AA77 FDR Data, Explained

[pgimeno]

(I doubt that there is a plane that's ever been built that could generate lift with MINUS 15° AoA.)

Harrier?

(j/k, I know that the lift doesn't come from the wings in that case. And not in level flight anyway, just at a certain moment during takeoff.)

 

[tfk]

Harrier?

(j/k, I know that the lift doesn't come from the wings in that case. And not in level flight anyway, just at a certain moment during takeoff.)

You're right! Harrier & F-35. Any AOA you want, from 0 to 359.9°.

But I bet that you snap the wings off at anything over ~200 kts or so.


Tom

 

[wstutt]

I now have version 1.7 of my AAL77 FDR Decoder available on my web site along with new output files.

I have removed the DENSITY C TANK, DENSITY L TANK, DENSITY R TANK and DENSITY S TANK parameters and replaced them with the CORRECTED AOA parameter which has data stored in the same location but produces values that are close to the values for the INDICATED AOA parameter and therefore appear to be more sensible.

I have also added raw values for some parameters.

You can read further notes on the parameters here.

Warren.

 

[tfk]

I now have version 1.7 of my AAL77 FDR Decoder available on my web site along with new output files.

I have removed the DENSITY C TANK, DENSITY L TANK, DENSITY R TANK and DENSITY S TANK parameters and replaced them with the CORRECTED AOA parameter which has data stored in the same location but produces values that are close to the values for the INDICATED AOA parameter and therefore appear to be more sensible.

I have also added raw values for some parameters.

You can read further notes on the parameters here.

Warren.

Sorry, Warren,

There is something fundamentally wrong with with the Indicated AOA and Corrected AOA.

AOA has a very specific meaning: the angle (in degrees) between the chord of the wing & and direction of free stream air past the wing.

And, whenever the plane is flying level or moving level (as when it is on takeoff roll), we KNOW what that number should be.

Whenever it is moving or flying level, the ACTUAL (i.e., corrected) AOA should be the Pitch Angle plus the Angle of Incidence (the angle of the wing chord with respect to the centerline of the plane).

Now, it turns out that the Indicated AOA is the angle that is given by the AOA vanes that are mounted on the "chins" of the plane. Further, the Angle of Incidence of the wings is not a constant from the wing root to the wing tip. The wing root has a higher angle of incidence than the wing tip does.

This variable camber give a couple of security effects: less lift from the outboard portions of the wing than from the inboard portions. This reduces the structural stress on the outboard portions of the wings, and reduces the size of the structural supports required. It also means that the inboard portions of the wing will stall first at high AOAs, and the outboard portion of the wing (where the ailerons are) will automatically be at a lower AOA, and therefore not be stalled. This means that the pilot will keep aileron authority thru the stall, and be able to control the plane & recover.

So, we know that the "Effective (i.e., average) Angle of Incidence" for the B757 is around 6°.

During take off roll, the FDR data shows that the Pitch Angle is 0°. This is perfectly normal. That means that, on the take-off roll, the actual AOA will be about +6°.

During level cruise flight, the FDR data shows the Pitch Angle is about +1.2°. This is a completely normal pitch angle for cruise, level flight. This means that, during level flight, the actual AOA is about 7 to 7.5°. This is also a completely normal, expected AOA for cruise flight.

This is what a B757 looks like when it is cruising in level flight.

The dashed lines are horizontal with respect to the ground. The plane is flying level, even though it nose is raised slightly (Pitch Angle = +1.5°). At this pitch angle, with level flight, the true AOA is about +7.5°. And you can also see the 6° Angle of Incidence.

Again, the -16° IAOA shown in the data is screwy. This is what a -16° AOA looks like. This plane will NOT fly horizontal.

I strongly suspect that this is getting redundant for you. And that you get the angles by now. Somehow the data is just nuts. I think it's time for an email to a Boeing engineer.

Tom

 

[beachnut]

-16 does make sense, label the axis. -16 ia a lower AOA than takeoff at -6 AOA. `

Add 20 or MAX lift number, you get 4 for -16. Figure out the value of MAX lift, add that and get a positive AOA. The AOA does not care what you label the axis, as long as the value is used correctly.

What was Balsamo's value for level AOA again? Too bad none of Balsamo's core member are not active or able to help him with math; the core members could be labeled core members, the bad math club.

 

[wstutt]

Sorry, Warren,

There is something fundamentally wrong with with the Indicated AOA and Corrected AOA.

<snip>

Tom

Hi Tom,

I actually used the same conversion from raw values to degrees for Corrected AOA as I did for Indicated AOA which produces values with a possible range of ±90°. If I had used the conversion that appears in the data frame layout 757-3b_1.txt, which produces values with a possible range of ±180°, the values for Corrected AOA would have been about double.

The values my program produces for Indicated AOA have a maximum difference of 1 in the last decimal place with the values in the NTSB CSV file.

I know this doesn't get us any closer to getting expected values for Indicated AOA and Corrected AOA.

Perhaps different conversions from raw values to degrees was supposed to be used as beachnut suggested. I have included the raw values for Indicated AOA and Corrected AOA so that people can try their own conversions.

Warren.

 

[applecorped]

This was the longest thread on 9/11 that could be bumped. For no good reason mind you.

