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The accident versus ready to fly aircraft
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larry(at)macsmachine.com
Guest

Posted: Sat Apr 26, 2008 8:20 am Post subject: The accident versus ready to fly aircraft

Hi guys,



Yesterday, my over zealous “spam-protection” ate a dozen emails that 

were sent me on this issue, so I’m going to try a blanket answer with a 

“do not archive” that only reflects my view. If there was a specific 

technical question on an item, please do not hesitate to resend your 

email. Thanks again, Larry McFarland



Professionally, I’ve only “studied” fatigue testing and failure on 

mechanical and structural elements, so I’m not qualified to make any 

statements that could prove anything. That experience did provide 

valuable insight on a few of the things seen in the images. After 

reading the NTSB sequence of events, I put the images on my computer to 

take an only slightly closer look via Photoshop, and did come to some 

conclusions on the damage characteristics. NTSB may offer a general 

statement, but the specific cause may never be answered in their report 

unless they take time to thoroughly investigate manufacture process, 

assembly errors and variant materials in the plane.



The observed leveling and low altitude suggests the pilot was aware of a 

progressive structural failure.



Complete failure of the center section front spar between and below the 

end points is telling. Bending stresses causing the center spar web and 

caps to crack and separate along lines nearly parallel to it, given the 

flight path, was progressive. Impact would not likely push or pull a 

long fractured line in the same direction as the design stress, but the 

length of center spar fracture and break up was so complete that it 

suggests that the shock that permitted folding wing(s) began here.



The loss of a rear spar attachment and flap could very well create 

excessive stress on the front spar, break the bottom caps, and initiate 

collapse of the wing(s).



The clean sheared rivet lines on the bottom spar cap versus the material 

that was last to tear from the top cap suggests that the web to cap line 

was torn from between the spar caps before being separated from the 

fuselage. Extensive separation of the center spar from top and bottom 

components far exceeds the damage seen in the wing, still attached. The 

fractures are not peeled and are parallel with the line of stress and 

are seen in the straight portions of still connected web and upper cap 

image 27. Broken out bolt holes are clean and likely impact related. The 

origin of failure is nearer the front lower spar cap and web than within 

the wing.



. The original still flying XL demo plane is representative of all the 

XLs flying today and it strongly argues the case for a defective 

material or construction process by the actual foreign manufacturer of 

the quick-build or ready to fly aircraft. It’s not the result of a 

defective design material or process call out in the Zenith plans.



Example: If pre-punched holes for the spar web didn’t match the caps, 

would the manufacturer just drill open the holes and continue to rivet? 

Very possible for people paid on product-volume, but I doubt a kit 

builder or scratch builder would ever tolerate such practice.



I believe the plans to be “golden” and safe for both the kit and the 

scratch builder. The 601XL is a fine aircraft that will be around for a 

long time, so stay the course and keep on building.



Larry McFarland 601HDS at www.macsmachine.com 

<http://www.macsmachine.com/> Do not archive

cookwithgas

Joined: 06 Nov 2007
Posts: 159

Posted: Sat Apr 26, 2008 9:57 am Post subject: Re: The accident versus ready to fly aircraft

Thanks Larry for your thoughtful input.  



This morning I put just over an hour on my 601XL and felt very good about it.  It flies like a dream and I have to pinch myself because I can't believe I built it and that it flies that well.  



I did a more thorough than usual pre-flight and found everything to be solid and tight.  The design is good and all the hard work has paid off with a very nice aircraft.  



For those still building, don't be discouraged.  Do quality work and you will have a well-built, safe aircraft.  



Scott Laughlin

601XL/Corvair

Finished & Flying as much as possible.

amyvega2005(at)earthlink.
Guest

Posted: Sat Apr 26, 2008 1:01 pm Post subject: The accident versus ready to fly aircraft

Righ ON! I just came back from flying and I as well am inspecting the plane throughout.  Scott please send more pics of your flying, I love those vids!  Sorry I missed you at the BBQ!



Juan



--

wjones(at)brazoriainet.co
Guest

Posted: Sat Apr 26, 2008 1:42 pm Post subject: The accident versus ready to fly aircraft

Hello all you newly licensed 601XL pilots . Did you use DARs or FAA ,if so 

was any special inspection requirements imposed since  3/1/08 . My local DAR 

said that he received information from the FAA that he must check to see if 

any additional inspection requirements apply to the 601XL .

