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Also....on the ground, and stopped, there is an option for a "fast align". This, after a full align has occurred....you may select the knob to "ALIGN", and then re-input position coordinates. Then back to "NAV". It will update that IRU (you can do one, or any of them as desired) in about a minute .... usually less.
On occasion, I have done this many times....at the gate, when there is a long delay, unexpected. You've already aligned, but you are unexpectedly delayed....and the IRUs can "drift"....quite a bit, actually. It's just a fact that some are more "tight" than others....so, a fast align "cleans" them up a bit. Still, you must not be moving. Any time the selector is taken out of "NAV", position alignment....where it "thinks" it is, is lost.
He (Balsamo) obviously believes by showing what appears to be a large position error on the ground at Dulles IAP and then a more accurate position during flight that the IRU was realigned during flight. The equipment in Airline use are not capable of alignment during flight. Some military type units are. Therefore, he's implying there was a substitute aircraft (aircraft swap) at Dulles. It is all poppycock, pure and simple.
I will address the military units as I have considerable experience with them. Weedwhacker will address the Airline units. There is no such thing as auto-align during flight. Military unit capable of alignment in-flight take hours, not minutes to align. Even then they will be miles in error after a long MANAGED alignment procedure. They need very precise updates during this process usually provided by high resolution Attack Radar. It takes considerable time to do this and the results are not very accurate if it will even complete successfully.
AA 77 automatically updated the IRU during flight as it's designed to do becoming more accurate as the flight progressed. By the time the aircraft reached the Pentagon it was in the vicinity of some 200' in error. There is NO WAY in hell that unit was aligned in flight, period. Those in use by the Airlines are not capable and those high quality units in use by the military would not be capable during that period of time and they would not be even close to 200' to the actual position at the end. I hope this helps.
You still are not understanding an ALIGNMENT versus UPDATES. They are two different things altogether. An alignment occurs on the ground and initializes the unit to a location/position on the surface of the earth. Then accelerometers and gyros detect movement and display that as a position from the original aligned position.
After airborne the units UPDATE their position automatically with either VOR/DME or DME/DME (look up these via google) to control drift and refine the position already present in the units. In other words, the UPDATES cause them to be more precise over time.
Read this: en.wikipedia.org...
If you can recall GPS was not in wide use in 2001. I believe only B-1's and B-2's did have GPS in the aircraft for use in programming precision guided GPS type bombs. I do know of any other aircraft who had GPS at that time. Selective Availability (SA) was removed in 2000, but to my knowledge no airline had GPS in use by 2001. Also, there were no WAAS satellites at that time, so it was not practical for the airlines to spend the huge cost in implementing GPS until WAAS was turned on in 2003.
Read about SA here: en.wikipedia.org...
Read about WAAS here: en.wikipedia.org...
Don't despair. If you still don't understand after this and after reading those articles we'll try again. As Weedwhacker said it's difficult to "dumb down" this stuff for the layman.
The FMC uses its calculated present position to generate lateral steering commands along the active leg to the active waypoint. The FMC requires position data from at least one IRS. All other position sources are validated against the IRS position and increase the accuracy of the FMC position.
FMC Position Update (Basic FMC)
On the ground, the FMC position is based on the IRS position.
Since inertial systems accumulate position errors as a function of time, the position information being used by the FMC is slowly accumulating errors. These position errors can be detected by observing the position of the airplane on the HSI map.
If an extended ground delay occurs and a significant map error is noticed the IRS should be realigned and present position re-entered.
As installed
When the autothrottle is engaged for takeoff, the FMC position is automatically updated to the takeoff runway position displayed on the TAKEOFF REF page.
In flight, the FMC position is continually updated from the navigation radios.
Originally posted by Reheat
You still are not understanding an ALIGNMENT versus UPDATES. They are two different things altogether. An alignment occurs on the ground and initializes the unit to a location/position on the surface of the earth. Then accelerometers and gyros detect movement and display that as a position (LT: away) from the original aligned position.
