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Why are pushers so noisy?


jsharr

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My office tower is close to and in line with the runway at Addison Airport.  Lots of planes go overhead every day.  I seldom notice the noise except for a twin engine turbo prop pusher.  Probably a Piaggio 180.  Maybe even this one.

N183AV - Piaggio P-180 Avanti II - Private

Anyway, why are pusher prop planes so much noisier than conventional prop forward planes?

 

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5 minutes ago, Wilbur said:

It is caused by square wave noise which is caused by exhaust hitting the props.  

I wondered about that in actuality when I looked at the top image of the one with the red stripe.  Big honking turbo exhaust right in front of the prop.
 

So do they change the pitch of the prop when landing?  I am at 635 and the tollway on the final approach to KADS, 2.6 miles from the end of the runway.

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3 minutes ago, jsharr said:

I wondered about that in actuality when I looked at the top image of the one with the red stripe.  Big honking turbo exhaust right in front of the prop.
 

So do they change the pitch of the prop when landing?  I am at 635 and the tollway on the final approach to KADS, 2.6 miles from the end of the runway.

Yes they do.  From coarse to fine pitch in case of a missed approach.

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19 minutes ago, Wilbur said:

It is caused by square wave noise which is caused by exhaust hitting the props.  

 

4 minutes ago, Wilbur said:

Yes they do.  From coarse to fine pitch in case of a missed approach.

See @Kzoo this is the kind of answer I was looking for, not some cut and paste crap from a toy website.  I knew I could count on my friend @Wilbur

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56 minutes ago, jsharr said:

 

See @Kzoo this is the kind of answer I was looking for, not some cut and paste crap from a toy website.  I knew I could count on my friend @Wilbur

Listen I was doing this for you.  I was not about to put a lot of research into it - you understand.  I did a cut an paste on the first Google thing I could find.  It was more a case of wanting to shut you up than getting you an accurate answer.  I can tell my attempt at shutting you up failed.

You are welcome.

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28 minutes ago, Kzoo said:

Listen I was doing this for you.  I was not about to put a lot of research into it - you understand.  I did a cut an paste on the first Google thing I could find.  It was more a case of wanting to shut you up than getting you an accurate answer.  I can tell my attempt at shutting you up failed.

You are welcome.

step brothers whatever GIF

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Maybe it's just as noisy as planes with props the other way, but it may be that in both cases, the body and wings minimize the noise when they are between you and the propeller.

So if it's a pusher, you don't notice the noise until you see the plane and it gets noisier as it passes.  In the opposite configuration, you may not associate the noise with the plane because you don't see it when it is noisiest - it's behind you.  Then, as it passes, you see the plane but the body and wings are helping with interference and you associate the plane with being quieter.

Additionally, the Doppler Effect would mean the pusher would be noisier as passes and the frequency is dropping to a lower pitch that penetrates walls, etc. more easily. But the front-facing propeller would be noiser approaching, hitting you with a higher, less penetrating frequency.

How's that for a lot of pseudo-scientific b.s.?

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