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Stall speed noise

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Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Sun Dec 17, 2006 11:52 pm Post subject: Stall speed noise

Hello everyone,

Saturday I wrote a question to the list. Unfortunately, trying to copy someone else's style, I wrote it in the "Dear Abby" style, something that wasn't appreciated by the list moderator. I apologized for that but my question still remains unanswered and it worries me because if none of you experience a certain noise when the plane starts a stall, then ... something could be wrong with my plane.



So, please, if any of you know the reason why I can hear a distinct sound that reminds of fabric tearing as my model 3 stalls, I'd appreciate it. Could it be that, as the air becomes turbulent around the wing, that a part of the fabric flaps like a whip on the fuel tank? Thanks in advance.



Michel

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_________________
Kitfox 3 - Jabiru 2200

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Mon Dec 18, 2006 3:43 am Post subject: Stall speed noise

I haven't experienced that, Michel. Mine just goes straight over at  

stall. I have my fabric poly-brushed firmly to the tanks wherever it  

happened to touch, which is probably 60-70% of the area.



Lynn

On Dec 18, 2006, at 2:52 AM, Michel Verheughe wrote:



 	  Quote: 	
		   Hello everyone,

 Saturday I wrote a question to the list. Unfortunately, trying to  

 copy someone else's style, I wrote it in the "Dear Abby" style,  

 something that wasn't appreciated by the list moderator. I  

 apologized for that but my question still remains unanswered and it  

 worries me because if none of you experience a certain noise when  

 the plane starts a stall, then ... something could be wrong with my  

 plane.



 So, please, if any of you know the reason why I can hear a distinct  

 sound that reminds of fabric tearing as my model 3 stalls, I'd  

 appreciate it. Could it be that, as the air becomes turbulent  

 around the wing, that a part of the fabric flaps like a whip on the  

 fuel tank? Thanks in advance.



 Michel

 <pre><b><font size  color="#000000" face="courier new,courier">



 www.aeroelectric.com">www.aeroelectric.com</a>

 www.buildersbooks.com">www.buildersbooks.com</a>

 www.kitlog.com">www.kitlog.com</a>

 www.homebuilthelp.com">www.homebuilthelp.com</a>

 www.matronics.com/contribution</a>

 List">http://www.matronics.com/Navigator?Kitfox-List</a>



 </b></font></pre>

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

experimental208nd(at)comc
Guest

Posted: Mon Dec 18, 2006 1:47 pm Post subject: Stall speed noise

Same here, I have the ribs and tank tops pollybrushed too, and rib stitched.

No sound on stall either,( except my heart beating ! 

jay

---

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Mon Dec 18, 2006 2:02 pm Post subject: Stall speed noise

On Dec 18, 2006, at 12:43 PM, Lynn Matteson wrote:

 	  Quote: 	
		   I haven't experienced that, Michel. Mine just goes straight over at 

 stall. I have my fabric poly-brushed firmly to the tanks wherever it 

 happened to touch, which is probably 60-70% of the area.


	


Thanks Lynn. It is the same with my plane and my guess was only ... a 

guess. I can be anything else. You see, I remember, when I started 

flying, that someone told me that I would know when I am about to stall 

because the plane will give me a signal. I think someone even mentioned 

something about the fabric. So, I never worried about it, thinking: 

That's my signal.

But after a few touch and go, last Saturday, flying slow and "landing 

in the sky" just to keep with the feeling of the plane - as I was told 

I should do from time to time, I started wondering where the sound came 

from.

Then I asked the question to the list, not in a worried but a humorous 

way. But now, I understand that it is not as usual as I thought it was. 

Never mind, I'll ask a passenger to fly with me and, without the 

headset, to listen to find the direction of that sound. I am not even 

sure at all it comes from the wings.



Cheers,

Michel



do not archive

_________________
Kitfox 3 - Jabiru 2200

lcfitt(at)sbcglobal.net
Guest

Posted: Mon Dec 18, 2006 4:21 pm Post subject: Stall speed noise

Michel,



I didn't respond earlier because I didn't know exactly what to say.  I did 

go flying for a bit this afternoon - a severe clear day after almost three 

weeks of rain. I did the deed and did some stalls.  I didn't hear anything, 

but do have noise cancelling headsets and turn my hearing aids to mode III 

which connects them to the voice coils in the headsets electro magnetically 

rather than through the microphones.  Still, their was no noticable noise.



