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Wake Turbulence Article

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bill_dom(at)yahoo.com
Guest

Posted: Wed Mar 07, 2007 6:18 am Post subject: Wake Turbulence Article

I was reading yesterday an article about wake turbulence in  the latest issue of Sport Pilot magazine and the author state that strong wake turbulence  from a heavy aircraft could potentially brake apart a small plane. I couldn’t help  but wander the possibility of this being the cause of the 601XL accident on 11/04/2006  where according to witness, “… observed the center section of the airplane  falling straight down” this means that both wings separated in flight. The NTSB  also report “no evidence of fire” and “airplane's structural components were  located in adjacent open fields.”

          I can imaging a structural failure in a 601XL that can make  both wings come apart unless there is an explosion however, there is no  evidence of fire.

          I guess it would be difficult to prove that wake turbulence brought  the plane down but it could be easier to rule it  out if no big plane when thru  the area prior to the accident.

                   

  William Dominguez

  Zodiac 601XL Plans

  Miami, Florida

     [quote][b]

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ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Wed Mar 07, 2007 7:30 am Post subject: Re: Wake Turbulence Article

[quote="bill_dom(at)yahoo.com"]I was reading yesterday an article about wake turbulence in  the latest issue of Sport Pilot magazine and the author state that strong wake turbulence  from a heavy aircraft could potentially brake apart a small plane. I couldn?t help  but wander the possibility of this being the cause of the 601XL accident on 11/04/2006  where according to witness, ?? observed the center section of the airplane  falling straight down? this means that both wings separated in flight. The NTSB  also report ?no evidence of fire? and ?airplane's structural components were  located in adjacent open fields.?

          I can imaging a structural failure in a 601XL that can make  both wings come apart unless there is an explosion however, there is no  evidence of fire.

          I guess it would be difficult to prove that wake turbulence brought  the plane down but it could be easier to rule it  out if no big plane when thru  the area prior to the accident.

                   

  William Dominguez

  Zodiac 601XL Plans

  Miami, Florida

      	  Quote: 	
		  [b] 	




Is there any further info on that accident? I haven't heard of any other XLs (or many plane for that matter) where the wings just broke off. If they broke off at the root it sounds like a problem with the main bolts or something. Grade 8 automotive bolts or worse, Home Depot bolts instead of aviation grade perhaps? No nuts on the bolts. Bad edge distance to the bolts. What kind of forces are going through those bolts. Just doing a quick and dirty engineering statics on the root bolts and using one bolt as the pivot and the others are the moment, and assuming 600 lbs for the fuselage,  and have to assume there's roughly a 300 moment on each wing at 6 feet. Even with only the two bolts, one at the outboard bottom position and one at the top inboard position, that would be 2400 lbs on the two bolts at 1G. Without doing a whole 6 bolts analysis of it, obviously the bolts would be sharing that load and carrying even less each with all 6 in place. I'd say the bolts are plenty strong then. So how about the structure. Is it really pushing it translating that force to the spar caps and then the web, and then the fuselage. I've seen pictures of XLs with 7200 pounds worth of sandbags on the wings, so probably not. The only conclusion then is the bolts weren't the right ones, or they came out due to no nuts, or the edge distance was wrong, which is probably even less likely, there's probably still plenty of strength there, or something happened with the rear attach point of the wing and the wing pivoted and snapped the whole main spar assembly. The main spar assembly will hold a lot of force, UP and DOWN, but not in a twisting fashion.

Where did the wings break off, at the root? Is there any structural problem with making the rear wing channel out of two spliced pieces? I'd have to think no.



Rivets in the center spar. Unlikely. Piss poor job reaming (or no reaming) of the main attach bolt holes, resulting in eggshaped holes over time. Possible. Someone overstressing the plane 2 weeks earlier. Possible.

