sitemap Mann's and Hirsch's Analyses of FDR

Article 1 - Pilot vs. NTSB

Retired TWA Pilot from Southold Interprets Flight 800 Data Differently

"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. "

Jerry Cimisi - Dan's Papers - June 25, 1999

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. (Note from website author:  the NTSB had crossed out the data) Mann said, "I read a printout of those last seconds and used a magnifying glass to read the figures that had that line through them." 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 plane's 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 'false readings.' 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.  Mann's 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 800's 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: "...a portion of the data recorded during TWA803 has mistakeningly been analyzed as if it were recorded during TWA800."   The addendum goes on to say that it has been the normal practice for the NTSB "to include the unsynchronized transition data" merely as a marking point to show the border or "transition from the newest to the oldest data."

A product called 'Magna See(r)' 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 'the erase-write gap' 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 'a gap between the newest and oldest data that approximates the distance between the erase and write heads,' 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 NTSB's 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.  "The point is," said Mann in a recent interview, "they are saying the data was transcribed out of snyc, but the original data is still there ­ so why can't they just go back to it?"

"The amplitude also decreases on either side of the erase write gap," the report goes on to say, then adds, "The degradation of the signal did not prevent RAPS from recovering the affected data."

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 NTSB's Sound Spectrum Study that analyzed the Cockpit Voice Recorder (CVR) on Flight 800 stated, "At time .73 seconds before the end of the recording and again at .68 seconds before the end," there was a "change in the background signal as observed on the Captain's radio channel."  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, "Under certain Fault Conditions individual Bus Tie Relays open to isolate individual generators and their load buses from the rest of the electrical system."  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 harmonic of their combined marching and put less stress on the structure of the bridge.

Citing the .73 and .68 'loss of upper harmonics'on the CVR, Mann says, "We can logically assume that the #4 Bus Tie Relay has tripped due to some sort of fault." He adds that the "next 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."  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 FBI's conduct and procedure in the Flight 800 investigation, one of the exhibits introduced was a March 28, 1997 letter from John C. Gannon, the CIA's 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, "Using the eyewitnesses' 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."  The agency's analysis arrives at the time of "the initial explosion" on Flight 800 as occurring "at 8:31:07.5 p.m."  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 "initial explosion" eyewitnesses and infrared intelligence from a surveillance satellite show is actually a missile launch. (CIA public affairs spokesperson Anya Guilsher confirmed that the 'infrared data' was indeed obtained via satellite.) If Flight 800 were at approximately 13,800 feet at the time, Mann says, "The difference from 7.5 seconds to 12.5 seconds is about right for something climbing to 13,700 feet at Mach 2.5 (2750 feet per second.)."

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 airplane's 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 '7' marking the month of the July, which is then followed by the date then the time.  "You 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."

Mann further questions the NTSB's 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, "If 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."

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. "If the NTSB says it's there, why don't they just go back to it and clear up some of these questions that people have been wondering about for nearly three years?"

Article 2 -NTSB Exhibit 10A Addendum 2

The NTSB has missed an opportunity to correct a serious mistake

"For some reason the NTSB does not want to reveal all 64 data words of the last data record".
An Analysis by Richard Hirsch

 Click for original article

The National Transportation Safety Board held it's long awaited hearings on the TWA Flight 800 disaster during the first part of December, 1997. In my opinion the most valuable thing to come from the hearings was the publication of most of the NTSB's TWA Flight 800 investigative docket on a CD. The little CD held the equivalent of about 4,000 pages of text, charts, and photographs, almost everything the NTSB knew about the crash of TWA Flight 800 at that time.

One NTSB exhibit which received a great deal of public scrutiny was Exhibit 10A. Exhibit 10A covered the examination of TWA Flight 800's Flight Data Recorder and attempted to explain what the data on the FDR tape meant. That's when the trouble with the NTSB's explanation of the FDR data began. The NTSB FDR group made a serious mistake by including some data from the FDR tape (which was from a previous flight, Flight 803)  in the same tabular presentation as the data from TWA Flight 800. To make matters worse the NTSB now admits that some of the "extra Flight 803 data" was also the cause some data anomalies.

