Did AA 77 loose radar contact?

[FannySS]

Hi,

arround 8:56 a.m. American Airlines Flight 77 transponder signal stops. So the "secundary radar" did not work any more. As far as I understand, the "primary radar" (= passive radar) could still work, couldn´t it?

But somewhere I heard that there are "holes" in this primary radar, that means not the complete US-territory is covered with primary radar.

Am I right?

That would explain the following:

9:05 a.m.: West Virginia flight control notices a new eastbound plane entering their radar with no radio contact and no transponder identification. They are not sure if it is American Airlines Flight 77. http://standdown.net/index.htm

So my question: Did AA 77 totally loose radar contact at any time?

Thanks a lot,

Fanny

Edit: see also this report: http://www.washingtonpost.com/ac2/wp-dyn/A32597-2001Nov2?language=printer

[ladjf]

1. An airplane at altitude will continue to be visible to primary

radar but will lack certain unique pieces of data that identify the aircraft such as flight#, altitude and other information in the flight plan.

[FannySS]

3. This is not sure, see message # 2 (nt)

[FannySS]

2. And this

And this (dis?)info:

But for eight minutes and 13 seconds, between 8:56 a.m. and 9:05 a.m., this primary radar information on American 77 was not displayed to controllers at Indianapolis Center. 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. http://www.usatoday.com/news/sept11/2004-06-17-panel-summaries_x.htm

Is it possible, that the terrorists made their turn to the east on purpose in a territory not covered by primary radar?

Fanny

[John Doe II]

7. What looks logically

Is it possible, that the terrorists made their turn to the east on purpose in a territory not covered by primary radar?

This looks logical to ask but:

Why would the hijackers risk that they still have to fly 32 minutes after 9:05, before hitting their target?

It's already quite a mystery why the air defence didn't work for the pentagon (the CR is of no help neither) but to assume that the hijackers flew from Washington DC till they arrived in an area where they would be invisbile even for primary radar (only for the sake of being invisble) and then accept the risk to stay 32 minutes still in the air is not very convincing for me.

And keep in mind:
After the transponder was switched off nobody knew what flight it was that flew in the direction of Washington.

And very bizarre:
How could all the television channels and even a manager of American Airlines believe it was AA 77 that hit the WTC at 9:03. This is physically impossible given its position at 8:56
Look: Thread: Flight 175: quite a mysterious plane.

So, to answer your question: Even if it looks logical at the first glance that the hijacker knew about the radar coverage of the area I find it rather strange the
at they ran this risk (what for??) if they still had to fly for 32 minutes while being seen on primary radar??

And in any case: Why didn't they make a U-turn early after their take off from Dulles airport. This seems much more logical to me!

[FannySS]

9. I am not sure

Why would the hijackers risk that they still have to fly 32 minutes after 9:05, before hitting their target?

Serious argument. I do not no an answer.

Just speculating:

1) May be it has something to do that flight 77 was late? Do I remember right that it had a 20-minute delay? Because of that they could have thought: "Now it´s too dangerous, the towers are already hit a long time ago, if we take over the plane now they will find out easily. So let´s wait, until we are in the "radar gap". Then we can confuse them..."

2) Or may be they just didn´t had another possibility; they didn´t manage to "roll" the cabin, may be because everybody had to keep the seat belts fasten? (Because of turbulences or whatever).

Well, just speculating. You are right that this is strange.

Fanny

[Old and In the Way]

13. I think it was 93 that was delayed 20 minutes on the tarmac

That bump in 77's flight path looks like some kind of holding/delaying pattern awaiting 93's arrival.

[FannySS]

14. AA 77 had 10 min delay (nt)

[John Doe II]

17. Your speculation

Your speculation already implies that it was not an intended plan of the hijackers to switch off the transponder in this area.
To your explanation why they waited so long:
It's very hard to see for me how the hijackers could possibly have assumed that because they are 11 minutes late it would be clever to wate even longer before attacking in order to confuse the air defence (keep in mind that as they tooko off form Washington DC that for every minute they waited they not lost two minutes as they had to go back to Washington). It's very hard to see because certainly one would expect that the air defence would take every threat after 9:03 very very seriously and not hesitate any more as they might have before 8:46. So, why take the risk.
Your second explanation: This is even harder to believe as the hijackers certainly didn't very much care for any fasten your seat belt signs. I agree that they had to wait till the plane had reached a certain hight but this was certainly reached BEFORE 8:56.

And strangely AA 77 was not the only flight with an illogical flight path. Look at AA 11 and UA 175: both didn't fly directly to their target after they had been hijacked and UA 93 certainly didn't fly directly to Washington DC neither. So, in the view of reducing the risk what did the hijackers do??

