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New FDR Decode

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posted on Dec, 22 2009 @ 04:09 PM
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The Captain's Altimeter change "bumps" you're talking about, like the one seen when the real pilots were flying, and as they passed through 18,000 feet might look different when (if) Hanjour re-set the Kollsman knob.

It is illogical to assume that he, an inexperienced pilot, likely not used to operating in the Flight Levels, would by habit re-set on descent through 18,000.

Here's another thought, just occurred. EVERY country has a different 'transition level' published. He (Hanjour) might have flown the simulator in another country (say in the Middle East somewhere) with different transition levels, and out of habit listened to the ATIS (as I explained above) and re-set the altimeter at some point well below 18,000.

Here's another thought, too.

The right turn around, before the final leg and Pentagon attack.

This somewhat indicates a person sitting in the RIGHT seat while flying...visibility out the right-hand number 2 window, in the turn, would be far better in order to acquire the target (Pentagon) as the turn commenced.

Was reviewing the NTSB autopilot usage data. The RIGHT autopilot was in use prior to the hijackers' takeover. Indicating that the First Officer Charles Charlesbois was flying that leg. (This could be further verified from ATC tapes, to identify Captain Burlingame's voice on the radio calls).

AFTER the takeover, the RIGHT autopilot was disengaged for a few minutes, then the LEFT was used until it was disengaged just before the turn and impact.

Also, the Captain's Flight Director switch remained ON the entire time, yet the First Officer's F/D was turned OFF at the same time as the autopilot.

What this indicates to me is that Hanjour, being unfamiliar with the Flight Director, and its usage, turned it off so as not to distract him on the EADI (Elec. Attitude Direction Indicator, or just 'attitude indicator'). This further suggests he was sitting in the right seat, for some reason, while flying.

SO.....perhaps, IF he bothered to re-set an altimeter to local baro, then it might have only been the F/O's.

Don't think that would show up on the FDR, since the Captain's ADC is supplying the data.




posted on Dec, 23 2009 @ 12:09 AM
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If I'm not mistaken, both the CAPT and F/O BARO were adjusted according
to the CSV file, but the change was not reflected in the animation through
descent (unlike climbing through 18K feet).

My point is: if the raw file contains the PA altimeter calibration for local
pressure, the animantion (which is created from the raw file through
software),
must reflect these pilot inputs.

The fact that there's a difference between the climb and descend for
the altimeter is bothersome (to me) because it's a software conversion
[IE: through the ROSE software].



posted on Dec, 23 2009 @ 12:20 AM
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Let me try explaining my point a different way. I'm not talking about any
sort of PA correction, or which ADC is active.

What I'm wondering is:

Why does the animation altimeter change when climbing through 18K feet,
but does not change when descending through 18K feet.

The reason I find this strange is because the animation is created via
software from the RAW file, and the CSV file is created from the RAW file
using software.

Why is there a difference between them?



posted on Dec, 23 2009 @ 02:27 AM
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Originally posted by turbofan
Why does the animation altimeter change when climbing through 18K feet,
but does not change when descending through 18K feet.

The reason I find this strange is because the animation is created via
software from the RAW file, and the CSV file is created from the RAW file
using software.

Why is there a difference between them?


Oh I got more why's than you do. Why is there an 'abnormal' shift in lateral acc v heading change for AAL77 when compared to UAL93? Why does the "Summary of Air Traffic Hijack Events, September 11, 2001" summary by the NTSB state, "08:54:43 AA77 began a left turn towards the south without air traffic authorization. The altitude indicated 35,000 feet. Shortly after the turn the aircraft was observed descending." I have the ATC's interview notes and he said nothing about the plane descending. Why are the lat and long data so dramaticly skewed in the NTSB CSV? I could go on.