Capt. Howard T. Mann, a retired TWA 727 pilot, was very much interested in the TWA Flight 800 investigation. Capt. Mann paid particular attention to the NTSB's Exhibit 10A (Caution: Long download) because he wanted to see if the FDR  data presented in the graphical data presentation and the tabular data presentation revealed any clues as to the reason for the crash of TWA Flight 800. After careful examination of the graphical and tabular data given in Exhibit 10A, Capt. Mann noticed that the last information presented in the tabular data could be interpreted to mean that there was an explosion near the forward portion of TWA Flight 800's fuselage. The last information was the last information recorded on the FDR tape before the FDR suffered a power loss.

I was immediately interested in what Capt. Mann had to say about the data as presented in the NTSB's Exhibit 10A. Capt. Mann wrote a paper explaining his views about the meaning of the tabular data which was titled, "Analysis of Flight Data Recorder (FDR) 12 Second Line". I read Capt. Mann's paper and saw how the data the NTSB presented in the tabular data could certainly be interpreted as a possible explosion outside the forward portion of TWA Flight 800's fuselage.

The NTSB responded to the furor created by Capt. Mann's paper by quietly deleting the troubling tabular data (which was shown in the original NTSB Exhibit 10A) from their website copy of Exhibit 10A. No notification of the update of Exhibit 10A was attached to the Hyperlink entry in their exhibits menu. I believe this was accomplished through the issuance of an Addendum 1 which was not seen by the public. The NTSB's action in quietly removing the data in question from the exhibit only led to more accusations by the independent investigators of wrong doing by the NTSB.

I decided to learn more about how the Flight Data Recorder actually operated so I could form my own opinions about the argument between the NTSB and Capt. Howard Mann concerning the meaning of the data from the TWA Flight 800 Flight Data Recorder. I spent quite some time researching the Sundstrand Universal Flight Data Recorder (used in TWA Flight 800). I ended up writing a paper on the research I did and what I learned about the FDR used on the TWA Flight 800 B-747.  The title of the paper is, "The Flight Data Recorder Study".

I found from my study of how the Sundstrand FDR operated, that the reason the NTSB had landed in so much hot water with the independent investigators was their method of presenting data from two different flight periods for the same aircraft in the same graphical presentation. How do you tell where the TWA Flight 800 (new) data ended and TWA Flight 803 (old) data continued? That was the problem.

The problem actually had a simple solution.

In the paper I sent to the NTSB on August 22, 1998 I proposed the solution to the FDR Group, headed by Dennis Grossi. The solution was so simple I was surprised that the NTSB would let the data argument continue without doing something to defend the credibility of their investigation. The solution I proposed was not my own, but was suggested to me by Glen H. Schulze of Littleton, Colorado. Glen is the past Chairman of ISO TC97/SC12 INSTRUMENTATION TAPE RECORDING STANDARDS GROUP.

Glen explained that you could examine the FDR tape directly by using a material called "ferrofluids" to develop the tape in a way which would show where the TWA Flight 800 (new) data ended and the TWA Flight 803 (old) data continued. Glen told me that he has performed examinations on FDR tapes hundreds of time during his career. He offered to go to the NTSB's laboratory and examine the TWA Flight 800 FDR tape for them if the NTSB would ask him.

Starting in September of 1998 I made phone calls to Dennis Grossi of the NTSB about the paper I had sent to him. I also sent extra copies of the paper to be distributed by Dennis Grossi to each of the parties in his group. Dennis told me by phone that a new addendum had been prepared to take care of the problem of the data anomalies present in the original release of Exhibit 10A. He told me he thought the corrections were already on the NTSB's web site. I checked the NTSB web site and saw that no new information on Exhibit 10A had been posted.

I thought it was odd that Dennis Grossi had not acknowledged receipt of my package of papers on the FDR study and asked him for a written confirmation of their receipt. I wanted to make sure that the copies had been distributed to the other parties in his group. I asked Dennis several more times for a written acknowledgment for the receipt of the paper when I was talking with him about the release date of the new Exhibit 10A addendum. I didn't receive an acknowledgment.

