Good to see (hear?). Noise is a significant issue with a lot of GA airplanes - tolerance for noise is much lower than it was last century.
Most people that are annoyed about overflying aircraft wouldn’t even know they were there but for the noise - they don’t look up like most of us do!
Now others need to do the same.
A light aircraft (Cessna type), travelling over a house, can be heard for a minute or two, depending on wind, before it arrives, maximum noise for 20 seconds and then another minute or two afterwards.
Which is why people think there are far more aircraft in the sky than there are.
I remember a huge local council row over Bournemouth in England over a request for more training flights in the early 1990s…
Residents filled out noise disturbance forms and flyers filled out logs of where and when they went.
The residents put 10 times more aircraft in the sky than existed, all in good faith as they heard them at different times.
Aircraft noise is much more intrusive than road traffic noise.
And the changes: better silencers, sound absorbing foam in engine compartment and quieter propellers are hardly revolutionary.
The first two became obligatory for cars in most parts of the world 30 years ago.
For PA 28 aircraft an STC exists taking down the noise by abt 65 % and increasing fuel efficiency by 8 %. All data verified in the STC.
You will find more at Hjelmco Oil & Environment
Thanks for sharing this Lars. I’ve written a pretty comprehensive plan for moving to the Whisper Sling shortly after they started discussing it last year (there’s several videos on it). I’ve been asking far and wide for any other examples of someone building a trainer that meets a quieter standard. This is the first one I’ve seen. Definitely a bummer that it never gained much traction. It’s definitely needed!
Brian
I developed the noise reduction STC some 30 years ago together with my second generation of unleaded Aviation Gasoline. Lycoming approved my unleaded AVGAS Hjelmco 91/96 UL already year 1995. For using my unleaded AVGAS you do not need any STC in EASA territory. It is a drop in fuel. We have the fuel at about 100 airports in Sweden now for 30+ ears. With the UL AVGAS and the STC for noise reduction it is the most environmentally ?? friendly GA aircraft in the World.