| June 25, 1999
Pilot
vs. NTSB
Retired TWA Pilot from
Southold Interprets Flight 800
Data Differently
It was almost exactly a year ago that
Howard Mann of Southold, retired
TWA pilot, outlined in this paper his
analysis of the Flight Data Recorder
(FDR), one of the "black boxes," from
TWA Flight 800. Mann began his career
with the airline as a mechanic, then
became flight engineer and, finally, pilot.
The gist of Mann's analysis concerned a
line of data that had come to be referred
to as the "12 second line"; the reading
that had been taken at 20:31:12 (or 12
seconds after 8:31 p.m.) on the evening
of July 17, 1996, when Flight 800, on its
way to Paris from JFK, came down out
of the sky, killing all 230 people aboard.
Further research by Mann, and an as yet
unreleased addendum by National
Transportation Safety Board (NTSB) on
the Flight Data Recorder have brought
further questions to light.
In the December, 1997 hearings on
Flight 800, the NTSB had presented this
12 second line of data, but with a line
through it. Mann said, ³I read a printout
of those last seconds and used a
magnifying glass to read the figures that
had that line through them.² It was
Mann, among the various private
individuals involved in investigations of
the tragedy of Flight 800, who said the
12 second readings indicated the sudden
transformation of an airplane from
normal flight to severe distress. The
readings, according to Mann, showed
that an external pressure wave had
struck the plane.
For instance, at eleven seconds after
20:31, the altimeter shows Flight 800
was flying at 13,772 feet. In less than a
second the plane¹s altitude is marked at
10,127 feet. For an object to plummet
3,645 feet through the atmosphere in
one second it would have a speed of .68
miles a second, or 40.8 miles a minute
or 2,448 mph. In other words, it was
not possible that Flight 800 fell at this
rate.
But there is a way in which the altimeter,
and other instruments on the plane, can
give ³false readings.² The altimeter
measures altitude by way of air pressure.
There is less air pressure the higher you
go, more as you descend. The altimeter
of Flight 800 registers, in the last
moments before the plane is blown
apart, a pressure wave from outside the
craft and thus registers it as an increase
in actual air pressure and translates this
into an apparent, abrupt, impossible
drop in altitude.
This external pressure wave, Mann
contends, was further indicated by,
among other things: the role altitude; the
angle at which the nose was raised; the
angle of attack which measures angle
at which air is striking the wing); and the
readings for the right rudder trim.
Mann and many other investigators said
this was evidence of a pressure wave
that could only indicate the plane had
been struck by a missile, one which
possibly blew up just outside the plane.
But there was an official explanation for
these aberrant readings, said the NTSB.
The FDR lays down readings on a spool
that takes 25 hours of continuous
information: 43 readings at a rate of 64 a
second. The key word is continuous: the
tape does not have a beginning or end to
its data, but simply records over old
data, data 25 hours old, as it goes along.
But the transition from the data from one
flight to another is not smooth, said the
NTSB. What had become the infamous
12 second line was in fact that transition
point; and, in addition, the Safety Board
said, those figures were actually for
Flight 803, Paris to JFK on July 16,
1996, the day before Flight 800 came
down.
Mann¹s comment at the time was that if
the 12 second readings were for another
plane, that was a plane in trouble.
Eventually the NTSB removed that 12
second line of readings from its website
report presented at the December,
1997 hearing on Flight 800¹s Flight
Data Recorder.
* * *
Coincidentally, on July 12, 1998, within
a week and a half of our first interview
with Howard Mann last year, an
addendum report on the Flight Data
Recorder was prepared by Dennis R.
Grossi of the NTSB. The report was
officially submitted to the NTSB on
September 9, 1998. But as of yet the
report has not been made available to
the public.
Grossi, National Resources Specialist,
Flight Data Recorders for the NTSB,
also oversaw the original FDR report
presented at the hearings. The impetus
of the addendum is to clarify the issue
about where the data for Flight 800 ends
and the data for Flight 803 begins. The
report reads: ³...a portion of the data
recorded during TWA803 has
mistakeningly been analyzed as if it were
recorded during TWA800.²
The addendum goes on to say that it has
been the normal practice for the NTSB
³to include the unsynchronized transition
data² merely as a marking point to show
the border or ³transition from the newest
to the oldest data.²
A product called ³Magna See(r)² that
contains an iron powder in a fast drying
liquid is placed on the recording tape.
The powder makes visible the magnetic
fields on what has been recorded on the
tape.
Apparently, according to the addendum,
the iron powder was used specifically to
pinpoint what is called ³the erase-write
gap² on the tape. Data on the tape is
erased just a bit ahead of new data
being placed down on the tape. This
results in ³a gap between the newest and
oldest data that approximates the
distance between the erase and write
heads,² the report says. The gap is about
three inches on the tape, or about seven
seconds.
In his analysis of the FDR and the
addendum, Howard Mann says that the
NTSB¹s Recovery Analysis and
Presentation System (RAPS) ignores the
erasure gap. RAPS, the digital system
used to transcribe the data, makes no
indication where the gap occurs.