I asked Dennis Grossi, once again, for an acknowledgment of the paper by email on February 25, 1999.

"Also I am again asking for an acknowledgment of the paper I submitted to you (and your FDR study group) on August 22, 1998 concerning the question of the clarification of the last seconds of data as shown in the original exhibit 10A. I'm sure that sending out acknowledgements to contributors of information received by the NTSB is normal procedure for the NTSB."

I know the NTSB to be a professional organization that would normally acknowledge the receipt of technical papers sent to them. I was puzzled by the NTSB's lack of good business practices and common courtesy. Rather than jump to conclusions I decided to write a letter to Chairman James Hall of the NTSB and bring the matter to his attention. I sent the letter to James Hall via certified mail and received a return receipt signed by an R. Underwood on April 1, 1999. A copy of the letter I sent to Chairman Hall can be found by clicking here. As of this date (06/29/99) I have not received a response from the NTSB. I can't help but wonder why the NTSB, from the top down, does not want to acknowledge the receipt of a paper sent to them in good faith?

Near the end of the month of January, 1999 I received a call from a source who had obtained a copy of the NTSB Exhibit 10A addendum 2. The source knew about the paper I had written concerning the problem the NTSB had with the original Exhibit 10A and asked if I would review the Addendum 2 and give him my opinion on it. I received a copy of the NTSB Addendum 2 by regular mail a few days later. The addendum was a copy of an original addendum which was obviously straight from the NTSB. The release date on the cover sheet was September 9, 1998 while the second sheet carried a July 12, 1998 release date. From hereon NTSB Exhibit 10A Addendum 2 shall be called Addendum 2.

The first thing I learned from reading the Addendum 2 was that my original paper on the FDR was correct about how the FDR functioned and how the data was organized on the FDR tape. The second thing I saw was the graphics on the copy of the addendum I had were not too good. The heart of the addendum was in the graphical presentation of the FDR tape data. I decided to construct my own graphics based on the graphical information contained in the NTSB Addendum 2. I also decided to write my own commentary on the written portion of the Addendum 2.

In order to be fair I am making this bargain with the reader, I will copy my copy of the Addendum 2 and mail the copy to the reader if the reader will cover the cost of the copying, a large envelope, and the postage. That way any interested reader will be able to obtain almost as good a copy of the Addendum 2 as I have. Requests for a copy of Addendum 2 can be sent to me through my email at I will figure the cost of furnishing a copy of Addendum 2 on a case by case basis.

I had previously mentioned that the NTSB started the problem of interpreting the data by mixing flight data from two different flights. Here's the NTSB's statement about that subject:

Excerpt from NTSB Addendum 2:

"This report describes the methods use to determine the end of the data recorded during TWA800, and the transition to the data recorded for TWA803 on July 16, 1996. Although the FDRFR clearly identifies the end of TWA800 data, a portion of the data recorded during TWA803 has mistakenly been analyzed as if it were recorded during TWA800. The data in question are the values written during TWA803, that are listed at time 20:31:12 in Attachment II, of the FDRFR. These values were transcribed as unsynchronized data and were labeled as "End of FLT 800 DATA", and a line was drawn through them."

End of excerpt

The above statement by the NTSB now gives us in writing an acknowledgment of their mistake which was the cause of the dispute over what the data in the last tape record of TWA Flight 800 meant. Capt. Howard Mann has seen the NTSB's Addendum 2 and isn't so ready to accept the NTSB's admission that a mistake was made in presenting the data. Before restarting the argument let me go on with the Addendum 2 revised explanation of the tape data.

The drawing above is from NTSB's Addendum 2. It is a line drawing of the FDR tape transport deck which is built into the orange box called a Flight Data Recorder. A more complete description of it's function can be found in my earlier paper I sent to the NTSB.

When the TWA Flight 800 Flight Data Recorder was opened at the NTSB facility, the position of the section of data tape that was between read/write  heads was noted.The reason for doing this was to locate the end of the TWA Flight 800 data. When the FDR lost power, the data tape could receive no more information about the flight characteristics of the aircraft.