[tngledwebb]

8. They are crafty, those ME youth.

Smarter and more evil than the Commies or the Krauts or the Japs. Probably because of their faith in Allah, tho I think they had fiends in other hi places.

[RH]

10. Flight 77 was covered by primary radar

Primary radar and the display seen by an ATC are not the same thing.

This was all explained in postings from Mercutio on previous DU threads.

[FannySS]

12. Thank you, RH, but ...

... all this is just quite confusing, even after reading Mercutios postings here;) http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=125x12865

I found this in the Washington Post:

But the radar installation near Parkersburg, W. Va., was built with only secondary radar -- called "beacon-only" radar. That left the controller monitoring Flight 77 at the Indianapolis center blind when the hijackers apparently switched off the aircraft's transponder, sources said.

(...)
Sources said the location of the hijacking is likely just a coincidence, although there is a remote possibility that the hijackers knew where to turn off the transponder.
There are a number of locations across the interior of the United States that operate solely with secondary radars.

And this is propably what you are pointing out:

When they reconstructed Flight 77's path, investigators determined that it was picked up by some distant radars, but none that were available to the Indianapolis controller, FAA officials said.
http://www.washingtonpost.com/ac2/wp-dyn?pagename=article&node=&contentId=A32597-2001Nov2

But anyway, RH, may I ask you for your personal opinion regarding the Air Defense: which scenario and which explanation of this "failure" do you have, or which scenario do you think is compatible with Ockams Razor? (I also would be thankful for a statemant of MercutioATC...)

Thanks a lot, Fanny

[RH]

15. Seems pretty clear to me.

As I understand it, Flight 77 when it was "lost", was seen by distant primary radar stations but those signals were not feeding into the actual ATC computer system in use at the time.

To whatever extent that they were recorded the extra primary sytems were nevertheless be available in retrospect.

In this context "Beacon" or "secondary" appears to be synonymous with "transponder".

[pa28]

4. Maybe they call passive coverage "primary"

but really air traffic control, especially commercial, works on transponder returns. The difference is specific assigned transponder codes can be passed from controller to controller easily and they also contain information about the altitude of the aircraft.

When the transponder along with two-way radio contact was shut off there was no reliable way to track the aircraft. Controllers are an insightful bunch and the one involved probably suspected problems ranging from electrical failure to accident.

So, I believe you are correct. The aircraft could have entered the airspace serviced by W. Virginia control as an unannounced radar target. The WV controller would have had no way of knowing a new aircraft was coming into his airspace unless the previous controller had handed the active transponder code to him.

[ladjf]

5. They should be able to "see" the target but not be able to

identify without radio contact. I'm not familiar enough with the latest FAA radar images that are actually shown to the controllers. It's possible that the computer might ignore targets with no transponder signal.

[RH]

11. The cumputer displays

a best guess interpretion not necessarily derived from just one radar source, because radar areas overlap.

[Woody Box]

6. The plane disappeared completely

as opposed to the other planes which continued to send primary radar signals, the blip supposed to be flight 77 vanished, and the Indianapolis controllers had no clue where it was.

Take this here with a grain of salt:

9:05 a.m.: West Virginia flight control notices a new eastbound plane entering their radar with no radio contact and no transponder identification. They are not sure if it is American Airlines Flight 77.

Who is "West Virginia flight control"? There is no long-range Air Traffic Control Center in West Virginia, so I have my doubts if this "eastbound plane" emerging at 9:05 really existed.

[MercutioATC]

16. An ATC response to these questions:

I'm not going to respond to these posts individually unless specifically asked to. I'll try to answer the questions posed so far...

1) Correct. There's no "West Virginia Control". West Virginia is serviced by Cleveland Center and Indianapolis Center.

2) The representations of primary and secondary radar presented so far have, for the most part, been accurate.

Primary radar sends out a signal the bounces off airborne objects and returns to the radar site. It can't identify WHAT it's "seeing", it just "sees" anything that will return a signal (mostly planes, but also the occasional densely-clustered flock of birds or bunch of runaway mylar party balloons). It doesn't identify the target or pravode altitude data, just a top-down location.

Secondary radar recieves transponder data (ID for the flight) and Mode C data (altitude encoding).

3) Center radar operates on a mosaic system (approach radar data is from one radar site). In a mosaic system, data from multiple radar sites is evaluated by the HOST computer. Occasionally, sites send slightly different data and it's the conputer's job to decide which data to use.

4) Primary radar sites are costly to maintain. Years ago, the FAA decided to decomission primary radar to save money. The controllers' union, NATCA, stopped the decomissioning, but sites that had alreadt been decomissioned were not returned to serviice. Most of these sites were in the western U.S., but parts on Indianapolis Center are without primary radar coverage.

Feel free to ask any other questions. I'll try to provide answers.