Today's Message Index:
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1. 07:04 AM - Re: Re: 601XL main spar question (Afterfxllc@aol.com)
2. 07:05 AM - Re: Re: 601XL main spar question (Afterfxllc@aol.com)
3. 07:37 AM - Re: Re: 601XL main spar question (Terry Phillips)
4. 10:23 AM - Re: Re: 601XL main spar question (Fred Sanford)
5. 11:40 AM - Re: Re: Re: 601XL main spar question (Terry Phillips)
6. 01:30 PM - Re: Re: Re: 601XL main spar question (purplemoon99@bellsouth.net)
7. 03:02 PM - Any Suggestions on a A&P PRep Course? (Jeffrey J Paris)
8. 03:43 PM - Re: Re: 601XL main spar question (Bryan Martin)
9. 04:37 PM - Re: Any Suggestions on a A&P PRep Course? (Paul Mulwitz)
10. 05:58 PM - Re: Re: 601XL main spar question (Larry McFarland)
11. 06:36 PM - Re: Re: 601XL main spar question (Larry McFarland)
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| Subject: | Re: 601XL main spar question |
In a message dated 4/16/2010 1:20:03 P.M. Eastern Daylight Time,
chicago2paris@msn.com writes:
if I recall correctly, the only person to live to tell about flutter dived
away rather than climbing...
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| Subject: | Re: 601XL main spar question |
In a message dated 4/16/2010 1:20:03 P.M. Eastern Daylight Time,
chicago2paris@msn.com writes:
if I recall correctly, the only person to live to tell about flutter dived
away rather than climbing...
No he chopped the power and climbed. And I know the guy and it did happen.
Jeff
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| Subject: | Re: 601XL main spar question |
At 11:59 AM 4/16/2010 -0400, Bryan Martin wrote:
>Why do you keep denying the possibility of pilot error in these accidents?
>It's a fact that pilot error is a factor in more accidents than all other
>causes combined. It is an especially prevalent problem for low time pilots
>with low time in type. Low time in type seems to be about the only common
>thread in these accidents, along with low time on the airframe.
While we do not know everything about the 601XL accidents, there are some
things that we do know. E.g. regarding common threads between the
accidents. First, lets list the accidents in question:
1. Oakdale, CA 2/8/06
2. Yuba City, CA 11/4/06
3. St. Fulgent, FR 7/7/07
4. Polk City, FL 4/7/08
5. Capao do Leao. BR 5/5/08
6. Barcelona, SP 6/1/08
7. Markemeer, NL 9/14/08
8. Antelope Island, UT 3/4/09
9. Agnos, AR 11/6/09
I see some common threads in these accidents.
One thread is that all these accidents involve structural failure. I
haven't listed the 601XL accidents that do not involve structural failure.
If I had listed those, it is likely that Bryan's assertion that many
accidents result from pilot error would shown to be correct.
Another thread is that they all involve Zenair CH601XL aircraft. There are
no 600's, 601HD's, 601HDS's, 701's, Kitfox's, Rans, etc. As Paul has
pointed out, it is almost impossible that, among all the homebuilt designs
out there, the 601XL has somehow been blessed with the most incompetent,
careless, unskilled collection of pilots and owners in the history of
aviation. Meanwhile, the 600, HD, and HDS apparently have only a single
inflight break up amongst them--Bramley, UK . Significantly, Bramley was
attributed to pilot error based on detailed analysis and the observation of
a very abrupt climbing maneuver. Personally, I do not find pilot error a
creditable explanation for the 601XL accidents.
A third common thread is the occurrence of flutter in the majority of these
accidents. Who says flutter occurred? Well, how about the NTSB and the FAA:
>>"Photographs and physical evidence:
>>
>>The FAA evaluated the photographic evidence of several accident aircraft
>>and observed
>>the physical evidence first hand of the Antelope Island accident
>>aircraft. The evidence
>>indicates the presence of compression failures in both the upper and
>>lower aft spar caps
>>(or skins). In some cases the evidence shows a complete wing failure in
>>one direction, yet
>>exhibits compression buckling consistent with bending in the other
>>direction as well. This
>>combined condition is indicative of complete load reversal and provides
>>consistent
>>evidence that flutter occurred in these cases.
