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AA77 FDR Data, Explained

I thought I'd post it here, seeing as Twoofers often bring up the "AA77 isn't listed in the BTS on 9/11, so it wasn't scheduled!", and then ignore that the BTS isn't a timetable.

Now, one of my pet hobbies is planespotting - something shared with people who collect timetables. And sure enough, a user on a board dedicated to planespotting and aviation in general has put up the American Airlines timetable from July 2, 2001: http://www.departedflights.com/AA070201intro.html

And sure enough, AA11 is listed as flying on all days:
http://www.departedflights.com/AA070201p54.html

.. and so is AA77:
http://www.departedflights.com/AA070201p90.html

I'm fairly sure this hasn't been linked before, so forgive me if is has :)
 
tfk said:
Hey Ap,



This is an interesting failure...

I believe completely the sequence of events that you describe. But the failure mode isn't immediately obvious.


(snip)

I don't believe that there is a VSI or air speed aneroid in the ADCs that I've seen for the 757s tho.

Bit of a mystery. We may never know.


Tom
Click to expand...

[OT]
It's been a good few years Tom, this was 99'ish. I'm pretty sure we blew the bellows, not sure which capsule, or what the ADC pressure limits were, or what else we were doing wrong. I was a n00b at the time and the guy working with me was even more clueless than I was. I didn't think much of my little snafu with air data cart at the time, but we really had problems with the check after that event and ultimately had to replace the ADC.
[/OT]

Back on topic...

I see Cap'n Bobby is flailing away at his newest strawman: "the JREFERS are now saying a damaged ADC is responsible for the PA error"

I'll bold and italicize the important parts, because it's apparent that Mr. Balsamo has a serious reading comprehension problem.

That was only one of the points that were made, and it was only offered as a possibility. But the ultimate point being made was: "the 757's air data system would never be operating past the damage threshhold range during certification."

What about our calibration range argument? I've shown that the ADC is never tested for such extremely high airspeeds(300 being the highest in the check) or for high speed, low altitude accuracy...?
What about the altimeter error not pertaining to an aircraft in flight? What about the fact that the airplane was a staggering 41 percent past VMO? The 757 was never certified for 488 knots at any altitude, nor was the Air Data System.

Do you get it now, Robby? We can't possibly know what the accuracy of the system is in these circumstances, because it's the only time in history a 757 has been flown that far outside the flight envelope.
 
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Ap, Heat,

Go check out Robbie.

He's trying to explain the difference between pitch angle & AoA.

In the posts following this one:
http://pilotsfor911truth.org/forum/index.php?showtopic=18453&view=findpost&p=10781212

It's friggin priceless...!!

Some instructor pilot...??!!!

I especially like the part where he explains that the cruises AoA for a 757 in level flight is MINUS 15.6 (something or other, he never puts a unit to it. But the standard units are, of course, "degrees".)

Yeah, I can see a 757 flying level with a -15.6° AoA ... if it's mounted on a pole in a wind tunnel.

I thought that I read that the AoA in level flight at cruise is about +2.5°. And that the mean angle of incidence for the 757 is about +6°. Which would put the level pitch angle at about -3.5°. Does this sound right to you?

He says something else that just sounds prepostrous, but I don't have the time to look it up. He claims that an F16 on take off roll has a zero degree pitch angle and a -15.6° AoA on take off roll. This would mean that, by definition, the angle of incidence on an F16 is -15.6°. Sounds absurd to me.

I don't believe either of these. I'd bet that the AoA is slightly below the "zero lift AoA" during roll, because you want to keep the nose on the ground. (The zero lift AoA is probably around +1 to 2°.) A quick look at a side view of an F16 shows the angle of incidence to be about 0°. So that'd put the pitch angle equal to, or perhaps at most a couple of degrees, below this.

Comments?

Tom
 
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apathoid said:
[OT]
It's been a good few years Tom, this was 99'ish. I'm pretty sure we blew the bellows, not sure which capsule, or what the ADC pressure limits were, or what else we were doing wrong. I was a n00b at the time and the guy working with me was even more clueless than I was. I didn't think much of my little snafu with air data cart at the time, but we really had problems with the check after that event and ultimately had to replace the ADC.
[/OT]

Back on topic...