I am a product of the Vietnam War era along with J. Edgar Hoover and 'tricky Dickie'. It was common during those times for the government to inject false or misleading information into the anti-war and civil rights movements to discredit their leaders and cause fracturing. Early on, the possibility of the NTSB work products falling into this category seemed the most reasonable hypothesis. Whether or not that was the intent, that certainly was the result. The Truth movement which had by 2006 gained momentum, suddenly came to a screeching halt with the introduction and wild speculation around these releases. P4T and CIT moved the TM into the realm of UFO's and JFK. When reasonable voices came along urging caution, the 'attack hounds' ripped into them with a vengence (as you just learned first hand).

Contrary to popular belief, I am not a GL. I don't trust government. Never have, never will. But bring facts and reason to the table, not fantasy.



posted on Dec, 23 2009 @ 12:48 PM
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Originally posted by turbofan
Let me try explaining my point a different way. I'm not talking about any
sort of PA correction, or which ADC is active.

What I'm wondering is:

Why does the animation altimeter change when climbing through 18K feet,
but does not change when descending through 18K feet.

The reason I find this strange is because the animation is created via
software from the RAW file, and the CSV file is created from the RAW file
using software.

Why is there a difference between them?

The animation is made from the FDR, but the corrected altimeter has to be added for what the pilot sees from takeoff to 18,000 feet, they did not correct decending through 18,000 feet the animation is a working copy, not completed. The NTSB said so.

The animation has the runway imagery at take off placed under the aircraft track when the FDR has the plane off the runway 2000 feet south. So the animation is a production to match where 77 really was not the 2000’ error in the INS/FMS.

For the animation they used 300 feet at takeoff meaning they had to apply the QNH to 40 feet (raw pressure altitude from FDR based on 2992). Thus the animation is clearly a product of the FDR with added changed to show what the PILOTS saw. The runway, the altimeter corrected up to 18,000 feet, then they failed to correct it on the way down, and they failed to place the Pentagon in the proper orientation for true north vs. magnetic north due to the 9 to 10 degree variation.

This is the funny part, because the animation failed to line up the Pentagon to the proper orientation the NoC is born, based on pure nothing. Show a few conspiracy minded folk a mistake and they take it and run with it making up lies about 911. Knowledge of FDR and how the animation is a product of the FDR, you can see the working copy of the animation was never finished. It was a working copy so you have to go back to the FDR for resolution of discrepancies.



posted on Dec, 23 2009 @ 12:58 PM
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reply to post by turbofan
 



Why does the animation altimeter change when climbing through 18K feet, but does not change when descending through 18K feet.


turbofan, I addressed this already.

During the taxi out, take off and climb to cruise altitude the airplane was in control by the REAL pilots, Capt Burlingame and F/O Charlesbois. They naturally changed th altimeter Kollsman settings to 29.92 as they passed through 18,000 feet, which is the transition altitude for the United States (and Canada AND Mexico....). The transition altitude/flight level is different in other jurisdictions (countries). You can look this up, or just take my word for it. Your choice.

I have already written an extensive post describing what I imagined happened in the cockpit of AAL 77, based on the NTSB autopilot study --

www.ntsb.gov...

Please pay attention to that for my references.

IF you have any questions about it, be sure to ask. I can thoroughly explain from a pilots' perspective.


AS TO the altimeter re-set, on descent??? I also covered that --- it does NOT follow, logically, that the hijacker as pilot of American Airlines 77 would dutifully re-set his altimeter to the local barometric setting as he passed through the transition altitude (which in the USA is 18,000 feet).

It might have been done later, at some other time in the flight. OR, not at all.

Point is...this is just another red herring of the P4T baloney, and they are well recognized for giving out bogus information already, in order to confuse and deflect.

More of the same.....



posted on Dec, 23 2009 @ 01:50 PM
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I'm not sure if you read my last reply Weedwacker, however the "terrorists"
DID change the Kollsman window on BOTH the CAPT and F/O altimeters.

If you were to look at the BARO columns, CG and CH in the CSV file,
you will see they were reset at about 17,000 feet.



posted on Dec, 23 2009 @ 01:56 PM
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reply to post by turbofan
 


Tino (turbofan)....

The FDR only looks at the LEFT (or Captain's) ADC information, correct?