>>
>>Reports and conclusions from the NTSB, other foreign government regulatory
>>agencies, and eyewitness accounts:
>>
>>The NTSB identified flutter as the primary cause for several accidents,
>>citing similar
>>evidence to what was stated in the previous section. Their expertise in
>>accident
>>investigation enables them to distinguish between damage that occurred in
>>flight during
>>the structural break-up sequence, and damage caused from impact with the
>>ground. The
>>NTSB has pointed out that the location of the buckling failures on the
>>upper and lower
>>surfaces of both wings has been observed consistently on several accident
>>aircraft.
>>Additionally the direction of the loading that would create those buckles
>>is typically in a
>>direction inconsistent with the loading from the impact with terrain.
>>However the
>>evidence is consistent with wing bending and/or twisting as would be
>>observed during
>>flutter where wing bending and torsion combine with control surface
>>rotation about the
>>wing torsional axis. Additionally the NTSB observed the compression
>>buckling of the
>>lower spar cap was at the lower edge of the hole that allowed the aileron
>>push rod to pass
>>through the rear spar web. The compression buckling of the upper spar cap
>>was several
>>inches inboard of the flap/aileron junction."
>>[Zodiac Special Review Team Report, FAA, p. 21]
The NTSB has published the photographic evidence in the Polk City Docket.
You can buy a copy of the Docket from General Microfilms. Alternatively,
the photos (from Oakdale, Yuba City, Polk City, Barcelona, Markemeer,
Antelope Island, and Agnos) are available for study here:
http://groups.yahoo.com/group/ZBAG/files/NTSB%20Flutter%20Evidence%20091021/
And yet, the FAA report also says,
>>"Based on the evidence and analysis available, it is clear that flutter
>>appears to be a causal
>>factor to the in-flight breakup of the airplanes. However, it is not
>>clear whether it was the
>>primary causal factor, or occurred after some other initial structural
>>deformation caused
>>local changes in wing section angle of attack. Flutter investigation
>>requires a highly
>>technical, detailed, and complex analysis. The FAA did not perform a
>>detailed analysis to
>>determine the flutter characteristics of the CH 601 XL ..."
One might ask why the FAA would say, "it is not clear whether it was the
primary causal factor," when there is unequivocal evidence that flutter
occurred in 7 of the 9 accident aircraft, and it is common knowledge that
aircraft structures cannot withstand the forces resulting from divergent
flutter.
I cannot answer that question with certainty, but I can suggest a rationale:
In their April 14, 2009, Safety Recommendation Letter to the FAA, the NTSB
wrote,
>>"Therefore, the National Transportation Safety Board recommends that the
>>Federal Aviation Administration:
>>
>>Prohibit further flight of the Zodiac CH-601XL, both special light sport
>>aircraft and experimental, until such time that the Federal Aviation
>>Administration determines that the CH-601XL has adequate protection from
>>flutter, (A-09-30) (Urgent)"
Moving quickly, three months later the FAA responded to the NTSB's "Urgent"
recommendation in a July 13, 2009 letter:
>>"The Federal Aviation Administration chartered a special review team to
>>investigate the details of each recommendation. The team consists of FAA
>>specialists from flight test, engineering, manufacturing, and accident
>>investigation. The special review team will analyze the Zodiac CH-601XL
>>and its derivatives.
>>=85
>>At this time, the FAA lacks adequate justification to take immediate
>>certificate action to ground the entire fleet."
So the FAA essentially rejected the NTSB recommendations and told the 601XL
community to go on flying their airplanes while the FAA studied the problem.