I see Cap'n Bobby is flailing away at his newest strawman: "the JREFERS are now saying a damaged ADC is responsible for the PA error"

I'll bold and italicize the important parts, because it's apparent that Mr. Balsamo has a serious reading comprehension problem.

That was only one of the points that were made, and it was only offered as a possibility. But the ultimate point being made was: "the 757's air data system would never be operating past the damage threshhold range during certification."

What about our calibration range argument? I've shown that the ADC is never tested for such extremely high airspeeds(300 being the highest in the check) or for high speed, low altitude accuracy...?
What about the altimeter error not pertaining to an aircraft in flight? What about the fact that the airplane was a staggering 41 percent past VMO? The 757 was never certified for 488 knots at any altitude, nor was the Air Data System.

Do you get it now, Robby? We can't possibly know what the accuracy of the system is in these circumstances, because it's the only time in history a 757 has been flown that far outside the flight envelope.
Click to expand...


Yeah, I'm done with his BS.

As far as I'm concerned, the PA altimeter is simply "out of calibration".

Because all instruments that whose calibration is has not been validated are, BY DEFINITION, "out of calibration".

And the calibration of the PA altimeter has never been validated this flight envelope.

Simple. "The instrument's out of calibration. Nothing left to explain."

If he wants to argue that he knows the proper transforms from the calibrated envelope to this one, well that's his job to prove.

Tom.
 
In flight 757/767 pilots use this as a guide. Facts kill Balsamo the 2,223 g.
The max allowable difference between the Captain’s and F/O’s altimeters in
flight is 200 feet.
The max allowable difference between the Captain’s or F/O’s altimeter and
field elevation is 75 feet at all field elevations. (757/767 pilot guide)
Click to expand...

Balsamo is talking AOA, and he proves again he is clueless. He has a level flight AOA; the stupid burns. It will be hard to find a dumber pilot spewing nonsense than 2,223 Gs of Balsamo. No clue what AOA is = Balsamo = 2,223Gs.

Proving your case is exactly what is required, especially if you want to grab a gun and start killing people in another land over it. All else is an argument based on your beliefs. An argument from incredulity, and is a logical fallacy. (parnoid nut case junk from bobby)
Click to expand...
p4t theory is the FDR is a belief. His neoNAZI side is showing.

The FDR was found in the Pentagon, Balsamo offers no theory. Clueless.

AOA for approach, final approach, best range, best endurance and it came in handy doing loops. Comedy is king as clueless dolts accuse Warren of being a government loyalist while posting mush about AOA.

Balsamo spews 2,223 Gs for his fantasy math game of lies, Balsamo claims 174 feet is the true altitude of 77 just under a second to go from the raw data -99 feet in the FDR. Remember the +- 75 feet for this value at a dead stop checking at a known elevation and Balsamo declares the value 174 feet. The RADALT read 4 feet at this time what is below flight 77, the highest object is the overpass at this time; oops.

The assessment that 483 KIAS is outside of the calibration of the system is better than Balsamo's silly junk; the fact is typical errors in pressure altitude rise with increased speed. ... using Balsamo's 174 MSL with errors for a value of altitude close to 70 to 80 real feet MSL means the error of the PA is 94 to 104 feet when 77 is going 483 KIAS in a dive of 3500 fpm pulling 2 Gs. Makes a lot more sense then Balsamo's 2,223 G pull it out of thin air math/physics for dolts.

I found 30 to 50 foot errors in PA at takeoff, making a 100 foot error at treetop level 483 KIAS decending 3500 fpm pulling 2 Gs very likely.
 
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tfk said:
He says something else that just sounds prepostrous, but I don't have the time to look it up. He claims that an F16 on take off roll has a zero degree pitch angle and a -15.6° AoA on take off roll. This would mean that, by definition, the angle of incidence on an F16 is -15.6°. Sounds absurd to me.

I don't believe either of these. I'd bet that the AoA is slightly below the "zero lift AoA" during roll, because you want to keep the nose on the ground. (The zero lift AoA is probably around +1 to 2°.) A quick look at a side view of an F16 shows the angle of incidence to be about 0°. So that'd put the pitch angle equal to, or perhaps at most a couple of degrees, below this.