I've prepared a graphic which you will see on the next page which depicts how that section of data tape that was in position to be written to might look. In the actual Addendum 2 there is a photograph of that section of data tape which had been "developed" to show where the data records appeared on the tape. The photograph of the tape section also shows the erase zone which separates the TWA Flight 800 data from the TWA Flight 803 data. Remember, although different flight numbers are being used we are still talking about the same aircraft.

The tape section we are interested in is less than six inches in length. It has been
"developed" by spraying on a special

fluid which contains microscopic magnetic particles which stick to magnetic fields on the data tape where data has been recorded. The drawing above shows how the data tape might look after being developed.

The gray rectangles shown on the drawing of the section of data tape (above) are "data records" which contain one second of flight data. The yellow rectangle is the last data record written for TWA Flight 800. The small green rectangle is the partially erased TWA Flight 803 record which was written 25 flight hours earlier. The blank space between the yellow rectangle and the small green rectangle is the "erasure zone" created when the data tape moved past the erase head.

The drawings above are enlargements of the ends of the tape segment showing the way the data tracks are numbered. Between each data record is a short blank space called the inter record gap. The inter record gap helps in the separation of data records when "reading" a FDR tape becomes necessary.

The small green (803) rectangle was originally as large as the yellow rectangle (Flt800). The reason the green rectangle is smaller than the yellow rectangle is that is was reduced in size by being partially erased as the tape passed over the erase head on the tape deck. Remember, the rectangles are actually flight data records containing one second of flight data. The green rectangle contains only a fraction of a second of flight data since part of the full record has been erased.

The diagram below depicts a full data record (yellow) and a partial data record (green). The structure of the data record can be a little confusing because of the fact that the aircraft flight data frame contains only 43 data words. Part of the flight data frame of 43 data words are repeated in the flight data record. A flight data record contains exactly 64 data words. The 8 bit preamble and 8 bit postamble define the boundaries of the flight data record.


Below there is a table which shows how the data is organized before it is recorded onto the FDR tape as a complete one second data record. The data record shown in the table is the last data record recorded before the FDR stopped working.The first entry into the table is the 8 bit preamble.

Now think of the yellow data record of having 64 "cells" in which to place information. We will number the first cell #1, the next cell #2 , and so on until the last cell which is numbered #64. Each "piece" of flight data also has a number, and that's where the confusion begins.

In the table below, the first cell (cell #1) of the data record contains data word #27 (Pitch trim stabilizer), The next cell (cell #2) contains data word #28 (Aileron position rt. inboard). Remember, the yellow column in the table on the next page contains the DATA CELL number and the column to its right contains the DATA WORD number. Data word #1 is always the KEY WORD (colored red). It is used to locate where the first word of a 43 data word sequence begins. Once the tape reader (machine) reads a data record it figures out what each of the data words are from knowing where the key word is in the 64 data word sequence. The gray area in the table is to show the area that a 43 data word sequence uses in the 64 data record. You can see how the 43 data word sequence is continuously repeated.

I haven't included any values for the data words in the table for a reason which I will explain later. Please spend some time studying the FDR data record organization because it is necessary to do so in order to understand the rest of this paper.

Now we are going to look at the end of the last full data record. The graphic below is of the 64th data cell which contains data word #4 (look at the bottom right hand side of the previous page). The graphic is from the NTSB Addendum 2. It represents about 3 inches of the actual FDR tape track #2. There should have been 12 bits shown for data word #4. The NTSB shortened the graphic showing only 9 bits because of space limitations.

Starting at bit 5 and continuing to bit 8, there is a four bit group 1110. It's a binary representation of the number 7 which represents the month of July. I'm used to seeing the binary 4 bit group in the reverse position of 0111. Here's a short translation of the 4 bit binary groups equated to our base 10 system with the bit order reversed.

(0000 = 0); (0001 = 1); (0010 = 2); (0011 = 3); (0100 = 4); (0101 = 5); (0110 = 6);

(0111 =7); (1000 = 8); (1001 = 9)

The postamble follows the last word in the 64 word data record. It's purpose is to mark the end of a complete data record. It's specially marked as 10000000. The area of the tape just after the postamble is the beginning of the "erasure" zone of the tape track. The erasure  zone is about 3 inches in length.