The FAA did not discover "adequate justification to take immediate action,"
until November 7, 2009 when the FAA issued SAIB CE-10-08 in which the FAA,
>>"strongly recommend that all owners and operators of Zodiac CH601XL/CH650
>>comply with actions outlined in a forthcoming Aircraft Manufacturing &
>>Design, LLC (AMD) Safety Directive / Safety Alert to address the
>>above-referenced concerns before further flight."
I must say that I am impressed. After considering the NTSB's
recommendations for 3 months before rejecting them in their letter of July
13, and then making no public statements on the 601XL for nearly 4 more
months, the FAA came into work on a Saturday(!) November 7, 2009 to issue
the SAIB!
Considering the above sequence of events, one rationale why the FAA would
say, "it is not clear whether it [i.e., flutter] was the primary causal
factor," becomes clearer. The FAA rejected the NTSB's Urgent recommendation
to ground the 601XL, and one could make a strong case that, as a direct
consequence of the FAA's inaction, the 9th 601XL structural failure
accident occurred on November 6 in Agnos, AR. If, in their final report,
the FAA acknowledged flutter as the probable cause of the 601XL accidents,
the FAA would, in effect, be saying, "The NTSB's April 14 recommendation to
ground the 601XL fleet was correct. We were wrong to ignore the strong
evidence for flutter in the 601XL accidents and to reject the NTSB
recommendation." Instead of acknowledging the obvious, the FAA chose to
obscure the issue by suggesting that flutter was only one possible cause,
and that the design's other documented flaws may have been primary. While
my conjecture may not be correct, I must say that I've observed similar
behavior in individuals and organizations. It can be difficult to admit you
are wrong. Even more so when a fatality results.
Of course, that is just one rationale for the FAA's action, and an infinite
number of others are possible.
My own personal view is that, while the original wing design is slightly
under strength, that weakness was not primary cause of the accidents. I
agree with the NTSB (as stated in the FAA final report) that the primary
cause in most, if not all, of the accidents was flutter. If we can
eliminate flutter, I believe the (structural failure) accidents will stop.
The FAA's report states that Zenair should retest the modified design for
flutter, and I agree that ASTM F2245 requires flutter testing before the
(modified) S-LSA model can be sold. But the ASTM flutter test requirement
does not apply to E-AB aircraft. I believe it's useful to consider the
requirements for certified aircraft. The FAA will waive flutter testing if
the control surfaces satisfy the criteria in A&E Report No. 45. I believe
that the counterbalanced ailerons satisfy the A&E Report No. 45 aileron
criteria, so I believe the upgrade will stop the flutter. That's good
enough for me. But don't take my word for it. A&E Report 45 is available
here:
http://groups.yahoo.com/group/ZBAG/files/
Do the calculations yourself and report back to the group.
I don't want to leave the impression that I believe the wing strengthening
is unimportant. The 601XL wing should meet spec. I just do not believe that
the weak wing caused the accidents. And I am equally sure that a practical
aircraft wing cannot be make strong enough to withstand divergent
wing-aileron bending flutter. Stop flutter and you'll stop the accidents.
Enjoy the build.
Terry
Terry Phillips
ttp44~at~rkymtn.net
Corvallis MT
ZU-601XL/Jab 3300 s .. l .. o .. o .. w build kit - Tail & flaps are done;
Upgrading wings & ailerons per the AMD Safety Directive
http://www.mykitlog.com/N47TP/
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| Subject: | Re: Re: 601XL main spar question |
Well said Terry - complete, concise, and with references. Good synopsis.
As far as I am concerned: case closed. Next subject????? I do have a
question though, do you know if all of the flutter incidents were with
piano hinged ailerons?? I know that Yuba City
was...............................Fred Sanford N9601 sold just before
the edict...............
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| Subject: | Re: Re: 601XL main spar question |
Fred
'Good question.
