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larry(at)macsmachine.com
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 Posted: Thu Apr 24, 2008 5:36 pm Post subject: [Probable Spam] Re: Re: CH601 Yuba City Photos Link |
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Hi guys,
The exposed portion of the center spar that's attached to the wing has a
great deal of
fracture, rivets still in place, which indicate failure along or near
the plane of stress. The
leveling corrections in flight and the low altitude suggest that the
pilot was aware of something
being amiss before the collapse or separation of the center spar. Folds
in the wing are prior
to the impact or wrenching stresses that unbuttoned the wing skin. Any
failure of the center spar
would progressively affect flap action and aileron responses. The major
pop would be the
center spar and its final break up. I'd conclude that construction or
materials or both will
be found to be compromised by the original builder within the center spar.
Larry McFarland 601HDS at www.macsmachine.com
do not archive
Rick Lindstrom wrote:
| Quote: | >
>
> I think the aileron being the weak link is unlikely.
>
> In my opinion, the rear spar attachment is much more likely to be the
> culprit. Consider that both of these planes were near destination (I
> think). Certainly the Polk City crash was near Lakeland. If the rear
> spar attachment is a problem area, then perhaps after this long
> uneventful trip, a few degrees of flaps are added near destination
> causing a failure of a weak joint. That would explain both of these
> planes having a problem near the end of their respective flights and not
> somewhere en route at cruise speed. If the joint is weak, then it is
> going to fail eventually with or without the added encouragement of
> engaging flaps. If the rear spar attachment failed. this would also
> cause a substantial low frequency flutter visible from a ground
> observer. The wing twisting would make the main spar fail rather easily.
> The wing would be loaded in ways that would cause a catastrophic
> failure. With the wing being exposed to these forces I can see the
> aileron unzipping. Notice in the pictures that the wing creased aft of
> center along a line perpendicular to the fuselage. (You can see where
> the ribs ripped) Also, a twisting motion of a wing as it separated would
> explain how it could possibly even break the interior attachments of the
> main wing spar in the fuselage. *One of the pictures shows a large
> section of center spar attached to the wing.*
>
> I hope the NTSB is thinking about these scenarios as much as we are.
>
> Jim
>
>
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Ron Lendon
Joined: 10 Jan 2006
Posts: 685
Location: Clinton Twp., MI
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| Posted: Thu Apr 24, 2008 7:30 pm Post subject: Re: [Probable Spam] Re: Re: CH601 Yuba City Photos Link |
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I was thinking the same thing Larry, pictures 27 & 29 look like a bomb went off on the center spar.
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_________________
Ron Lendon
WW Corvair with Roy's Garage 5th bearing
CH 601 XLB
N601LT - Flying
http://www.mykitlog.com/rlendon
Corvair Engine Prints:
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jim.lanier(at)charter.net
Guest
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| Posted: Thu Apr 24, 2008 10:39 pm Post subject: [Probable Spam] Re: Re: CH601 Yuba City Photos Link |
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"The leveling corrections in flight and the low altitude suggest that the pilot "
I think you are referring to the Polk crash here. In this instance, the wings were still attached with damage to the lower cap.
"Initial examination of the wreckage revealed that the horizontal stabilizer and rudder were separated from their respective attach points, but remained co-located with the wreckage. Detailed examination of the left wing revealed that the lower main wing spar cap was fractured at the wing root. Portions of the left wing spar were retained for further examination. The remainder of the main wing spar, which extended through the fuselage and the right wing, was bent but remained largely intact."
I would like to see if the rear spar attachment failed on this one. I am sure you read where they said the pilot had the aileron trim all the way to one extreme. Yes, he knew he had a problem and was struggling with control prior to his accident.
Jim
LarryMcFarland wrote: [quote]--> Zenith-List message posted by: LarryMcFarland <larry(at)macsmachine.com> (larry(at)macsmachine.com)
Hi guys,
The exposed portion of the center spar that's attached to the wing has a great deal of
fracture, rivets still in place, which indicate failure along or near the plane of stress. The
leveling corrections in flight and the low altitude suggest that the pilot was aware of something
being amiss before the collapse or separation of the center spar. Folds in the wing are prior
to the impact or wrenching stresses that unbuttoned the wing skin. Any failure of the center spar
would progressively affect flap action and aileron responses. The major pop would be the
center spar and its final break up. I'd conclude that construction or materials or both will
be found to be compromised by the original builder within the center spar.
Larry McFarland 601HDS at www.macsmachine.com
do not archive
Rick Lindstrom wrote:
| Quote: | | Quote: | --> Zenith-List message posted by: "James E. Lanier" <jim.lanier(at)charter.net> (jim.lanier(at)charter.net)
I think the aileron being the weak link is unlikely.
In my opinion, the rear spar attachment is much more likely to be the culprit. Consider that both of these planes were near destination (I think). Certainly the Polk City crash was near Lakeland. If the rear spar attachment is a problem area, then perhaps after this long uneventful trip, a few degrees of flaps are added near destination causing a failure of a weak joint. That would explain both of these planes having a problem near the end of their respective flights and not somewhere en route at cruise speed. If the joint is weak, then it is going to fail eventually with or without the added encouragement of engaging flaps. If the rear spar attachment failed. this would also cause a substantial low frequency flutter visible from a ground observer. The wing twisting would make the main spar fail rather easily. The wing would be loaded in ways that would cause a catastrophic failure. With the wing being exposed to these forces I can see the aileron unzipping. Notice in the pictures that the wing creased aft of center along a line perpendicular to the fuselage. (You can see where the ribs ripped) Also, a twisting motion of a wing as it separated would explain how it could possibly even break the interior attachments of the main wing spar in the fuselage. *One of the pictures shows a large section of center spar attached to the wing.*
I hope the NTSB is thinking about these scenarios as much as we are.
Jim
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