Lowell



---

MichaelGibbs(at)cox.net
Guest

Posted: Mon Dec 18, 2006 5:47 pm Post subject: Stall speed noise

Michel sez:



 	  Quote: 	
		  ...if any of you know the reason why I can hear a distinct sound 

that reminds of fabric tearing as my model 3 stalls, I'd appreciate 

it.


	


I'm sorry Michel, I thought you were kidding around.  I never heard 

such a sound in my Model IV and I stalled and spun it many times.  I 

think you are probably right, a careful inspection of the fabric on 

the wings is in order.  I wouldn't limit the inspection to the fuel 

tanks, though, check the entire upper and lower surfaces to be safe.



Mike G.

N728KF

henrysfork1(at)msn.com
Guest

Posted: Mon Dec 18, 2006 7:23 pm Post subject: Stall speed noise

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->  Is it possible the fabric is separating from the cap stips on the  ribs or the tubing on the air frame???

  

 Dee Young 

 N345DY

  

 Do Not Archive

 [quote]   ---

smokey_bear_40220(at)yaho
Guest

Posted: Mon Dec 18, 2006 7:43 pm Post subject: Stall speed noise

Hi Michel,

I agree with Mike G.  You need to do a careful

inspection and look for fabric seperating from a rib

or tank surface on the top.  I expect that this is

hard to find since the fabric tension will hold it

down until you get enough lift on the spot.

Any inspection ideas for this from the list?

Michel, is your fabric stitched to the ribs?

Do take someone up with you and do the stall as

quietly as you can, power wise and headsets off, to

find it.  Then stop doing stalls!

A very famous pilot named Steve Whitman lost his life

when his fabric seperated enough to cause flutter in

his wing.  You don't want it to come loose!

Than again, sound testing in flight, you may find that

it is not in the wing and something else is bothering

you for attention.  The baggage sack or other velcroed

part?

The normal indications for stall are shuttering in the

flight controls or entire plane, a flapping sound from

the wind seperating, control response way down (except

in a Fox) the rear window shuttering, that sudden

feeling that the bottom is just about to drop out.....

 probably some others I am forgetting.  But there

should be no tearing sound.

Our planes will tell us when they are hurting.  We

just need to learn to listen and know what they are

saying.

Kurt S.  S-5

--- Michael Gibbs <MichaelGibbs(at)cox.net> wrote:

 	  Quote: 	
		   Michel sez:

 >...if any of you know the reason why I can hear a

 distinct sound 

 >that reminds of fabric tearing as my model 3

 stalls, I'd appreciate 

 >it.

 I'm sorry Michel, I thought you were kidding around.

  I never heard 

 such a sound in my Model IV and I stalled and spun

 it many times.  I 

 think you are probably right, a careful inspection

 of the fabric on 

 the wings is in order.  I wouldn't limit the

 inspection to the fuel 

 tanks, though, check the entire upper and lower

 surfaces to be safe.

 Mike G.

 N728KF

__________________________________________________

kitfox(at)ida.net
Guest

Posted: Mon Dec 18, 2006 8:52 pm Post subject: Stall speed noise

You could use a suction cup of the right strength to pull up on the fabric. 

Could it be air coming in a place not normally in the stream except just at 

stall?

Albert Smith

temco(at)telusplanet.net
Guest

Posted: Mon Dec 18, 2006 11:13 pm Post subject: Stall speed noise

Michel



Are your wings rib stitched?? If not then perhaps you have fabric separation

at some location. Just a thought



Ted



Do NOT ARCHIVR

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Tue Dec 19, 2006 2:50 am Post subject: Stall speed noise

Thank you guys, it looks like this is not normal, after all.

I don't know if my wings are rib stiched. How can I check? My plane was built between 1991 and 1993 by a excellent builder - it was his second Kitfox - and according to the specifications of that time. 



The first time I heard that sound was the first time I stalled the plane, nearly three years ago. I assumed it was "the signal" people were talking about. Now I understand it needs further investigation. I'll keep you informed, of course. Thanks for your answers.



