Federal regulations also require that rate of load application be considered as well, so your instincts are correct. These days, a power-spectral-density model is used to access turbulence response for "Part 25" (commercial) aircraft. You can also introduce a periodic driving force on a wing for purposes of testing using devices known as "thumpers".
I know I'm only scratching the surface here, but I just wanted to let you know that you accessment is correct, and those test are done.
Follow this link: http://rgl.faa.gov/ Click on Federal Aviation Regulations and hunt for 25.341, from there, you should be able to find more data on the PSD model currently in use.
The load at the wingtip is probably the more dramatic one as far as video is concerned, but it's only one of many - 1/3 span is another.. The "thumper" test is also pretty cool; that's were they intoduce a small periodic driving force to various parts of the wing and measure it's response.
In fact, there is a seperate "limit load" test that is performed at 100% and must show no detrimental permanent deformation. It is not unheard of that a structure will pass the ultimate load test yet fail the limit load test because of this criterion even though the limit load is smaller.
If something does go wrong, is the FAA culpable if it turns out the limit was too low?
In practice, the regulations are the product of generations of actual aviation experience and are driven by the industry itself. In fact, every proposed regulation or change to an existing regulation is subject to public review. In theory, any citizen is free to comment but, in practice, the aviation industry experts have far more clout. I have actually sat on such advisory committees and participated in the drafting of recommendation (not wings but, other critical structural elements)
So, in short, the FAA will not be culpable because they didn't dictate that limit, it evolved over time and experience. Also, bear in mind this is only the ultimate static load test - there are others, including a power spectral density analysis which evolved from the old "sharp-edged gust load".
I have rarely seen a safety factor of 1.5 for something that involves human life.
Okay....can't really speak to your personal experience, I'm mearly referencing the regulations themselves.
Then again, Tresca and Von Mises criterion may themselves differ by a factor of close to 2...
Where the Von-Mises criterion will plot as an ellipse set at 45 degrees, The Tresca criterion is a hexagon inscribed in that ellipse (Tresca's Hexagon) [Refernce Bruhn, Meyers & Chawla, et. al]. You'd be hard pressed to show any point where they differ by a factor of 2.
In short, I find that hard to believe but feel free to site a reference, I'd love to see it.
There are a few ways of handling that issue but, suffice to say, aero-elastic behaviour is a discipline in and of itself. I'll throw out a couple of possibilities knowing full well that there is no way I can go into much detail in this forum.
ONE OPTION: Use the layup to tailor the bending axis of the wing so that it will respond to a gust in a self-correcting fashion.
SOMETHING COMMONLY DONE TODAY: Hang the wing mounted engines in on pylons that put the engine CG ahead of the wing, this has a tendancy to stabilize it's aero-elastic response.
The actual requirement from Title 14, Code of Federal Regulations, Part 25, Subpart C, paragraph 303 is where ultimate load definition comes from:
Unless otherwise specified, a factor of safety of 1.5 must be applied to the prescribed limit load which are considered external loads on the structure. When a loading condition is prescribed in terms of ultimate loads, a factor of safety need not be applied unless otherwise specified
The three second requirement comes out of paragraph 305(b):
(b) The structure must be able to support ultimate loads without failure for at least 3 seconds. However, when proof of strength is shown by dynamic tests simulating actual load conditions, the 3-second limit does not apply. Static tests conducted to ultimate load must include the ultimate deflections and ultimate deformation induced by the loading. When analytical methods are used to show compliance with the ultimate load strength requirements, it must be shown that-- (1) The effects of deformation are not significant; (2) The deformations involved are fully accounted for in the analysis; or (3) The methods and assumptions used are sufficient to cover the effects of these deformations.
If our intrepid engineers manage to test to 200% for 3 second, then somebody is going to come along and say, "let's see if we can make the wings lighter"
Good thing or bad thing?....depends upon your point of view I guess.
As it turns out, validating airframe structures with respect to FAA airworthiness requirements is kinda what I do for a living.
Sadly, much like cynicism is used a lazy-man's substite for critical thought, outrageous, contraversial, or vulgar statements are often used as a lazy-man's substitute for humor.
For what it's worth, may the truth of the matter, whatever that is, be ultimately determined.
While I agree that the government should watch out for such abuses, this does not, by extension absolve corporations like Monsanto from responsibility for such an apparantly reckless action.
For example, if I make a decision to drive home drunk one night, that's a bad decision regardless of whether or not someone is there to enforce the law (i.e. I get caught), or even if there was an accident as a result.
no...it is not the corporate world's job to put greed above corporate responsibility
He also held a press conference after he lost and challanged Deep Blue to play him in a "regular match", where both sides can review each others games....IBM didn't accept those terms and that does diminish their victory.
First off, let me say that he always struck me as a bit on the arrogant side, but then again, I really don't know the guy.
I remember that match though. Time and time again, Kasparov would give IBM rematch after rematch after rematch until Deep Blue finally won. It seems that, as soon as they did, Deep Blue was re-assigned and that was the end of it (maybe someone will correct me, but that's my recollection). So, you never really knew if the win was just one of those "on any given day" phenomena. One win is just not convincing against an opponent that has a history of beating you.
