United Airways 175

[Omega Supreme]

Matt, the problem with your point is if there is one hole in any of your assumptions, then the whole premise is suspect.

I think some of these so-called facts are unconfirmed at best and purely wishful thinking at worst. It took me about 3 minutes on Google to find other people having this discussion and commercial pilots who say a 767 could in fact exceed 450 knots at low altitude, at least a few times without breaking up.

This, to me seems like one of those times where the level of knowledge required to understand an issue for yourself is so high that it's probably best if we just admit we have no fucking clue.

Actually I will be one of those people that agree that a 767 can indeed withstand higher speeds. Such factors to be included into evidence is the amount of cargo being carried at the time.

[mike321]

Either the speed to disintegration estimate for a Boeing 767 is wrong, or, if it is correct, then that can not be a Boeing 767. That's simple Logic.

If you do get a chance to watch the first vid, there are several angles where one can see the extremely stressful maneuver carried out before the plane hits the tower clearly. Does anyone have a problem with my assuming a maneuver like that would tend to destroy the plane before the power dive that EA990 experienced? Because UA175 was going faster at that moment, not slower.

Edit: 4:47 of the first video is a good angle on the maneuver.

You forgot the speed estimate being wrong as a possibility for the discrepancy I am leaning towards the 767 being able to withstand that speed.

[Devil]

Prop planes do not have the thrust to travel at speeds where turbulence causes the plane's wings to distort and sheer off

I missed this post earlier. Would you like to qualify this statement? As it stands it is untrue.

Piston driven or turboprop? Take a look at the speeds achieved by some propeller aircraft. Even if you're looking at piston engines only, you'll find some pretty significant speeds are possible. You'll also find some pretty damn big and heavy propeller aircraft.

What level of turbulence are we talking? Are you insinuating that no level of turbulence can cause a wing to fail on a propeller aircraft? Not true.

I think I understand what you were trying to say, but what you actually said was false.

[Devil]

The problem with forming an opinion and digging in like a tick when you don't have the independent knowledge to arrive at your own informed conclusion is that you're at the mercy of whichever party argues their position with the most charisma. I know this to be true because I have won many arguments and influenced many people while basically talking out of my ass. (Don't quote me on that.)

For this reason, I'll put this one in the **** If I Know column.

[Matt Phillips]

Matt, the problem with your point is if there is one hole in any of your assumptions, then the whole premise is suspect.

I think some of these so-called facts are unconfirmed at best and purely wishful thinking at worst. It took me about 3 minutes on Google to find other people having this discussion and commercial pilots who say a 767 could in fact exceed 450 knots at low altitude, at least a few times without breaking up.

Most arguments suffer from this characteristic, as do all proofs. There is a word for an element of an argument that can be false without affecting the conclusion: extraneous.

If one assumes that a 767 can travel at the observed speeds without breaking up, then the conclusion that the plane that hit the south tower could not be a Boeing 767 does indeed become invalid. That would be a good thing, because I for one do not want to imagine what else it could be. Unfortunately we have precedent for this model aircraft becoming unstable and disintegrating at these speeds, so we are inclined to believe that this limit is real, regardless of opinion to the contrary.

In any case, structural failure is irrelevant to the conclusion that it is incredibly unlikely that al-Sheshhi could perform the observed maneuvers that day.

This, to me seems like one of those times where the level of knowledge required to understand an issue for yourself is so high that it's probably best if we just admit we have no fucking clue.

No thanks. I'm scientifically trained and posting in a community of skeptics. There is nothing in this discussion that is above pay grade.

[W. Rabbit]

Summarizing: The plane that struck 9/11 was traveling at speeds that should have destroyed a stock Boeing 767

This is an absurd claim.

Maximum cruising speed is intended for an altitude of 35,000 ft, not sea level where the plane becomes extremely difficult to control, and can disintegrate.

The planes were never at "sea level". Flight 175 was at an altitude of approximately 1000 feet at the time of impact. While not "sea level" there is a significant air pressure difference between actual sea level and 1,000 feet above (around 5% per 300m, depending on the weather and temperature).

You'd have to conclude that the hypothesis that Marwan al-Shehhi piloted a 767 into WTC1 on 9/11/2001 is falsified.

No, you are just jumping to conclusions based on hearsay.

[submessenger]

I said it before - Vmo is not "disintegration speed." It's the speed at which FAA has said "you can't take this aircraft any faster without risking safety." It's not a hard line that says the airplane will fall apart if you go faster. It's certainly slower than Vdf, which is the maximum descent speed (generally in jets 0.5 mach greater than Vmo - sorry, misplaced the source on this one).

At some point, you need to consider that you're on the wrong side of Occam's razor.

Here, read this:
http://911blogger.com/node/20232

In short:
a) 767s have 2 engines so they can operate fully on just one.
b) .86 mach at sea level would be 654mph
c) Given 2 engines, it is possible to reach .86 mach at sea level
d) Given descent angle, it is possible to exceed .86 mach
e) a fully FAA certified simulator achieved the speeds at altitudes seen on 9/11

Also, food for thought: http://www.law.cornell.edu/cfr/text/14/23.253

(b) Allowing for pilot reaction time after occurrence of the effective inherent or artificial speed warning specified in § 23.1303, it must be shown that the airplane can be recovered to a normal attitude and its speed reduced to VMO /MMO, without—
(1) Exceeding VD /MD, the maximum speed shown under § 23.251, or the structural limitations; or
(2) Buffeting that would impair the pilot's ability to read the instruments or to control the airplane for recovery.

(emphasis mine)

[Matt Phillips]

You forgot the speed estimate being wrong as a possibility for the discrepancy I am leaning towards the 767 being able to withstand that speed.

The speed estimates are not wrong. That is the point of the first vid. It shows the measured radar values (at 12 second intervals), and shows that the actual observed path of the plane is right along the path described by them.

[Matt Phillips]

I missed this post earlier. Would you like to qualify this statement? As it stands it is untrue.

Piston driven or turboprop? Take a look at the speeds achieved by some propeller aircraft. Even if you're looking at piston engines only, you'll find some pretty significant speeds are possible. You'll also find some pretty damn big and heavy propeller aircraft.

What level of turbulence are we talking? Are you insinuating that no level of turbulence can cause a wing to fail on a propeller aircraft? Not true.

I think I understand what you were trying to say, but what you actually said was false.

Are you saying propeller driven aircraft can travel fast enough to sheer off their own wings? I thought you said the exact opposite earlier.

[Devil]

Unfortunately we have precedent for this model aircraft becoming unstable and disintegrating at these speeds, so we are inclined to believe that this limit is real, regardless of opinion to the contrary.

Come on, man. You gave one example of an airframe failure in different conditions with a slew of other potential variables. You're scientifically trained, right? So you'll know that's not exactly a fucking smoking gun.