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posted on Oct, 30 2009 @ 12:52 AM
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Originally posted by 911filesNo, I am not going to read the trash at P4T, because I have found very few people have a clue what they are talking about.


There's your first problem! You think the pilots don't know how to
calibrate, use and correct for the parameters you are overlooking?

What is the altitude when corrected to local pressure on the date for
flight #11?



What you seem to be missing is the central issue


What you seem to be missing is the WHOLE issue.

What was the local pressure for that day?

What is the final reading once corrected?

Please tell us that much, and then ask yourself if it's "out of spec".

Once you correct the data, the PA will be within +/- 20 feet ASL as
per MANUFACTURER SPECIFICATION!

[edit on 30-10-2009 by turbofan]




posted on Oct, 30 2009 @ 01:15 AM
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reply to post by turbofan
 


Wrong again Turboman. The plane shows a PA of 40 as it begins its departure down the runway. The runway elevation (USGS source, linked in earlier post) is 280 feet at that point, gaining in elevation to ~305 feet when the wheels begin to leave the ground. At that time the PA is ~70 showing a gain in altitude of ~30 feet while still on the runway. Using the 300 foot local barometric, that puts the PA off by ~60 feet, so either the measurement system is out-of-spec, or P4T does not know what they are talking about.

I am not going to jump through hoops for you, the data is right there in the CSV and/or Warren RO. I do know the barometric pressure for both dates and have the graph of the actual barometric pressure for both days. It is not a static number, but varies hour-by-hour. Conditions at take-off would have been different than even an hour before or after...please wake up and understand that it does not matter what the barometric pressure was. What matters is that the PA is dependent upon barometric pressure and will require changes to compenate when atmospheric conditions change. Since the operation of the aircraft at the end of the RO are so extreme and outside normal parameters, there is uncertainty as to what the impact would be on the air flow being measured.

There is not that uncertainty with RA.



posted on Oct, 30 2009 @ 01:34 AM
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Originally posted by 911files
reply to post by turbofan
 


Wrong again Turboman. The plane shows a PA of 40 as it begins its departure down the runway. The runway elevation (USGS source, linked in earlier post) is 280 feet at that point, gaining in elevation to ~305 feet when the wheels begin to leave the ground. At that time the PA is ~70 showing a gain in altitude of ~30 feet while still on the runway. Using the 300 foot local barometric, that puts the PA off by ~60 feet, so either the measurement system is out-of-spec, or P4T does not know what they are talking about.

I am not going to jump through hoops for you, the data is right there in the CSV and/or Warren RO. I do know the barometric pressure for both dates and have the graph of the actual barometric pressure for both days. It is not a static number, but varies hour-by-hour. Conditions at take-off would have been different than even an hour before or after...please wake up and understand that it does not matter what the barometric pressure was. What matters is that the PA is dependent upon barometric pressure and will require changes to compenate when atmospheric conditions change. Since the operation of the aircraft at the end of the RO are so extreme and outside normal parameters, there is uncertainty as to what the impact would be on the air flow being measured.

There is not that uncertainty with RA.


Wow, do Reheat and WeedWacker actually agree with the quote above?

Also, John Farmer writes:

"Using the 300 foot local barometric,"

John Farmer, who said IAD is a 300 foot local "barometric" correction?

You know less than a student pilot!

Unfortunately I can't download the code and look through it; I'm currently
at work. Since you say you have all this info and refuse to share it, then
let's do this:

What is True altitude with a local pressure of 30.20 and PA of 41?

Next, what is True Altitude with a PA of 120 and local pressure of 30.12?

John, do you know the definition of True Altitude? Clearly you have not a
clue why there is an 80 ft difference between landing the night before and
departure in the morning, apparently nor do Reheat or Weedwhacker.


[edit on 30-10-2009 by turbofan]



posted on Oct, 30 2009 @ 01:54 AM
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reply to post by turbofan
 


Turboman, your leader Cap't Bob said it was a 300 foot correction. The ASR-9 radar uses the 300 foot correction. And yes, Reheat understands exactly what I am talking about and so would anyone else who has half-a-brain not overcome with proving some hair-brain 'fly-over' scheme.

The PA is a value. To represent a 'real world' equivilant, a correction must be applied. The accuracy of the system depends on the correction applied. So are you saying that Cap't Bob has now changed his mind and it is no longer a 300 foot correction? Oh the fun he had when I insisted the correction woud only be ~240 feet years ago. Oh no, he said, I was not a pilot he said, the correction was 300 feet. So today it is something different? Darn, I missed that memo.

