Air Vent Noise

Antoine · Post by **Antoine** » Mon Mar 10, 2014 5:58 pm

Well I am glad that other admit of this happening.
I was not thinking of the tape anymore and it really caught me by surprise!

Diamond13 · Post by **Diamond13** » Mon Mar 10, 2014 6:06 pm

I have heard of guys putting in a plastic dish-wash 'scrubbie' from the outside (inside naca) which helped reduce noise level......

rwtucker · Post by **rwtucker** » Mon Mar 10, 2014 6:40 pm

Diamond13 wrote:I have heard of guys putting in a plastic dish-wash 'scrubbie' from the outside (inside naca) which helped reduce noise level......

Isn't this SOP for C150-210s? Any Cessna owners who can enlighten us?

Antoine · Post by **Antoine** » Mon Mar 10, 2014 6:51 pm

Diamond13 wrote:I have heard of guys putting in a plastic dish-wash 'scrubbie' from the outside (inside naca) which helped reduce noise level......

Robert I think our Steve(s) has / have done an amazing job of documenting the problem and developing the fix.
We get less noise and more airflow by blocking one half. Experiments with plugs, filters etc... are also documented in this thread and it seems taping is the very best solution.

I would much prefer a factory-approved composite cover, but this is probably just wishful thinking, right?

Diamond13 · Post by **Diamond13** » Mon Mar 10, 2014 6:57 pm

I'll talk to engineering, could be classed as a 'minor' and would not have to go through Diamond Austria (Certificate holder)

Antoine · Post by **Antoine** » Mon Mar 10, 2014 7:03 pm

... wow. I wasn't expecting this! I thought we were really on our own for fixes.
Regardless of what engineering says - thank you, Robert

Diamond13 · Post by **Diamond13** » Mon Mar 10, 2014 7:07 pm

I'll do my best, I'll go through your data here, see what you guys have, try to summarize it for Engineering, rob

Rick · Post by **Rick** » Mon Mar 10, 2014 10:46 pm

I taped the top half of mine, too, back a while ago. I used the white sailplane tape, and it's still there and holding well. It also blends so well I don't even notice it's there. But a factory solution that would hold up long-term would be better!

CFIDave · Post by **CFIDave** » Mon Mar 10, 2014 10:51 pm

Here's another idea but I can't test it now that I don't have a DA40 anymore. (The DA42 thankfully doesn't have noisy eyeball vents. :-D )

I was reading about a Long-EZ experimental aircraft homebuilder who had the same problem of an air resonance forming across his composite fuselage NACA duct -- akin to the low frequency hum that occurs when a person blows across the opening of an empty glass jug. The resonance caused excessive noise to come out of the eyeball vents in his plane's interior. (Sound familiar?)

To get rid of the resonance he placed a small hole in the duct leading from the NACA intake to each eyeball vent. By creating a small air leak, it "de-tuned" the duct and got rid of the noise.

Chris B · Post by **Chris B** » Mon Mar 10, 2014 10:56 pm

Rick wrote:I taped the top half of mine, too, back a while ago. I used the white sailplane tape, and it's still there and holding well. It also blends so well I don't even notice it's there. But a factory solution that would hold up long-term would be better!

+1 to the sailplane tape. That stuff is amazing. Sticks like crazy, but counter-intuitively is easy to remove without any sticky residue. Must be some kind of magic adhesive.

But I would also *really* like a factory solution!

BTW, I used the 1" sailplane tape to cover seams on the wing tips, around the landing lights, and a few places on the tail. Definitely increased TAS by 5 knots.

With a sufficient number of these mods, I should be eventually be supersonic!

Chris

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