HOW can you assert with any veracity that BOTH the Captain's and F/O's altimeters were re-set, passing through 17,000 feet (as you claim) AFTER the hijackers had taken control and taken the airplane off its original course?

There ARE, by the way, THREE altimeters installed in a Boeing 757/767 cockpit (ans is common to ALL modern jets).

The STBY altimeter, though, is certainly not recorded on the FDR.

(Tino...you have come a long way, once you began to realize how the numbskulls at P4T were lying to you....don't falter on your path to enlightenment now, when you are so close to reaching REAL truth...)



posted on Dec, 23 2009 @ 02:01 PM
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posted on Dec, 23 2009 @ 02:10 PM
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reply to post by weedwhacker
 


Weedwacker,

I can say this for certain because it's shown in the CSV file and therefore
raw data file.

CAPT is set to 30.22
F/O is set to 30.23

Both of them are set at ~ 17,000 feet upon descent.

Isuntzu:

The correction is applied to the setting of the window, not the animation
itself. The software recreates the gauge movement, rudder movement, yoke movement, etc.



posted on Dec, 23 2009 @ 02:18 PM
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OK...the moderation has said their piece, and it's important to heed.

I, as have many, have often been guilty of getting wrapped up into a discussion, as the thread 'weaves' and 'wends' its way (why do you think they call it a "thread", hmmmm?)


Anyway, as is the pertinent point there, the "TOPIC is always paramount, and is "King" on ATS.

So, in honor of the OP (original poster) Reheat....I re-introduce his original OP (with minor redactions...) for the ongoing, from here, discussion:



Originally posted by Reheat
As I mentioned in another thread an Australian has decoded AA77's FDR raw data and read 5 more frames of data than the pffft decode.

It was partial frames, but the most important data was there to include Radar Altitude. This shows the actual height above what's beneath the aircraft (normally terrain), or to the layman the height above the ground.

This data also showed that the time of impact was later than initially published by the NTSB and [redacted] as many of us have said after the RADES and area radar data was released.

I'm just an ATP rated pilot, so I'll allow the "technologist" [redacted] to reveal what the data from the FDR shows in this new decode. After all, he believes it was perfect as has been touting all over the Internet for over a year.

Explain this data to everyone here, Mr. "Technologist". Remember now, you told everyone that Stutt was "on your side".

Pssst: AA77 impacted the Pentagon as we've known all along.



posted on Dec, 23 2009 @ 02:38 PM
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reply to post by turbofan
 


OK, turbofan....so BOTH the Capt and FO altimeter setting information is relayed to the FDR?

That is interesting to know. It is NOT stuff that we'd normally be taught. It is NOT a 'need to know' item for a pilot to have in his quiver of knowledge.

However, this begs more investigation. AND it requires explanation.

IF BOTH the Captain and FO altimeters were re-set at about the same time, then that infers that TWO people were in the American Airlines 77 cockpit, after the hijacking had taken place.

Because, it is unreasonable to assume that ONE pilot would have reached way over to adjust the OTHER altimeter Kollsman knob. It is quite a reach, and would require more than just a casual thought to accomplish.

So, it implies at least ANOTHER educated and trained pilot up there, to assist with the flying duties of Hani Hanjour. IF this information is correct.

Now, I'm going to reference the approximate location of flight 77 as it passed, while descending, through 17,00 feet.

OK, based on the NTSB printout the airplane descended through 17,000 feet at about 09:24:00

www.ntsb.gov...

(See page 9, Figure 1. Top graph, showing the altitude trace.)

There is no 'bump' in the DFDR altitude trace, on that graph. But, it is a 'gross' representation, and the FDR .csv files are expected to be more precise, anyways.

Unlike the NTSB United Airlines flight 93 graph, the Mode Control Panel (MCP) information is not presented. Meaning, it does not show WHAT was dialed in to the MCP altitude setting window, on the MCP.

Since the autopilot was engaged until about 09:29:00, and the airplane leveled off at about 8,000 at 09:28:30, it is fair to assume that 8,000 was also set in the MCP altitude window on the MCP.