Wade Jones    South Texas

601XL plans building

Cont. 0200

---

amyvega2005(at)earthlink.
Guest

Posted: Sat Apr 26, 2008 2:27 pm Post subject: The accident versus ready to fly aircraft

Wade,

we went to a DAR, and my thoughts on your DAR's comment,  Go to another DAR.



JUan



--

cookwithgas

Joined: 06 Nov 2007
Posts: 159

Posted: Sat Apr 26, 2008 3:31 pm Post subject: Re: The accident versus ready to fly aircraft

I used the FAA.  LOOONG wait and very picky.  My inspector told me that if I flew with my ever-so-slightly-slanted N-numbers that he would write me up.  Never mind that I bought them from Aircraft Spruce specially made.  His interpretation of "block letters" is plumb vertical with no slant.  While he was there he did a ramp inspection on a crop duster and busted him. 



I sent my paperwork off in May and I got my pink slip in December, 2007.

sdthatcher

Joined: 13 Mar 2008
Posts: 91
Location: Port Saint Lucie

Posted: Sun Apr 27, 2008 6:23 am Post subject: The accident versus ready to fly aircraft

Just a quick note for those who are concerned about flying their 601XL amid 

the recent accident paranoia (I include me as well).



Use a Borescope: The 601XL that sustained vibration damage during a 

descending turn and who has successfully repaired that damage has mentioned 

that prior to his first flight, he used a borescope to inspect the inside of 

the wing, spar and caps, and found them in excellent condition. He was 

planning to fly shortly.



Nylon Flap Stop: Also, another reminder to be sure you have installed the 

nylon flap stops as indicated in the plans. I have seen two aircraft without 

them and one stated that he felt vibration in the wing during cruise flight! 

The flaps should not exhibit any movement whatsoever when in the up position 

and the nylon stop guarantees that condition will apply. Naturally, when you 

lower the flaps, there is a certain amount of movement however the speed at 

which you lower the flaps is (should be) significantly lower.



Getting ready for first flight this month!



Scott Thatcher, Palm Beach Gardens, FL

601XL with Corvair, Registered as E-LSA

N601EL, http://placestofly.com, EAA203

_________________
Scott Thatcher, Port Saint Lucie, FL
601XL with Corvair, Registered as E-LSA
N601EL, EAA203 140 hours and not flying currently.

notsew_evets(at)frontiern
Guest

Posted: Sun Apr 27, 2008 7:01 am Post subject: The accident versus ready to fly aircraft

ok, I give...  What Flap stop ?????

---

PatrickW

Joined: 27 Oct 2006
Posts: 380
Location: Fort Worth, Texas

Posted: Sun Apr 27, 2008 7:39 am Post subject: Re: The accident versus ready to fly aircraft

 	  sdthatcher wrote: 	
		  The 601XL that sustained vibration damage during a 

descending turn and who has successfully repaired that damage has mentioned that 	




What vibration damage...? 



This sounds like another data point.  



And something we should add to the list of things to check.



Thanks,



Patrick

XL/Corvair

N63PZ (reserved)

Jaybannist(at)cs.com
Guest

Posted: Sun Apr 27, 2008 7:51 am Post subject: The accident versus ready to fly aircraft

Steve,



See Drawing 6-S-3.



Jay in Dallas

"steve" <notsew_evets(at)frontiernet.net> wrote:



[quote]



ok, I give...  What Flap stop ?????

---

notsew_evets(at)frontiern
Guest

Posted: Sun Apr 27, 2008 8:06 am Post subject: The accident versus ready to fly aircraft

OMG !



I love this website !!!



SW

---

sdthatcher

Joined: 13 Mar 2008
Posts: 91
Location: Port Saint Lucie

Posted: Sun Apr 27, 2008 6:14 pm Post subject: Re: The accident versus ready to fly aircraft

<<What vibration damage...? 

<<This sounds like another data point. 

<<And something we should add to the list of things to check. 

<<Thanks, 

<<Patrick 

<<XL/Corvair 

<<N63PZ (reserved)



Hi Patrick. A 601XL sustained rapid vibrations of the wings during a descending turn. I published the data on this site some time ago but the summary basically stated that a fix was attempted to a damaged rudder which shifted the CG of the rudder rearward and may have contributed to the vibrations which went through the fuselage and wings and may have been exacerbated by pilot induced response to the vibrations.



If you were referring to the flaps, this was mentioned to me by another pilot while visiting a hangar that housed a 601XL and was missing the nylon flap stops.

