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Eye bolt tie down through wing/flap hinge block (trike on

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frans(at)privatepilots.nl
Guest

Posted: Mon Nov 21, 2011 4:06 pm Post subject: Eye bolt tie down through wing/flap hinge block (trike on

Hi Bob,



 	  Quote: 	
		   I would draw your attention to a simple fact that when the flaps are

 extended at  82 knots a large proportion of the aircraft weight is

 carried on the flap hinges.


	


Yes, but this load is in the opposite direction and from quite a 

different nature, and most likely in an angled direction whereas the 

flap exerts a "straight" line of load.

Many of us have a "no push" or "no step" mark on the flap, while it is 

very unlikely that someone weighs more than the lift potential of the 

flap. Apparently some people feel that not all loads are of a similar 

nature. I'm a bit cautious, I have to admit, I couldn't help wondering 

about this. I just prefer to limit the use of critical parts to their 

intended usage.



 	  Quote: 	
		   With regards to receiving snatch blows through the aircraft "bucking

 about" this is entirely without foundation since on tying down through

 these points it is possible to load up and deflect the main gear legs

 to ensure the system is constantly in tension.


	


We all know what happens with the doors when they are in constant 

tension by the support springs: they deform. I can imagine when you load 

up the structure of the aircraft while being parked in the sun that it 

may deform a bit over time. Maybe just a millimeter, but that said, 

while building the airplane I did the measurements down to a precision 

of better than 1 millimeter. So if I tie down the aircraft I make sure 

not to tie any load on the wing. Downside of course is that if the 

airplane rocks in the wind that it will jerk on the tie downs. But I 

don't use the flap hinges as tie down points. But who knows? Maybe your 

method is better. We are just guessing here, aren't we?



 	  Quote: 	
		   In conclusion I can advise that G-PTAG has always been tied down in

 this manner and has withstood some severe gusting wind conditions

 without any damage ensuing what or where ever over it's 900 hours life

 time.


	


It is impressive, but no guarantee by itself that it could never have 

any negative consequences. You are probably right but I had an uneasy 

feeling when I red about it. If it was about a bicycle I would have 

ignored it, but we are talking airplanes here and I feel that if any of 

us has an uneasy feeling about something that he should bring it up.



 	  Quote: 	
		   May I thank Neville Eyre for his kind intervention on this matter and I


	


I hope I didn't irritate you, I was just wondering whether using a 

critical aircraft part outside the scope of its intended usage would be 

safe by definition. I have to admit that I would never have thought that 

just a pencil mark would compromise the strength of that part either.



I think it is a good thing if we discuss the safety of some ideas before 

they become common practice. I would really hate to read someday that 

one of us lost his flap during flight and that a hinge with an eyebolt 

was discovered some distance away from the wreckage... Especially if I 

remember having questioned it silently and never brought up the subject.



I guess we won't be able to obtain a definite verdict on this matter, 

everyone should make his own decision. It is probably ok to use the flap 

hinge for this but you can't know for sure I think.



Frans

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nigel_graham(at)m-tecque.
Guest

Posted: Mon Nov 21, 2011 4:38 pm Post subject: Eye bolt tie down through wing/flap hinge block (trike on

Frans, 

Don't forget that this mounting point was originally designed and stressed to mount the outrigger on the original mono-wheel. Consider if you will, the compressive shock loads imposed by an unforgiving landing on rough grass, or the lateral loads imposed during turning. I cannot recall a single incidence of this part of the wing/flap/outrigger mounting ever failing (and there have been numerous mono groung handling "incidents").  Your arguments are however,  all valid. 

Nigel 

  

  Hi Bob, 

  

    	  Quote: 	
		  I would draw your attention to a simple fact that when the flaps are 

  extended at  82 knots a large proportion of the aircraft weight is 

  carried on the flap hinges. 

  	


  Yes, but this load is in the opposite direction and from quite a different nature, and most likely in an angled direction whereas the flap exerts a "straight" line of load. 

  Many of us have a "no push" or "no step" mark on the flap, while it is very unlikely that someone weighs more than the lift potential of the flap. Apparently some people feel that not all loads are of a similar nature. I'm a bit cautious, I have to admit, I couldn't help wondering about this. I just prefer to limit the use of critical parts to their intended usage. 

  

    	  Quote: 	
		  With regards to receiving snatch blows through the aircraft "bucking 

  about" this is entirely without foundation since on tying down through 

  these points it is possible to load up and deflect the main gear legs 

  to ensure the system is constantly in tension. 

  	


  We all know what happens with the doors when they are in constant tension by the support springs: they deform. I can imagine when you load up the structure of the aircraft while being parked in the sun that it may deform a bit over time. Maybe just a millimeter, but that said, while building the airplane I did the measurements down to a precision of better than 1 millimeter. So if I tie down the aircraft I make sure not to tie any load on the wing. Downside of course is that if the airplane rocks in the wind that it will jerk on the tie downs. But I don't use the flap hinges as tie down points. But who knows? Maybe your method is better. We are just guessing here, aren't we? 

  

    	  Quote: 	
		  In conclusion I can advise that G-PTAG has always been tied down in 

  this manner and has withstood some severe gusting wind conditions 

  without any damage ensuing what or where ever over it's 900 hours life 

  time. 

  	


  It is impressive, but no guarantee by itself that it could never have any negative consequences. You are probably right but I had an uneasy feeling when I red about it. If it was about a bicycle I would have ignored it, but we are talking airplanes here and I feel that if any of us has an uneasy feeling about something that he should bring it up. 

  

    	  Quote: 	
		  May I thank Neville Eyre for his kind intervention on this matter and I 

  	


  I hope I didn't irritate you, I was just wondering whether using a critical aircraft part outside the scope of its intended usage would be safe by definition. I have to admit that I would never have thought that just a pencil mark would compromise the strength of that part either. 

  

  I think it is a good thing if we discuss the safety of some ideas before they become common practice. I would really hate to read someday that one of us lost his flap during flight and that a hinge with an eyebolt was discovered some distance away from the wreckage... Especially if I remember having questioned it silently and never brought up the subject. 

  

  I guess we won't be able to obtain a definite verdict on this matter, everyone should make his own decision. It is probably ok to use the flap hinge for this but you can't know for sure I think. 

  

  Frans 

  

  ===========   BODY { font-family:Arial, Helvetica, sans-serif;font-size:12px; } 

  

  [quote][b]

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