Stephen had more complete access to the accident data than I did. (I.e., he
saw everything I saw, but he managed to get access to info that he could
not share further.) After Markemeer he told me that he did not have info
about Polk City or St Fulgent, but that the rest of the accident aircraft
had piano hinges. From the accident flutter evidence photos referenced
earlier, it is clear that Polk City and Agnos had piano hinges. It appears
to me from the photos that Antelope Island had flex hinges, and the Factual
Report refers to "flexible skin ailerons." I conclude that Antelope Island
had flex hinges. I suspect that the preponderance of piano hinges in the
accident aircraft (at least 7 of 9) is much greater than the occurrence of
piano hinged ailerons in the fleet. So, I would conclude that flutter is
more likely with piano hinges than with flex hinges. But, Antelope Island
and the experience of at least two "flutter survivors," indicate that flex
hinges are not proof against flutter in the 601XL. (ZBAG questionnaire's
and other "flutter survivor" naratives are included in the ZBAG Forum
Files.) 'Hope that helps.
Terry
At 10:16 AM 4/17/2010 -0700, you wrote:
>Well said Terry - complete, concise, and with references. Good synopsis.
>As far as I am concerned: case closed. Next subject????? I do have a
>question though, do you know if all of the flutter incidents were with
>piano hinged ailerons?? I know that Yuba City
>was...............................Fred Sanford N9601 sold just before the
>edict...............
>
>
Terry Phillips
ttp44~at~rkymtn.net
Corvallis MT
ZU-601XL/Jab 3300 s .. l .. o .. o .. w build kit - Tail & flaps are done;
Upgrading wings & ailerons per the AMD Safety Directive
http://www.mykitlog.com/N47TP/
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| Subject: | Re: Re: 601XL main spar question |
PerfectTerry. End of story.... It IS time to move on,No more wing spar,wing
spar,wing sparrrrrrrrBlaBla- go to work on your planes so you can fly ag
ain. Joe N101HD 601XL-R Ram/Subaru- ( now Corvett yellow- red and black
)=0A=0A=0A=0A=0A________________________________=0AFrom: Fred Sanford <sona
r1@cox.net>=0ATo: zenith-list@matronics.com=0ASent: Sat, April 17, 2010 1:1
6:29 PM=0ASubject: Zenith-List: Re: Re: 601XL main spar question=0A=0A=0AWe
ll said Terry - complete, concise, and with references. Good synopsis. As f
ar as I am concerned: case closed. Next subject????? I do have a question t
hough, do you know if all of the flutter incidents were with piano hinged a
ilerons?? I know that Yuba City was...............................Fred Sanf
-========================
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| Subject: | Any Suggestions on a A&P PRep Course? |
Hello Listers,In the process of building two amateur built experimentals, wh
ich are a Zenith Zodiac CH601XL and currently finishing up a Europa Monowhee
l Classic =C2-I have accrued enough hours to convince my local FSDO to sig
n off on taking the Airframe and Powerplant exams. =C2-Does anyone out in
internet airplane building land know of or can vouch for a quality A&P prepa
ration course to satisfy all 3 parts of the FAA A&P requirements i.e., writt
en, oral and practical tests? =C2-Prefereably somewhere close to Rochester
, NY if possible?Thanks for your time and consideration.Jeff Paris
Message 8
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| Subject: | Re: 601XL main spar question |
As far as I have been able to determine, all the accidents involved failure in
positive G loading except for Yuba City. There has already been a recommendation
to limit the nose down elevator travel to about half of the nose up travel.
I don't know if the Yuba City airplane had this modification.
>
>>> the upgrade shows +6/-3 for both the 601 and the 650<<
>
> My mentors were concerned that although the upgrade does appear to strengthen
the wings as to torsional rigidity and positive Gs it may well detract from their
ability to handle negative Gs due to the decision to only upgrade the top
spar cap...
>
> According to my plans, which CH still stands behind, if I don't upgrade I am
at -6G, if I upgrade, I am at -3Gs, according to the upgrade paperwork.
