AAL77

On Sep 11, 2001, American Airlines Flight 77 was one of 4 aircraft hijacked. It was subsequently utilized as a weapon of mass destruction as it was flown into the Pentagon. At approximately 8:56 a.m. EDT, while in Indianapolis Center (ZID) airspace, cruising at FL350 (approximately 35,000 feet above sea level), the transponder was simply turned off. Normally, disabling a transponder does not make an aircraft invisible to air traffic controllers, as the high-altitude Center controller need only select the “ALL PRIM” (all primary) filter to view the aircraft’s SEARCH radar (i.e. “primary” aka “skin paint”) targets. As a matter of fact, Chuck Thomas, the radar controller who was working AAL77, selected the ALL PRIM filter within one second of AAL77’s datablock displaying “CST” (Coast Mode...which indicates that the aircraft’s datablock is no longer being updated with radar data). The disturbing thing is, there was no primary target on AAL77 available for Thomas. AAL77 ultimately flew the entire way back to its impact, some 41 minutes later, unnoticed by Air Traffic Control.

Key 9/11 Commission findings about radar data processing:

On page 25 of THE 9/11 COMMISSION REPORT, they write

“The reasons are technical, arising from the way the software processed radar information, as well as from poor primary radar coverage where American 77 was flying.”

Footnote 142 (pg 460) states

“142. Primary radar contact for Flight 77 was lost because the “preferred” radar in this geographic area had no primary radar system, the “supplemental” radar had poor primary coverage, and the FAA ATC software did not allow the display of primary radar data from the “tertiary” and “quadrary” radars.”

Comments on above findings:

The above findings by the 9/11 Commission help to shed light on the fact that even though an aircraft may be detected by radar, that aircraft may not necessarily appear on the air traffic controller’s display. My emphasis for over the past two decades has been on the low-altitude aspects of this unsatisfactory condition, where even an aircraft with a perfectly working transponder, that is properly replying to interrogations, can be invisible to the air traffic controller (learn more about my criticism of multiple radar data processing here).

I feel that the 9/11 Commission was not able to dig deep enough into the radar picture concerning AAL77, otherwise they wouldn’t have stated that there was “...poor primary coverage where American 77 was flying.” AAL77 was over southern Ohio at the time the transponder was disabled, and being approximately five-and-a-half miles high, there was considerable overlapping coverage from surrounding Air Route Surveillance Radar (ARSR) sites that do (or could) feed to Indianapolis ARTCC (ZID).

Those long-range radar sites, their distance and direction from AAL77 at the time the transponder was disabled, and a graphic depicting the relationship of AAL77’s return flight with respect to those individual ARSR sites, are available below. [A special thank you to Glen H Schulze <contact>, who provided the “picture is worth a thousand words” graphics.]

Thomas G. Lusch
June 10, 2010

Dec 2, 2010 update:

For the past year I had intentions to write, and submit for publication to the Journal of Air Traffic Control, an authoritative paper that called into question the displayed symbols of AAL77. Specifically, this paper would center on the fact that once AAL77’s transponder had been turned off, the SEARCH (i.e. primary radar return, aka “skin paint”) targets that represented AAL77 showed that there may be a latent error in the presentation software. I would call into question the algorithm that determines if the Center controller’s target symbol will be displayed as a STRONG radar return versus a WEAK radar return. This is important for a controller in being able to easily maintain radar contact (or spot) an aircraft when a transponder is not working properly. Finding the time to write that paper has been difficult. So, as my ATC career is about to be terminated (see my “about” section), I leave you with a copy of an email from me to the creator of (the no longer available) AAL77.COM web site. In my message (see Lusch2FarmerEmailDec2009.pdf), you will see that in my analysis of the NTAP data, I determined that over 2/3’s of the time, AAL77 was available on Washington Center displays as a weak primary target on its trip back to the Washington DC area. However, a Boeing 757 should have been displayed as a strong signal most of the time. But at least it was available on the Washington Center displays (unlike how it was invisible on the Indianapolis Center displays for an extended period of time). If you wish to review the data from which I made this determination, you may contact me, or John Farmer, and we’ll be happy to share this FOIA data.

Dec 12, 2010 update:

When I updated this page last June to include Glen Schulze’s graphical representations of AAL77’s return flight path in relation to seven long-range radar sites, I inadvertently left out an earlier analysis I had published. (I’m afraid I got preoccupied with dealing with ageism...see my “about” page for more on that.) The point of my earlier analysis was that there is considerable radar data that is available, but most of it goes unused. Of course, that’s been the whole point of my earlier papers and the reason why this web site exists. The problem is NOT radar...the problem is the processing of the radar data. That is what Will Meilander has been stating for decades (see this).

Here’s the file I inadvertently left out... Lusch_review_AAL77_radar_data_20090708.pdf. It exemplifies that there is considerable radar data that was not utilized in the display of AAL77. It also shows that AAL77 was detected as a SEARCH (aka “primary”, aka “skin paint”) target by, CLE (QDB), and QWO, not just QBE, directly after AAL77’s transponder was turned off.