Comments?

Tom
Click to expand...

It not only sounds absurd it is, in fact, absurd! Maybe he's been around Lear so long that he thinks F-16's are burrowing underground attempting to reach that submarine base in Nevada!
 
Reheat said:
It not only sounds absurd it is, in fact, absurd! Maybe he's been around Lear so long that he thinks F-16's are burrowing underground attempting to reach that submarine base in Nevada!
Click to expand...

Lear admits he is full of BS and is not selling DVD for 10 bucks. It is odd Balsamo pushes Lear as a core member. Balsamo says his core membership is growing. At least the airlines have a list of nut case conspiracy theorists and they can have the doctors check them out before they fly passengers. Where else can you find a list of possible crazy people who might have problems with reality.


In the tanker the AOA was normalized to total lift, 0 to 1. I could use the AOA in theory to fly best range, best endurance and approach speeds without using the airspeed.
 
This is why the business of reading out FDR's is typically left to competent professionals; not two proverbial monkeys trying to **** a football.

tfk said:
It's friggin priceless...!!

Some instructor pilot...??!!!

I especially like the part where he explains that the cruises AoA for a 757 in level flight is MINUS 15.6 (something or other, he never puts a unit to it. But the standard units are, of course, "degrees".)

Yeah, I can see a 757 flying level with a -15.6° AoA ... if it's mounted on a pole in a wind tunnel.
Click to expand...


If the "researchers" at PfT had any clue as to what they were doing, they would have noticed the "out res" in the data frame descriptor. That is basically a multiplier to convert the raw data to engineering units. The out resolution for the AoA is 0.175, so when you multiply the 15.6 * 0.175 - you get a pretty standard AoA value of 2.7.

:solved1
 
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Hey beach,

beachnut said:
Lear admits he is full of BS...
Click to expand...

Really. I've never seen him admit it. He's always stayed "in character" in all the videos that I've seen. Got a link where he admits this?

My conclusion is that he really can't be that delusional. (That'd be a "Gary Busey caliber brain scramble" that he's working on.) I always figured that he just took up the hobby of goofing on people. Poking around to see if he could move some listener to the absolute most absurd conclusion possible, if he did it in small steps.

(There used to be a guy named Phil Hendried (IIRC) who had a radio show in LA / Orange county who did the same thing. Just goofed on credulous callers.)

beachnut said:
In the tanker the AOA was normalized to total lift, 0 to 1. I could use the AOA in theory to fly best range, best endurance and approach speeds without using the airspeed.
Click to expand...

I can imagine that after a couple thousand hours, you could probably nail your actual airspeed within a knot or two by the seat of your pants. But, considering the risk/reward ratio, I'd also wager that, even tho you could do it theoretically, you still snuck a peek during each & every final approach. Just to make sure your ass was still in calibration.
:D


Tom
 
tfk said:
Hey beach,

Really. I've never seen him admit it. He's always stayed "in character" in all the videos that I've seen. Got a link where he admits this?

My conclusion is that he really can't be that delusional. (That'd be a "Gary Busey caliber brain scramble" that he's working on.) I always figured that he just took up the hobby of goofing on people. Poking around to see if he could move some listener to the absolute most absurd conclusion possible, if he did it in small steps.

(There used to be a guy named Phil Hendried (IIRC) who had a radio show in LA / Orange county who did the same thing. Just goofed on credulous callers.)

I can imagine that after a couple thousand hours, you could probably nail your actual airspeed within a knot or two by the seat of your pants. But, considering the risk/reward ratio, I'd also wager that, even tho you could do it theoretically, you still snuck a peek during each & every final approach. Just to make sure your ass was still in calibration.
:D

Tom
Click to expand...
It is more of a feeling after hearing him in interviews and on radio shows. He said something like if Balsamo thought he was too far out to drop him. Evidence for both sides... He is full of strange stuff, I heard him during the holidays on coast to coast while I was driving coast to coast.


