get away with it in their car, don't think it will hold up in a plane.

Same thing goes for cooling systems. Aircraft builders may have unique adventures in ductwork, but most of the rest of the problems have been dealt with and solved by the car guys. There are a lot more of them, and they've been at it longer.

On Sun, Mar 20, 2011 at 6:16 PM, Al Gietzen <ALVentures@cox.net> wrote:

Bobby;

Very capable handling of an emergency. We are thankful for that.

A couple of comments. It seems to me your EGT readings are suspiciously low. I run NA 9.0:1 rotors in my 20B, and the peak EGTs are up around 1675F. At rich climb they are maybe 50 less; and I lean to just under 1600 for lean cruise. I’m measuring about 2” form the port. So maybe your muffler is seeing higher temps than you think.

We’ve heard of a number of muffler failures on this list. It troubles me that some of you are taking the risk of flying an off-the-shelf muffler; the internal failure of which can cause blocking of the exhaust flow. It seems to be a known risk of an off-airport landing. There are options. Yeah; a custom inconel muffler (or some heavy walled 321) will set you back some bucks; but . . .

Al

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bobby J. Hughes
Sent: Sunday, March 20, 2011 3:03 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Forced Landing.

It’s supercharged. My EGT’s never get over 1540F. Most of the time they run in the 1400’s. I am also not 100% convinced the muffler was to blame. But it seems to fit the symptoms. I can’t confirm the muffler was blocked after landing while trying to taxi. One theory is the exhaust pressure was enough to keep all the little pieces in place until after shutdown. Then towing the plane shook everything loose. Wonder if I could talk Mark S. into sticking a banana in the tail pipe on a full power ground run to duplicate the problem? This is my second HP-2 muffler in about 100 hours of engine time. It may have 25 hours of flight time. The first one was inside the cowl and angled down and back. It lost all the mesh and cone material. The angle may have helped some of the loose material exit the muffler. But it’s all speculation.

Bobby

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bryan Winberry
Sent: Sunday, March 20, 2011 3:25 PM

To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Forced Landing.

I believe he is supercharged, not turboed.

BW

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bill Bradburry
Sent: Sunday, March 20, 2011 5:11 PM

To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Forced Landing.

Bobby,

That is an excellent job of both flying and troubleshooting to discover the cause of the problem. I am wondering why you have a muffler if you have a turbo?

My Hushpower is welded in and up inside the cowl. I would not be able to see inside if or remove or replace it with the current setup. This incident has really made me start to think about the muffler.. Thanks for the great report!

Bill B