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Last edited by ashontz on Wed Mar 07, 2007 7:51 am; edited 1 time in total

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Wed Mar 07, 2007 7:49 am Post subject: Wake Turbulence Article

I think it would take a very close encounter with the large airplane  

for wake turbulance to do that much damage. An explosion wouldn't  

necessarily leave evidence of a fire. I hope the NTSB does a thorough  

investigation of this accident and provides some answers.



On Mar 7, 2007, at 9:18 AM, William Dominguez wrote:



 	  Quote: 	
		   I was reading yesterday an article about wake turbulence in the  

 latest issue of Sport Pilot magazine and the author state that  

 strong wake turbulence from a heavy aircraft could potentially  

 brake apart a small plane. I couldn’t help but wander the  

 possibility of this being the cause of the 601XL accident on  

 11/04/2006 where according to witness, “… observed the center  

 section of the airplane falling straight down” this means that both  

 wings separated in flight. The NTSB also report “no evidence of  

 fire” and “airplane's structural components were located in  

 adjacent open fields.”

 I can imaging a structural failure in a 601XL that can make both  

 wings come apart unless there is an explosion however, there is no  

 evidence of fire.

 I guess it would be difficult to prove that wake turbulence brought  

 the plane down but it could be easier to rule it out if no big  

 plane when thru the area prior to the accident.


	




-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

do not archive.

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_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

p.mulwitz(at)worldnet.att
Guest

Posted: Wed Mar 07, 2007 7:55 am Post subject: Wake Turbulence Article

Hi William,



 I don't think the report of this accident indicates any possibility of wake turbulence as a cause for this accident.



 The report mentions sound of an explosion, rough engine sounds, and it seems the parts of the plane all came apart at once and landed very near each other.  It also mentions there was no indication of fire or oil stains.  This indicates something like a bomb went off but it didn't leave any obvious marks.  None of this sounds like a wake turbulence incident to me.



 Wake turbulence, like other forms of turbulence, seems more likely to result in loss of control of the plane than in structural failure.  If the plane is operating at normal speeds, then structural failure would indicate a severe design error.  Even if this happened, I would think it unlikely that the plane would break up into many different parts including two wing separations and engine separation.  I just can't imagine any phenomenon in weather or air condition which would cause this kind of catastrophic structure failure in a well designed and well built aircraft.



 While I think wake turbulence is a deadly problem, the circumstances that make it deadly include the likelihood of encountering it while very close to the ground.  In low speed operations while landing and taking off the disruption of pilot control can easily lead to impact with the ground.  This is most likely to happen when operating near very heavy planes or very heavily loaded wings like fighter planes in landing configuration.  None of these situations seem likely from the report.



 I think we need to exercise patience and wait for the NTSB to complete its investigation of this accident before reaching any conclusion about the cause of the accident.  They have all the data and airplane parts for examination.  I am sure they will let us know what actually happened.



 Paul

 XL fuselage

 do not archive



 At 06:18 AM 3/7/2007, you wrote:

  	  Quote: 	
		  I was reading yesterday an article about wake turbulence in the latest issue of Sport Pilot magazine and the author state that strong wake turbulence from a heavy aircraft could potentially brake apart a small plane. I couldn’t help but wander the possibility of this being the cause of the 601XL accident on 11/04/2006 where according to witness, “… observed the center section of the airplane falling straight down” this means that both wings separated in flight. The NTSB also report “no evidence of fire” and “airplane's structural components were located in adjacent open fields.”

 I can imaging a structural failure in a 601XL that can make both wings come apart unless there is an explosion however, there is no evidence of fire.

 I guess it would be difficult to prove that wake turbulence brought the plane down but it could be easier to rule it out if no big plane when thru the area prior to the accident.

  

 William Dominguez

 Zodiac 601XL Plans

 Miami, Florida



 	
 

 ---------------------------------------------

 Paul Mulwitz

 32013 NE Dial Road

 Camas, WA 98607

 ---------------------------------------------

     [quote][b]

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bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Wed Mar 07, 2007 8:16 am Post subject: Wake Turbulence Article

The NTSB preliminary report is out but not the probable cause report.

http://www.ntsb.gov/ntsb/brief.asp?ev_id 061115X01677&key=1

Other than a few news accounts about it, that's about all there is at  

this time.