Whether that was a 'true' altitude, as reflected by the altimeter's setting (Kollsman window) or just the pressure altitude is irrelevant, as far as the autoflight system is concerned. It just 'does' what it's programmed to do.

BTW, for American Airlines flight 77, the LEFT autopilot was engaged and used by the hijacker, so it would reference the LEFT altimeter and the LEFT ADC.

Hope this helps.....
~~~~~~~~~~~~~~~
Forgot to add....

Depending on the altimeter setting at departure, and dialling it in to the Kollsman window to the 29.92 (10.13mb for our foreign pilots) the altitude 'bump' will be different.

I've tried to explain this before...

It varies depending on whether you are climbing or descending at the time, what the initial setting is, and the target setting (29.92, in this case) and how rapidly you re-set the knob...meaning, how fast you spin the knob.

Other pilots will understand what I'm trying to say, here.....





[edit on 23 December 2009 by weedwhacker]



posted on Dec, 24 2009 @ 02:28 AM
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reply to post by weedwhacker
 


I could reach both altimeters in a KC-135 if I tried if the co-pilot was out of his seat; you implied the same. I could also direct anyone in the other seat to set the altimeter, the same as you would if you wanted. The two altimeters on 77 were set different. Baro 2 was set first to 3023 on decent. Was Hani in the right seat? He made a right turn. He flew a lot of left seat as a student maybe the dolt thought the right seat was the best seat since the instructor sat there. Maybe he wanted to sit in the seat of supreme source of pain for his bad flying skills.

So the Baro 1 took many second of wrong settings to finally get it right. 30.24 finally set after being 30.22 after the many seconds of all the way up and back 3029, back to 2999, and then back. The Baro 2 was set and left within 4 seconds or shorter. Baro are, Sampled at .25 hertz.

The animation has to be calculated to show the altimeter change, there is only a PA based on 2992 in the FDR, not a corrected one.

Going up the Baro 2 was set early to 2991, passing 15,300 feet. Bet the animation is a manual setting to get the corrected altitude at the beginning of flight, plus it is easy to remember to do since the runway is about 300 feet, you would quickly catch the animation is not what the pilots see; on decent it is easy to forget correcting the animation to what the pilots saw, plus you have to find the Baro1 and it was all over the place for many more seconds than a normal switch on the way down; the animation is a working copy. Baro 1 took less than 8 seconds to set to 2992 going up pasting 18,000 feet or so.

Whoever set Baro 1 on the way down was challenged.

Tino, how do you know what the software does? Baro 2 was not used, the bump down comes at close to 18,280 corrected, down to 18,056 or 66 uncorrected at 12:28:01. BARO 2 was set early at 15,000 feet.

The animation is not tied to the Baro 1 readings in the FDR! I know this for a fact. If the animation was tied to Baro 2 the altimeter seen rolling back would be much lower. And when Baro1 was reading 30.21, the altimeter in the animation was already rolling back. The roll back starts at 28:00, yet the Baro1 was set to 30.21 past 28:02. There is nothing in the FDR that prompts the animation automatically; it is a manual setting just like putting in the visual for the runway, and the placement of the Pentagon. All in the working copy of an animation possibly responsible for the insanity of the NoC.

The FDR has raw PA for a 29.92 setting, no correction. The animation change of the altimeter is a manual setting place back to 29.92 at 12:28:00, not when the Baro 1 was changed from 30.21 to 29.92 sometime past 12:28:02. The animation was a working copy.

I used the Warren’s decode, new stuff, and the NTSB decode to solve the what made the animation change the altimeter setting. Warren’s baro settings is right next to the PA. Like cheating, and the NTSB has the time.

[edit on 24-12-2009 by iSunTzu]



posted on Dec, 24 2009 @ 10:06 AM
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reply to post by weedwhacker
 



OK, turbofan....so BOTH the Capt and FO altimeter setting information is relayed to the FDR?


Yes



However, this begs more investigation. AND it requires explanation.


I agree




IF BOTH the Captain and FO altimeters were re-set at about the same time, then that infers that TWO people were in the American Airlines 77 cockpit


Yes


