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RV-9 whistle

R

rv9aviator

Well Known Member
Has anyone figured out what is causing the whistle that seems to be in most if not all RV-9's? My son heard me from 9 miles out and he thought it was a turbine coming in to land. He heard the whistle before he ever heard the engine and prop. I asked him if it was annoying and he said not at all. It just sounded like a jet coming in. Does this mean I will have to be careful that a lineboy doesn't fill my tanks with JetA? :D
 
My -9 had the whistle and that's exactly what people would tell me - sounds like a turbine in the pattern. I do not want my beautiful, prop driven RV to sound like that. :(
So..I took a look at the tail surfaces and figured that it might be coming from the hinge openings at the elevators and rudder. Much like producing sound from a flute - air passing over an opening. I took some of that UHMV tape and covered the openings. Problem solved, and you can still see through the tape to check hinge bolts during preflight.
I recently repainted the airplane and removed the tape. Sure enough, when the plane was back in the air someone said it was whistling. I covered the rudder hings openings only this time and no one has said anything so I guess the rudder hinge openings are the culprit.
 
RV 9 whistle

My RV 9 has a noticeable whistle even for non aviation friends. There's no mistake about it coming by. Haven't tried to find out why . Anyone experimented with tape on various places to see if it can be located. Not sure I want to fix it. It's just part of its character. For those needing to fix it , I have a sliding canopy, Prince P tip prop and 0320 160HP. I however think it might be in the tail section faring or other tail config.
 
Hey, a Corsair has a very prominent whistle when it flies past, too. Not always a bad thing.

Hinge openings, huh? Maybe I should look into enlarging mine to get Smokey to whistle. Sounds pretty cool ... :D
 
free bird repellent???

I'll just leave mine..... and consider it an eco-friendly way to ward off other flying objects! :)
 
Interesting....

bsacks05 said:
I recently repainted the airplane and removed the tape. Sure enough, when the plane was back in the air someone said it was whistling. I covered the rudder hings openings only this time and no one has said anything so I guess the rudder hinge openings are the culprit.
Click to expand...

If it's caused by the rudder hinge openings, why doesn't the RV-7 whistle? It uses the same vertical and rudder as the -9.
 
I always knew when Ted Chang was coming in. It is nice to have a unique sound. My wife commented the other day on how our -10 sounds compared to the rental 172.
 
Mel said:
If it's caused by the rudder hinge openings, why doesn't the RV-7 whistle? It uses the same vertical and rudder as the -9.
Click to expand...

Great question Mel. I don't know the answer but my first guess would be the differences in the wing airfoils changes airflow around the part that's whistling. My experience, albeit limited and not scientific, is on at least some flutes, it doesn't take much difference in the angle of the wind blowing over the hole to change a loud tone to a near silent woosh.

If I ever finish my 9A, and if it whistles, I'll be curious to see if I can isolate which hole or holes cause it. The it would be interesting to tuft test the area around that/those hole(s) and compare the results to a 7A, if the whistling parts are the same.
 
Whistling airplanes

May not really be germane, but back when I was employed by Noise Engineering at Boeing, a lot of flight testing revealed that a very loud whistle heard on 737s approaching to land was caused by an uncapped tube in the landing gear. Boeing capped the tube for a measurable noise decrease on landing. The uncapped tube produced the same effect you get blowing over the open neck of a Coke bottle. The effect even has a name: a Helmholtz resonator. Being unfamiliar with RV-9 elevator hinges I cannot say for sure that the same effect is involved here, but the "takeaway" is that any uncovered opening to an enclosed volume can potentially produce a tone in flight. Whether its loud enough to be heard or even be a problem, like on the 737, is dependent upon the geometry, airspeed and density.
 
I missed the last paragraph of Bruce's post. I agree with Mel that VS and rudder of 7 and 9 are the same. HS and elevator hinge openings are the source of the whistle. I had them covered for a few years until my duct tape fell off. Now I am whistling in the sky again (as Wayne G. has observed).
 
How do you cover the holes such that you still have full elevator travel? I assume you're not covering the elevator-HS gap - just the elevator cutouts? Got any pictures?
 
Horz stab end ribs.

I notice one post indicated that the horiz stabilizer end ribs which have an obvious lightening hole exposed to the elements at times may also be part of the cause. Anyone tried taping just that hole to see if the whistle stopped? That appears quite easy job. Not sure I understand how to tape off the rudder or elevator rod end attachment holes, besides all the other models have same type opening as the 9 on those.
 
With just the rudder hinges taped I haven't heard anyone comment about whistling from my plane, but then I never asked anyone to listen for it. Next time I am at the airport I will have someone do just that.
The elevator hinges make sense because the -9 horizontal is bigger and it may make an effective resonator more so than the other, less awesome, RVs.
 