Cheers,

Michel

do not archive

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_________________
Kitfox 3 - Jabiru 2200

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Tue Dec 19, 2006 3:11 am Post subject: Stall speed noise

 	  Quote: 	
		   From: kurt schrader [smokey_bear_40220(at)yahoo.com]

 The normal indications for stall are shuttering in the

 flight controls or entire plane, a flapping sound from

 the wind seperating


	


That might be it, Kurt. How do you describe "a flapping sound from the wind separating?" Here is a description of what I hear:

I once had the tail of my seat belt hanging outside the door (I am rather skinny and the belt is long). As soon as I started the engine, I could hear the belt flapping on the fuselage.

Now, what I hear when stalling is about the same noise but only one flap. And I am not even sure it happens at every stall. I haven't been thinking much about it before now. 

In fact, as I flew alone last Saturday, I was thinking: Whenever I fly with a friend, I can explain that an aircraft doesn't fall out of the sky like a brick if the engine stops or we go in a gentle stall. The intention then was to say: "Whenever you hear this warning sound, push the stick forward and you'll stay in control." Then I came to think that I should ask the list what is the physical cause of the sound.



Cheers,

Michel



PS: I suppose we all experience the same thing but when I ask passengers if he/she wants to steer the plane, they have usually no problem holding the stick. It is when I ask them to coordinate a turn with the pedals that things get ugly!  

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_________________
Kitfox 3 - Jabiru 2200

dosmythe(at)cox.net
Guest

Posted: Tue Dec 19, 2006 3:48 am Post subject: Stall speed noise

Michel,

    You should easily be able to see the small lump of each rib lace under 

the 2" tapes.  Should be about 3 or so inches apart.



Don Smythe



---

smokey_bear_40220(at)yaho
Guest

Posted: Tue Dec 19, 2006 5:35 am Post subject: Stall speed noise

--- Michel Verheughe <michel(at)online.no> wrote:



 	  Quote: 	
		   That might be it, Kurt. How do you describe "a

 flapping sound from the wind separating?" Here is a

 description of what I hear:

 I once had the tail of my seat belt hanging outside

 the door (I am rather skinny and the belt is long).

 As soon as I started the engine, I could hear the

 belt flapping on the fuselage.

 Now, what I hear when stalling is about the same

 noise but only one flap. And I am not even sure it

 happens at every stall. I haven't been thinking much

 about it before now. 

 In fact, as I flew alone last Saturday, I was

 thinking: Whenever I fly with a friend, I can

 explain that an aircraft doesn't fall out of the sky

 like a brick if the engine stops or we go in a

 gentle stall. The intention then was to say:

 "Whenever you hear this warning sound, push the

 stick forward and you'll stay in control." Then I

 came to think that I should ask the list what is the

 physical cause of the sound.

 

 Cheers,

 Michel


	


Michel,



Mine sounds like a big flag flapping just once in the

wind.  Not a fabric tearing sound, but a "FWOUMP" as

the air reattaches to the wing.  When I hear it, the

plane is in recovery from already stalled.  Too late

to stop the stall, but soon enough to recover in a few

feet.  If I hold it in the stall, the sound happens

each time the plane rocks forward and is flying

again....FWOUMP....FWOUMP....FWOUMP seconds apart.



I am wondering about your turtledeck......  It could

make noise from the air behind the wing (top of

cockpit) where the air over the rest of the wing has

nothing behind it to feel the air.  Make sure your

turtledeck is firmly attached and the window is too. 

It could simply be the air beating the turtledeck,

since the center of the wing should stall first.  That

would be a pre-stall, or partial stall warning and

more normal.  Like I said, the rear window can rumble,

or make some noise as the stall starts in the center.

 

 	  Quote: 	
		   PS: I suppose we all experience the same thing but

 when I ask passengers if he/she wants to steer the

 plane, they have usually no problem holding the

 stick. It is when I ask them to coordinate a turn

 with the pedals that things get ugly! 


	


You should try helicopters!  Talk about ugly!  Luckily

you can stop a helo and just get ugly in one place. 

Like first week music lessons...



My first time hovering I was told to stay over a rock.

 Wild ride!  then I was told to stay in this large

field.  Smooth as glass.  Good lesson.  Watch the

world and don't get bogged down in the details.  Big

picture wins.



Kurt S.  S-5  Strato-various (cloud buster)



__________________________________________________

kerrjohna(at)comcast.net
Guest

Posted: Tue Dec 19, 2006 7:11 am Post subject: Stall speed noise

Could one follow each rib cap strip with a shop vacuum to see if there was any latent separation with out it becoming destructive testing?

