# Is it possible to build a practical powered aircraft that operates silently? **URL:** \ **Category:** Factual Questions\ **Created:** [May 1, 2006, 10:57am UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932 "2006-05-01T10:57:52Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![R.P.McMurphy](https://avatars.discourse-cdn.com/v4/letter/r/7993a0/32.png) [@R.P.McMurphy](https://boards.straightdope.com/u/R.P.McMurphy)\ **Post date:** [May 1, 2006, 10:57am UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/1 "2006-05-01T10:57:52Z")
It seems that all powered aircraft are inherantly noisy. Jet engines, turbo props, prop engines, all noisy. Everybody recognizes the sound of a helicopter. Rockets, forget it. Cars can be built that are almost silent. Is it possible to build a powered aircraft that would transport people that would be silent or nearly silent? Forget gliders, (not powered) or balloons (not practical enough). Is the problem of air turbulence just too much to overcome? ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [May 1, 2006, 11:14am UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/2 "2006-05-01T11:14:50Z")
The engines on piston powered aircraft are not muffled. You could add a muffler, but why would you want to? More weight, less preformance to cut the noise. Doesn’t seem like a good trade off to me. FWIW a B2 is fairly quiet at cruise when I have seen them do fly bys. ---
**Author:** ![N9IWP](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/n9iwp/32/3154_2.png) [@N9IWP](https://boards.straightdope.com/u/N9IWP)\ **Post date:** [May 1, 2006, 12:10pm UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/3 "2006-05-01T12:10:46Z")
Well, there are electric planes. Like that soloar one that NASA flew up to 86,000 feet or something. Since the props were fairly slow turning, I think it would be pretty quiet. At what about human poered planes? Those were pretty quiet. Brian ---
**Author:** ![SuperNelson](https://avatars.discourse-cdn.com/v4/letter/s/7feea3/32.png) [@SuperNelson](https://boards.straightdope.com/u/SuperNelson)\ **Post date:** [May 1, 2006, 12:25pm UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/4 "2006-05-01T12:25:48Z")
I’ve been passed by a glider on close approach - and they are LOUD up close. Granted, we didn’t hear this one until it was within a few hundred feet, but it got really loud really fast. Wing noise will be a concern. ---
**Author:** ![Sevastopol](https://avatars.discourse-cdn.com/v4/letter/s/cdc98d/32.png) [@Sevastopol](https://boards.straightdope.com/u/Sevastopol)\ **Post date:** [May 1, 2006, 12:26pm UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/5 "2006-05-01T12:26:48Z")
Dirigible with muffled, internal combustion or, battery-electric engines. Silence is generally a second order consideration with aircraft, as power-to-weight ratio and fuel consumption dominate. Remove the need for engines to provide lift (_pace_ that thread) and you can introduce noise control as a consideration for powered aircraft. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [May 1, 2006, 1:19pm UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/6 "2006-05-01T13:19:53Z")
If you want to be able to put the craft where you want it to be, then I don’t think you have a hope. Even dirigibles, up close, are incredibly loud. The problem is that you have to move a _lot_ of air very fast in order to go where you want. An unpowered ballon (or a dirigible with itas motors off – which isn’t really “dirigible” then) would be pretty quiet, but that’s explicitly outside of what you suggest. I would’ve thought gliders were pretty quiet, but **superNelson** says that ain’t so. Too bad – they’re more controllable, although whatever lasunches them into the air is still pretty noisy. Face it – it takes a lot of energy to get the mass of a planer into the air and to keep it there. I don’t know how quiet human-powered (and solar, or small-scale electric) craft are, but even ultralights make a lot of noise. And I understand Ospreys are insanely loud. We really need anti-gravity devices, but I’m not holding my breath for that. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [May 1, 2006, 1:49pm UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/7 "2006-05-01T13:49:14Z")
