Aircraft silencers and mufflers

14 Jul 2006 Aircraft silencers and mufflers

Update: 20210918 I ended up removing the Eggenfellner Subaru engine and replacing it with a Lycoming. Any post that references the Eggenfellner or the Subaru should be there only as an example of what not to do. Listen to the designer, and install the engine that that designer recommends – which for the RV-8 is a Lycoming IO-360.

There is a lot of discussion about aircraft silencers and mufflers. Many feel that they don’t need them, since they just wear noise cancelling headsets to reduce the sound level in the cockpit. These are very effective. However, the bigger problem is the noise that the aircraft generates that annoys people on the ground. Not everyone likes the sound of aircraft, believe it or not!

I’ve spoken to residents of the area around a nearby airport, and the only complaint they have about aircraft is the noise. If we eliminate this issue, we’ll also eliminate most of the reasons the general population wants airports closed. Of course, the people behind airport closure usually want to buy the land cheap and develop it, so money is their motivation, and they will use whatever issues they can muster to get people to support closing the airport. Making our aircraft quiet will go a long way towards ensuring that we will always have an airport to use. I wish AOPA would wake up to this issue.

In many European countries, landing fees are directly related to the noise classification of your aircraft. Quieter aircraft means lower landing fees. This puts an economic incentive towards installing a silencer.

There are several ways to reduce the sound level from your engine. Mufflers or silencers are the best method. Others include reducing engine RPM, and adding a turbocharger.

A silencer can be built that will reduce the noise to basically zero. There are a lot of aircraft flying with these mufflers here in Switzerland. Some are under the cowl, and others are out in the airstream.

Another option is to buy a silencer from a company like http://www.gomolzig.de/

The most fun would be a home made muffler. Here’s a picture of one on a beautiful RV6:

Here is a link to the Tony Bingelis article on the “Swiss Muffler”: http://www.piteraq.dk/flight/muffler.html

Eggenfellner is working on a muffler that will go under the cowl. That should be interesting to see.

Whatever method you chose, be aware that the noise your aircraft generates is annoying people on the ground who want to close your airport. Everything we can do to reduce this noise impact will help aviation survive and thrive.