 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
cgbrt(at)mondenet.com
Guest
|
 Posted: Mon Dec 24, 2007 2:30 pm Post subject: Zenith-List:Recovery from flutter |
 |
|
Mack,
You are correct, if flutter occurs time is of the essence. This is what I
would do:
First recognizing flutter. The most likely indication will be buzz or
strange vibration in the control stick/wheel or rudder pedals. At first
indication reduce power (idle if altitude and speed permits) and
simultaneously pull up to reduce speed. This will: 1- less speed should
reduce the destructive forces caused by the flutter, and ; 2-increased "G"
from the pull up will change the pressure pattern over the offending control
surface (s). Either one or both of these changes should cause the flutter to
stop. Avoid return to the same flight conditions that existed when flutter
occurred and land asap to check for damage and the cause.
Any change in speed, loading, control input, configuration, etc. may break
the flutter. Because flutter causes more drag., trying to increase speed may
prolong flight in flutter mode (not a desirable outcome). Higher speed also
equate to higher aerodynamic loads and early control failure. I would not
increased speed.
Flutter can be caused by too much elasticity in the wing or stabilizer
surfaces. When they bend (Twist) they transfer forces to the attached
control surface which bends and moves in the opposite direction thereby
amplifying the oscillation on the wing. This can lead to rapid wing or stab
failure.
Loose bushing in control hinges, too much play in control rods/cables can
also induce flutter. Balancing the control surfaces can help prevent flutter
and minimize the effect if it does occur.
Testing for flutter is not for the faint of heart. That is why test pilots
make big money and wear parachutes. They fly the envelop and tease the
control by bumping the stick to try and induce flutter. Fortunately computer
simulation can predict most flutter modes.... but not all.
Mack I hope this info helps you or someone else avoid flutter. Clearly,
flutter is not common and we are fortunate that most of the a/c we fly have
been tested by the designer and proven by the many who have built and flown
them before us.
Merry Christmas to list members.
Carl
701\912\amphibs
---
| | - The Matronics Zenith-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Zenith-List |
|
|
|
| Back to top |
|
 |
MaxNr(at)aol.com
Guest
|
| Posted: Tue Dec 25, 2007 9:20 pm Post subject: Zenith-List:Recovery from flutter |
|
|
This discussion about the safety of the 601 series wings may or may should be a matter of concern. Not to me. I have confidence in the design and the designer. If there are some that would like another layer of security, this country boy -- clodhopper humbly offers the suggestion that one could construct their top and bottom wing skins with the next heavier sheet size. It would add a small increase in weight but would stiffen up the structure somewhat. Many builders are now doing this in the fuselage without a second thought. Another way to stiffen the wing would be to add drag braces internally like a rag-wing. Even I don't think much of that idea.
Bob 601XL Do not archive
**************************************
See AOL's top rated recipes (http://food.aol.com/top-rated-recipes?NCID=aoltop00030000000004) [quote][b]
| | - The Matronics Zenith-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Zenith-List |
|
|
|
| Back to top |
|
|
ashontz
Joined: 27 Dec 2006
Posts: 723
|
| Posted: Thu Jan 03, 2008 4:11 am Post subject: Re: Zenith-List:Recovery from flutter |
|
|
If going to the next gauge up in sheet thickness helps then an extra rib between each rib oughta help too. The idea behind the next gauge up is just increasing the bending resistance of the sheet between each rib station, decreasing the distance between each rib station by decreasing the bending/twisting moment between rib stations by shortening the distance between ribs would also achieve the same end.
[quote="MaxNr(at)aol.com"]This discussion about the safety of the 601 series wings may or may should be a matter of concern. Not to me. I have confidence in the design and the designer. If there are some that would like another layer of security, this country boy -- clodhopper humbly offers the suggestion that one could construct their top and bottom wing skins with the next heavier sheet size. It would add a small increase in weight but would stiffen up the structure somewhat. Many builders are now doing this in the fuselage without a second thought. Another way to stiffen the wing would be to add drag braces internally like a rag-wing. Even I don't think much of that idea.
Bob 601XL Do not archive
**************************************
See AOL's top rated recipes (http://food.aol.com/top-rated-recipes?NCID=aoltop00030000000004)
| | - The Matronics Zenith-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Zenith-List |
|
|
|
| Back to top |
|
|
steveadams
Joined: 10 Jan 2006
Posts: 191
|
| Posted: Thu Jan 03, 2008 6:11 am Post subject: Re: Zenith-List:Recovery from flutter |
|
|
Keep in mind that a stiffer wing does not equal a stronger wing, and may in fact may be more prone to failure. The flexing and twisting going on in the wing as you fly through turbulent air is spreading the load through the entire span. Stiffening the wing concentrates more of that load directly on the wing attach points, which doesn't seem like a good idea unless you really know what you are doing. Does anyone know where the XL wing fails? Every chain has a weakest link, and Zenith should know where the "weakest link" in the Zodiac wing is. For increasing overall strength of the wing, that would be the place to start if you really want a stronger wing, not a bandaid.
Steve
Zodiac CH640
| | - The Matronics Zenith-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Zenith-List |
|
|
|
| Back to top |
|
|
ashontz
Joined: 27 Dec 2006
Posts: 723
|
| Posted: Thu Jan 03, 2008 6:29 am Post subject: Re: Zenith-List:Recovery from flutter |
|
|
I've thought of this. At the same time, this is not a 100 foot 747 wing that REALLY needs to flex. None of the NTSB reports indicated a failure at the root. Even so, you could easily beef the root as well.
| steveadams wrote: | Keep in mind that a stiffer wing does not equal a stronger wing, and may in fact may be more prone to failure. The flexing and twisting going on in the wing as you fly through turbulent air is spreading the load through the entire span. Stiffening the wing concentrates more of that load directly on the wing attach points, which doesn't seem like a good idea unless you really know what you are doing. Does anyone know where the XL wing fails? Every chain has a weakest link, and Zenith should know where the "weakest link" in the Zodiac wing is. For increasing overall strength of the wing, that would be the place to start if you really want a stronger wing, not a bandaid.
Steve
Zodiac CH640 |
| | - The Matronics Zenith-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Zenith-List |
|
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
