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Not How, But When Did the Tail Fail?
April 21, 2004
By Brett Hoffstadt
The NTSB is planning to release their final report
on Flight
587 in the summer of 2004. Many
people are hoping to find answers to troubling questions related to
this tragic
flight of November 12, 2001. But
based on the first public hearing held by the NTSB in October 2002, and
public
statements since then, many others believe the NTSB has committed
itself to
pursuing a mistaken and unsatisfying path – believing that the loss of the
vertical tail was the cause of the crash.
As explained in previous articles at U.S.Read, the
pilot of
Flight 587 commanded a rudder deflection of less than 7 degrees during
the
fifth and final rudder movement.
But to create the force necessary to break the tail at this
time, as the
NTSB claims happened, the rudder deflection would have to be 11.5
degrees or
greater. This number comes from
Airbus, whom the NTSB has relied upon for these calculations.
The NTSB, in their final report, might blame
American
Airlines training programs and the pilot for using excessive rudder
controls.
But as was shown in our March 26th article, if the NTSB is correct about when the tail
fell off
they have so far failed to explain how the rudder deflected beyond the
pilot's
input (and beyond the value set by the rudder limiter unit). Or, if
Airbus'
calculations are shown to be incorrect, they have failed to explain the
premature failure of the vertical tail structure. "Premature",
because the tail would have failed before the
ultimate design loads were exceeded.
Perhaps the NTSB should take a step back, and
instead of
asking "why" the tail separated, ask "when" did it separate?
The NTSB has assumed since very early in the investigation that the tail separated at 9:15:58.5 AM. But it's very difficult, if not impossible, to make the rudder data, debris path, aircraft loads, and pilot input form a consistent and scientifically valid story based on this assumption.
How did they arrive at a tail separation at this
time? One answer is a mysterious clue
caught
on the cockpit voice recorder (CVR).
The NTSB transcript describes a "loud bang" at 9:15:58.5 AM.
Ever since releasing this transcript, the NTSB has
claimed
the Loud Bang was the sound of the vertical tail structure experiencing
catastrophic
failure and separating from the aircraft.
However, this claim has not been supported with a detailed audio
analysis of the event or a reproduction of the sound on a test aircraft.
To the contrary, the NTSB's Sound Spectrum report
stated
that no sounds on the CVR
could be
associated with the separation of the tail or rudder.
Is the NTSB trying to make the facts fit their
hypothesis
rather than the opposite? That is
what a number of aviation professionals and concerned citizens suspect.
In fact, significant evidence points to vertical
tail
separation occurring much later than the sound of the Loud Bang. Some of that evidence includes the
location of the vertical tail in the Bay and other debris as well as a
tollbooth video. This video shows
what appears to be smoke trailing from the aircraft before the time of the Loud
Bang.
Amazingly, the NTSB has yet to take a close look
at the
original tollbooth video in their search for clues or explanations. The original video remains in the
possession of the FBI, which has failed to release it under Freedom of
Information Act requests from U.S.Read.
Perhaps most disturbing – the FBI hasn't even released a
digital,
uncompressed copy of this video to the NTSB for their investigation.
Nor has
the FBI submitted a report of their analysis of the original tape.
The NTSB hasn't asked for the original video
either. They used a second or
third-generation
VHS copy of this video (provided by the FBI) for their superficial
video
analysis. Of the two video forensic
experts contacted by U.S.Read, both said that any conclusions drawn
from these
copies are immediately discredited since the NTSB wasn't working from
the
original.
Then of course there are statements from many
eyewitnesses
to the crash, some of whom are trained observers like policemen and
firemen.
They reported seeing the vertical tail separate, but only after they saw smoke and flames on the aircraft.
Whenever the vertical tail separated, all
hydraulic lines to
the rudder would have been severed.
This would have created a repetitive
audible alarm in the cockpit (known as a Level 3 warning).
No such alarm was heard after 9:15:58.5. It
was first heard
nine seconds later, at
9:16:07.55.
If, as it seems most likely, the vertical tail
separated
several seconds after 9:15:58.5, the NTSB has a growing list of
questions that
ought to be answered in their upcoming final report.
And there are a growing number of citizens who will expect
considerable answers. Weighing on the minds of many is – if that Loud
Bang
wasn't the separation of the vertical tail, what was it?
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