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Creative Speculation

In reply to the discussion: Skygate 911 [View all]

William Seger

(11,731 posts)
8. Cowboy Bob rides again
Tue May 27, 2014, 01:21 AM
May 2014

The design dive velocity is one of the design inputs used to calculate the loads the plane needs to withstand. As I said, this is definitely NOT the point at which the plane will begin to fall apart:

http://www.flyingmag.com/technique/proficiency/technicalities-are-you-feeling-lucky#YilDUX7dgskkUFgk.99

All of these loadings are due to air pressure, which grows in proportion to the square of the speed — double the speed produces four times the force; they are functions of the indicated airspeed, not the true. Now, VD, which is an indicated speed, is by definition a safe speed; the forces at VNE are just 81 percent of those at VD (0.9 x 0.9 = 0.81), and so there is a comfortable margin of safety, so far as structural strength is concerned, at VNE.

But there is a complication that muddies the water considerably. It is flutter. Flutter is a vibration that may be augmented by aerodynamic forces. It is the one challenge to aircraft structures that does not increase gradually with speed. It is possible for a structure to perform normally right up to a certain speed and then, with a gain of two or three more knots, to explode into fragments in a split second. That is what most likely happened to the South African VL-3. The accident has not yet been investigated, but it has the earmarks of wing flutter induced by a vibrating aileron.

Flutter is affected by a number of factors, one of which is the true, not the indicated, airspeed. As you will have immediately perceived, this fact raises a logical difficulty. VNE, the redline on the airspeed indicator, is an indicated airspeed, but the critical flutter speed may be a true airspeed. So the margin separating VNE from the critical flutter speed gets smaller as you gain altitude. Furthermore, if you get really high up, the difference can be larger than the margin that separates VD from VNE, simply because the difference between indicated and true airspeed is greater than 10 percent.

That doesn't mean the airplane will flutter, because VD is not the critical flutter speed. Manufacturers are not required to determine the critical flutter speed for each design, but only to demonstrate that it is free of flutter up to VD and that there is good reason to believe, based on various kinds of ground tests and mathematical analyses, that it will remain so up to 1.2 times VD. It is noteworthy that the section of Part 23 regarding flutter, 23.629, makes no mention of altitude. The cumulative margin between VNE and 1.2 times VD is 33 percent, and this probably provides a good cushion in all normal operations, but if I were to ride a wave to 35,000 feet in a 172, I would not be in a hurry to peg the airspeed at redline on the way back down.


And as I said, the way that the engineers will insure that Vd "is by definition a safe speed" is to multiply the calculated loads by a Factor of Safety, which is typically 1.5:

http://en.wikipedia.org/wiki/Factor_of_safety

Choosing design factors

Appropriate design factors are based on several considerations, such as the accuracy of predictions on the imposed loads, strength, wear estimates, and the environmental effects to which the product will be exposed in service; the consequences of engineering failure; and the cost of over-engineering the component to achieve that factor of safety. For example, components whose failure could result in substantial financial loss, serious injury, or death may use a safety factor of four or higher (often ten). Non-critical components generally might have a design factor of two. Risk analysis, failure mode and effects analysis, and other tools are commonly used. Design factors for specific applications are often mandated by law, policy, or industry standards.

Buildings commonly use a factor of safety of 2.0 for each structural member. The value for buildings is relatively low because the loads are well understood and most structures are redundant. Pressure vessels use 3.5 to 4.0, automobiles use 3.0, and aircraft and spacecraft use 1.2 to 3.0 depending on the application and materials. Ductile, metallic materials tend to use the lower value while brittle materials use the higher values. The field of aerospace engineering uses generally lower design factors because the costs associated with structural weight are high (i.e. an aircraft with an overall safety factor of 5 would probably be too heavy to get off the ground). This low design factor is why aerospace parts and materials are subject to very stringent quality control and strict preventative maintenance schedules to help ensure reliability. A usually applied Safety Factor is 1.5, but for pressurized fuselage it is 2.0, and for main landing gear structures it is often 1.25.[11]


Seems to me that you are the one who needs to do some reading and learning if you want to pretend to be an expert. Without justification and contrary to the facts, you are claiming that 757s and 767s cannot withstand 1.2 times Vd, despite Boeing's reputation for producing rugged planes. Anyone who cares to search for it will see how well that claim is holding up around the internets, but I won't waste time beyond substantiating what I said.

Speaking of which, are you saying that you still don't know the difference between critical Mach and drag divergence Mach -- even though the first sentence in this Wikipedia definition warns against that confusion? And are you trying to deny that planes typically cruise just above Mcrit to save fuel? This is the "expertise" you're selling in your videos?

