Other than the usual weight, cost and complexity arguments, why did so little of this "technology" make its way to piston GA?

http://www.nasa.gov/centers/armstrong/F ... trong.html

https://en.wikipedia.org/wiki/Lockheed_YO-3

Cars used to be as noisy as airplanes, but in 2015 I would rather walk than take a three hour trip in a soft-top Jeep, which is still way quieter than an unpressurized piston airplane. I have always been curious why the aftermarket has been generally devoid of noise reduction STCs.

Am I the only one that hates wearing a headset for hours at a time?

It's why God invented Halos.

Somewhat off-topic, but when's the last time you rode in a late-model soft top Wrangler (JK)? The newer tops, as long as you have full doors, are pretty quiet even on the highway. I had a 2012 JK with both tops, and I think the soft top was just as quiet as the hard top. It's not luxury sedan quiet, but probably as quiet as any other rag-top convertible out there. Of course, I've had multiple Wranglers over the years (95, 2000, and the 2012), and the early ones were horribly loud, so I am willing to accept that my 2012 may have just seemed relatively silent

We've got a 2014 Acura MDX ,it is like a tomb,very quiet,very pleasant on the roadtrips.

Edward

try a Tesla if you want quiet

Presumably because the major innovation is reducing prop speed by 3x. Which makes the aircraft really slow (top speed = ~100 mph with a Continental IO-360).

Chris

In more noise-sensitive environments, this is available.

This is the price-list for the Gomolzig muffler system:

http://wp.gomolzig.de/wp-content/upload ... glisch.pdf

At times, it requires things like a 4-blade propeller, but the resulting planes are pretty quiet. In a Robin DR400 used for aero-tow, the 'whoosh' of the propeller becomes dominant over the exhaust.

[quote="Jake Stroud"] I have always been curious why the aftermarket has been generally devoid of noise reduction STCs./quote]

The regulatory hurdles are also $ignificant when compared to ANR headsets. If it is permanently installed in an aircraft; the vendor is gonna need: STC, AML & PMA. That takes a LOT of money and time ... which equals risk. And if it's a 135/121 ops, a TSO.

ANR headsets are a much lower risk "business" and significantly simplify/control the problem (variables). Ex: When I flew the Trimotor, My Bose Series II actually increased the noise (because the ANR maps were not engineered for three [3] unmuffled R985's).

The auto industry has looked at full cabin ANR technology off & on for 20+ years. Lotus and Harman have tried to build general purpose solutions, but it's a very hard problem to develop ANR map all the possible cabin configs.

Doug, I suspect that the bigger advantage is for those outside the aircraft, not inside. It's not exactly practical to give all the residents of Santa Monica a set of ANR headsets to reduce noise complaints near the airport

While this is certainly an issue, you don't see Southwest handing out O2 cannulas and headsets upon boarding. For the 99% that aren't GA pilots, it seems absurd to suffer through ambient noise by wearing $1,000 headsets. The ambient noise of say an ATR-72 or SAAB 340 is what the airplane flying public deems barely acceptable. I have always thought that it would take another 1,000 lbs of weight to obtain this noise level in a garden variety piston single, but it sounds like a slower, larger prop and a proper engine muffler would get there.

I appreciate the cost and riskiness of regulatory hurdles as the primary deterrent, I am just looking for a physics (weight) argument that prevents a low-noise unpressurized receip.

Thanks!

The weight penalty is that you lose a lot of horsepower by putting a muffler on an engine. To get the same horsepower, you'll need a bigger and heavier engine.

Also, you lose a lot of efficiency in the propeller. I suspect it's only practical in a relatively low horsepower and airspeed range.