P.S. Miles Kara, professional staff member of the Congressional Joint Inquiry and the 9-11 Commission, served on Team 8. He continues his interest. Learn more here.

May 7, 2012 update:

Back in 2009 I had written to the National Archives and Records Administration (NARA), and they replied (see 37 page reply NARA to Lusch 20090820.pdf). Of particular interest, from the notes titled “5/4/04 Interview with Chuck Thomas” (the radar controller that was working AAL77 at the time it disappeared), are two notes from page 19 of the pdf. “He knew there was a large area in HNN Sector that had no primary radar coverage.” and “This was not pointed out to him by management but rather was just common knowledge to him as a controller.” (see NARA2LuschPage19.pdf). At the very bottom of pdf page 24 we see the note “ZID has the same radar gaps today.” (see NARA2LuschPage24.pdf). In the “5/4/04 Interview with Dave Boone” (the ZID Air Traffic Manager during 9/11), we see the notes on the bottom of pdf page 33, “Gap in Radar: Did you know on 9/11 about blank space in primary radar coverage? Lynch radar site - There are probs...don’t display weather properly.” (see NARA2LuschPage33.pdf). And on the very last page (pdf 37), we see “Boone was aware of a gap in the radar but was never worried about not being able to see primary targets.” (see NARA2LuschPage37.pdf).

Thus, it appears that the Lynch, KY site (QRI) must’ve been the SEARCH (aka “primary,” aka “skin paint”) site that was adapted as “preferred” within the radar sort box that AAL77 was flying thru at the time the transponder was deactivated. And being as the radar data processing methods do not automatically “track” based on the primary targets (it tracks based upon transponder targets), whatever SEARCH site was adapted as “supplemental” didn’t matter whatsoever. Everything depended upon Lynch (QRI) working perfectly...and it hadn’t been...apparently for quite some time. It didn’t matter that 3 other long-range radars were adequately detecting AAL77 (QWO, QDB, & QBE), or that 3 other long-range radars (PIT, IND, & QRM) were most likely detecting AAL77 adequately. This tragedy emphasizes the importance of utilizing all radar data, especially the primary (aka “skin paint”) radar data, from all radars, all the time. Until multiple radar data processing can achieve that goal, we are making extremely poor use of the available radar data.

Dec 18, 2012 update:

In consideration of my May 7, 2012 update, wherein the 9/11 Commission Report footnote 142 states...

...the footnote would be more correct to state, “...the “preferred” radar (for SEARCH, aka “primary” returns) had poor primary coverage, and the FAA ATC software did not allow the display of primary radar data from the “secondary”, “tertiary,” and “quadrary” radars.

June 1, 2013 update:

Early this year I was contacted by journalist Paul Schreyer. Schreyer had many questions regarding the disappearance of AAL77. He recently published his paper “Radar Loss on 9/11.” My purpose in this update is to supplement Schreyer’s article, and thereby allow the reader to consider different possibilities. As opposed to wondering if there was some grand scheme to utilize a virtually unknown “radar gap,” consider the possibility of LATENT ERRORS becoming activated. Latent errors are basically shortcomings in technological systems. Combine LATENT ERRORS with NORMALIZATION OF DEVIANCE, and the result, in my opinion, are failures like we observed with the disappearance of AAL77 from the screens of Indianapolis Center controllers. In an effort to provide more insight into this, you may wish to read my replies to Schreyer in Lusch emails to Schreyer.pdf.

July 16, 2013 update:

In my email exchange with Paul Schreyer (see previous update), I wrote about how I’ve been missing the information that describes the precise adaptation of the radar sort boxes in the vicinity of AAL77’s turnaround/disappearance. Late last month I received a Power Point Presentation that was created by FAA’s Stephen Snyder (AOS-310) back in 2004. It provides the information I lacked. See 1 AWA 26 AAT AAL77 Brief V2.ppt. Inspired by that information, I have created my own presentation. See .

July 29, 2013 update:

I have updated the presentation I created on 7/16. See .

July 31, 2013 update:

In my recent presentation “Radar Sort Boxes in the area of American Airlines Flight 77 Turnaround/Disappearance” (dated July 16, 2013, updated July 29, 2013), I advise as to how the Lynch, KY Air Route Surveillance Radar (ARSR) had been operating in a substandard manner, for apparently quite some time. I deemed this a LATENT ERROR, and indicated that it was representative of “Normalization of Deviance,” as characterized by Diane Vaughan in her book “The Challenger Launch Decision: Risky Technology, Culture, and Deviance at NASA.” Follow this link to read a safety concern that was written about the Lynch, KY ARSR, well before 9/11.

Aug 4, 2013 update:

Yet another major update to my recently created presentation (up to v3.1 dated Aug 4, 2013). See . Also, I have long neglected to provide a link to John Farmer’s “Zoe’s Flight” web site. I so appreciate John’s extensive work on AAL77 over the past many years. Another very worthwhile site covering AAL77, which I just recently learned of, can be found here.

Aug 10, 2013 update:

I got some excellent feedback on my prior presentations, so I updated. Please see TomLusch.com analysis AAL77 RSB adaptation v4.0.pdf.

© 2013 by TomLusch.com. All rights reserved.