UA 175 - Pilots Discuss WTC Attack

Originally posted by Alfie1


This seems to me to be a very feeble area for truthers to take issue with.

All the terrorist pilots had received flight training and surely crashing into huge buildings would not have stretched their skills. If it would, why is there not a great groundswell of protest from the aviation community ?

"Feebele" is exactly the word for it. Are these truthers genuinely claiming that the hijackers had such bad flying skills that they couldn't crash a plane...?

reply to post by GoodOlDave

If it would, why is there not a great groundswell of protest from the aviation community ?

This is the "gotcha" key. In so far as the "truth" community is concerned, their argument is that any pilot or aviation expert that has not gone on the record as accepting that 19 Islamic terrorists hijacked the planes and crashing them accordingly is, by default, a supporter of one or not all of the secret government conspiracies.

Very interesting about the pro pilots saying that they couldn't pull it themselves. I think any investigation should have started from this point.

[edit on 28-6-2010 by masterp]

reply to post by masterp


Perhaps it would be illuminating for you if you read my post, from another thread, that addresses this.

(Note: The very, very few actual pilots at the "PilotsFor9/11Truth" do NOT speak for the majority of other pilots who have no "hidden" agenda...IOW, we do not sell DVDs):

www.abovetopsecret.com...

Originally posted by weedwhacker
reply to post by masterp

 

Perhaps it would be illuminating for you if you read my post, from another thread, that addresses this.

(Note: The very, very few actual pilots at the "PilotsFor9/11Truth" do NOT speak for the majority of other pilots who have no "hidden" agenda...IOW, we do not sell DVDs):

www.abovetopsecret.com...

Thank you, very interesting. If it's difficult for a pro to hit the WTC in simulation, then it should be impossible for someone on the ground to achieve it in real life. The remote controlled scenario seems weak.

Is there a possibility that the flight path was pre-programmed into the airliners?

Is there a possibility that the flight path of the planes was altered in real time from the ground?

reply to post by masterp


To answer:

If it's difficult for a pro to hit the WTC in simulation....

I'm not buying for one second his (Ralph Kolstad's) or anyone else's claims to that effect. It isn't hard at all, have steered simulators into "buildings" for 'fun' before...(It is only 'fun' the first time...quickly, becomes boring and pointless. Do it once or twice, "fly" under the Golden Gate Bridge...and then on to serious business).

Is there a possibility that the flight path was pre-programmed into the airliners?

Not to that level of accuracy. The Inertial Reference System is not accurate to the few dozen feet required, not even close. AND, the autoflight system will NOT allow the airplanes to exceed published speed and other limits.

Is there a possibility that the flight path of the planes was altered in real time from the ground?

No. There is NO uplink capacity to the autoflight systems, from the ground. Anyway, you run into the problem answered above.

Here's an example of a (fairly) high-speed B-757 at low altitude:



Notice he's lined up with a runway that's about 150 feet wide, yet he's going MUCH faster than "landing speed"!!! (He's ~250 - 300 knots)

Kolstad's claims just debunked!

reply to post by weedwhacker


Some questions, if you don't mind:

1) what is the Inertial Reference System and why would it prevent the insertion of a flight path to the WTC?

2) what if the autopilot safety constraints were overriden by software?

3) why is there a need for a big network capacity in order to transmit a few waypoints? I am not talking about frequent updating of aircraft position.

reply to post by masterp



1) The IRS is the gyroscopic 'platform' that provides attitude information (pitch, roll) and also position. Earlier versions were called INS for 'Inertial Navigation System'...basically same thing, but the "reference" adds another dimension, as the platforms provide pitch and roll that an INS does not. Used separate instruments.

Modern platforms actually have no moving parts, unlike the older bulky rotating gyroscopes. The technology today uses devices called "laser ring gyros", (so did some more modern INS, too)...where a laser light beam is 'bounced' around a series of mirrors (One 'gyro' for each of the three axis') and acceleration is detected by the incredible tiny deviations of the light beams. This, as they detect the accelerations in three axes, allow them to infer and compute new position information, due to the inferred movement...very complex machines, and hard to visualize. I'm sure more info can be found online, no need to repeat at great length here.

Just to add, though...the IRS has no idea where it is: it has to be "told", and that process is called 'initialization'. The known current latitude/longitude coordinates are input by the crew (even before this happens, it CAN know its approximate latitude, because it can sense the Earth's rotation...but can't tell North from South, only distance from equator). Not equipped on American 77 at the time, but most of today's fleets have GPS, which is used for the more accurate initial position entry.

Otherwise, (no GPS) we just use the info from our charts for lat/long...AND, the units 'remember' where they were last shutdown and will alert if the input coordinates are well outside a certain 'logical' range.

Anyway, once intialized, they (there are three, typically) are independant, and each calculate from then on, as they sense movement, (laterally only, they have no altitude reference) to determine where they are, in relation to the starting point. UNTIL they are given outside updating info (whether GPS, if installed...or, like with AA 77, VOR/VOR or VOR/DME position updates) they will each merrily crunch the numbers....and have no other reference, except for what I mentioned.

