reply to post by Rewey
Thanks, I'll see if I can be more clear:
...ignoring the 40º pitch from the FDR, what would YOU estimate the actual impact angle to be (relative to the horizon). Or is it simply
not possible to even estimate because there are too many other variables involved?
Well, we only
have the FDR data to go on....however, (and this occurs to me now) it is such an unusual attitude I am not entirely
certain the EXACT pitch attitude, relative to the horizon, was recorded. Again, I assume it was similar to the 40 degrees NOSE DN...(that would be
below the horizon) but being inverted, and with the speed (yes, the
speed of the event --- the rapidity of occurence --- not the
airplane's velocity) it is conceivable that the laser-ring gyros and accelerometers that constitute the guts of the Inertial Reference System could
have some lag induced by the quick attitude changes....IF the ground had not been there, then there would have been time for the system to sort itself
out with greater accuracy. I know, I know, I was going to try to be clear...but this is me, thinking out loud.
In other words, the ~40-degrees recorded at impact
could have been more, as I would assume the airplane's attitude would have been
continuously increasing throughout the dive.
3. With respect to your comments on the time factor meaning there would be no horizontal momentum transferred to the ground, I have a little
trouble accepting this.
I understand that you do. I will repeat a simplified version of the arrow analogy...or, just even something as simple as a rock. Try it...throw a
rock into sand at an approximate 40-degree angle, and see the pattern of ejecta. maybve not very scientific, but sometimes experimental observation
is better than just doing the math....
Back to my arrow, for a minute...my point
there was that the arrow, impacting at ~40-degrees, doesn't have the rear end break off
and/or fold over as any part of it's horizontal vector component, at impact.
Like I've said in other posts, I can't imagine Mr. Laws of Physics saying "You know, normally I'm pretty reliable, but golly, everything
just happened so fast!"
Yes...that's why they are referred to as "Laws" and not 'theories'.
But, as I tried to point out, there are other 'Laws' at work, as well, besides just the Laws of motion. There is inertia, and with it, momentum.
AND, yes, the timing involved.
Think --- The airplane at ~500 MPH (let's convert to Knots, I use those) so for argument, let's use 435 Kts. (conversion factor is about 15%)
That works out to 733 fps. Correct? The B757 is 155 feet long...so tell me, from the moment the nose HIT the ground, until the tail HIT...how many
seconds of time elapsed?
Remember, the 733 fps is the velocity along the vector component of the airplane's longitudinal axis. Same as in the analogy, along the shaft of the
arrow. Capice?
You can do a vector diagram, and determine the 90-degree (horiz. and vert. velocity components...) and calculate an approximate velocity horizontally
over the ground given the angle relative to the ground.
Also, it will give the vertical velocity component...which should be far, far higher. (Acceleration due to gravity is a fctor, here --- in addition
to the thrust provided by the engines).
*side note* I noticed that the N1 was 70%, from your OP. That is a fairly normal cruise power setting, while they were at 5,000 MSL in level flight,
before rolling over and crashing. It did not seem to increase, which indicates that no action was taken to add power in the descent.
Taking a look at the FDR tracings, I see a few things:
ALL tracings stop at time index 10:03:15 EDT (approx). All at same time.
The last recorded HDG is 235 degrees.
The chart tops out at 500 KIAS....so speed was AT LEAST 500 knots.
The vertical velocity was AT LEAST -35,000 fpm. (That is so outside normal range, I'm surprised it calculated it...)
The autopilot was DISCONNECTED at about 10:00:20. (There was some maneuvering, shown by some erratic tracings just PRIOR to disconnect...tells me
that the struggle had begun, and the terrorists began the maneuvers to try to disoriente the passengers, who were not seatbelted in). Just prior to
10 o'clock, the altitude was 5,000 MSL, and KIAS was about 290 Kts. In all of the maneuvering, the airplane climbed another 5,000 feet UP, reaching
10,000 MSL at about 10:02:10, then began the final dive.
So, the reast....the "horizontal motion" given the short span of time for the entire impact sequence...perhaps you can calculate it for us.
2. Although it's technically irrelevant to the argument being raised, what's your view on the plane crash pic in the OP? Moving bottom to
top? Left to right? Flat spin?
Can't tell, but I would certainly rule out a flat spin, because of the impact velocity from a flat spin isn't much greater than terminal velocity.