Anyone who still takes you seriously hasn't been paying attention.


Recommendations

0 members have recommended this reply (displayed in chronological order):

Skygate 911 [View all] damnedifIknow May 2014 OP
Good grief. B-List conspiracy huckster Rob Balsamo William Seger May 2014 #1
Please address the content of this video damnedifIknow May 2014 #2
I did. Read the links (n/t) William Seger May 2014 #3
Do you agree with analysis done on the WTC by the same people in your links? johndoeX May 2014 #7
I'm not surprised that you missed the point William Seger May 2014 #9
In other words.... johndoeX May 2014 #10
Here's some content: William Seger May 2014 #4
Seger once again shows his lack of aeronautical knowledge. johndoeX May 2014 #5
Cowboy Bob rides again William Seger May 2014 #8
Read and Learn Seger johndoeX May 2014 #11
SSDD William Seger May 2014 #12
You are so lost it would be funny if not so sad. johndoeX May 2014 #13
Maybe you've been watching that spinning wing logo too long William Seger May 2014 #14
Wow, look at all that tap dancing... lol johndoeX May 2014 #15
Welcome to the Rob Balsamo Show William Seger May 2014 #17
You still don't get it Seger? johndoeX May 2014 #18
Oh, I "get" what you're asserting William Seger May 2014 #19
Whoops, I missed this one..... johndoeX Jun 2014 #26
And you still missed it by a mile William Seger Jun 2014 #27
The Gish Gallop of fake Vg diagram and BS superbeachnut Jun 2014 #34
While you're at it, please explain this, too William Seger Jun 2014 #20
No, you still don't get it Seger.... johndoeX Jun 2014 #23
ROFL. There's that bizarra Balsamo "debating" technique again William Seger Jun 2014 #28
fake Vg diagram superbeachnut Jun 2014 #33
Using a journalist for aero knowledge, quote mining failure superbeachnut Jun 2014 #22
Still unable to read the credentials page Beachy? johndoeX Jun 2014 #25
Fake defintion used to help fake Vg diagram superbeachnut Jun 2014 #35
Any valid points in the video which prove it was not 175 hitting the WTC superbeachnut Jun 2014 #36
Jetblue Captain and Aeronautical Engineer Reviews Skygate 911 johndoeX May 2014 #6
Jetblue Captain and Aeronautical Engineer falls for Skygate 911 lies and fake Vg diagram superbeachnut Jun 2014 #71
Navy Top Gun and American Airlines 757/767 Captain Reviews Skygate 911 johndoeX May 2014 #16
Navy Top Gun and American Airlines 757/767 Captain Fooled by Skygate 911 superbeachnut Jun 2014 #72
Fraud from failed pilots superbeachnut Jun 2014 #21
Aww... how sweet... johndoeX Jun 2014 #24
Wow, that is lame, even for you William Seger Jun 2014 #29
Wrong again Seger... johndoeX Jun 2014 #30
LOL, so you didn't IGNORE the point William Seger Jun 2014 #31
Seger says - "If A > B and B > C, then A > C" johndoeX Jun 2014 #37
767 designed for 1.2Vd, and it can do better, why the fake Vg diagram superbeachnut Jun 2014 #39
Censura.net? Really? This is you "expert"? johndoeX Jun 2014 #41
math expert debunks pilots for truth math, pilot for truth forum thread confirms it superbeachnut Jun 2014 #44
Source fail johndoeX Jun 2014 #45
pilots for truth fail to decode what a mathematician can, so much for experts superbeachnut Jun 2014 #48
Post #27 William Seger Jun 2014 #49
It's much more simple than that Seger johndoeX Jun 2014 #51
Fake Vg diagram, inability to post the structural failure speed - pilots for truth superbeachnut Jun 2014 #53
Game over William Seger Jun 2014 #61
Wrong again Seger johndoeX Jun 2014 #63
Balsamo folds but continues to bullshit William Seger Jun 2014 #69
And yet.... johndoeX Jun 2014 #73
Our guest on the Rob Balsamo Show today is... William Seger Jun 2014 #76
You're still wrong Seger johndoeX Jun 2014 #79
Jeez... Yes, Rob, as I said, that is Flight Load William Seger Jun 2014 #82
Nice backpedaling... johndoeX Jun 2014 #83
more nonsense from pilots for truth superbeachnut Jun 2014 #85
Bullshit William Seger Jun 2014 #87
The Limit Case johndoeX Jun 2014 #90
Really? William Seger Jun 2014 #92