_________________
Scott Thatcher, Port Saint Lucie, FL
601XL with Corvair, Registered as E-LSA
N601EL, EAA203 140 hours and not flying currently.

lgingell

Joined: 10 Jan 2006
Posts: 50
Location: Lake California Airpark 68CA

Posted: Mon Apr 28, 2008 9:06 am Post subject: Re: The accident versus ready to fly aircraft

My 6-S-3 from 12/03 has no nylon flap stops on it.  Someone care to post a scan?



..lance

_________________
Zodiac XL/Jab 3300
http://lancegingell.com

notsew_evets(at)frontiern
Guest

Posted: Mon Apr 28, 2008 10:25 am Post subject: The accident versus ready to fly aircraft

I didnt think mine did either til I looked again.  It shows a 90 by 25 mm 

1/8 nylon piece (2) that goes under the flange of the drag spar .  I removed 

the three rivets from point of rib 7 outwards....

Whalla! I have a stop....

---

Tim Juhl

Joined: 21 Mar 2006
Posts: 488
Location: "Thumb" of Michigan

Posted: Mon Apr 28, 2008 11:17 am Post subject: Re: The accident versus ready to fly aircraft

Flap Stop comment - The nylon stop does a good job of preventing movement of the retracted flap at the outboard end, while the inboard end is restrained by the actuating pin which rests in a slot.  I am considering installing a second stop at the inboard end to make it even more solid.



Comments?



Tim



Do not archive

_________________
______________
CFII
Champ L16A flying
Zodiac XL - Jabiru 3300A
Almost done! It'll fly in spring!

notsew_evets(at)frontiern
Guest

Posted: Mon Apr 28, 2008 12:24 pm Post subject: The accident versus ready to fly aircraft

Sounds like an excellent idea Tim...

---

Terry Phillips

Joined: 11 Jan 2006
Posts: 346
Location: Corvallis, MT

Posted: Mon Apr 28, 2008 12:48 pm Post subject: The accident versus ready to fly aircraft

Steve



Along the same lines of general enlightenment, a while back you mentioned 

"drag spar" in one of your posts. I assume from the context that the drag 

spar is the rear spar. Is that correct? Thanks.



Terry

At 09:02 AM 4/27/2008 -0700, you wrote:

 	  Quote: 	
		  OMG !



I love this website !!!



SW


	




Terry Phillips

ttp44~at~rkymtn.net

Corvallis MT

601XL/Jab 3300 s .. l .. o .. o .. w build kit - Tail, flaps, & ailerons 

are done; working on the wings

http://www.mykitlog.com/N47TP/

_________________
Terry Phillips
Corvallis, MT
ttp44<at>rkymtn.net
Zenith 601XL/Jab 3300 slow build kit - Tail feathers done; working on the wings.

notsew_evets(at)frontiern
Guest

Posted: Mon Apr 28, 2008 1:11 pm Post subject: The accident versus ready to fly aircraft

Yes em.

Wings have "usually" two spars per side.  The main spar and the drag 

spar....

"Some" designs these days have a humongous main spars and dont have a drag 

spar.

These terms are from the 1940s til ???...

Whatever they call them now is "what it is", my man...



SW

---

ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Mon Apr 28, 2008 1:12 pm Post subject: Re: The accident versus ready to fly aircraft

This is probably one of the more informative threads I've read on here in awhile. Thanks. Possible problems make more sense now. More than likely, the only problem is bad maintenance or construction.

leinad

Joined: 19 Sep 2006
Posts: 283
Location: Central Virginia

Posted: Mon Apr 28, 2008 3:55 pm Post subject: Re: The accident versus ready to fly aircraft

Tim,

It might work, but I think it could have the opposite effect.  By having the stop along way from the flap actuating lever, the flap is allowed to twist a little in the up position so that it's solidly held.  By putting a stop inboard, there won't be any twist and you may have it held firm on the inboard side but the flexibility of the flap will allow it to just rattle against the other stop.  If they could be adjusted so that the outboard one engaged first, allowed the flap to twist or spring a little, then the inboard one touches it might work.  All this just to say, I don't think your idea is a simple slam dunk.

Dan



 	  Quote: 	
		  ="Tim Juhl"]Flap Stop comment - The nylon stop does a good job of preventing movement of the retracted flap at the outboard end, while the inboard end is restrained by the actuating pin which rests in a slot.  I am considering installing a second stop at the inboard end to make it even more solid.



Comments?



Tim



Do not archive

_________________
Scratch building XL with Corvair Engine

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