Vulcan 607 and transponder switch off support RC theory

[scienceplease 2]

On the assumption of the 9/11 "remote controlled planes scenario", on the basis of my own experience and research, the the fact that the hijacked aircraft transponders being switched off would be critical to the aircraft being remote controlled.

The transponders allowed the aircraft to be viewed easily by the FAA and switching them off makes them less visible to civil authorities.

However the opposite would be true for military radar! Switching off the transponders would allow the hijacked aircraft to be more visible since radar operators can filter the radar display to remove all civilian aircraft, leaving only the "unidentified" aircraft on the display.

The success of US military to intercept unidentified aircraft can be viewed in the book "Vulcan 607" by Roland White. In 1960, the RAF engaged in an exercise where Vulcans, our V-bombers, attempted to penetrate US airspace. The Vulcans were extremely difficult to detect on radar: relatively small, with few sharp edges and moving quickly, just below the speed of sound. In other words they were "Stealthy". The first exercise demonstrated just how easily the V-bombers could get through the US air defences. Of the 3 aircraft in the trial all three made it to NY and, if so armed, could have nuked the city. Throughout the 1960s, these tests were repeated and each year one or more Vulcans got through. This was not the case in later years as US defences improved.

All this means that:

a) US Defence forces could detect unidentified aircraft entering and flying over US airspace
b) E4B (the white "mystery" plane seen on 9/11) and AWACS could provide a radar picture over continental USA, separate from FAA and indeed other military establishments' radar pictures
c) Switching off the hijacked aircraft's transponders would make the aircraft easier to identify on a military radar picture by filtering the radar picture and reducing "information overload".

These facts support the theory that the hijacked aircraft on 9/11 were remote controlled.

[TonyGosling]

Journal of 9/11 Studies
Volume 41, May 2017
Implications of September 11 Flight Transponder Activity
Aidan Monaghan B.Sc. EET
http://www.journalof911studies.com/implications-of-september-11-flight -transponder-activity/

Abstract
It has been the consensus of informed observers that the loss or alteration of Secondary
Surveillance Radar (SSR) information for the four September 11 flights was caused by
accused hijackers allegedly seizing control of the aircraft flight decks and manually
turning off or adjusting each plane’s Mode S (Mode Select) transponder. This was
presumably for the purpose of evading detection and interception by U.S. air defense
systems. However, this view appears to be based only on circumstantial information -
the simple loss or change of SSR flight data to Air Traffic Control (ATC) – and seems
unsupported by conclusive facts. Following these transponder operation changes, ATC
was still able to tag and track the primary radar returns of three flights and estimate
their locations, directions, ground speeds, and even altitude changes.

Introduction
Perhaps the most significant consequence of lost September 11 flight SSR data to ATC
was a circumstantial impression of accused hijacker flight deck takeovers. As can be
shown, aircraft Mode S transponder SSR information can be caused to vanish from ATC
radar displays by other documented means. Coincidentally or not, the only September 11
flight with a continuously operative transponder (United 175) was also the only flight
with a transponder able to warn away commercial flights in serious danger of collision
thus facilitating its subsequent impact with World Trade Center 2 (WTC 2). This
capability was enabled by its Mode S transponder dependent Traffic Collision Avoidance
System (TCAS). The TCAS feature warns aircraft flight crews of mid-air collision risks
posed by similarly equipped nearby aircraft.

From the Federal Aviation Administration (FAA):
The secondary radar uses a second radar antenna attached to the top of the primary
radar antenna to transmit and receive area aircraft data for barometric altitude,
identification code, and emergency conditions. Military, commercial, and some general
aviation aircraft have transponders that automatically respond to a signal from the
secondary radar by reporting an identification code and altitude ... The primary
surveillance radar uses a continually rotating antenna mounted on a tower to transmit
electromagnetic waves that reflect, or backscatter, from the surface of aircraft up to 60
miles from the radar. 1
The four September 11 flights reportedly contained what are known as Mode S
transponders:
The Mode S transponders aboard Boeing 767 and 757 aircraft, such as those used on
9/11 as "flying bombs," deliver aircraft identification and altitude and can supplement
FAA’s radar by "providing ATC and traffic alert collision avoidance system (TCAS)-
equipped aircraft the ability to determine position and heading information," according
to DoT. 2


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Volume 41, May 2017

Mode S transponders transmit information about the aircraft to the Secondary
Surveillance Radar (SSR) system, TCAS receivers on board aircraft ... This information
includes the call sign of the aircraft and/or the transponder's permanent ICAO 24-bit
address in the form of a hex code. 3
Just prior to year 2000, a major modernization of the FAA’s entire Air Route Traffic
Control Center computer system in the continental United States was scheduled to be
completed.
From the FAA:
The computers receive, process, coordinate, distribute, and track information on aircraft
movement throughout the nation's airspace that includes oceanic international air
traffic. The computers provide data interfaces to all types of FAA facilities ... and the
military. 4
In the case of UA 175, although its transponder-broadcasted flight ID number reportedly
changed several times following its alleged hijacking, the transponder itself continued to
transmit unlike the other three flights, making it known to the TCAS of nearby aircraft.
Of the four wayward September 11 flights, only UA 175 experienced serious near mid-air
collisions with other non-wayward commercial flights. These were Delta Flight 2315, US
Airways Flight 542 and Midwest Airlines Flight 7 5 .
Again, UA 175 was the only September 11 flight with a transponder that continued to
operate following its unauthorized course change, helping it avoid at least one mid-air
collision with another TCAS equipped flight and thus facilitating its own impact with
WTC 2.