Go ahead! johndoeX Jun 2014 #95
ROFLMAO William Seger Jun 2014 #98
Translation johndoeX Jun 2014 #100
1.2Vd, 580 mph for flight 175 flutter free, better call for help superbeachnut Jun 2014 #93
Go ahead provide the source, make up more nonsense, and never explain superbeachnut Jun 2014 #70
In other words.... johndoeX Jun 2014 #74
Why can't the super pilots for truth source what they say they can source superbeachnut Jun 2014 #77
And now for accuracy... johndoeX Jun 2014 #80
pilots for truth talk Technobabble with aerodynamics and can't explain their dumb-speak superbeachnut Jun 2014 #81
"50'% Factor of Safety beyond VD" William Seger Jun 2014 #89
Math? johndoeX Jun 2014 #91
pilots for truth, making up more nonsense superbeachnut Jun 2014 #94
Yes, math, your worst nightmare William Seger Jun 2014 #97
Wrong again Seger. johndoeX Jun 2014 #99
Done William Seger Jun 2014 #101
School's out William Seger Jun 2014 #102
Wrong again Seger... johndoeX Jun 2014 #103
ROFLMAO William Seger Jun 2014 #104
Translation - johndoeX Jun 2014 #106
next stop, 11.2g physics applied to make up fake engine claims superbeachnut Jun 2014 #107
"You've already proven you are intellectually dishonest" William Seger Jun 2014 #108
The Score johndoeX Jun 2014 #109
Hmmm, looks like the score is still 1-0 William Seger Jun 2014 #110
Where is the core, why do they not help spread lies of impossible speeds, and fake Vg diagrams superbeachnut Jun 2014 #111
Balsamo's Corner delphi72 Jun 2014 #113
Great summary superbeachnut Jun 2014 #114
pilots for truth lies fail, structual failure at 425 KEAS remains a lie superbeachnut Jun 2014 #105
weak attack does not make the fake Vg diagram real superbeachnut Jun 2014 #32
"Debunkers" unable to plot their own VG when data is known... johndoeX Jun 2014 #38
a fake Vg diagram, photoshopped to fool superbeachnut Jun 2014 #40
Wrong... johndoeX Jun 2014 #42
pilots for truth unable to state the structural failure speed on their fake Vg diagram superbeachnut Jun 2014 #43
ATP? johndoeX Jun 2014 #46
no ATP yet? That is a test score, your FAA records show no ATP superbeachnut Jun 2014 #47
Why block out the date? delphi72 Jun 2014 #50
How does one erase knowledge? johndoeX Jun 2014 #52
I understand now delphi72 Jun 2014 #54
Boeing? johndoeX Jun 2014 #56
The big lie posted in the video preview superbeachnut Jun 2014 #58
Beachnut Flew a Desk johndoeX Jun 2014 #59
Fake Vg diagram supported with... nothing, pilots for truth fake Vg diagram supports lies about 911 superbeachnut Jun 2014 #60
sign of no evidence, for lies of "structual failure at 425 KEAS", and fake Vg diagram, flying a desk superbeachnut Jun 2014 #88
Boeing Phone Answer Lady Top Engineer delphi72 Jun 2014 #112
How does this save the fake Vg diagram or the structural failure speed lie superbeachnut Jun 2014 #55
Wrong again Beachy... n/t johndoeX Jun 2014 #57
Aw, Rob, I never said you were "nuts" William Seger Jun 2014 #62
I'm confused... johndoeX Jun 2014 #64
Paranoid conspiracy theorist fall for pilot for truth fake Vg diagrams and other lies superbeachnut Jun 2014 #65
"Paranoid"? johndoeX Jun 2014 #66
paranoid conspiracy theorist post more lies and paranoia instead of evidence superbeachnut Jun 2014 #67
Wow. There's one born every minute William Seger Jun 2014 #68
"fake VG" johndoeX Jun 2014 #75
A fake Vg diagram appears in the Skygate video with the lie of structual failure at 425 KEAS superbeachnut Jun 2014 #78
25 to 65 johndoeX Jun 2014 #84
pilots for truth make fake Vg diagram and explain how to fake the Vg diagram, without engineering superbeachnut Jun 2014 #86
structural failure zone for the 767, big lie, pilots for truth fail superbeachnut Jun 2014 #96
The Score remains... johndoeX Jun 2014 #115
In Your Corner delphi72 Jun 2014 #117
Well, you've definitely painted yourself into a corner William Seger Jun 2014 #118
The score, pilot for truth claims, zero evidence superbeachnut Jun 2014 #116
Operational Envelope Diagram delphi72 Jun 2014 #119