> [@Rick](#): > > The engines on piston powered aircraft are not muffled. Dad’s did. They worked fairly well. Not as good as car mufflers though. But then again, they don’t need to be. [Aircraft mufflers](http://www.2aps.com/aeroheat_exhaust_systems.htm). > [@Spartydog](#): > > Everybody recognizes the sound of a helicopter. I’ll admit that the Schweizer 300CB I was flying sounded a lot like a tractor, even with the muffler. But in flight, most of the noise comes from the anti-torque rotor. It spins pretty fast, and so makes a lot of noise. When I lived in L.A. I’d see MD500 NOTARs frequently. They were very quiet. The turbine whined, but it wasn’t objectionable. The rotor was pretty quiet as well. While most of the noise in helicopters comes from the tail rotor, there is also something called ‘blade slap’. Blade slap happens when a rotor blade passes through its own vortex, or a vortex generated by another blade. IME it usually happend at cruise speeds during a shallow descent. For piston powered aircraft, I think much of the noise comes from the propeller. The prop, much like the anti-torque rotor on a helicopter, is of relatively small diameter and spins relatively fast. If you’re not careful, some airplanes’ propeller tips can reach the speed of sound. So I think that much of the noise you hear comes from the prop and not necessarily the engine. I’ve never flown a glider, but I’ve seen them fly and have seen video recorded in the cockpit. Lots of wind noise there. I was also surprised at the amount of noise generated by hang gliders when they were flying fast. So basically, powered aircraft are noisy. Wind noise is a factor, but I think this is a short-distance noise. Nothing you can do about it, for an aircraft’s given role, because surfaces must interact with the air. Props could be designed to be quieter, but weight and cost are critical in light aircraft. Tail rotors are just plain noisy. You’re pretty much stuck unless you go to a NOTAR system, which is impractical on most helicopters. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [May 1, 2006, 1:51pm UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/8 "2006-05-01T13:51:05Z")
Oh… I [heart] airplane noise. Does anyone remember how to make the heart symbol in vB? ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [May 1, 2006, 2:25pm UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/9 "2006-05-01T14:25:25Z")
I Y airplane noise. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [May 1, 2006, 2:30pm UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/10 "2006-05-01T14:30:08Z")
{FONT=webdings]{SIZE=4]{COLOR=Red]Y{/COLOR]{/SIZE]{/FONT] Thanks. Is there a ‘map’ to the characters? ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [May 1, 2006, 2:34pm UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/11 "2006-05-01T14:34:26Z")
> [@Johnny L.A.](#): > > Thanks. Is there a ‘map’ to the characters? I like [The Font Thing](http://members.ozemail.com.au/~scef/tft.html), a shareware font utility with lots of font management features as well. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [May 1, 2006, 2:38pm UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/12 "2006-05-01T14:38:57Z")
I may have to try that. ---
**Author:** ![SpectBrain](https://avatars.discourse-cdn.com/v4/letter/s/a87d85/32.png) [@SpectBrain](https://boards.straightdope.com/u/SpectBrain)\ **Post date:** [May 1, 2006, 7:43pm UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/13 "2006-05-01T19:43:55Z")
Let me google something…yeah I thought I remembered this the [YO-3A](http://www.yo-3a.com/pages/3/index.htm) > [@](#): > > Lockheed developed the YO-3A from a Schweizer SGS-2-32 sailplane during the 1960s as an observation plane for use in the Vietnam War. The aircraft¹s ultra-quiet design and large bubble canopy allowed pilots to move stealthly and at low altitudes over enemy territory to visually observe troop locations and movements, particularly at night. ---
**Author:** ![Bookkeeper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bookkeeper/32/281_2.png) [@Bookkeeper](https://boards.straightdope.com/u/Bookkeeper)\ **Post date:** [May 1, 2006, 8:33pm UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/14 "2006-05-01T20:33:20Z")
> [@SpectBrain](#): > > Let me google something…yeah I thought I remembered this the > [YO-3A](http://www.yo-3a.com/pages/3/index.htm) More on the YO-3A and the [Lockheed Q-Star](http://www.historynet.com/ahi/bl-sailplane/) prototypes. ---
**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\ **Post date:** [May 1, 2006, 10:50pm UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/15 "2006-05-01T22:50:43Z")
Even gliders are loud? I am amazed. I would have thought that the engines on a plane would be much louder than any air noise. Speaking of engines, though: I have read hints that Stirling-cycle engines are [very quiet](http://en.wikipedia.org/wiki/Stirling_engine). Perhaps they could be used in place of other piston engines inj a plane? ---
