Posted on 11/16/2001 1:19:06 PM PST by The Magical Mischief Tour
This is Bull $h!t!!!
The NTSB is LYING like rugs!!!
NTSB dude just claimed that .3 to .8 g's encountered during the wake encounter caused the Airbus to break up in flight...
Even a male reported asked "is this even possible".
"Isn't this normal bumping encountered when flying?"
Even the media don't believe them!!!!!
Because Dubbya just found out that something really atrocious from the Clinton administration was not cleaned up, and it's too late to tell the populace about it, because of all the worry over Muslim terrorists.
It's not that Dubbya wants to cover it up; it's that the can or worms is too ugly to let us know.
Can someone do a quick calculation and determine the lateral acceleration generated generated by a 20 mph right turn around the corner? I think it would help people understand the absurdity of this claim.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.
While 0.3g's laterally is a lot, with normal onset it is no where near enough to rip the vertical off a healthy airplane. If there were other prior damage it might do it. There have been questions about design load spectra on an unidentified Airbus type but I can't know if is a contributing factor here.
So far the most excessive thing I've seen is the amount of talking the NTSB is doing at this stage of the investigation. Now THAT's extraordinary.
Fighter jets pull more like 6-7 g's, sometimes higher. Seatbelts are typically rated to 9Gs. Most rollercoasters impart 3-4Gs. Stand up from a squat, and you'll experiencing about 1.3 - 1.4 Gs. This is nonsense, pure and simple.
The problem with the report is that planes should be capable of experiencing a full 1 or 2 g (or more) sideways forces.
I’m guessing at the numbers, but a .3 g force is not very much.
A “wake” in airplane terms is just the turbulent wind swirling around behind a big plane that is ahead of yours, like the rough water in the “wake” of a boat.
There is discussion that the vertical stabilizer had been damaged either during manufacture or shortly thereafter, something about coming de-laminated, repaired by the contractor, then attached to the plane. Also, this aircraft had suffered a severe turbulnece incident about 7 years ago - severe enough that 42 passengers were injured. I had heard this information on the news this morning. Now, if the vert. stab. already had a problem and then suffered some severe forces later on, is it outside the realm of possibility that it could shear off later on? On the thread above, there are photographs of the stabilizer - it looks like it broke off pretty cleanly. I ain't no expert here, but is it possible that this really was an accident? Also, there is another thread on this forum about the airbuses now being inspected.
I expect now i'll be flamed as a gubbmnt sympathizer.
Having taken graduate-level aero courses and specializing in dynamics in general, I can tell you that the information here is not technically complete enough from which to form an opinion (as is usually the case with this sort of info).
Yes, fighters and commercial airliners can sustain far, far more than 0.8 g's. However, acceleration is a vector which has both magnitude and direction. They are giving us only magnitude.
No commercial plane that I know of can sustain more than about 2 g's in a yaw-only induced turn without having problems. Think about it - twice the plane's weight applied only to its vertical tail surface. It's not that big a stretch to imagine if the tail fin had already some stress concentration such as a damaged bolt, that it would rip off in a 0.8g yaw-induced turn. In fact, I can;t imagine any pilot directing his plane to do so, but it is possible that wake turbulence alone could cause it.
What is unlikely is that the plane was executing a proper turn - ie, roll + yaw, and fell apart at 0.8g. That would mean that the wings would fall off, and the plane would have likely not gotten off the ground in the first place.
Than why would the crew have been talking about VIBRATIONS?
Let's see...for a 40 ft turning radius:
(20 m/hr)*(5280 ft/sec)*(1 hr/3600 sec) = 30 ft/sec
a = v*v/r = (30 ft/sec)*(30 ft/sec)/(40 ft) = 23 ft/sec^2,
or about .7 g.
All figures approximate to 20 sig. figs.
BTW, the A300 was the first commercial jet to use composites in the construction of the airframe, including the rudder and vertical stabilizer assemblies.
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