Because, it is unreasonable to assume that ONE pilot would have reached way over to adjust the OTHER altimeter Kollsman knob. It is quite a reach, and would require more than just a casual thought to accomplish.


I Agree




BTW, for American Airlines flight 77, the LEFT autopilot was engaged and used by the hijacker, so it would reference the LEFT altimeter and the LEFT ADC.


Please explain “auto pilot”. If someone moves the yoke, or any other controls (IE: Rudder), the autopilot will disengage correct?

Autopilot from what I’m aware is a preset altitude, speed, heading, etc. set by the pilot (sort of like cruise control for your car)?



[edit on 24-12-2009 by turbofan]



posted on Dec, 24 2009 @ 10:10 AM
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reply to post by iSunTzu
 



I could reach both altimeters in a KC-135 if I tried if the co-pilot was out of his seat; you implied the same.


You’re suggesting that Hani would have set both altimeters, through
17,000 feet of descent even though It’s not required?

Why would a terrorist feel the need to stretch across and set the CAPT
altimeter if he’s going to crash the aircraft…let alone his own F/O altimeter?

Weedwacker tends to disagree with your position on this (as do I).



The animation has to be calculated to show the altimeter change, there is only a PA based on 2992 in the FDR, not a corrected one.


Agree



The animation is not tied to the Baro 1 readings in the FDR! I know this for a fact.


I don't believe anyone ever made this claim. I said both CAPT and F/O
BARO are recorded in the FDR, and were adjusted through 18,000 feet.

The animation gauge would be tied to the PA Altitude data.

I said , the BARO columns were adjusted through 18,000 feet.

I also said the correction would be a software correction through ROSE...
not something changed graphically in the animation.

IE: Nobody remade the animation and "adjusted" the altimeter. The altimeter
is assigned to a set of data. The correction would have been made in
the software (to the data)...NOT in the animation.


[edit on 24-12-2009 by turbofan]



posted on Dec, 26 2009 @ 11:11 AM
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reply to post by turbofan
 


Very reasonable evaluation.

And, yes, Tsuntzu is right, it IS possible for a person of normal height to reach all the altimeter set knobs, especially for a person sitting in the right seat, because of the placement of the instruments. I was thinking it was quite a reach, from the Captain's seat, all the way over to the F/O's altimeter. One would likely have to have long arm, and/or unstrap seat belt and lift up a little, while reaching over.

About the autopilots:


Please explain “auto pilot”. If someone moves the yoke, or any other controls (IE: Rudder), the autopilot will disengage correct?


They are NOT that sensitive to control wheel movement, not so much that they would disconnect from the slightest touch. (AND, the rudder is moot, in any case. The ONLY time the A/Ps have authority over the rudder is during the Autoland engagement, when all three A/Ps are being used. This is not to be confused with the yaw dampers, although they ARE an aspect of the autoflight system in a sense, --- really they fall under the category of "FLIGHT CONTROLS' in system description --- they are passive, meaning they operate in the background and are not programmable by the crew).


So, back to the autopilot, and its pitch and roll authority. A gross manipulation of the control column will cause the A/P to disconnect, or depending on circumstances, it might just change a programmed mode, from a higher-level mode to the basic "degraded" pitch attitude and heading hold (or, roll attitude hold, depending on the bank angle at the time).

Depending on the change in A/P status, different visual and aural annunciations will occur. A full disconnect, by any means, results in the red EICAS 'AUTOPILOT DISC' message, the red light on the panel ("A/P DISC") and the Master Warning red lights, and the aural warning. If the A/P simply defaults from a programmed mode to basic attitude control stabilization mode, then it is an AMBER Master caution, [color=gold]AMBER EICAS "AUTOPILOT" and the [color=gold]AMBER "AUTOPILOT" light on the panel. The "Master Warning" aural alarm is loud, unmistakable. The "Master Caution" amber messages are accompanied by a single chime, less strident in tone.

Here's a good reference source, these are reproductions of the same sorts of panel drawings handed out to airline pilots when they train on the equipment, in this case they represent the Northwest Airlines configurations, of which there are various minor differences within their fleet, due to the histories of the airplanes, and how they were acquired over the years (mergers, purchases, etc. NOW with the Delta merger, even MORE differences!)