It's worse than that William Seger Jun 2014 #120
Boeing Comment on Flight Beyond Vg delphi72 Jun 2014 #121
Bump for Balsamo delphi72 Jun 2014 #122
My apologies 'delphi72' johndoeX Jun 2014 #127
Experience in Aviation? delphi72 Jun 2014 #140
Bump (II) for Balsamo delphi72 Jun 2014 #162
Seger is STILL unable to find the relevant FAR? johndoeX Jun 2014 #123
Why can't pilots for truth explain what they post? They never do. superbeachnut Jun 2014 #124
Why can't Beachnut post a source for his claims? johndoeX Jun 2014 #125
767 built to 1.2Vd, pilots for truth can't find the info superbeachnut Jun 2014 #126
Beachy Epic Fail johndoeX Jun 2014 #128
Pilots for truth can't find the spec the 767 was built to, a reflection of their fake 767 Vg diagram superbeachnut Jun 2014 #129
Beachy once again fails to source his claim johndoeX Jun 2014 #130
Here ya go William Seger Jun 2014 #133
Epic Fail Seger johndoeX Jun 2014 #135
You post stuff you can't explain; why superbeachnut Jun 2014 #137
You STILL don't understand structural engineering or the FAR William Seger Jun 2014 #131
Seger, are you familiar with real world exercise, practical application, and precedent? johndoeX Jun 2014 #134
Flight 175, oops, you lost this debate, superbeachnut Jun 2014 #136
ROFLMAO, so predictable, and yet... William Seger Jun 2014 #138
Wrong again Seger johndoeX Jun 2014 #139
So far... so true.... johndoeX Jun 2014 #172
Fake speeds, fake Vg diagram, failed physics, what is the next fake claim from pilots for truth superbeachnut Jun 2014 #132
Beachy cannot determine a VG Diagram when the data is known. johndoeX Jun 2014 #141
The silly lie Balsamo spreads based on failed research. superbeachnut Jun 2014 #142
Thank you for your insight Beachy... johndoeX Jun 2014 #143
p4t can't explain what they post superbeachnut Jun 2014 #144
Beachy -for more than the 5th time johndoeX Jun 2014 #147
No aero engineers at pilots for truth superbeachnut Jun 2014 #148
Wrong again Beachy.... johndoeX Jun 2014 #150
jet blue pilot goes crazy, talking conspracy theories superbeachnut Jun 2014 #155
Actually, that's more than the 5th time William Seger Jun 2014 #145
Wrong again Seger johndoeX Jun 2014 #146
Why can't pilots for truth explain their own questions, their own posts superbeachnut Jun 2014 #149
It means just what it says.... johndoeX Jun 2014 #151
I knew it, you can't explain your own points superbeachnut Jun 2014 #152
Use a dictionary if you are unfamiliar with the terms... johndoeX Jun 2014 #154
You can't explain your post? Why superbeachnut Jun 2014 #156
Wrong again Beachy.... johndoeX Jun 2014 #157
Of Course he Can't Explain His Posts delphi72 Jun 2014 #163
Fake Vg diagram, and more lies superbeachnut Jun 2014 #153
To any person with a WORKING brain SOMETHING IS TERRIBLY WRONG WITH WHAT WE'VE BEEN TOLD ABOUT 9/11. dballance Jun 2014 #158
Really? William Seger Jun 2014 #159
Yes, Really. dballance Jun 2014 #160
Phillip Marshall? delphi72 Jun 2014 #161
Too funny William Seger Jun 2014 #165
From The Supposed Excerpt: delphi72 Jun 2014 #166
American 88 was MY Typo when I transcribed. Thanks for pointing it out. dballance Jun 2014 #169
Anything else? All your claims are nonsense superbeachnut Jun 2014 #170
Of course, 'duhbunkers' never make a typo... johndoeX Jun 2014 #177
Yes, I have experienced similar results... johndoeX Jun 2014 #167
More nonsense sponsored by pilots for truth, more hearsay and exageration superbeachnut Jun 2014 #171
Working brain? You fell for lies in the "The Big Bamboozle", you were Bamboozled superbeachnut Jun 2014 #168
Just Dawned On Me delphi72 Jun 2014 #164
Uninspired Lies from pilots for truth superbeachnut Jun 2014 #173
Beachy, why have you not supported Seger? johndoeX Jun 2014 #174
Answer My Question delphi72 Jun 2014 #175
pilots for truth can't defend impossible speed lie, no support from rational Aero Engineers superbeachnut Jun 2014 #176
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