Flying Silently (Part 1)

September 26th, 2013 by John Petersen

Some years ago I went down the hall in the E-ring in the Pentagon to see the then 3-star admiral friend of mine who ran all of naval aviation.  At one point I got around to asking him what his biggest problem was at that time.  I was surprised at his answer: neighborhood encroachment at his naval air stations.  What he was telling me was that as civilians built houses closer to his airfields the noise from the aircraft were causing a problem with the homeowners and they were raising a ruckus with their politician friends . . . and that was causing a significant issue for the Navy all over the world.

It reminded me of when I was a nugget junior officer living on base at the Alameda Naval Air Station in the middle of San Francisco Bay.  Every time the repair facility would do an engine test on the J57 engines for the A-3 aircraft that I then flew, even though they had the test stand sticking as far out in the bay as they could, it rattled the windows in the bachelor officer quarters such that all conversation would stop for the 3-5 minutes while they ran the engine through its high-power run-up test.

I was young then and didn’t think much about it.  If I had, I may have had the bumper sticker opinion that all that noise was just the “sound of freedom” as I’ve heard some old soldiers referring to the disruption produced by helicopter operations near residential areas. Maybe it’s just my problem, but I’ve never equated patriotism with pollution, although I guess some people do.

It’s interesting that we in the GA business have such a low sensitivity to the noise that our machines produce.  What other job can you think of where a goodly number of the profession puts on a coat and tie and goes to work in an environment where the ambient noise level is so loud that they have to use headphones to muffle the outside noise and amplify the normal speaking voice of the folks that they are communicating with – some just a couple of feet away.  Ours is not a steel mill or an aircraft carrier deck.  We’re not stamping metal with giant presses that shake the ground.  Think about it, we’ve got engines the size of those in every car and truck in the country, but ours make far more noise.

In my profession of looking at future trends it is clear that people all over the world are becoming increasingly concerned about their environment.  It’s certainly the case with smoking in public places, tail pipe pollution pumped into the air, industrial and agricultural run-off finding its way into streams and rivers, and sound levels in neighborhoods.  There have been mini-revolts in the spiffy suburbs around Hollywood generated by the disruption produced by weedeaters and leaf blowers wielded by foreign workers who were impervious to the noise because they were wearing Mickey Mouse ears (that’s what we called noise suppression devices in the Navy).

Of course, the AOPA has full-time people fighting the neighbors all around the country who want to close local airports.  San Jose, San Mateo, Naples, and any of a number of other places where GA flies close to the people. Why?  Mostly because of the noise.  Can you imagine what the problem might be if there wasn’t any noise – or if it was the level of an automobile or a pickup?  I don’t think there would be a problem.  People aren’t concerned about low flying aircraft – they don’t want to be disrupted.

(More on this subject next month.)

John Petersen

John L. Petersen is a futurist, strategist, and pilot. He is a former aircraft carrier based naval aviator, aircraft builder, and author of three books. He founded The Arlington Institute, edits and publishes the free e-newsletter FUTUREdition, and is the chairman of the Lindbergh Foundation.

The opinions expressed by the bloggers do not reflect AOPA’s position on any topic.

  • Jim Hausch

    Interesting article…

    While I realize a large portion of small aircraft noise comes from the prop, are there any light aircraft which have exhaust pipes that point “up”.

    Pipe covers would be needed on the ground, just like pitot covers, but would this make a difference without affecting performance? Certainly seems like a beret solution than the “swiss mufflers” I have seen in pics of Euro fly-ins.

  • http://www.rapp.org/ Ron Rapp

    I don’t know, John. Even if planes were virtually silent, I’d bet opponents of SMO would still be trying to close it. They don’t like the leaded fuel. Or the “danger” of those little airplanes buzzing around. Or the fact that the land is being used by rich 1%-ers instead of as a public park, public housing, or a strip mall. Or… well, there are a dozen other reasons. Noise is just one small part of it.

    There’s money for politicians when they close an airport. Development fees, payoffs, parks they can name after themselves.

    When it comes to noise, airplanes are getting quieter — dramatically so — every year. Ever heard an Eclipse jet fly by? Virtually silent. Older stage 3 jets are all but gone. New piston airplanes have quieter props, we use smarter operating techniques, they have better exhaust systems. We have noise abatement procedures, voluntary (and sometimes not-so-voluntary) curfews. And last but not least, there are fewer pilots flying fewer hours than ever before.

    –Ron

  • http://www.rapp.org/ Ron Rapp

    Oops, I meant stage TWO, not three…

  • Dan Marotta

    It is indeed true that our engines don’t have mufflers, but it is the propeller that makes the majority of the noise, not the engine, as the author suggests.