After airborne the units UPDATE their position automatically with either VOR/DME or DME/DME (look up these via google) to control drift and refine the position already present in the units. In other words, the UPDATES cause them to be more precise over time.
It is simply not possible for the airline type to ALIGN in a position other than stationary, period.
weedwhacker : Finally...as to the old, pre-GPS IRS "drift"...it was constantly correcting it (them)selves...and, to repeat for emphasis once more, the airplane referenced and displayed the "triple mix" average of all three units.
To keep an "eye" on the "health" of each individual unit, it was (still is) a requirement to log into the aircraft LogBook, end of every flight, the "IRS accuracy" readings.
(I would have thought that Rob Balsamo, and Ralph Kolstad, of all people, knew this......funny, they omit explaining in proper detail, isn't it???)
The units keep track of elapsed time they are in align mode, for each flight...and the average amount of MILES they calculated their accumulated errors to be. The hours of operation are divided into the average "drift", and those numbers are displayed on an info page, you access from the menu....and you write those figures into specific places, in the LogBook, designed to record the values.
I am so glad I only devoted a small fraction of effort to the latest red herring from the "P4T" crowd....because, THIS is what it all boils down to, their (incredibly false and deceptive) claim:
There was a slight error in the FMC position relative to actual, physical airplane position, when on the ground at KIAD;
The John Farmer / FOIA / NTSB (etc) data show that the FMC position information "corrected" itself after takeoff;
THEREFORE ('they' allege) AAL 77 "could not" have been a real civilian airliner, since no commercial airliner of that time could do an INU system "alignment" in-flight.
Does that about sum it up??
What we NOW all know (I hope) are these facts:
---The FMC Position updating shown, after takeoff and in flight, is PERFECTLY NORMAL for all commercial civlian airplanes with an INU system (called the "IRS").
---The Map Shift (if even noticed, before takeoff) is an insignificant factor for a flight that operates on routes that do NOT require precision RNAV capability. (I haven't even begun to address the concept of "RNP" yet...I will just drop that hint, and let everyone do their own research on it....).
---The attempts by the so-called "Pilots" for so-called "Truth" to muddy the issue, the facts, the circumstances, the reality and use innuendo-dropping of the worst kind in order to further their twisted agenda? Despicable.
Originally posted by iSunTzu
reply to post by backinblack
Look it up. The FMS does not only use IRS data.
www.biggles-software.com...
This is just an overview, think of the details in the system.
A 3,000 foot error or more at take off in the IRS is not news, it is called reality.
Now what is recorded in the FDR is from the FMC, not only from an IRS. The FMC updates its position based on rules and algorithms. The FMS-FMC is seen auto-tuning DME after take off to update the FMC position. The FDR information proves the FMC was working. The only way to verify this is to learn more. There is no inside job on 911, 19 terrorists did it. Saying the FDR is not from 77 is a lie.
IRS alone, ANP is around 0.4 NM and drifts. This does not mean the position from IRS at take off can't be better than 2400 feet, it means that it is typical, and guess what? After a few minutes it drifts. IRS drifts at a rate ~0.8 NM/hr. Guess who keeps the "real" (best guess position) the aircraft is? FMC. The FMC can use VOR, DME, LOC, to update the position. The FMC keeps track of IRS errors, and can use the IRS to pick up navigation if other sources are lost. The FMC knows the IRS are drifting off, and can use them to navigate because it applies the errors to correct from that point, even if the IRS are off miles.
www.inral.com...
Not related to 77, but to how the FMC works.
77 had no GPS, else the FMC after take off would drift to perfection of 0.1 NM or better.
Drift, I meant the algorithm in the FMC refines/defines the position of the aircraft.
What do Pilots for Truth say the ANP for an IRS only is?
They can not, it will ruin their story.
There are many references to learn more about Nav :
www.vatnz.net...
boeing.com...
en.wikipedia.org...
boeing.com...