manager.laxpm.com...


Of course, in all cases, the alarms can be canceled various ways, in the case of the A/P you can use the disconnect switch on the control wheel. Pressing the big red "Master Warning" light switch will cancel. And, there's the 'CANCEL' button next to the 'RECALL' button that is normally associated with clearing and recalling EICAS messages. (When you have a lot of messages, they clutter the screen. Also, it resets the caution system for any new alerts. 'RECALL' is used to see if any alerts are still pending, after having been cleared).





[edit on 26 December 2009 by weedwhacker]



posted on Dec, 26 2009 @ 02:00 PM
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Thanks Weedwacker for your reply and the link. I'll be sure to read further
and ask questions if needed.

I just wrote a massive reply based on some information I found in the
757-200 manual, but it got wiped out when I pressed the preview button.

I'm not in the mood to re-type everything, but here are some point form
facts that I'd like to address. You can bet that once a certain pilot organization
catches wind of this, they'll parade around as if the discovery was theirs.
Let it be known, they learned it from my post on ATS backed up with proper
documentation.

#1. There is no EICAS connection for FLT_DECK_DOOR. The only instance
of a FLT_DECK "anything" is the Flight Deck Temperature:



Therefore there is no data / documentation to supprt the FLT_DECK_DOOR
theory which also goes against all logic presented in the FDR file.

#2. The ADC uses a Frequency Modulated sensor to measure pressure
from the static port. These are highly accurate and very quick to respond
unlike aneroid devices. The chance of lag is non-existent.

#3. The Altitude also has a correction circuit which accounts for angle of
attack using the AoA sensor. I'm not fully aware how the data is measured,
or how/if it's recorded but i will look into this diagram further. It appears
any error from PA during rotation is corrected.




posted on Dec, 26 2009 @ 02:13 PM
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reply to post by turbofan
 



The Altitude also has a correction circuit which accounts for angle of attack using the AoA sensor.


Yeah, not surprising that there's a lot of 'magic' in those modern electronic computers....you're referring, here of course to the Air Data Computer (2 installed).

I'm going to suggest, however, a possibility about the limits to what the AoA info will accomplish, when the airplane was being operated outside of its normal flight envelope, as when it was exceeding VMO at near sea level.

Now, as to the altimeters' behavior during rotation on takeoff, we generally aren't paying attention to them at that point...



It appears any error from PA during rotation is corrected.


Of course, that's neither here nor there, except it HAD been pointed out by someone else that there were anomalies in the pressure altitude information recorder, during the takeoff sequence at KIAD. Again, the accuracy of the altimeters at that point in a flight isn't important, as they aren't referenced for any particular reason.

Still, I do recall, way back in the dim, dark past of the extent of my experience, there may have been mention OF a slight lag, during rotation, but that also may refer to older pitot/static installations diff airplanes.



posted on Dec, 26 2009 @ 06:55 PM
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Happy Holidays to you and yours Tino,



Originally posted by turbofan

#1. There is no EICAS connection for FLT_DECK_DOOR. The only instance
of a FLT_DECK "anything" is the Flight Deck Temperature:

Therefore there is no data / documentation to supprt the FLT_DECK_DOOR
theory which also goes against all logic presented in the FDR file.



Well, in the interest of transparency, we can only say that "There is no EICAS connection for FLT_DECK_DOOR" on the 757 fleets we have access to. For me, that would be Delta, TWA/American, Northwest, British Airways, ATA, Omni Air International and Ryan International - about 300 airplanes in all.

If we get on Robs case about his saying that the FDD parameter definitely is working on Americans fleet, despite not having any documentation to that effect, we can't say that it definitely isn't working for the same reasons. The only thing we can say is that its not a stock feature on the 757; its a customer option. That is, the customer needs to pay extra for that feature, or install it themselves. I can say that none of the 300 ships, which I have manual access to, has this feature installed.