³The point is,² said Mann in a recent
interview, ³they are saying the data was
transcribed out of snyc, but the original
data is still there so why can¹t they just
go back to it?²
³The amplitude also decreases on either
side of the erase write gap,² the report
goes on to say, then adds, ³The
degradation of the signal did not prevent
RAPS from recovering the affected
data.²
Mann points out that the place on the
tape at which the NTSB concludes
power on Flight 800 was lost to the
FDR may not be the last moment at
which power was available to record
data. The NTSB¹s Sound Spectrum
Study that analyzed the Cockpit Voice
Recorder (CVR) on Flight 800 stated,
³At time .73 seconds before the end of
the recording and again at .68 seconds
before the end,² there was a ³change in
the background signal as observed on
the Captain¹s radio channel.²
Mann said that each of the 60 kilowatt
generators on each of the four engines
operate at the same rotation and speed
and are linked together by what is called
the Sync Bus. In his own analysis, Mann
says, ³Under certain Fault Conditions¹
individual Bus Tie Relays open to isolate
individual generators and their load
buses from the rest of the electrical
system.² Thus one generator may fall out
of sync, disrupting the even flow of
power. Mann gave the analogy of
soldiers purposely marching out of step
when crossing a bridge in order to
disrupt the harmonic¹ of their
combined marching and put less stress
on the structure of the bridge.
Citing the .73 and .68 ³loss of upper
harmonics² on the CVR, Mann says,
³We can logically assume that the #4
Bus Tie Relay has tripped due to some
sort of fault.² He adds that the ³next
automatic function would be for the #4
Main Generator Relay to trip and the
result is no power to #4 and the
Essential Load Bus and the FDR.²
Mann calculates that the first power loss
falls within .021 seconds of what the
NTSB cited as the end of Flight 800
data and power loss to the FDR:
20:31:12.031. And then Mann goes on
to make an interesting connection.
In the Grassley hearings last month in
Washington D.C., regarding the FBI¹s
conduct and procedure in the Flight 800
investigation, one of the exhibits
introduced was a March 28, 1997 letter
from John C. Gannon, the CIA¹s
Deputy Director for Intelligence to the
FBI agent in charge of the Flight 800
investigation, James Kallstrom. The
letter was accompanied by a CIA
analysis that read, in part, ³Using the
eyewitnesses¹ visual and sound
observation combined with tracking
data from the radars and infrared data
from an intelligence sensor CIA
analysts were able to reconstruct the
approximate path of Flight 800 from the
instant its recordings ended until it hit the
water.²
The agency¹s analysis arrives at the time
of ³the initial explosion² on Flight 800 as
occurring ³at 8:31:07.5 p.m.² In other
words, 4.5-5 seconds before the FDR
apparently lost power.
The 4.5-5 second lapse could be the
result of a normal few seconds time
before the power was affected, or, as
Howard Mann postulates, the ³initial
explosion² eyewitnesses and infrared
intelligence from a surveillance satellite
show is actually a missile launch. (CIA
public affairs spokesperson Anya
Guilsher confirmed that the ³infrared
data² was indeed obtained via satellite.)
If Flight 800 were at approximately
13,800 feet at the time, Mann says, ³The
difference from 7.5 seconds to 12.5
seconds is about right for something
climbing to 1370 feet at Mach 2.5
(2750 feet per second.).²
Evidence that power returned to the
FDR at least for another second comes
from the transponder signal from Flight
800 that was picked up by Mega Data
of Bohemia at 20:31:13. An airplane¹s
transponder records hits from radar.
Mega Data receives transponder
information from flights overhead and
records them for the airlines.
Another pertinent point Mann brings out:
the point at which the NTSB fixes as the
beginning of data from Flight 803, the
reading that records the date is absent,
as well as the time of day. The date and
time are recorded in sequence: a
numeral, in this case ³7² marking the
month of the July, which is then followed
by the date then the time.
³You have the FDR reading for the
month but not the day. If we knew if this
was the 16th, when Flight 803 was
recording, or the 17th for 800, and or if
we had the time, the whole problem
would be solved.²
Mann further questions the NTSB¹s
assigning the 12 second line to Flight
803 and not Flight 800 by his analysis of
the stabilizer trim parameter readings.
Mann says the horizontal stabilizer
moves one unit every seven seconds.
The point on the tape at which the
NTSB claims is the gap between Flight
800 and Flight 803 shows what would
be a normal rate of change for readings
from one flight. A gap between readings
assigned to two separate flights would
not, except by extreme coincidence, be
in agreement. But if the erasure gap
occurred later on the twelve second line,
where Mann contends it does, then the
divergent readings that are given make
more sense.
The altitude data referred to at the
beginning of this article on the 12
second line has another revealing
dimension to it, Mann adds. There are
two types of readings the FDR records:
fine altitude and coarse altutude. The
coarse alttude reading is in increments or
brackets of 5,000 feet. In other words it
shows if a plane is between 0-5,000
feet, then 5,000-10,000, then
10,000-15,000 and so forth. The fine
altitude shows to the foot the height of
the plane. The fine altitude reading on
the 12 second line is 10,127.
Mann said, ³If the fine altitude is
incorrect, it would still be in the bracket
of 10,000-15,000. Yet the NTSB says
that this is data from Flight 803, which,
according to their own report, was at
33,000 feet at that point on the tape.²
As of presstime, Dennis R. Grossi of the
NTSB had not returned calls to discuss
his addendum to the Flight Data
Recorder report.
Ultimately, Mann once more contends,
the controversy over Flight 800 data
could be resolved if the readings that
were supposedly transcribed out of sync
can be lifted again, this time correctly. ³If
the NTSB says it¹s there, why don¹t
they just go back to it and clear up some
of these questions that people have been
wondering about for nearly three years?²
Jerry Cimisi
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