Referring to UA 175 and US Airways Flight 542:
Shortly after that, the hijacked plane was headed straight for a US Airways flight. The
US Airways plane's collision-avoidance system detected the approaching plane and
advised the US Airways pilot to descend, which he did, averting a collision. 6
Delta Flight 2315 and US Airways Flight 542 were TCAS compatible Boeing 737s.
Midwest Airlines Flight 7 was a TCAS compatible DC-9. The role played by TCAS
during UA 175's conflicts with the Delta and Midwest flights is unclear.
Interestingly, the FAA's "Host" ATC computer system provided an ability to anticipate
route conflicts like those experienced between UA 175 and Delta 2315, US Airways 542
and Midwest 7, based on filed aircraft flight plans:
HCS is the key information processing system in FAA’s en route environment. It
processes radar surveillance data, processes flight plans, links filed flight plans with
actual aircraft flight tracks, provides alerts of projected aircraft separation violations
(i.e., conflicts). 7


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Journal of 9/11 Studies
Volume 41, May 2017
UA 175’s transponder was reportedly unique to at least the United Airlines fleet, but
could nevertheless be turned off. Interestingly, much of the source document containing
this fact regarding September 11 flight transponders was redacted.
An Air Traffic Control supervisor at New York Center opined that the transponder on
United 175 was a newer model peculiar to the United-operated B767 fleet that could not
be turned off. That was the supervisor's possible explanation of why the transponder on
United 175 changed code as opposed to being turned off. A senior pilot from both
United and American Airlines, familiar with cockpit details, each separately
demonstrated how transponders were manipulated in the cockpit and conclusively
demonstrated that the transponder in United 175 could have easily been turned off. 8
According to a safety bulletin published by the International Civil Aviation Authority
(ICAO), a given Mode S transponder broadcast can be suppressed or “jammed” by
another transponder broadcasting via an ICAO 24-bit aircraft address identical to the one
already assigned to the given aircraft, causing the given aircraft’s SSR flight information
to disappear from ATC radar displays, not unlike the disappearance of SSR information
for all but one of the September 11 flights. The same circumstances can also cause a
given aircraft’s transponder to become invisible to the TCAS systems of other aircraft.
When two (or more) aircraft with the same (duplicate) ICAO 24-bit aircraft address are
operating within range of a specific Mode S interrogator, then potentially hazardous
situations can arise: One (or more) of the aircraft involved may be assessed by the
Mode S interrogator to be a false or reflected echo, and subsequently ignored. These
aircraft will not then be displayed to air traffic controllers. 9
To date, only military aircraft seem to be capable of mid-flight changes of the 24-bit
aircraft address that is contained within its Mode S transponder broadcasts:
Military use of 24-bit aircraft addresses: The relatively large number of aircraft
addresses for military use allows rotating the assignments of 24-bit addresses on
military aircraft on a frequent basis. This rotation of 24-bit addresses however must not
be done during flight. SSR Mode S Interrogators & Radar trackers: The uniqueness
property of the 24-bit aircraft address is important for the unambiguous identification of
the aircraft. Effects of duplicate addresses are unpredictable. This can cause
synchronous garbling, radar track swapping or dropping. 10
Interestingly, just prior to the September 11 attacks, French aviation authorities
investigated unexplained transponder signal jamming that caused ATC SSR returns of
commercial Boeing 767s to drop from radar screens.
During the month of October 2000, Roissy Charles de Gaulle International Airport
approach controllers reported several incidents of temporary label loss and multi-
secondary surveillance radar track loss on their screens ... the presence of a jamming
device was soon suspected ... the disappearances could happen at any time ... the
phenomenon suddenly reappeared between the 21st and the 26th March 2001 and then
again between the 13th and the 26th April 2001 ... in late March 2001 Air France
pilots, flying B767s equipped with new transponders, reported many TCAS warnings in
the Roissy Charles De Gaulle Airport area ... during the label losses, only the primary


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Journal of 9/11 Studies
Volume 41, May 2017
radar information remained displayed on the screen ... the first incidents appeared in
Creil area, Creil being the site of a military base. So this installation was suspected
because wide spread military exercises had been in preparation. 11
Yet despite September 11 flight transponder signal losses, ATC was still able to track
these flights (just as with the afore mentioned flights in France a year earlier),
complicating official assumptions that September 11 flight transponders were manually
turned off by hijackers to evade detection and interception by U.S. air defenses.
Regarding ATC coverage of American Airlines flight 77 on September 11, 2001:
The radar track is untagged, so he attaches a data box to it with the word “LOOK” in it.
This will allow other controllers to quickly spot the aircraft. It also causes its ground
speed to appear on the screen. 12