There was one other 601 accident where the wings folded up in flight  

but in that accident they stayed atached to the fuselage at the main  

spar. There was some who reported that the new owner  forgot to  

install the rear wing bolts in that case.



On Mar 7, 2007, at 10:30 AM, ashontz wrote:



 	  Quote: 	
		  

 Is there any further info on that accident? I haven't heard of any  

 other XLs (or many plane for that matter) where the wings just  

 broke off. Sounds like a problem with the main bolts or something.  

 Where did they break off, at the root? Is there any structural  

 problem with making the rear wing channel out of two spliced  

 pieces? I'd have to think no.

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_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Wed Mar 07, 2007 8:20 am Post subject: Re: Wake Turbulence Article

http://ntsb.gov/ntsb/brief.asp?ev_id=20061115X01677&key=1



http://ntsb.gov/ntsb/brief.asp?ev_id=20060217X00209&key=1



This is two seperate accidents with a 601XL in-flight break-up, no?

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bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Wed Mar 07, 2007 8:43 am Post subject: Wake Turbulence Article

This is the second accident I mentioned. If you read the full  

narrative you'll notice that it reports that both wings remained  

attached at the forward spar with all bolts intact. The report makes  

no mention at all of the rear wing attach bolts although it does say  

the aft spar attach point was intact. This may indicate that the rear  

bolts were missing. That would certainly explain why the wings folded  

as they did.



On Mar 7, 2007, at 11:20 AM, ashontz wrote:



 	  Quote: 	
		  

 http://ntsb.gov/ntsb/brief.asp?ev_id 060217X00209&key=1



 This is two seperate accidents with a 601XL in-flight break-up, no?



 --------

 Andy Shontz

 CH601XL - Corvair

 www.mykitlog.com/ashontz


	


-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

do not archive.

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_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

marinegunner(at)gmail.com
Guest

Posted: Wed Mar 07, 2007 4:06 pm Post subject: Wake Turbulence Article

We need to wait for the NTSB report. However, those who think wake

turbulence only occurs near the ground and cannot tear an airplane

apart need to study wake turbulence in more depth. Wake turbulence

from one large (not necessarily heavy) airplane at altitude can and

has caused a smaller airplane to go out of control and lose various

parts - just as a strong wind shear will do.

I personally watched a DC-9 enter the wake turbulence of a DC-19 and

end up doing a complete roll. Pilot managed to stop roll about 200' on

short final and land with extensive structural damage. I also watched

a Luscombe enter the wake turbulence from an F-27 while on take off.

Lost his left stabilizer and subsequent crash totaled the airplane. If

there were any airliners flying past where last years 601 crashed,

wake turbulence could in fact be the cause. However, I am sure the

NTSB will look into that possibility. They have on many of the

accidents investigations that I have been involved with.

I may be wrong here, but I think the A300 that crashed a week or so

after 911 in New York encountered wake turbulence or wind shear that

caused extensive rudder damage. When coupled with the co-pillots

aggressive control movements, the rudder came off the airplane and

over a hundered folks died.



Do No Archive

-- 

Semper Fi,

Steven R. Hulland

CH 600 Taildragger

Amado, AZ



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kkinney

Joined: 11 Jan 2006
Posts: 42

Posted: Thu Mar 08, 2007 9:25 am Post subject: Re: Wake Turbulence Article

I agree the NTSB (or courts) will have the final say as to the accident cause.



http://tinyurl.com/2zsnls 

As noted in the above link, the rear spar bolts were present but did not have nuts on them.



Wake turbulence may have played a part, though in my opinion, a secondary one.  Extending flaps without having the rear spar firmly attached probably had a larger role in the accident.



It's a tragedy, but we can all learn from it.



Regards, 

Kevin Kinney

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