IRU and INS equipped airplanes are eligible to be qualified for time limited RNP-10 approval as Group 2 airplanes (8400.12A, Section 12, paragraph b) if they have inertial systems approved in accordance with part 121, Appendix G. Group 2 airplanes have limited qualification of the RNP-10 requirements for up to 6.2 hours of flight time. This time starts when the system is placed in the navigation mode. Following an automatic DME/DME update, a Group 2 airplane is again approved for 5.9 hours of flight time. Following an automatic DME/VOR update, a Group 2 airplane is again approved for 5.7 hours of flight time (8400.12A, Section 12, paragraph e.).
IRS that have drifted off are still good because the FMC can update with other systems and essentially start the IRS position "new", updated. The IRS are only good for a 10 mile accuracy to 6.2 hours, but the FMC can use other systems, update, and use IRS for another 5.9 hours. But the raw IRS is still way off.
Pilots don't taxi to the runway using IRS, we use a white line painted, like the yellow brick road. For takeoff we use our eyes and the ADI/HSI, plus a white-line. This is why we don't taxi to the grass where the IRS thinks it is, or the FMC showing the IRS position.
Text still disinformational, as per Sunday 2 Oktober :
After adjusting a Lat/Long offset based on drift prone to the navigational equipment utilized, the positional data has the aircraft departing a gate further east of Gate D26 and on the north side of the Concourse.
Radar altimeters are frequently used by commercial aircraft for approach and landing, especially in low-visibility conditions (see instrument flight rules) and also automatic landings (autoland), allowing the autopilot to know when to begin the flare maneuver.
In civil aviation applications, radio altimeters generally only give readings up to 2,500 feet (760 m) above ground level (AGL).
Approximately 10 steps out from between Wings 4 and 5, I was making a gentle right turn towards the security check-in building just above Wing 4 when I became aware of something unusual. I can’t remember exactly what I was thinking about at that moment, but I started to hear an increasingly loud rumbling behind me and to my left. As I turned to my left, I immediately realized the noise was bouncing off the 4-story structure that was Wing 5. One to two seconds later the airliner came into my field of view. By that time the noise was absolutely deafening. I instantly had a very bad feeling about this but things were happening very quickly. The aircraft was essentially right over the top of me and the outer portion of the FOB (flight path parallel the outer edge of the FOB).
Originally posted by LaBTop
But I am no wide body commercial airline pilot, so your help and expertise will be much appreciated.
Just as that from Weedwhacker, whatwasthat, and iSunTzu.
And for the FDR expertise, Warren Stutt and 911files (John Farmer?)
Originally posted by LaBTop
This is a turn calculator :
www.csgnetwork.com...
When I enter 285 KTS (328.035 MPH) as the speed entering the turn, and 180 KTS (207.180 MPH) as a 757 its rated stall speed (a guess), and a bank angle of 15°, I get a turn radius of about 4.45 Nmiles (5.1 Miles).
Is that about the radius I used in my above viable flightpath arc?
When I change only the bank angle to your proposed 60°, I get a turn radius of only 0.8 miles (0.7 NM). I think my proposed turn radius is quite a bit longer.
Edit : When I change the bank angle to 30 °, the turn radius changes to 2.35 Miles.
edit on 3/10/11 by LaBTop because: Added 30° bank angle.
All your "evidence" is circumstantial. It's time to accept the cold hard reality that there are people out there who are evil and wish to do you harm. Maybe you have to tell yourselves that the GOV is out to get you because your mind can't except that fanatical religious psychopaths want to slaughter as many infidels as they can. Time to grow up people.
Myth: All serial murderers travel and operate interstate.
Most serial killers have very defined geographic areas of operation. They conduct their killings within comfort zones that are often defined by an anchor point (e.g. place of residence, employment, or residence of a relative). Serial murderers will, at times, spiral their activities outside of their comfort zone, when their confidence has grown through experience or to avoid detection. Very few serial murderers travel interstate to kill
Myth: Serial killers are all dysfunctional loners. The majority of serial killers are not reclusive, social misfits who live alone. They are not monsters and may not appear strange. Many serial killers hide in plain sight within their communities. Serial murderers often have families and homes, are gainfully employed, and appear to be normal members of the community. Because many serial murderers can blend in so effortlessly, they are oftentimes overlooked by law enforcement and the public.