Conclusion
All references to deactivated September 11 flight transponders within the 9/11
Commission Report infer that the losses of SSR ATC data were due to hypothesized
manual transponder deactivation by accused hijackers following the alleged seizures of
the respective flight decks.
At 8:54, the aircraft deviated from its assigned course, turning south. Two minutes later
the transponder was turned off and even primary radar contact with the aircraft was
lost. 13
On 9/11, the terrorists turned off the transponders on three of the four hijacked aircraft.
With its transponder off, it is possible, though more difficult, to track an aircraft by its
primary radar returns. But unlike transponder data, primary radar returns do not show
the aircraft's identity and altitude. Controllers at centers rely so heavily on transponder
signals that they usually do not display primary radar returns on their radar scopes. But
they can change the configuration of their scopes so they can see primary radar returns.
They did this on 9/11 when the transponder signals for three of the aircraft disappeared.
14
At 8:21, American 11 turned off its transponder, immediately degrading the
information available about the aircraft. The controller told his supervisor that he
thought something was seriously wrong with the plane, although neither suspected a
hijacking. The supervisor instructed the controller to follow standard procedures for
handling a "no radio" aircraft. 15
Because the hijackers had turned off the plane's transponder, NEADS personnel spent
the next minutes searching their radar scopes for the primary radar return. American 11
struck the North Tower at 8:46. 16
At 8:51, the controller noticed the transponder change from United 175 and tried to
contact the aircraft. There was no response. 17


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Journal of 9/11 Studies
Volume 41, May 2017
The failure to find a primary radar return for American 77 led us to investigate this
issue further. Radar reconstructions performed after 9/11 reveal that FAA radar
equipment tracked the flight from the moment its transponder was turned off at 8:56. 18
On American 11, the transponder signal was turned off at 8:21; on United 175, the code
was changed at 8:47; on American 77, the signal was turned off at 8:56; and on United
93, the signal was turned off
at 9:41. 19
However, these references do not support the contention that September 11 flight
transponders were manually turned off by hijackers and no additional evidence has been
provided. Despite the reported losses of September 11 flight transponder signal, ATC
should have been able to track the flights.


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Journal of 9/11 Studies
Volume 41, May 2017


References:
[1] Airport Surveillance Radar
http://www.faa.gov/air_traffic/technology/asr-11/
[2] The Post 9/11 Transponder
http://www.aviationtoday.com/av/issue/feature/12731.html
[3] Aviation Transponder Interrogation Modes
http://en.wikipedia.org/wiki/Mode_S#Mode_S
[4] Fact Sheet – Host and Oceanic Computer System Replacement (HOCSR) Program
http://www.faa.gov/news/fact_sheets/news_story.cfm?newsId=4950
[5] September 11, 2001: Flight 175 Nearly Collides with Two Other Planes
http://www.historycommons.org/context.jsp?item=a855nearcollision#a855n earcollision
[6] A Sky Filled With Chaos, Uncertainty and True Heroism
http://www.washingtonpost.com/ac2/wp-
dyn?pagename=article&node=nation/specials/attacked&contentId=A41095-20 01Sep16
[7] Air Traffic Control: FAA Plans to Replace Its Host Commuter System
http://archive.gao.gov/paprpdf2/160369.pdf
[8] COMMISSION SENSITIVE UNCLASSIFIED MEMORANDUM FOR THE RECORD:
Interviews of United Airlines and American Airlines Personnel
http://media.nara.gov/9-11/MFR/t-0148-911MFR-01098.pdf
[9] Mode S Transponder – Incorrect Setting of ICAO 24-Bit Aircraft Address
http://ad.easa.europa.eu/ad/2011-14
[10] Mode S - Assignment of 24-bit Aircraft Addresses to State Aircraft
http://www.eurocontrol.int/mil/public/standard_page/cns_sur_modes_24bA A.html
[11]Transponder Jamming
http://www.icasc.co/sites/faa/uploads/documents/resources/12th_int_fli ght_inspection_symposiu
m/Transponder_Jamming.doc
[12] Reagan Airport Controllers Notified of Unidentified Aircraft Approaching Washington
http://www.historycommons.org/context.jsp?item=a933reaganwarned#a933re aganwarned
[13] The 9/11 Commission Report, Page 9
http://www.9-11commission.gov/report/911Report.
[14] The 9/11 Commission Report, Page 16
http://www.9-11commission.gov/report/911Report.pdf
[15] The 9/11 Commission Report, Page 18
http://www.9-11commission.gov/report/911Report.pdf
[16] The 9/11 Commission Report, Page 20
http://www.9-11commission.gov/report/911Report.pdf
[17] The 9/11 Commission Report, Page 21
http://www.9-11commission.gov/report/911Report.pdf
[18] The 9/11 Commission Report, Page 25
http://www.9-11commission.gov/report/911Report.pdf
[19] The 9/11 Commission Report, Page 454
http://www.9-11commission.gov/report/911Report.pdf