>
> If it "might be" negative Gs causing the failures, does an upgrade sound like
a good idea without first addressing the stick sensitivity issue?
>
>>> Is your comment below the reason you felt uneasy about the upgrade? ...wing
fails first in negative gs?<<
>
> Scott, this is what I meant by cold feet/feeling uneasy and why I am considering
running a top mounted 1/8" cable between each wings' new rear spar mid-span
doublers, and 3/16" cable between the inboard AN47 bolts of the new main spar
struts.
--
Bryan Martin
N61BM, CH 601 XL,
RAM Subaru, Stratus redrive.
do not archive.
Message 9
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| Subject: | Any Suggestions on a A&P PRep Course? |
Hi Jeff,
I spoke to an FAA guy at one of the shows on this point. He informed me
the experience needed to get an A&P license must be on certified planes.
This precludes work on Amateur built planes to qualify for the license.
Also, it prevents people who work on planes in the manufacturer's
factory since they are not yet certified.
Good luck,
Paul
From: owner-zenith-list-server@matronics.com
[mailto:owner-zenith-list-server@matronics.com] On Behalf Of Jeffrey J
Paris
Sent: Saturday, April 17, 2010 3:02 PM
Subject: Zenith-List: Any Suggestions on a A&P PRep Course?
Hello Listers,
In the process of building two amateur built experimentals, which are a
Zenith Zodiac CH601XL and currently finishing up a Europa Monowheel
Classic I have accrued enough hours to convince my local FSDO to sign
off on taking the Airframe and Powerplant exams. Does anyone out in
internet airplane building land know of or can vouch for a quality A&P
preparation course to satisfy all 3 parts of the FAA A&P requirements
i.e., written, oral and practical tests? Prefereably somewhere close to
Rochester, NY if possible?
Thanks for your time and consideration.
Jeff Paris
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| Subject: | Re: 601XL main spar question |
Yes Patrick,
The angle of the spar related to the load would definitely make a
plausible rationale for the oblong holes and bent bolts. Otherwise how
would they
ever get to a point of beginning failure. Very good point!
Larry McFarland 601HDS at www.macsmachine.com
>
> Torsion.
>
> Take a cardboard shoe box. Tape it up nice and tight. You can stand on it.
>
> Take that same cardboard shoe box. Tape it up nice and tight, but with a 9 degree
tilt to it. Then try to stand on it. Not nearly as strong.
>
> The question is, "do the upgrades make the wing strong enough...?" It appears
that as far as Zenith and the FAA is concerned, the answer is "yes".
>
> Time will tell as more of us complete the upgrades and return to the air.
>
> Patrick
> XL/Corvair/BRS
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=294356#294356
>
>
>
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| Subject: | Re: 601XL main spar question |
Exactly right Paul. The elongated holes and bent bolts suggest
improperly tightened bolts, or misalignment of the line of structural
connections. (Obviously the latter)
and the number of cracks in the center spar suggests over-stress was
prevalent a good bit before the failure. Moving the stress out through
the fuselage attach sheets
and angle works out to a rapid total failure when it all lets go. Still
don't think flutter had anything to do with it.
Larry McFarland 601HDS at www.macsmachine.com
paulrod36@msn.com wrote:
> Opinions being like another part of our anatomy (everybody has one),
> I'd like to throw in an unfounded suspicion for your consideration:
> If you take a piece of flat metal, any thickness or length will do,
> set it at 9 degrees (forward) from vertical, and subject it to a true
> vertical stress, it tries to bend backward under that stress. Could
> it be that the main spar bends backward some, puts pressure at the
> rear spar attach point, and starts the failure there, followed
> immediately by the main spar failure when the rear breaks? I have no
> evidence, stats, or analysis to back this up, but I can't think of any
> aircraft with a canted spar. Thoughts, anyone?
>
> Paul R
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