No Turboman, it does not matter what the barometric pressure was. What matters is the correction applied by someone using barometric pressure. Since barometric pressure is in a state-of-constant change, it would be impossible for someone to get it exactly right, hence error. When air is flowing over the sampling instrument at 500 knots, there is also going to be an effect on pressure. I cannot quantify that for you, hence uncertainty.

The point is, wth all of this variability and inaccuracy, why not just go with measurements from four different instruments not affected by it? Maybe a pilot would go with what his PA was telling him and ignore what his RA was telling him, but I'd state my life on how close to the ground my radar was telling me.

Oh, and by the way, stop it with the silly "do you know..." questions. I stopped playing such childish stuff back in elementary school.

[edit on 30-10-2009 by 911files]



posted on Oct, 30 2009 @ 03:08 AM
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Originally posted by 911files
Turboman, your leader Cap't Bob said it was a 300 foot correction.


I have been following this for some time and I'm not quite sure why Reheat nor weedwhacker hasn't corrected 911Files and only let him bury himself more.

911Files, the 300 foot correction done by Capt Bob was done at the Pentagon using DCA local pressure of 30.22. Rule of thumb as per FAA Pilots Operating Handbook is 1 inHg per 1000 feet. So, 30.22 - 29.92 = 0.3 = 300 feet.

Capt Bob has also stated this is a rough estimate based on rule of thumb. He shows a more accurate measurement in the altimeter simulator linked by Turbofan.

Capt Bob never did an altimeter correction at IAD.

The reason there is an 80 foot difference at IAD between take-off and landing the night before is due to pressure changes, Capt Bob is right on this issue if you would like to check the altimeter simulator linked below. Unfortunately Reheat nor weedwhacker picked up on it and instead chose to support your misinformation.

Sorry all, I'm just getting a bit tired of all the personal attacks and misinformation being spread by those who claim to be debunkers.

Altimeter Simulator
www.luizmonteiro.com...

1. Put 41 feet into the left altimeter indicated altitude, put 30.20 into the right "New Altimeter Setting". Note True Altitude on top.

2. Put 120 into simulator on left indicated altitude. Put 30.12 into simulator "New Altimeter Setting" on right.

Note the difference, compare to IAD Field Elevation in the Jeppesen Airway Manuals (IAD is 313 feet, unlike the upper limit told by 911Files as 290). Its well within 20 feet as Turbofan described.

Pressure Altitude is very accurate.

[edit on 30-10-2009 by R_Mackey]



posted on Oct, 30 2009 @ 03:25 AM
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Originally posted by turbofan
Not a bad response, however let's pick apart this critical point.

The animation altimeter upon descent does not reflect the changes in
the PA adjustment.

Why/how can this happen if the animation is derived from the raw file
just like the CSV file?

Research how the animation is created (look up Flight Software sites if
needed) and ask yourself how these two files have different values.


Why all the concentrated effort on what is simply an animation that contains other obvious errors?
For whatever reason, the animation is flawed but in no way does it invalidate the data being discussed.

You're also not doing your credibility any favours by adhering to a claim that a PA reading at about 100' or less from the ground (within 20' at best) is superior in accuracy to the radio height indication (within 1'). It's fair enough that the odd RA reading could be caused by something on the ground like a vehicle or whatever but not all of the readings and there are enough of them to get an idea of the aircraft's final motion if we were to mix in the topography of that area.

You could, of course, attempt to throw out all of the recorder data as invalid (faked or whatever) but you'll need some powerful proof to do that, not to mention the counter-productivity after having invested so much time on it.



posted on Oct, 30 2009 @ 03:34 AM
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Originally posted by Pilgrum
You're also not doing your credibility any favours by adhering to a claim that a PA reading at about 100' or less from the ground (within 20' at best) is superior in accuracy to the radio height indication (within 1'). .


The Main altimeter on an aircraft comes off the Air Data Computer. It is based on pressure and is highly accurate.

It is true that the Radar Altimeter is more accurate, but where the difference resides is in the fact Baro Altitude is above a known object (sea level) whereas Radar Altitude is not above any known object. This is why a Baro altimeter is primary for IFR flight and a Radar Altimeter is not even required to fly an approach to minimums served by 99.9% of the flying public.

Being that you know exactly how high you are above a determined object within 20 feet in Baro Alt (MSL), verses the fact you do not know how high you are above any specific object in Radar Altitude, Baro altitude is more accurate for placement of an aircraft in time and space.



posted on Oct, 30 2009 @ 03:51 AM
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Originally posted by R_Mackey

Originally posted by 911files
Turboman, your leader Cap't Bob said it was a 300 foot correction.