Give me AOA and I don't need much more besides an attitude source and altimeter. We did cover up the airspeed and AOA and we used fuel flow based on aircraft weight to set our pattern speed.
 
apathoid said:
If the "researchers" at PfT had any clue as to what they were doing, they would have noticed the "out res" in the data frame descriptor. That is basically a multiplier to convert the raw data to engineering units. The out resolution for the AoA is 0.175, so when you multiply the 15.6 * 0.175 - you get a pretty standard AoA value of 2.7.

:solved1
Click to expand...


Ap,

Sorry, I should be doing this myself, but I'm in the midst of a big job.

When linearizing data, frequently there are two terms, a multiplier and an offset:

In the general case, it read:

Calibrated output = m*(raw data) + b

where m is the multiplier (.175, in this case) and b is an offset.

Is there an offset parameter listed along side that "out res" calibration factor?

Or does b = 0?


Tom
 
beachnut said:
Give me AOA and I don't need much more besides an attitude source and altimeter. We did cover up the airspeed and AOA and we used fuel flow based on aircraft weight to set our pattern speed.
Click to expand...

:eek:

"You're a better pilot than I am, Gunga Din."

But I suspect that both of us already knew that...

Tom
 
beachnut said:
Give me AOA and I don't need much more besides an attitude source and altimeter. We did cover up the airspeed and AOA and we used fuel flow based on aircraft weight to set our pattern speed.
Click to expand...

AoA can obviously be used for a lot of purposes. In the F-111 we established on speed for fuel weight on final approach and then adjusted wing sweep to an AoA value (4.5 degrees) in order to ensure CG was correct for landing.
 
Warren,

Sorry to be the bearer of bad news, but it looks to me like your PA data and your AoA data are hosed on your last spreadsheets.

It looks like one or two other pieces of data are interspersed with the PA data. If you calculate & plot a running average vertical speed from the PA data (just subtract each value from the previous one (giving one second sampling), you'll see the spikes. Three up spikes and then one down spike & the pattern repeats. Periodically, the pattern reverses (3 down & 1 up), so it may be the same data that's stepping on your PA data.

Is there something else that shares this frame slot with the PA?

OK, I found your m = .175781 and b=0, in the 757-3b_1 text under "indicated AoA".

It also shows "corrected AoA" scaling factors as "m = 0.35156 & b = 0".

What is the definition of the difference between "indicated" & "corrected" AoA? (And, ap, why the hell are they showing the pilot anything other than "corrected AoA"?)

But you say that you don't use this conversion, but rather the one in D226A101-3G.pdf.

Unfortunately, the version of that which I've downloaded doesn't contain the text info. It seems to be a bunch of picture files, and therefore the search function doesn't work.

My personal search function (looking in the table of contents) seems to be coming up short too. No info seen on Indicated AoA. Or AoA of any sort.

Is this only the file that I've downloaded? Do you have the text encoding and search function working in your copy of D226A?

Could you post the scaling & offset numbers that you did use for the figuring indicated & correcte AoA.

Regardless, the numbers in the spreadsheet just don't make any sense.

If you plot the pitch angle and AoA vs. time during the take off roll & climb out, you'll see that the trends are OK. This tells you that this is not a sign issue. The sign of the multiplier is correct (positive). It also suggests that the offset is not zero for some reason. (But just using a different multiplier won't fix the problem.)

But it looks like there is about a -15 to -20 degree offset to the AoA. The data says that the AoA stays negative all thru the climb out.

As my petulant 6 year old niece used to say, "I don't think so... " (Complete with foot stamp.)

Good luck digging up the problem. "You're doing a heluva job, Brownie."
:)


Tom
 
Hi Tom,

tfk said:
Ap,

Sorry, I should be doing this myself, but I'm in the midst of a big job.

When linearizing data, frequently there are two terms, a multiplier and an offset:

In the general case, it read:

Calibrated output = m*(raw data) + b

where m is the multiplier (.175, in this case) and b is an offset.

Is there an offset parameter listed along side that "out res" calibration factor?

Or does b = 0?


Tom
Click to expand...
D226A101-3G.pdf has an out res of 0.17578125 and a range of +/- 90 degrees. Since the raw data is a 10 bit signed integer, my decoder program uses m = 0.17578125 and b = 0.

Warren.
 
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