**Author:** ![Broomstick](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/broomstick/32/246_2.png) [@Broomstick](https://boards.straightdope.com/u/Broomstick)\ **Post date:** [May 2, 2006, 12:27am UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/16 "2006-05-02T00:27:40Z")
> [@Spartydog](#): > > It seems that all powered aircraft are inherantly noisy. Jet engines, turbo props, prop engines, all noisy. Everybody recognizes the sound of a helicopter. Rockets, forget it. > > Cars can be built that are almost silent. Is it possible to build a powered aircraft that would transport people that would be silent or nearly silent? I doubt it. Strongly doubt it. I’d say “impossible” but I try hard never to say that word. > [@](#): > > Forget gliders, (not powered) I’ve flown a glider. They’re not silent. Quite a bit of noise is generated by their motion through the air (as previously noted) > [@](#): > > or balloons (not practical enough). The burner on a hot air balloon makes a surprisingly hellacious amount of noise. (Another fact I picked up during my aviation adventures) > [@](#): > > Is the problem of air turbulence just too much to overcome? If by “turbulence” you mean “sound of stuff passing fast through the air”, yeah, I think that’s the issue. Last summer, when the engine on the Citabria (temporarially) quit working there was still so much noise that niether of in the airplane noticed at first that the engine has quit. Not only were there the usual glider noises, but the windmilling prop continued to make significant racket. Even an electric or solar airplane is going to make “glider noises” going through the air, and their props will at least make a _whoosh!, whoosh!_ as they go 'round. A human-powered aircraft, due to extremely slow speed of both it and its prop, probably comes closest, but I doubt even the likes of Lance Armstrong would consider pedel-powered flight to be “practical”. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [May 2, 2006, 12:35am UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/17 "2006-05-02T00:35:09Z")
Owls manage it. Is that because they create less turbulence than other birds? Maybe what we need is a giant genetically-engineered owl. ---
**Author:** ![RealityChuck](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/realitychuck/32/195_2.png) [@RealityChuck](https://boards.straightdope.com/u/RealityChuck)\ **Post date:** [May 2, 2006, 12:46am UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/18 "2006-05-02T00:46:01Z")
Mr. Memory knows. Am I right, sir? ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [May 2, 2006, 2:55am UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/19 "2006-05-02T02:55:02Z")
> [@Johnny L.A.](#): > > Dad’s did. They worked fairly well. Not as good as car mufflers though. But then again, they don’t need to be. [Aircraft mufflers](http://www.2aps.com/aeroheat_exhaust_systems.htm). Learn something new every day. [Johnny Carson] I did not know that[/JC] Johnny, I Y airplanes too. ---
**Author:** ![Tuckerfan](https://avatars.discourse-cdn.com/v4/letter/t/eada6e/32.png) [@Tuckerfan](https://boards.straightdope.com/u/Tuckerfan)\ **Post date:** [May 2, 2006, 8:33am UTC](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932/20 "2006-05-02T08:33:05Z")
Apparently, there _are_ designs for electric powered drone aircraft that are quiet, but I’ve not heard any of them, nor can I remember any of the names of the models to dig up a cite for that. I don’t think that you’d be able to design a craft that moved at a good clip to be completely silent. In theory, you might be able to do something with amplifiers and noice cancelling equipment, but I imagine that it would only be something you could get work in the lab, if it all. Given conventional technology, the best you could hope for is a design that used something like helium in the wings of the craft (to get it airborne) and then electric motors driving specially designed props made to be a silent as possible (no doubt at very slow speeds). It’d only be really suitable for remote observation or communications platforms (Cox communications is supposed to be working on something like that for cell/sat phone service). [Next page](https://boards.straightdope.com/t/is-it-possible-to-build-a-practical-powered-aircraft-that-operates-silently/354932.md?page=2)