I have been following this for some time and I'm not quite sure why Reheat nor weedwhacker hasn't corrected 911Files and only let him bury himself more.

911Files, the 300 foot correction done by Capt Bob was done at the Pentagon using DCA local pressure of 30.22. Rule of thumb as per FAA Pilots Operating Handbook is 1 inHg per 1000 feet. So, 30.22 - 29.92 = 0.3 = 300 feet.

Capt Bob has also stated this is a rough estimate based on rule of thumb. He shows a more accurate measurement in the altimeter simulator linked by Turbofan.

Capt Bob never did an altimeter correction at IAD.

The reason there is an 80 foot difference at IAD between take-off and landing the night before is due to pressure changes, Capt Bob is right on this issue if you would like to check the altimeter simulator linked below. Unfortunately Reheat nor weedwhacker picked up on it and instead chose to support your misinformation.

Sorry all, I'm just getting a bit tired of all the personal attacks and misinformation being spread by those who claim to be debunkers.

Altimeter Simulator
www.luizmonteiro.com...

1. Put 41 feet into the left altimeter indicated altitude, put 30.20 into the right "New Altimeter Setting". Note True Altitude on top.

2. Put 120 into simulator on left indicated altitude. Put 30.12 into simulator "New Altimeter Setting" on right.

Note the difference, compare to IAD Field Elevation in the Jeppesen Airway Manuals (IAD is 313 feet, unlike the upper limit told by 911Files as 290). Its well within 20 feet as Turbofan described.

Pressure Altitude is very accurate.

[edit on 30-10-2009 by R_Mackey]




Is this "the" R_Mackey?

Much respect for doing the right thing if so.



posted on Oct, 30 2009 @ 03:51 AM
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reply to post by R_Mackey
 


Mackey, you just made the point I was trying to make. This has not been a discussion of how accurate the system is under normal circumstances. It is a discussion of the error subjected to it by the person applying the corrections. You are using numbers from one source, I am using numbers from the USGS and I will go with those because that is the source of 90% of the measurements in the vicinity of the Pentagon that P4T throws around. So lets use a consistent standard.

Second, barometric pressure was 30.2 as given by Turboman, but more specificly, it was 30.22 at take-off and rising at IAD. At the time of impact, the pressure was closer to 30.24. As you have pointed out, the value for 'true altitude' is entirely based on the inputs used to correct for atmospheric pressure. It is not instrument accuracy that I am talking about, but application accuracy. Now if you want to join the P4T crowd and assert that PA was correct at the Pentagon within 25 feet, be my guest, but I am not comfortable with the change curve or other estimates I have heard thus far.

Third, you have no idea what Capt Bob and I discussed and his assertion two years ago was that a 300 foot correction was required at take-off from IAD.

Fourth, I started this exchange to get Turboman (and others) to understand that the PA is based on atmospheric pressure, NOT barometric pressure. Certainly, barometric pressure is one contributor to atmospheric pressure as measured by the instrument (altimeter in this case). That is the important element, 'as measured by the instrument'. However, when one instrument not subject to such subjective measurement error is in opposition to the subjective instrument, there is also another factor yet to be identified that is affecting atmospheric pressure (as read by the instrument) beyond barometric pressure.

Fifth, I don't need you to dig me out of a hole I have not dug. I am not a pilot. I am not a rocket scientist. But I am an expert on measurement systems and wrote the book on how to assess their operation in practice. In the case of the PA at the EOF at 500 knots, there are some big time measurement error issues when compared to other measurement systems. So yes, as stated before, PA is extremely inaccurate and subjective.

By the way, I used a calculator months ago and estimated the correction for local conditions at that time to be 257.99 feet, very close to my USGS/FDR estimate of 240. So, yes at take-off I agree that at take-off the PA was within instrument spec. But obviously I was talking over the head of a rocket scientist too


[edit on 30-10-2009 by 911files]



posted on Oct, 30 2009 @ 03:59 AM
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Originally posted by Pilgrum
Why all the concentrated effort on what is simply an animation that contains other obvious errors?


If you understand how the animation and CSV are created, you wouldn't
be asking this question.


For whatever reason, the animation is flawed but in no way does it invalidate the data being discussed.


For whatever reason, it has error...but it has been corrected. The final
PA altitude is too high. See the P4T analysis if you haven't already.


You're also not doing your credibility any favours by adhering to a claim that a PA reading at about 100' or less from the ground (within 20'
at best) is superior in accuracy to the radio height indication (within 1').


