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s_thatcher(at)bellsouth.n
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 Posted: Sat Dec 22, 2007 6:19 am Post subject: 601Wing Failures - a different perspective |
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Although I generally don't like to second guess the reason for these wing
failures, I feel I personally need to get additional data in order to make
an informed decision as to how to correct the problem, if there is one.
Here is my take on what we know so far. I would also like to get additional
information from others based on the questions I have listed below.
1. The wing failures do not appear to be failing under flight loads. All
static tests indicate that the wings are structurally sound.
2. I have spoken to two people who have experienced "wing flutter" and lived
to tell about it (one directly and one second hand report). This condition
appears without notice and can cause catastophic wing failure in a few
seconds. The first one was in Georgia and the second one occured just a few
days ago in Lantana, FL (so far unreported).
The conditions that cause this "flutter" have not been investigated by
anyone that I know of. However I do feel that we need to get more
information on this type of "potential" failure.
The following are questions I would like those who have experienced flutter
to provide.
1. What was the speed of the aircraft at the time of the flutter?
2. Do you have wing lockers?
3. Were you using flaps?
4. Were you making left or right turns?
5. Were you decending, ascending or in level flight?
6. Had you attempted any aerobatics prior to this flight?
7. Did you notice any smoking rivets along spar?
8. How did you recover from the flutter?
9. Was there any advanced notice of the pending flutter?
10. What make of engine were you using?
11. Did you notice any unusual vibrations prior to the flutter (prop or
engine)?
12. Did you fly through unusual weather conditions?
13. Did you make any structural changes to the wing itself during or after
construction?
14. Any other information you feel is important.
Please send your answers to me and I will compile the data and report to the
list, or , if you prefer, please answer the questions directly on this
forum.
Thanks for your input,
Scott Thatcher, Palm Beach Gardens, FL
601XL with Corvair, Still 99% complete but Registered as E-LSA
N601EL
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larry(at)macsmachine.com
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| Posted: Sat Dec 22, 2007 7:34 am Post subject: 601Wing Failures - a different perspective |
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Scott,
I think you're "running lemmings" here as most people wouldn't recognize
flutter if it happened to them. Flutter occurs when you have a plane at
excessively high speed and unbalanced control surfaces. One could
easily run into convective and think it was flutter or load the plane in
a dive pullout
and get flutter at the bottom when as wings were unloading, but flutter
within the published limits for the XL is highly unlikely.
I don't think just flying the XL normally will ever get you to that
point, otherwise you'd have lots of people reporting it and many more
fatalities.
Because the XL is a consistently good tested design, the rarity of these
accidents are more in line with pilot error and/or workmanship.
A solution to unbalanced control surfaces is to balance them, but Chris
Heintz has said "that was unnecessary as speeds were never that high".
Larry McFarland 601HDS at www.macsmachine.com
Scott Thatcher wrote:
| Quote: |
<s_thatcher(at)bellsouth.net>
Although I generally don't like to second guess the reason for these
wing failures. I feel I personally need to get additional data in
order to make an informed decision as to how to correct the problem,
if there is one.
The conditions that cause this "flutter" have not been investigated by
anyone that I know of. However I do feel that we need to get more
information on this type of "potential" failure.
Scott Thatcher, Palm Beach Gardens, FL
601XL with Corvair, Still 99% complete but Registered as E-LSA
N601EL
|
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Jaybannist(at)cs.com
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| Posted: Sat Dec 22, 2007 9:24 am Post subject: 601Wing Failures - a different perspective |
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I think that you guys have a semantics problem. The "flutter" Larry is talking about is a technical term, and it refers to the divergent and increasing amplitude of control surface oscillations. The wing flutter earlier reported by a poster is a "common" usage, probably more appropriately called "vibration" or "oscillation"; and as I recall, referred to the whole wing, not just control surfaces. Aerodynamic flutter may not be controllable and usually results in the departure of the control surface or whatever it is attached to.
Correct me if I'm wrong (I think that usually goes without saying).
Jay in Dallas 601XL N2630J
Do not archive
LarryMcFarland <larry(at)macsmachine.com> wrote:
| Quote: |
Scott,
I think you're "running lemmings" here as most people wouldn't recognize
flutter if it happened to them. Flutter occurs when you have a plane at
excessively high speed and unbalanced control surfaces. One could
easily run into convective and think it was flutter or load the plane in
a dive pullout
and get flutter at the bottom when as wings were unloading, but flutter
within the published limits for the XL is highly unlikely.
I don't think just flying the XL normally will ever get you to that
point, otherwise you'd have lots of people reporting it and many more
fatalities.
Because the XL is a consistently good tested design, the rarity of these
accidents are more in line with pilot error and/or workmanship.