#2. The ADC uses a Frequency Modulated sensor to measure pressure
from the static port. These are highly accurate and very quick to respond
unlike aneroid devices. The chance of lag is non-existent.


Disagree. For a few reasons:

I looked this up in the CMM(Component Maintenence Manual) and came to a different conclusion. While its not like a purely mechanical aneroid, as in older altimeters and ADC's, there is still a sealed diaphragm that looks for changes to its resonant frequency with changes in ambient pressure. The bellows moves in older altimeters, causing a mechanical motion. The contraction or expension is where most of the lag comes from in those systems. In the 757's ADC, the diaphragms don't expand or contract but they vibrate. The change in ambient pressure still has to completely fill the sealed area on one side of the diapraghm(much like a bellows needs to have its sealed "test area" completely filled before the motion is accurate)before its frequency changes. Based on that, I'd say there is still a chance for lag, but not as much as traditional systems. Maybe you'd only see the lag under very high rate of climbs/descent, but it's there.

That brings me to my second point. I know there is lag on the 757 because I've seen it when doing my pitot-static tests. I use a rate of about 5000' per minute when changing test altitudes and every single time I pass an altitude at 5000 fpm, I notice the altimeter is a bit behind my test set remotes reading(which represents the atmosphere around the pitot and static ports). Maybe its only a 1/2 second or so, but its there.



#3. The Altitude also has a correction circuit which accounts for angle of
attack using the AoA sensor. I'm not fully aware how the data is measured,
or how/if it's recorded but i will look into this diagram further. It appears
any error from PA during rotation is corrected.


I mentioned this a few times at JREF in the "AA77 FDR Explained" thread.

Check your manual. IIRC the ADC starts looking at AoA at Mach 0.55 and higher. The runway discrepancy is probably just standard error of about 20' or so.

Again, if I remember correctly, the AoAs need to be at 10 degrees positive(relative to the index point, which strangely is about 7 degrees nose down) in order for the altitudes to be accurate during a standard accuracy test. If you move the AoA vane at 0.55 Mach number or higher, with no change of test altitude, the altitude will fluctuate by +/- 300 feet or so. Again, this is also something I've seen with my own eyes. So, it would seem to me that in a dive or climb in which AoA is changing; the altitude will be less accurate above M 0.55.

Lastly, as I mentioned, since you can move the AoA and register a change of altitude with no change in ambient pressure....doesn't it follow that there can only be one correct AoA for a given altitude/airspeed combination within the ADC calibration range(above 0.55 M)?

One last point I'd like to make is that when doing accuracy checks for altitude, you always use an airspeed as well. This is because the ADC needs to know both altitude and airspeed for calibration purposes. These airspeed/altitude test points are low speed/low altitude, med/med, and high/high. Off the top of my head, something like:

0' 120 kts.
5000' 180 kts
10000' 220 kts
20000' 300 kts
30000' 350 kts
40000' 400 kts

For this reason, its my opinion that the ADC's are not calibrated to be as accurate in a low altitude/high speed flight regime. I admit that I cannot know for sure, such information is not at our disposal, but it's only logical.



posted on Dec, 26 2009 @ 07:18 PM
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Originally posted by weedwhacker

And, yes, Tsuntzu is right, it IS possible for a person of normal height to reach all the altimeter set knobs, especially for a person sitting in the right seat, because of the placement of the instruments. I was thinking it was quite a reach, from the Captain's seat, all the way over to the F/O's altimeter. One would likely have to have long arm, and/or unstrap seat belt and lift up a little, while reaching over.


I concur. With the seat all the way forward, it'd be easy for a person in the F/O's seat to change the Capts baro knob, long arms or short arms. I can even reach the offside Instrument Source Select switches. I'm awesome.

Now as to why Hani would change both altimeters...thats another argument. Why not, right?

[edit on 26-12-2009 by 767doctor]



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