I NEVER said it was superior. NEVER. THere are several posts I have
made showing the tolerance of RAD Alt., so I don't know where you
read/interpet otherwise?

I said PA within -/+ 20 feet tolerance is still too high to hit light poles.

Hope I made myself clear.

[edit on 30-10-2009 by turbofan]



posted on Oct, 30 2009 @ 04:01 AM
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Originally posted by 911files
Mackey, you just made the point I was trying to make.


911Files, this is the point you were trying to make.


Originally posted by 911files
Looking at PA on the ground at Dulles at the end of Flight #11 (as recorded in the FDR), the altitude is 120 - 121 feet! Now which is it turbo? Is the altitude at landing correct, or is it the PA at take-off?

So yes, I repeat, PA is highly inaccurate for these purposes. Or at least I call a difference of 80 feet a significant difference.


Its on page 4. The answer to the above is the answer given by Capt Bob.

The altitude at landing AND the altitude at Take-off, is correct, once you adjust for local pressure at that time of day.

also, 80 feet difference from the night before to the next morning is not "significant". It's only a pressure change of 0.08.

For some reason Reheat thought this to be out of tolerance for flight?


Originally posted by Reheat
80' difference between a corrected barometric altimeter indication and field elevation (known reference point) is OUT OF TOLERANCE for flight. The limit is 75'. The bench test limit for a radar altimeter is 1'.


No Reheat, this is a case of the fact air moves on earth.



posted on Oct, 30 2009 @ 04:32 AM
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No Mackey, the point is that the inputs change over time and one significant input is missing in the discussion. Further, the inputs are subjective. The point you are obviously trying to make is that you are the 'rocket scientist' and no one is going to upstage your limelight.

So, you are asserting that the PA is highly accurate under this circumstance (~500 knots, low altitude flight). Go on then, explain to us all how the plane flew over the Pentagon at 200 foot altitude, since we know the PA is certainly accurate within 25 feet under all circumstances. Oh wait, here comes the 'other input' known only to Mackey. But then again, that was the point I was laying the foundation for, you can have the floor now and enlighten us all.



posted on Oct, 30 2009 @ 04:39 AM
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Originally posted by 911files
No Mackey, the point is that the inputs change over time and one significant input is missing in the discussion. Further, the inputs are subjective. The point you are obviously trying to make is that you are the 'rocket scientist' and no one is going to upstage your limelight.


911Files, I'm not trying to take away your limelight here. But if you want to continue to assert 41 PA with a 30.20 altimeter is "significantly" different than 120' PA with a 30.12 Altimeter on a field with an elevation of roughly 300 feet, be my guest. You are wrong. It has been shown that in every way possible including a 3rd party altimeter sim. It's just that simple. I'm sorry you cannot see that and I'm even more sorry Reheat nor Weedwhacker could not/did not correct you.



[edit on 30-10-2009 by R_Mackey]



posted on Oct, 30 2009 @ 04:42 AM
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reply to post by 911files
 


Considering that ATC will issue a new METAR if weather changes are
significant, your position on "atmospheric changes" means nothing.

Once again, when converting for local pressure the PA will never be
out of specification.

That is +/- 20 feet below 1000 feet.

This is a fact.



posted on Oct, 30 2009 @ 04:56 AM
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No Mackey, by all means continue. My assertion was that the two values were diffferent so that Turboman could 'enlighten' me. I knew then (and you know from JREF that I do), why they are different. I have the charts for barometric pressure for IAD right here on my laptop showing the continuous change in the variable, not just a single sampling.

However, since you now have felt the need to stop turboman's development process in understanding why the PA is what it is, I really want to hear more how this PA is so infallable and the cuckoo flew over the cuckoo's nest.



posted on Oct, 30 2009 @ 05:01 AM
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Originally posted by 911filesI have the charts for barometric pressure for IAD right here on my laptop showing the continuous change in the variable, not just a single sampling.


You've been saying that for several posts and will not produce the data.
It's tough to believe you have this information at all.

Since you wont give me/us the weather info for that day, or the flight
date so I can check, please tell me the delta in highest / lowest pressure
change so we can convert to inches of Merc.

[edit on 30-10-2009 by turbofan]



posted on Oct, 30 2009 @ 05:02 AM
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Originally posted by 911files
My assertion was that the two values were diffferent so that Turboman could 'enlighten' me.



Turbofan did enlighten you. I tried to as well. The values are NOT different when you adjust for local pressure at that time of the day. The values are the SAME. They both adjust to a True Altitude of roughly 300 feet. This is within 20 feet of field elevation, as stated by manufacturers specs.

