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

CNN | 11/15/2001 | me

[cc2k]

Total then is 1.4 G. Not 2.4 G.

I think if you read my post, I said it would be 1.4G. Nowhere in my post did I state the number 2.4G.

You are also correct that the 1.4G of force would be "down", perpendicular to the wings and fuselage of the plane. At 1.4G, there would be 1G of gravity acting straight down towards the ground, and 1G of lateral force from the turning. This gives a triangle, with 1 unit of downard G force vector and 1 unit of lateral G force vector. The total vector would be approximately 1.414G at a 45 degree angle. The plane would be banked aproximately 45 degrees, so that total G force vector of 1.4G's was straight down relative to the plane of the wings and fuselage.

If the banking were not correct, the turn would not be a coordinated turn, and the plane would slip sideways throught the air. This is not generally done in normal flight, though it might be done very slightly during landings, especially cross wind landings.

[attagirl]

Don't have time to read all the comments, so excuse if this is just a "me too:" But after the public bought the line about the "center fuel tank" it shows anything is possible.

[pgkdan]

With all the government spending during war time we will see the economy rise soon.

Unless we see a major decline in the airline industry...and that industry was wobbly before 9.11.01

[pgkdan]

like the 12 airbus engineers who work with me? they seem to buy into it with no problem.

I have no idea...I'm a plastics distributor, not an AE, but my friend Paul is a very reliable, very intelligent and experienced guy. I'd put him up against your 12 and raise you two.

[Don Corleone]

As a reference, in a 60 degree bank, the aircraft experiences 2 Gs of load, perpendicular to the wing.

(Coordinated 60 degree bank)Opposite the lift vector! The wing may have dihedral/incidence/sweep etc. How 'bout helos?

[monsterbunny]

The computer was programmed to spool the engines down upon the aircraft entering a final approach to landing configuration, which the pilot was in. His effort at regaining power failed because of that throttle override. That 'feature' of override was done away with immediately.

[KQQL]

But I think it's terribly important that the gov't tell the truth and start rebuilding America's confidence in gov't. These last eight years have been hell. It's time for a real fresh start.

I hope you are right, that the Govt tells the truth for once.

[Semper911]

Planes are heavy. They don't like to change position that fast. That's a lot of force, and a lot of stress, in a direction that the tail was not designed to withstand very much of.

Thank you for taking the time to explain the physics of it all. I couldn't said it better myself. It is beyond me why 90% of the posts on this thread are from people who do not seem to understand the concept of LATERAL.

For those of you who still don't get it, we are talking about the plane suddenly being forced SIDEWAYS. The vertical stabilizer (tail fin) is in no way designed to do that. We are not talking about a turn here, with the fin slicing through the air. The tail took the force BROADSIDE, and I can see how it could fail under those conditions.

And for whoever said that laying on your side is the same as a lateral g force, you BETTER have been kidding. (I am too lazy to go back through the thread to get your name.)

After watching the news conference, I was confident that the structural failure was caused by the lateral g forces exerted on the vertical stabilizer.

Accidents sometimes happen.

[DugwayDuke]

One must always wonder what other "features" may be found in software.

[discostu]

Thanks, very intregueing Gforce discussion. Always good to have others watching FR for you, too much cool stuff to find by yourself.

[monsterbunny]

Curiouser and curiouser.

One of the problem with composites is there is very little middle ground between the approach to tensile or shear maximum and catastrophic failure wheras metals usually bend or stretch a bit well below dissassembly. Talk to pilots that have flown tweaked F4s. Composites also do not fatigue unless the matrix(glue)is compromised in some way. Heat, Cold, UV degradation, chemical contaminations and overstress are typically the only reasons a delam might result. Graphites or Carbon composites have lousy impact or shock resistance. The best visual is that carbon fibers are very brittle. This is why Kevlar is the best choice for armor. However Kevlar has little in the way of compressive strengths so is not a good stand-alone fabric for loads that require both compressive and tensile considerations. Interleave Graphite and Kevlar and one gets a pretty decent, incredibly lightweight, strong and shock resistant part.

All in all, a properly engineered composite part is far superior to most metals. IMHO.

[Fred25]

That looks like too sharp of a turn to be safe. It looks like a 90-degree turn within one mile.

[ijk]

"I wonder how the FDR would actually record this phenonemon - anybody know? "

It's pretty elementary, actually. If you know the speed of the plane and it's turn rate, then you know it's acceleration (for those that did not realize it, 'gs' are acceleration). The "Indicated Air Speed" is drawn from the same source that the speed indicator in the cockpit draws it from (they used to use "pitots" for that, but I'm sure they've got something fancier now). The turn rate can then be calculated from the combination of the position of the flight surfaces during a turn and IAS (this would be well known for a particular aircraft). The rest is solved with:
F = dp/dt.
In other words, all you really need to know is where the flight surfaces are and the IAS.

[TC Rider]

Demosthenes, meet Bernouli.

At 33 feet of depth, you meet one additional atmosphere of pressure, or an additional 15 psi enveloping you in all directions. But no G force.

Divers don't feel the extra pressure because the body is filled with mostly water anyway. If you held your breath from the surface, a lungful of air would only occupy half the space. OR, if you had a lungful of air at 33 feet and surfaced without exhaling, you would blow out your lungs or experience an embolism.

G force is observed only through gravity of a large mass or through changes in velocity.

I'm not an engineer, but did stay at a Holiday Inn Express last night.

[michigander]

Is that considered unsafe?

[ijk]

If .8 g's trashed an A-300 Airbus, I don't care what it's orientation or status, then we should be bombing France for building the d@mn thing! Oh wait...that's right, it WAS made in Europe...oooopppssss

[Ciexyz]

"Nothing to see here, go buy some clothes, a dishwasher, or a car...."

I did my bit for the economy at Kohl's 50 percent off sale.