This may be a silly question but could the whistle also be a source of drag that might effect airspeed. I hope not because I kinda think it's cool.:)
 
When I had the tape on I only taped the bottom openings (used yellow duct tape to match my paint) to the extend that does not interfere with the down elevator. Yes, it is very easy to test.
 
rv9aviator said:
This may be a silly question but could the whistle also be a source of drag that might effect airspeed. I hope not because I kinda think it's cool.:)
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If its making noise, its making drag!

Never noticed any whistling on my 9. Can't say I've really noticed it on others either. Probably just a little plane to plane variation.
 
Mine doesn't whistle...

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Maybe it is installation dependent. I know quite a few RV-9/As whistle. I did not hear it until friends mentioned it to me. Several of them told me that they heard it when I flew over the city. I do have the ends of my HS closed. Of course the whistle does not bother me. It is my calling card :D.

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Why, Where & How??????

...I am still awaiting an answer as to the source of this whistle the Nine seems to have. Mine has it as well and I have no idea why. Allan...:D
 
Quote:
Originally Posted by Mel
If it's caused by the rudder hinge openings, why doesn't the RV-7 whistle? It uses the same vertical and rudder as the -9.
Good point Mel. Guess it's back to the drawing board.
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It is caused by the elevator hinge openings and not rudder. Put a piece of duct tape over the bottom openings and see whether others on the ground can still hear your whistle.
 
Originally Posted by bsacks05
I recently repainted the airplane and removed the tape. Sure enough, when the plane was back in the air someone said it was whistling. I covered the rudder hings openings only this time and no one has said anything so I guess the rudder hinge openings are the culprit.

If it's caused by the rudder hinge openings, why doesn't the RV-7 whistle? It uses the same vertical and rudder as the -9.

I was told by some friends on the ground that my -7 had a "whistling sound" when I flew over. That's how they knew it was me. I never thought anything of it until I saw this post today. I wonder if anyone has a video of one that you can hear a whistle?
 
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DRBuilder said:
Originally Posted by bsacks05
I recently repainted the airplane and removed the tape. Sure enough, when the plane was back in the air someone said it was whistling. I covered the rudder hings openings only this time and no one has said anything so I guess the rudder hinge openings are the culprit.

If it's caused by the rudder hinge openings, why doesn't the RV-7 whistle? It uses the same vertical and rudder as the -9.

I was told by some friends on the ground that my -7 had a "whistling sound" when I flew over. That's how they knew it was me. I never thought anything of it until I saw this post today. I wonder if anyone has a video of one that you can hear a whistle?
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I now think the whistle is coming from the elevator hinges. I can hear it sometimes in the pattern. When I move the elevator a little, the sound changes. Maybe I will tape them and see what happens.
 
airguy said:
How do you cover the holes such that you still have full elevator travel? I assume you're not covering the elevator-HS gap - just the elevator cutouts? Got any pictures?
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I'd like to see pictures of this too... Having a hard time visualizing where this is coming from.
 
What's the big deal?

I haven't flown yet so I haven't heard the whistle. What is the concern with having a whistle? I gather that you can't hear it from the cockpit. It is bad enough cause a ruckus with the airport neighbors? Is the concern added drag?

Seems to me that it might be kinda cool to have your own special sound. Somebody in one of the posts described it as sounding like a turbine. How cool is that? Now don't get me wrong, I would love to fly along in complete silence but if the whistle doesn't make life miserable for myself or airport neighbors, what's the big deal?

I hope to listen for my whistle very soon.
 
Love the whistle.

Between the very throaty gurgle of the engine (io320 with pipes) sounds like a mustang 5 litre v8, and the whistle...lots of people have said it sounds like a turbo v8. Very distinctive. Wouldnt change it.

Whistlin and proud of it.:p
 
I don't think there is anything wrong with the whistle. People at airports and around town will notice it. Knowing what caused it you have a choice of keeping it or eliminating it. I choose to keep it.
 
rv9aviator said:
Has anyone figured out what is causing the whistle that seems to be in most if not all RV-9's?
Click to expand...

Well, I can provide an intersting data point - landing my RV-8 at the local public use airport, I've received the same "turbine" description multiple times. They say the really notice it when I pull the throttle to idle on final. I've flown both with and without gap tape on the elevator and rudder hinge cutouts. The comment persists.
 
Is everyone sure that this sound can't be heard in the cockpit? My last two passengers report that they can hear a whistling in the cockpit in flight. I wear a Lightspeed ANR and can't hear it (except maybe faintly, muffled by the ANR) but my passengers say it's quite piercing if you hold your head at certain angles. I'm wondering if it might be a gap seal around the canopy somewhere.
 
Ok, now I''m jealous--that sounds like a Corsair. How do I get my 9 to whistle?

Steve Johnson
RV-9A 185 hours
Abilene, Tx
 
BF 109

I am very happy that my RV 9 whistles just like a BF 109 during a low pass...
 
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