NTSB Briefing, NTSB claiming .3 to .8 g wake encounter caused crash?!?!?!

CNN | 11/15/2001 | me

[demsux]

all your g's are belong to us

[rebapiper]

The Bird story won't fly because so they had to come up with something a little more confusing, that way many may beleive it and anyone that doesn't is just a right wing nut.

[Eyes Now Opened]

Just a question - if it was a bomb, wouldn't the tail piece be more jagged and torn from an explosion unless the bolts were loose to begin with? I'm definitely not a scientist - thought maybe someone can explain this.

[thesharkboy]

All figures approximate to 20 sig. figs.

Yeah, right. You're an idiot.

[Fred25]

I like planes with three or four engines, completely made out of metal.

[jpthomas]

Vortex shedding off a natural formation caused the failure of the Tacoma Narrows Bridge. The vortex shed off the wingtips of the 747 that preceeded this a/c in takeoff is a plausible source of periodic loading of the tail that could have stimulated a harmonic oscillation.

[KQQL]

ditto.....

[samuel_adams_us]

Sounds like sabotage to me, maybe some weakend welds?

[justlurking]

It depends on the radius of the curve. The signs on sharp curves are generally posted to keep you under 0.25g. So, the 0.3g figure is not much higher than following the speeds posted on the signs exactly. Most people when driving will feel comfortable taking a corner at 0.4g to 0.5g. Most SUV's can generate 0.6g to 0.8g of cornering force. Automobiles generally can attain 0.7g to 0.9g, with the best sports cars capable of 1.0g or a little more on street tires.

Thanks, I knew that .3g laterally was within the capability of most cars. But, I was looking for an example. I chose the "right turn around a corner" as an example of turn most people would recognize.

So, if we presume that we are turning right 90 degrees at an intersection, in a short radius turn (say, 3/4 of a turn of the wheel, not to lock), from right lane to right lane (not fair straying into the center or left lane). What speed would you need to generate a .3g lateral acceleration due to centrifugal force?

[Daus]

NEW QUESTION!!!

Given this information.... How did the engines come off the airplane? I can see a lateral push knocking off an already damaged VERTICAL tail.... but what about the engines?

The afore mentioned ocillation?

[hound]

Consider this: If you could turned the plane on its side so that the tail fin is horizontal to the ground, you would be exerting 1.0G on the fin. In other words, this is hogwash

[samuel_adams_us]

What would happen if you scored those composite eyelits with a sharp instrument?

[justlurking]

I should think in a normal banking turn then that as much force as .3 - .8 would be experienced on the vertical surface no?

Not necessarily. The rudder is used to control the yaw axis of the plane. A normal banking turn, once established, doesn't require much rudder. See my earlier post #36.

[Map Kernow]

It was a combination of wake turbulence and composite material failure. Obviously, this A300 had undetected composite fatigue prior to this flight. Now, put that fatigue in a situation with the different loads from significant wake turbulence and you get what we have here...a tragic crash and a call for inspections of all A300's.

Thank you for letting us know in advance the official government explanation of this tragedy. Yes, let's all call for inspections of all Airbuses, an end to wake turbulence, and a rest for airframe composites in order to combat their fatigue. Book your airline reservations today!

[Darth Reagan]

so they had to come up with something a little more confusing, that way many may beleive it and anyone that doesn't is just a right wing nut.

Admitting you don't know what they are talking about because all that science is too "confusing", then jumping to the conclusion that it is an orchestrated cover-up of some sinister plot . . . well, I don't know about "right wing" but "nut" certainly fits.

[clamper1797]

What the hell is going on?

It's pretty obvious .... if they announce that it was a terrorist attack the airline industries would go broke cause very few people would fly again for QUITE a while. Oh ... and I used to be a jet mechanic and this story is PURE Bravo Sierra.

[Starrgaizr]

This is exactly what I was thinking. The ENTIRE PLANE experienced lateral acceleration of .3-.8 Gs. If the entire plane were shoved to the side that hard based on a vortex striking only a small surface area, the force exerted on that small area had to be very significant. In small prop planes we have a slipstream effect where the spiraling prop wash hits the vertical stabilizer. The tail is designed to counteract that and pilots step on the rudder. But a sudden blast on a jet's vertical stabilizer when perhaps already mechanically weakened seems like it could be a problem, perhaps more so if the pilot did not stomp on the rudder quickly to fight the yawing movement and one-sided force on the stabilizer. Just an amateur...

[Solson]

In general I would agree with that. But, detecting fatigue in carbon composites is generally difficult. If the cracks were too small to be seen with visual contact, they would have been missed. For a reference on non-destructive examiniation please look at this:

http://www.aviation-industry.com/atem/Acrobat/at53ndt.pdf

[Steve_Seattle]

"how come it has never happened before"

That has been my main question about the wake theory. Planes take off and land at about 2 minute intervals hundreds of times a day, every day of the year, and there are a lot of old, stressed planes flying. If this kind of accident is possible for the reasons given, you would think it would have happened a long time ago and that the minimum time between takeoffs and landings would have been significantly increased.