 

[beachnut]

This was the longest thread on 9/11 that could be bumped. For no good reason mind you.

My mom's birthday; good enough reason. How did you know?

It would be interesting to know if wstutt was interested in decoding the FDR because he thought something was fishy about 911.

It was funny wstutt decode the "missing seconds" Balsamo was sitting on with his FOIA request for years and the p4t expert decode failed to decode the last 5 seconds of data.

With the missing seconds, the too high for hitting the Pentagon comes to end. Is p4t forum still running?

 

[WildCat]

Is p4t forum still running?

Running from facts, evidence, expert opinion, etc.

 

[ElMondoHummus]

This was the longest thread on 9/11 that could be bumped. For no good reason mind you.

 

[applecorped]

http://i110.photobucket.com/albums/n94/elmondohummus/icon_slap.gif

Now why would I slap you?

 

[ElMondoHummus]

Now why would I slap you?

You bastage.

 

[applecorped]

You know, of course, this means war!

Here's an oldy, but a goody. Needs to be updated on the year though.

 

[ElMondoHummus]

Needs to be updated on the year though.

No it doesn't.

 

[applecorped]

No it doesn't.

Updated backwards to perhaps 2002?

 

[stewieg]

My mom's birthday; good enough reason. How did you know?

Is p4t forum still running?

It appears that way. Rob is still begging for money. Money for computers and research and not money for rent, food or beer.

 

[wstutt]

Hi beachnut,

<snip>

It would be interesting to know if wstutt was interested in decoding the FDR because he thought something was fishy about 911.

It was indeed the case that I had suspicions about 9/11 and that led me to want to decode the FDR file.

I learnt about Pilots For 9/11 Truth and their claim that the FDR showed that AAL77 was too high to hit the Pentagon from a magazine article. I thought that this would be hard evidence of a conspiracy. I purchased the DVDs and downloaded the FDR files and the NTSB and ReadOut2 decodes.

From this information it appeared that there was 2 seconds of data missing and I was certain that there should be at least one more Radio Height value than what was in the ReadOut2 decode since as you have said, it contains one less second of data than the NTSB decode. This got me wanting to write my own decoder to shed more light on what happened in those critical last seconds of the flight. This was just after Christmas 2007.

Sometime around March 2008 I discovered that there were about 20 more frame markers for the final flight than what I was expecting from the previous decodes. This would have equated to about 80 seconds more data which could well have been evidence for CIT's flyover theory which I was already aware of. I later discovered that the extra frame markers were due to the fact that the baseline frames which are recorded at regular intervals are only repeats of the last delta (difference) frames.

At one point I was considering that the reason I was having difficulty matching up the FDR file with the ReadOut2 decode was that somebody had produced a fake decompressed FDR file and that the NTSB and ReadOut2 decodes had been produced from that faked file. I later discovered that I needed to treat the two flight data streams as independent from each other to successfully match up the FDR file with the ReadOut2 decode.

It was funny wstutt decode the "missing seconds" Balsamo was sitting on with his FOIA request for years and the p4t expert decode failed to decode the last 5 seconds of data.

To be fair the NTSB also did not decode the last seconds of data.

With the missing seconds, the too high for hitting the Pentagon comes to end. <snip>

Well not according to Rob Balsamo. See his reply to me:

<snip>

If trends are continued as shown in your data from last interval (59 f/s drop) and considering the descent would be less than 59 f/s based on positive G's over 1 for that segment, but, lets just do 1 G linear trend.. 59*1.5 = 88.5... 174 - 88.5 = 85.5. Still too high for the impact hole. Again, this is at 1 G linear descent rate using 'best' case scenario for an impact based on your data. If we incorporate the increase in positive G loads, whoosh... right over the top... and would be consistent with the radalt bouncing off the top of the pentagon and Turcious statements of "pulling up to clear...".

<snip>

Warren.

 

[beachnut]

Hi beachnut,


It was indeed the case that I had suspicions about 9/11 and that led me to want to decode the FDR file.

...

Great work. Poor Balsamo remains clueless.

 

[fess]

I still find it hard to believe that there are people walking the streets unattended that AAL77 flew over the Pentagon. I mean, look at how many witnesses actually seen this aircraft, some of which seen the aircraft hit the Pentagon.
If AAL77 actually flew over the Pentagon, why is it that there are no witnesses that seen it continue on its flight path? This flight path would have taken it over two major thoroughfares, parallel to the I395 Bridge, less than one mile from the departure end of DCA runway 1, and climb out over the city of DC. Yet no one reported seeing this aircraft, or hearing it.

 

[A W Smith]

I still find it hard to believe that there are people walking the streets unattended that AAL77 flew over the Pentagon. I mean, look at how many witnesses actually seen this aircraft, some of which seen the aircraft hit the Pentagon.
If AAL77 actually flew over the Pentagon, why is it that there are no witnesses that seen it continue on its flight path? This flight path would have taken it over two major thoroughfares, parallel to the I395 Bridge, less than one mile from the departure end of DCA runway 1, and climb out over the city of DC. Yet no one reported seeing this aircraft, or hearing it.

CIT's excuse? all those imaginary flyover witnesses had their 911 phone calls hidden/destroyed/erased, or otherwise unavailable to even FOI requests.. I kid you not. That's how deluded and ill the CIT tree fort gang are.