A solution to unbalanced control surfaces is to balance them, but Chris
Heintz has said "that was unnecessary as speeds were never that high".
Larry McFarland 601HDS at www.macsmachine.com
Scott Thatcher wrote:
>
> <s_thatcher(at)bellsouth.net>
>
> Although I generally don't like to second guess the reason for these
> wing failures. I feel I personally need to get additional data in
> order to make an informed decision as to how to correct the problem,
> if there is one.
> The conditions that cause this "flutter" have not been investigated by
> anyone that I know of. However I do feel that we need to get more
> information on this type of "potential" failure.
> Scott Thatcher, Palm Beach Gardens, FL
> 601XL with Corvair, Still 99% complete but Registered as E-LSA
> N601EL
>
|
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planecrazydld(at)yahoo.co
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| Posted: Sat Dec 22, 2007 3:30 pm Post subject: 601Wing Failures - a different perspective |
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very precisely accurate descriptions Jay. Have a very blessed Christmas.
do not archive
Jaybannist(at)cs.com wrote:[quote] --> Zenith-List message posted by: Jaybannist(at)cs.com
I think that you guys have a semantics problem. The "flutter" Larry is talking about is a technical term, and it refers to the divergent and increasing amplitude of control surface oscillations. The wing flutter earlier reported by a poster is a "common" usage, probably more appropriately called "vibration" or "oscillation"; and as I recall, referred to the whole wing, not just control surfaces. Aerodynamic flutter may not be controllable and usually results in the departure of the control surface or whatever it is attached to.
Correct me if I'm wrong (I think that usually goes without saying).
Jay in Dallas 601XL N2630J
Do not archive
LarryMcFarland wrote:
[quote]--> Zenith-List message posted by: LarryMcFarland
Scott,
I think you're "running lemmings" here as most people wouldn't recognize
flutter if it happened to them. Flutter occurs when you have a plane at
excessively high speed and unbalanced control surfaces. One could
easily run into convective and think it was flutter or load the plane in
a dive pullout
and get flutter at the bottom when as wings were unloading, but flutter
within the published limits for the XL is highly unlikely.
I don't think just flying the XL normally will ever get you to that
point, otherwise you'd have lots of people reporting it and many more
fatalities.
Because the XL is a consistently good tested design, the rarity of these
accidents are more in line with pilot error and/or workmanship.
A solution to unbalanced control surfaces is to balance them, but Chris
Heintz has said "that was unnecessary as speeds were never that high".
Larry McFarland 601HDS at www.macsmachine.com
Scott Thatcher wrote:
> --> Zenith-List message posted by: "Scott Thatcher"
>
>
> Although I generally don't like to second guess the reason for these
> wing failures. I feel I personally need to get additional data in
> order to make an informed decision as to how to correct the problem,
> if there is one.
> The conditions that cause this "flutter" have not been investigated by
> anyone that I know of. However I do feel that we need to get more
> information on this type of "potential" failure.
> Scott Thatcher, Palm Beach Gardens, FL
> 601XL with Be a better friend, newshound, and [quote][b]
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shilcom
Joined: 28 Sep 2007
Posts: 63
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| Posted: Sat Dec 22, 2007 4:08 pm Post subject: 601Wing Failures - a different perspective |
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<<<I think you're "running lemmings" here as most people wouldn't recognize
flutter if it happened to them>>
A more accurate statement would be "most people don't live over a control flutter incident. bob U.
[quote] ---
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shilcom
Joined: 28 Sep 2007
Posts: 63
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| Posted: Sat Dec 22, 2007 4:12 pm Post subject: 601Wing Failures - a different perspective |
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This seems to be being called "wing flutter". Is it wing flutter or "aeleron flutter". Bob U.
[quote] ---
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larry(at)macsmachine.com
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| Posted: Sat Dec 22, 2007 5:10 pm Post subject: 601Wing Failures - a different perspective |
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Bob,
For the concern over "wing failure", one has to know if there's enough
leveraged flexure in the wing and weight in an unbalanced aileron
to multiply the wings harmonic and damage the wing root structure.
Probably seen only at excessive speeds.
I'd call it aileron flutter because the corrective action is balancing
the control surface.
Larry McFarland 601HDS at www.macsmachine.com
Bob Unternaehrer wrote:
[quote] This seems to be being called "wing flutter". Is it wing flutter or
"aeleron flutter". Bob U.
---
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purplemoon99(at)bellsouth
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| Posted: Sat Dec 22, 2007 6:57 pm Post subject: 601Wing Failures - a different perspective |
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Scott,was the plane in Lantana a AMD factory built, and are we talking about
high sspeed wing viberation? Joe N101HD 601XL/RAM
---
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