  

 John Kerr

  

 [quote]-------------- Original message -------------- 

From: kurt schrader <smokey_bear_40220(at)yahoo.com> 



 	  Quote: 	
		   --> Kitfox-List message posted by: kurt schrader 

 

 Hi Michel, 

 

 I agree with Mike G. You need to do a careful 

 inspection and look for fabric seperating from a rib 

 or tank surface on the top. I expect that this is 

 hard to find since the fabric tension will hold it 

 down until you get enough lift on the spot. 

 

 Any inspection ideas for this from the list? 

 

 Michel, is your fabric stitched to the ribs? 

 

 Do take someone up with you and do the stall as 

 quietly as you can, power wise and headsets off, to 

 find it. Then stop doing stalls! 

 

 A very famous pilot named Steve Whitman lost his life 

&gt  ; when  his fabric seperated enough to cause flutter in 
	


 	  Quote: 	
		   his wing. You don't want it to come loose! 

 

 Than again, sound testing in flight, you may find that 

 it is not in the wing and something else is bothering 

 you for attention. The baggage sack or other velcroed 

 part? 

 

 The normal indications for stall are shuttering in the 

 flight controls or entire plane, a flapping sound from 

 the wind seperating, control response way down (except 

 in a Fox) the rear window shuttering, that sudden 

 feeling that the bottom is just about to drop out..... 

 probably some others I am forgetting. But there 

 should be no tearing sound. 

 

 Our planes will tell us when they are hurting. We 

 just need to learn to listen and know what they are 

 saying. 

 

 Kurt S. S-5 

 

 --- Michael Gibbs wrote: 

 

&gt  ; >  Your L  
	


&g  [quote][b]

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Tue Dec 19, 2006 1:51 pm Post subject: Stall speed noise

Thanks again everyone and from the photos Lynn has sent me privately, I 

can definitively say that my wings are not rib laced. I don't know how 

they are made, though, because there is an inspection hole in the wing 

but it has never been cut out of the fabric, so I can't look inside. 

But ... since my wings are of the old Avid type and undercambered,  

there must be something holding the fabric in upward, isn't it? Yet I 

can't see any stitch as in the wings of Lynn.



Anyway, I always do a very thorough pre-flight, inspecting carefully my 

wings and polish them carefully about twice a year. If anything was 

loose, I would have seen it.



The thing is, I assumed the "stall noise" was normal, so I never gave 

it much attention. But I will, next time I fly. Maybe it's the turtle 

deck, as Kurt says. The strange things is, if it was the stall itself, 

I should hear it also when I land, wouldn't I? But, as far as I 

remember, that has never happened. Weird! But I'll keep an eye on it 

and let you informed. Thanks again, everyone.



Cheers,

Michel



do not archive

_________________
Kitfox 3 - Jabiru 2200

Tom Jones

Joined: 12 Mar 2006
Posts: 752
Location: Ellensburg, WA

Posted: Tue Dec 19, 2006 6:38 pm Post subject: Re: Stall speed noise

Michel,

If the wings were built according to the Skystar manual the fabric is attached to the wing ribs with Poly Tack (glue).  The vacume on the top of the wing is strongest when lift is being generated.  At a stall I would think the pull (vacume) on the fabric on the wing top would be minimal.



Those undercambered wings have quite a curve on the bottom rib cap strips.  In my opinion the bottom of the wing would be more likely to be the place fabric might generate a sound during stall.



Don't focus entirely on looking at the fabric on the top rib cap strips.  Be sure to check the bottoms too.



For what it is worth.  I once removed the fabric from one of my wings.  I found it was very securely attached to the ribs with poly tack.  I had to pull really hard to peel it off.



Also, I heard that seat belt slapping sound when I started the stinson the other day.  Yes, I'm skinny too and the tail end of the seat belt was hanging outside the door.  I think for loose fabric to make that sound it would have to be very loose.



Tom Jones, Classic 4, Ellensburg, WA

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Wed Dec 20, 2006 12:52 pm Post subject: Stall speed noise

On Dec 20, 2006, at 3:38 AM, Tom Jones wrote:

 	  Quote: 	
		   Don't focus entirely on looking at the fabric on the top rib cap 

 strips.  Be sure to check the bottoms too.


	


WILCO. Thanks, Tom.



Michel



do not archive

_________________
Kitfox 3 - Jabiru 2200

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