Yea, Kasparov whined a bit about it but he had a point, let the machine play him in a regular tournament and see what happens.
My personal opinion is, on that day, Kasparov was not really taking Deep Blue seriously enough and it surprised him. I certainly remember his reaction when he saw he was loosing....and it was right toward the beginning of the game as well as I recall.
Mute point I guess....I don't think Deep Fritz can be beaten by any human anyways.
There have been a couple of games I've been in where I'm winning and, entering the end game, my opponent is suddenly getting very tough. I guess I won't complain if it helps me sharpen my end game, but, with tools like SCID so easily available, I can't help but wonder if I'm actually playing Crafty for the last third of the game sometimes.
This is only once in a while mind you. I think most correspondance players are like me, they'd rather loose on thier own then use an engine to chalk up a win they didn't really earn.
Frankly, I think I've made enough grizzly blunders that no one would ever accuse me of using a chess engine;)
"Education is the first step. Granted, some people paid so little attention in their high school physics class that they are completely unable to have any kind of rational, reasonable discussion on the subject, but my solution is to euthanize them and move on:D"
or, do you mean "Youth-a-nize"... I.E. send them back to high school physics?
Although, the only thing I really learned is high school physics was that, if you see a pair of forceps lying next to a bunsen burner, dribble some water on them before you just pick them up.
I believe it was the "Beowulf Cluster Revolt". Apparantly it all started when the employee offered to give the boss a sign he'd made for him (saying, "here's your sign"), and he was just being an insensitive clod about.....then, there was this third event that no one really recalls but the result was PROFIT!
Slashdot Mirror
I didn't even read your comment...
PROFIT!!!
too obvious not to be said I suppose
just cheapened every +5 funny mod I've ever got....thanks ;)
Q. What do you do after raping a deaf, blind and dumb girl?
A. Go to prison
And the follow up (this is really funny)
Q. What do you do when your fellow inmates discover you assaulted a Handicapped woman?
A. They all make you their "deaf, blind, and dumb girl".
Not funny? oh well, I guess you had to have been there.
Federal regulations also require that rate of load application be considered as well, so your instincts are correct. These days, a power-spectral-density model is used to access turbulence response for "Part 25" (commercial) aircraft. You can also introduce a periodic driving force on a wing for purposes of testing using devices known as "thumpers".
I know I'm only scratching the surface here, but I just wanted to let you know that you accessment is correct, and those test are done.
Follow this link: http://rgl.faa.gov/ Click on Federal Aviation Regulations and hunt for 25.341, from there, you should be able to find more data on the PSD model currently in use.
The load at the wingtip is probably the more dramatic one as far as video is concerned, but it's only one of many - 1/3 span is another.. The "thumper" test is also pretty cool; that's were they intoduce a small periodic driving force to various parts of the wing and measure it's response.
In fact, there is a seperate "limit load" test that is performed at 100% and must show no detrimental permanent deformation. It is not unheard of that a structure will pass the ultimate load test yet fail the limit load test because of this criterion even though the limit load is smaller.
Then again, Tresca and Von Mises criterion may themselves differ by a factor of close to 2...
You wouldn't use Von-Mises criterion on a composite material, you'd probably go with Tsai-Hill, or possibly Tsai-Wu.
Cheers
First off:
If something does go wrong, is the FAA culpable if it turns out the limit was too low?
In practice, the regulations are the product of generations of actual aviation experience and are driven by the industry itself. In fact, every proposed regulation or change to an existing regulation is subject to public review. In theory, any citizen is free to comment but, in practice, the aviation industry experts have far more clout. I have actually sat on such advisory committees and participated in the drafting of recommendation (not wings but, other critical structural elements)
So, in short, the FAA will not be culpable because they didn't dictate that limit, it evolved over time and experience. Also, bear in mind this is only the ultimate static load test - there are others, including a power spectral density analysis which evolved from the old "sharp-edged gust load".
I have rarely seen a safety factor of 1.5 for something that involves human life.
Okay....can't really speak to your personal experience, I'm mearly referencing the regulations themselves.
Then again, Tresca and Von Mises criterion may themselves differ by a factor of close to 2...
Where the Von-Mises criterion will plot as an ellipse set at 45 degrees, The Tresca criterion is a hexagon inscribed in that ellipse (Tresca's Hexagon) [Refernce Bruhn, Meyers & Chawla, et. al]. You'd be hard pressed to show any point where they differ by a factor of 2.
In short, I find that hard to believe but feel free to site a reference, I'd love to see it.
There are a few ways of handling that issue but, suffice to say, aero-elastic behaviour is a discipline in and of itself. I'll throw out a couple of possibilities knowing full well that there is no way I can go into much detail in this forum.
ONE OPTION: Use the layup to tailor the bending axis of the wing so that it will respond to a gust in a self-correcting fashion.
SOMETHING COMMONLY DONE TODAY: Hang the wing mounted engines in on pylons that put the engine CG ahead of the wing, this has a tendancy to stabilize it's aero-elastic response.