911Files, we're beating a dead horse. It's clear you cannot admit a mistake.



posted on Oct, 30 2009 @ 05:12 AM
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Originally posted by turbofan
Since you wont give me/us the weather info for that day, or the flight
date so I can check, please tell me the delta in highest / lowest pressure
change so we can convert to in./Hg.


Actually, 911Files did give the data. He edited into his post after you already replied:


Originally posted by 911files
Also, pressure at IAD was 30.12 on 9/10/2001 and 30.19 on 9/11/2001. So yes, it could be a significant factor if the pressure was significantly different, but it was not. Also, the runway is below 300 feet elevation. Once again, a highly variable and inaccurate measurement for these purposes.
[edit on 29-10-2009 by 911files]

[edit on 29-10-2009 by 911files]


It's exactly what P4T predicted (30.12) based on 911Files first claims of 120 feet.

pilotsfor911truth.org...\

Although 911Files is wrong with 30.19 at 41 feet. The CSV file shows 30.20. But even so, 0.01 is only 10 feet, still within specs.

There is no such thing as a 'significant' 80 foot difference between landing the night before and take off the next morning. They are both the same when adjusted for local pressure at that time of the day. If 911Files would like to claim a 0.08 pressure gradient between the approach/departure end of the runway, I guess he also feels Hurricane force winds were present?

This is just getting absurd.



posted on Oct, 30 2009 @ 06:38 AM
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Originally posted by R_Mackey

This is just getting absurd.


Yes it is...

Well, as I said before, the fun is all gone now thanks to Mackey pointing out the error of my ways. Not sure why he did since he knows that I don't work in a vacuum and consult with dozen's of people much smarter than I am in a wide range of specialties and know in great detail every data point available and what it means in context with others.

So here is the 'punch line' that I was developing for what it is worth. I can make the point now because everyone seems to be on the same page in regards to what we are discussing. If I had said this multiple posts ago (and most likely even now) I would have gotten nothing but laughs. So here it is.

PA is NOT a measure of altitude. The system measures air pressure which it then interprets as estimated altitude. I was letting Turboman argue this so that it would not be a debatable point later. Through the entire flight of the plane, air pressure varied based upon local conditions, altitude, etc. As with the example calculator which Mackey was so kind to post, the ‘raw’ PA must be adjusted to local conditions to provide a ‘true’ altitude estimate. Under normal operating circumstances when every variable is known, the interpretation is generally a good one.

The issue at hand is what happens to air pressure (which is what the PA is measuring) at the point of measurement at extreme speeds beyond the specifications of the measurement instrument and/or plane? Mackey has an idea (as do I), but he just argued beyond any shadow of a doubt that the PA is a 100% reliable indicator of altitude. Too bad it is measuring air pressure and some funny things happen in that regards at those speeds in dense air. Those things are small, but as pointed out, it does not take a lot to really impact the altitude interpretation. It would have been fun to develop the topic further.

Forgive Reheat, he was just helping me draw Turboman out. He knows what the difference is too. So take it away ‘rocket man’.



posted on Oct, 30 2009 @ 07:20 AM
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Originally posted by 911files
PA is NOT a measure of altitude. The system measures air pressure which it then interprets as estimated altitude.


Partially correct, but mostly Wrong.

Pressure IS altitude. This is why the main altimeter REQUIRED for flight in Instrument Meteorological Conditions (IMC, or fog for the layman) is called a Sensitive Pressure Altimeter and a Radar Altimeter is not even required in such conditions. This type of altimeter senses pressure differentials sensitive to 10 feet, ie. 0.01 inHg. It is accurate to within 10 feet! 20 feet tolerance when considering manufacturers specifications, above a KNOWN object, sea level, and therefore the ground, when consulting charts. You call this an "estimate"? Who you trying to kid?

911Files, if you had such consultants, you would be more confident to debate P4T who are verified and have proven you wrong time and time again. Instead, you refuse to even sign up to their forums and instead chose to write rebuttal posts on ATS at all hours of the night, day after day.


Originally posted by 911files
So which is it? 40 something or 100+? Let's pick and choose whichever we want, so don't go saying I made a PA error, because the readings are in the Warren decode.

I stand by my assertion. The PA is too unpredictible and inaccurate for these purposes.


911Files, just admit your mistake and be done with it.


Originally posted by 911files
Forgive Reheat, he was just helping me draw Turboman out. He knows what the difference is too. So take it away ‘rocket man’.


Your bait excuse won't work among those who read your posts and know the difference. But since you're backpedaling, is baiting other ATS members against the TOS?


[edit on 30-10-2009 by R_Mackey]





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