There is inevitably a bit of error that accumulates...but since they aren't used, solely, for precise navigation, it isn't an issue. They are simply not designed for precision....couple tenths of a mile is "tight", usually....

FYI....after every trip, as part of the post-flight, we go to a page in the computer database that has kept a record of the 'drift' rate, divided by the time they were in operation. We log that in the aircraft Logbook, andif it is greater than --- I have to look it up, but greater than 3 miles per hour of operation comes from memory, that has to be written up for maintenance action. Usually, we log something like 0.3 to 0.6....rarely over 1.0

Now, to follow with the rest...the IRS ONLY accepts initialization inputs, and radio/GPS updating...actually, the base IRS position where it 'thinks' it is never changes...the radio/GPS updating is averaged, and then presented as the 'computed' position (and, when all three are operating, they are additionally "mixed" to make another average...it's called "triple mix").

This 'computed' position is now the 'official' postion, and is fed to the Flight Management Computer (FMC).

Within the FMC is also included the navigation database, for airports, waypoints, intersections, etc. AND, it's the FMC that is directly accessible by pilots, to program the autoflight and other guidance functions.

There is a feature, via ACARS uplink, when tied into the FMC, for flight plan data to be uploaded (most regularly programmed flight plans are sent that way when at the gate, nowadays...not sure about AA 77, back then...other, older way was from a stored database in memory...).

BUT, this only sends the data...it must be accepted and "executed" by physical button pushes by a human. THEN, it will just be sitting there, until it is utilized by other buttons, to make it "active" for the autoflight guidance systems. In any case, as I've noted, the computed IRS POS isn't nearly accurate enough to hit a building a few hundred feet wide.


2) IS the simplest....the A/P programming, in order to change it, would require a COMPLETE code rewrite --- and, the servos that operate the controls, in response to A/P commands, do not move the controls as rapidly, or to the extent that a human can. Further, in terms of pitch control (and any pilots will understand this better) changing the pitch attitude requires a force on the elevator controls...but that is NOT a 'neutral' operation. Each change in pitch (or in power settings, which also alter the 'balance') results in the force, and requires a sustained force be maintained...OR, we use the "TRIM" function, to re-align the (in the case of big jets) the horizontal stabilizer, and relieve the need for the sustained pressure. (Small private airplanes usually have small adjustable 'tabs' on the elevators themselves to accomplish this).

The TRIM on the B-757/767 has two speeds...and the A/P can ONLY access it in the slower, about one-half normal speed of trim change. This would mean that, in terms of pitch attitude adjusting, the A/P is very limited, as it doesn't have the control authority, nor the 'strength', that a human can employ.


3) Not clear on this one...would not need a "big" network, of course. But, point is, there just is no provision built in .... except, as I mentioned above, which still needs human activity.



[edit on 29 June 2010 by weedwhacker]

reply to post by weedwhacker


After sleeping on it, I'd like to add...the above was a (sorry, rather long) explanation of some details, but by no means all, of the IRS and other systems on modern airliners.

If I recall, it initially came about partly because of questions whether the two 767s (American 11 and United 175) had sufficient navigational ability, and accuracy, via the onboard programming and autoflight systems, to be "pre-set" to fly into the Twin Towers. NO, is the short answer to that.


The other part that cropped up, again regarding the NAV systems, is some of AAL 77's DFDR info...especially the part that showed where the recorder thought it was, during the takeoff run at Dulles.

The post above attempts to describe in some detail the inherrent lack of refined accuracy in the IRS platform computed position data...and those small accumulated errors could certainly have arisen during the several minutes of taxi out for take off, after leaving the gate.

What is so troubling is when a site like "PilotsFor9/11Truth", and similar ilk, try to use ANY little aberration they can in order to bamboozle the lay public --- Those guys at "PFT" are supposed to be pilots? Yet, they intentionally (?) omit details, and then disingenuously use ridicule, and the fact that by not sharing ALL information, they can twist the "story" to their liking.

I came back to expand on the 'initialization', by entering 'known' coordinates into the IRS....pre-GPS era (as in AAL 77).

Our 'gate coordinates' that are used are not accurate to within a small degree, like a few feet...the entries are in degrees, minutes and tenths of minutes...e.g., to type in coordintes (just a random gate at Dulles) the 'N' key is pressed, then the degres, minutes and tenth. Then, the 'W' key, and the appropriate (with leading zero) numbers.

An example is:--- N38*56.7 W077*27.3

ONE degree of latitude is ~69 miles. A minute is ~1.15 miles. (Those are statute miles...we normally use Nautical in aviation, so it's 60 NM and 1 NM, respectively).

As you see, the minutes are only broken down by tenths...so that is ONE TENTH of a mile units after the decimal point. THAT is the extent of the accuracy, even for initialization. (One tenth of a NM is ~600 feet).

SO...just because the DFDR position information for takeoff (it gets ITS data from the LEFT IRS position...or the triple mix, will depend on installation parameters) showed the airplane "off to the side" of the runway, that is not to be taken literally, nor does it reflect poorly on the quality of the DFDR information, once you understand the system and how it works, and what its limitations are.



[edit on 30 June 2010 by weedwhacker]