Just a couple of thoughts.
The actual requirement from Title 14, Code of Federal Regulations, Part 25, Subpart C, paragraph 303 is where ultimate load definition comes from:
Unless otherwise specified, a factor of safety of 1.5 must be applied to the prescribed limit load which are considered external loads on the structure. When a loading condition is prescribed in terms of ultimate loads, a factor of safety need not be applied unless otherwise specified
The three second requirement comes out of paragraph 305(b):
(b) The structure must be able to support ultimate loads without failure for at least 3 seconds. However, when proof of strength is shown by dynamic tests simulating actual load conditions, the 3-second limit does not apply. Static tests conducted to ultimate load must include the ultimate deflections and ultimate deformation induced by the loading. When analytical methods are used to show compliance with the ultimate load strength requirements, it must be shown that--
(1) The effects of deformation are not significant;
(2) The deformations involved are fully accounted for in the analysis; or
(3) The methods and assumptions used are sufficient to cover the effects of these deformations.
If our intrepid engineers manage to test to 200% for 3 second, then somebody is going to come along and say, "let's see if we can make the wings lighter"
Good thing or bad thing?....depends upon your point of view I guess.
As it turns out, validating airframe structures with respect to FAA airworthiness requirements is kinda what I do for a living.
Can't say I know the man from Adam however.
Sadly, much like cynicism is used a lazy-man's substite for critical thought, outrageous, contraversial, or vulgar statements are often used as a lazy-man's substitute for humor.
For what it's worth, may the truth of the matter, whatever that is, be ultimately determined.
Don't take this one for granted, I haven't practiced enough of this psychic stuff to be sure about this.
'preciate the heads-up
How do you do it?
Sincerely,
The Amazing Sarcasmo
"I'd rather think I'll find him in the 20-30 year old crowd. No kids, expendable income, party person."
Replace "Party Person" with "Virgin"
That should do it
"I personally favor the rack"
Yup, bring out an intern with a nice enough rack and he might just tell her anything she wants to know
or is that yet another non-sequitor?
Along with all that spam would come technology from the future to eliminate baldness and increase penis size.
While I agree that the government should watch out for such abuses, this does not, by extension absolve corporations like Monsanto from responsibility for such an apparantly reckless action.
For example, if I make a decision to drive home drunk one night, that's a bad decision regardless of whether or not someone is there to enforce the law (i.e. I get caught), or even if there was an accident as a result.
no...it is not the corporate world's job to put greed above corporate responsibility
Don't ever call anything "Slackerpedia Galactica" mmmkay?
He also held a press conference after he lost and challanged Deep Blue to play him in a "regular match", where both sides can review each others games....IBM didn't accept those terms and that does diminish their victory.
First off, let me say that he always struck me as a bit on the arrogant side, but then again, I really don't know the guy.
I remember that match though. Time and time again, Kasparov would give IBM rematch after rematch after rematch until Deep Blue finally won. It seems that, as soon as they did, Deep Blue was re-assigned and that was the end of it (maybe someone will correct me, but that's my recollection). So, you never really knew if the win was just one of those "on any given day" phenomena. One win is just not convincing against an opponent that has a history of beating you.
Yea, Kasparov whined a bit about it but he had a point, let the machine play him in a regular tournament and see what happens.
My personal opinion is, on that day, Kasparov was not really taking Deep Blue seriously enough and it surprised him. I certainly remember his reaction when he saw he was loosing....and it was right toward the beginning of the game as well as I recall.
Mute point I guess....I don't think Deep Fritz can be beaten by any human anyways.
There have been a couple of games I've been in where I'm winning and, entering the end game, my opponent is suddenly getting very tough. I guess I won't complain if it helps me sharpen my end game, but, with tools like SCID so easily available, I can't help but wonder if I'm actually playing Crafty for the last third of the game sometimes.
;)
This is only once in a while mind you. I think most correspondance players are like me, they'd rather loose on thier own then use an engine to chalk up a win they didn't really earn.
Frankly, I think I've made enough grizzly blunders that no one would ever accuse me of using a chess engine
"Education is the first step. Granted, some people paid so little attention in their high school physics class that they are completely unable to have any kind of rational, reasonable discussion on the subject, but my solution is to euthanize them and move on :D"
or, do you mean "Youth-a-nize"... I.E. send them back to high school physics?
Although, the only thing I really learned is high school physics was that, if you see a pair of forceps lying next to a bunsen burner, dribble some water on them before you just pick them up.
"It would be nice if laws could be simple and unambiguous, like a well-written piece of software."
Which do you suppose we will see first?
And would the expression "GO TO JAIL" be replaced by:
IF {Guilty}
WHILE (sentence)
jail
ENDWHILE
ELSE
home
I believe it was the "Beowulf Cluster Revolt". Apparantly it all started when the employee offered to give the boss a sign he'd made for him (saying, "here's your sign"), and he was just being an insensitive clod about.....then, there was this third event that no one really recalls but the result was PROFIT!