    Though retired, I tow gliders part time and it is the tip noise of a 94 inch propeller spinning at 2,700 RPM which is so obnoxious. I make it a point to reduce RPM as soon as possible (after release of the glider) just to reduce the impact on the ground.

  • Cary Alburn

    One of the things I’ve noticed here and there flying about the country is that noise-abatement procedures aren’t very often published in the obvious place–on a sign right at the end of the taxiway leading to the runway. While locals may know and follow local noise abatement procedures, and while they may be published in the AF/D, transients are much less likely to do so unless they’re whacked in the face with them. Even then, they’re optional in most cases, at pilot’s discretion–which of course, they should be for safety reasons, but I suspect some pilots simply ignore them and fly like usual. I recall when Fort Collins Downtown was still open, there was a sign at the entrance to the runway which asked pilots to turn (30 or 45–can’t recall for sure) to the right after taking off, to avoid overflying a residential area. My son lived in that residential area, and he told me that it was really obvious when some airplanes would ignore that sign’s request.

    My little airplane (1963 P172D, built in October ’62) is very noisy inside (in 1962, Cessna hadn’t yet heard of noise insulation, I think!), and if the prop is at 2700 rpm, I’m told it’s also noisy outside. Habitually, except if I must climb at full power to clear terrain, I crank back the prop to about 2550 rpm at about 400′ AGL, which I assume lessens its noise footprint quite a bit and only reduces the climb capability a little, and I don’t increase the rpm on landing until I’ve throttled back enough that the governor has no effect, usually about mid-base. That’s my contribution to reducing noise pollution–and if everyone would do something similar, there might (maybe?) be fewer neighbor complaints. But there will always be those late comers who knew about the airport before moving in but still complain about this or that airport-created effect upon their sensibilities–a variation of the NIMBY crowd.

  • Fred Fourcher

    Everything is a tradeoff and the manufacturers of GA Aircraft have chosen performance over quiet. What if we had quiet GA aircraft available to us? Would we buy them? So far manufacturers have not given us the choice to make that decision. We now drive really quiet cars, which we have become accustomed to and with local community pressure we may choose to purchase one aircraft over another based on how quiet they are both inside and out.

    For the current fleet, mufflers and props wear out over time and if there were quieter alternatives with moderate performance sacrifices, I would choose to replace them with the quieter alternatives.

    I work next to an airport and when a high performance single takes off it stops your conversation. When an LSA takes off you hardly notice it. I think the GA industry should set standards and measurement criteria, which an owner can use to gage the quietness of aircraft and components. This way we can make informed choices about how quiet we want to fly. I think it is important for one or more of the GA organizations to step up and set the standards and invite the manufacturers to offer new aircraft and parts which help GA reduce it’s noise footprint.

  • Kayak Jack

    Mufflers will cut horsepower some percentage. Maybe that’s one of the reasons for an open exhaust stack? Props can be quieter, and some are now. When my 2blader wears out, I’ll get a 3blader. They’re quieter (more efficient) and more effective (better performance).
    In the meantime, when you build or buy a home next to an airport, you can expect to see and hear aircraft to be flying around. I wish that I could make it simpler – I can’t.

  • Dan Winkelman

    As others have mentioned… most of the noise in a modern GA airplane is propeller noise. Development is ongoing to reduce that, but it will always be there. Ever listen to a 182 turbo… or any other turbocharged or turbonormalized airplane? The turbo acts like a muffler and the actual engine noise out the exhaust pipe is minimal. The prop is where most of it is at.

    If we want to see the widespread adoption of quieter props, I would suggest a review of Part 35 (propeller testing) and the regulatory burden of getting an STC for every airplane you want to install a given propeller on. Flight safety is number one, but we need to be thinking of ways to keep aviation safe with less regulatory burden and overhead expense. If we can bring the price down and increase the availability of acoustically optimized propellers, we could start making real progress on reducing our noise signature.

    That said… I am one of those yahoos with an “I (heart) airplane noise” bumper sticker. I am an enthusiast, and love all kinds of engine noises.

  • John Worsley

    I ride dirt bikes, which have traditionally been loud. There have been quieter aftermarket mufflers available for them for many years. My Cherokee 6 has a muffler (of sorts) but it doesn’t muffle much. If my airport had a noise problem I would buy a quieter aftermarket unit as I have for my dirt bikes. Evidently pilots aren’t demanding them or I would think somebody would be building them. Quieter mufflers have little or no horsepower penalty on dirt bikes.

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