The NTSB has clarified part of the end of record problem by showing the end of the last data record and the erasure zone of data track #2. For some reason the NTSB does not want to reveal all 64 data words of the last data record.  I called Dennis Grossi, the group chairman of the FDR Exhibit 10A report and asked why the NTSB didn't include an extra page in Addendum 2 stating the complete data set for the last data record of TWA Flight 800.

Dennis Grossi told me he already knew what the data was, and didn't see any reason for repeating the data. I countered with the fact that since the NTSB caused the problem by publishing the erroneous last second data set to begin with, they should publish the complete last second of flight data just as it appears on the actual FDR tape. What better way to restore the confidence in their presentation of the data from the FDR tape.

Look at the red zone on the previous page marked "Key record". Read the type of information contained in data words #2 through #10. Data words #2 through #10 tells you everything about which aircraft flight, on which date, at which time the flight data for that
last data record is being collected and recorded. Why would the NTSB not want to set the record straight by publishing the identifying information for TWA Flight 800 and the rest of the flight data information for that last data record? I asked Dennis Grossi to furnish me with the last 64 data words and I would organize and publish the data on my web site. Dennis Grossi told me there would be little chance of that happening.

I want to finish describing the rest of the 6 inch long section of the FDR tape. The graphic below is a continuation of the previous graphic. It represents the remaining 3 inches of the FDR tape beginning with the last part of the erasure zone. In Addendum 2 the two FDR tape graphics I have just discussed are shown together on a single line

Everything AFTER the Erasure zone on data track #2 is data collected from TWA Flight 803, a TWA flight flown at a time about 25 FDR tape hours earlier. It's OLD flight data. The NTSB says that some of this data was accidentally tabulated along with TWA Flight 800's flight data causing the confusion of the meaning of the last TWA Flight 800 data record. That's where the data is interpreted as showing the possibility of an outside explosion near the front left hand side of the fuselage of TWA Flight 800.

The partial data record of TWA Flight 803 (above) starts with the last 3 bits of data word 6 which normally gives the GMT hours of the flight. Being incomplete, data word 6 gives us no information. Data words 7 and 8 together give the minutes and seconds of the time the partial data record was recorded by the FDR. There's approximately 9 data words left in the partially erased TWA Flight 800 data record. Not enough information remains in the partially erased data record to identify the aircraft for which the data was collected. Looking at the next complete flight data record would yield all of the identifying information needed to show which aircraft flight number the data record covered.

Two problems remain with Addendum 2.

The first problem is the NTSB doesn't want to produce a complete record of the last few seconds of flight data from TWA Flight 800. Showing only the last data word, postamble of the flight record of TWA Flight 800, and the Erasure zone of the FDR tape is hardly a show
of good faith. The problem of the tabular data mix-up in the last second of flight data between TWA Flight 800 and TWA Flight 803  is the NTSB's. There is no reason for the NTSB not to completely clarify Exhibit 10A by publishing Addendum 2.

Problem 2 is caused by the NTSB not wanting to publish ALL of the flight data on either side of the erasure zone.

The last second flight data record (just before the erasure zone) of TWA Flight 800 should be published as part of Addendum 2 showing the values of ALL 64 data words. The partial flight record of TWA Flight 803 which is old flight data (9 data words) should also be published showing the values of  ALL 9 data words. The aircraft identifying information contained in the flight data record after the partial flight data record should be published to show the flight number, date, and time of the record being recorded.

I don't understand why the NTSB is conducting their investigation into the crash of TWA Flight 800 with so much secrecy. The TWA Flight 800 investigation has been bought and paid for by the American tax payer. The American people "own" all of the information discovered during the investigation. The NTSB is mandated by law to make all information pertaining to an aircraft crash available to the public.

Why are the American people not being allowed to see ALL of the evidence pertaining to the crash of TWA Flight 800?

Copyright 1999 by Richard Hirsch, All Rights Reserved


Note from website author:  For related analysis of the Flight Data Recorder see
The Smoking Gun - The Flight Data Record
Report to the Subcommittee on Aviation on the Crash of TWA Flight 800