Tcas
 

On the Swiss/French UIR Border this morning I heard an a/c at around FL330 report a same level TCAS at 5 miles, the reply was we have nothing on radar, must be military, followed bt a long and fragmented exchange re filing an "Airprox", during which ATC offered to obtain data from other radar sites, the decision was not to file since separation was 5 miles, fine. Imagine my surprise when in the security of Maastricht airspace later in the day when an a/c reported trafic at the same level at 5 miles and the reply was...Nothing on radar it must be military!!

If these returns are genuine military a/c then this is not the right time for un co-ordinated traffic and if they are not then

"BEAM ME SCOTTY"

'Stealth' military one presumes.

That's pretty unnerving. As a controller, I'd be a little concerned if things were flying around my airspace that I couldn't see.

Best keep your eyes peeled up there:eek: !

A couple of years ago I was flying an A320 in french airspace and requested a 2000 ft step climb, which was granted. On this particular airbus TCAS returns only showed in 40nm range. Just before starting the climb I reduced map range to 40 miles to find two contacts at my cleared level just 3 miles ahead. On querying the controller, I was told that they must be military traffic and was not under his control!

Though MIL may not have TCAS aboard, especially TACAIR, boggles the mind there is no Mode S or Mode C.


Then again I boggle easily

stealth aircraft? I dunno... I guy i know whos in the US military told me that stealth aircraft have to have a radar reflective shield, so that they can be spotted by Radar during Peace time operation. I assume this also includes training exercises.

I dont know how true it is, but it makes sense.

The nothing on radar line sounds like a crock.

With no transponder the TCAS can't see the other aircraft. Ergo if the TCAS can see the intruder so can ground based radar......

Must be UFO's!

Just seen Men in Black II and it had aliens - and if it is on filum it MUST be true!

Unless the traffic is operating a Mode C transponder you will not get an altitude read out. If it's Mode C ATC would see it too.

Well, strange things do happen.. I can recall several instances of aircraft refusing to take my headings "due to traffic dead ahead", for example, with absolutely nothing showing on radar. Bizarre, but it really does happen. Equally, we sometimes see returns on our radar which certainly look like a/c... and against which we have taken avoiding action only to find that there was nothing there!

can't vouch for europe, but stealth, and all other military are APPARENTLY required to be squawking in commercial airspace, and do so...ala the united incident in cal where ual followed a tcas ra due to f-117 fighter in proximity

As to the military aircraft near you but not within the 5nm. If you are flying in controlled airspace, military aircraft will route around that airspace whilst operating in the open FIR or their restricted airspace.

As far as military aircraft not squawking. In the 16 years that I was in the game, we would have a Mode 3A and C return (plus a bunch of others that you can't see). The squawk would either be assigned by ATC, Fighter Control or be a standard conspicuity code. In the UK we always used to have those nice VFR slots through airways but still normally took a RIS. Even when we were transiting the open FIR we would normally make use of a RIS until we got to our play area.

My guess would be that ATC are feeding you a line coz guess what even if the yanks were flying their new super-invisibility hyper-sonic space spy speeder plane through your airspace they would have a radar reflector attached so that all players could see a primary return. Think about it from their point of view, they don't want you to know what they know about what you want to know about what you would really see on the radar as it flies by.
:confused:

Ghost

;) I absolutely agree on this. I was "playing the game" on F16 for 12 years as well and I can only make the same comment with maybe a little extra:
One should know that in many circumstances, Tatical controllers do not have a full picture like most area/terminal controllers have. The reason is simple, in some areas (surrounded by airways, sometimes even below and above) the amount of traffic is too large and clutters the picture. Their responsability is mainly to check participants do not leave the working area whilst CIVILIAN controllers will monitor if their traffic is not converging towards an unwillingly exiting from the zone traffic. When this happens all phones become red in the tactical room and the military pilot is urged to manoeuvre sharply towards the working area. This working method only works if a positive radar contact is mainained==> mode 3/C always used. PS: I never flew without mode 3/C, even for some missions over Bosnia/Kosovo...

On top of this, military aircraft have an on board radar and as soon as a CIVILIAN traffic is called, the fighter pilot will both try to acquire it on radar and avoid at the same time, increasing the safety given by ground controllers.

Re : 'Stealth & UFO'

Daventry Sector - Yesterday. FL240 (level capped)

TCAS target left wingtip - 1nm, solid diamond, indicating '00'
Followed us for about 10mins. altered Heading & Level with us.
Suddenly disappeared, no warnings !!

Is this a 'ghost' generated by TCAS ? if so how ?
Capt. PB care to comment ?

Seen this phenomonen before.

TCAS is not infallible.

Very wise remark fmgc...

as to the "UFOs," have you never heard of ( e.g. Air defence ) 2 digit familly codes being filtered out civil ATC systems.?
France does it, I know of at least 2 other countries doing it....

Here is what could have happened:
 

As stated above, it is true, that normally, if you get something on TCAS, it should be on ATCs radar as well. I can think of two instances where it is not so.

1. The aircrafts transponder is partly broken and so weak that the signal cannot reach the ATC radar 100 miles away, but can reach the other aircraft a few miles ahead.

More probable in this case though:

2. A low altitude aircraft has an altitude encoding problem (this is very common - have you never been told in low altitude something like "your mode charley indicates FL145, please switch to mode alpha"). If there is a low altitude aircraft 5 miles away from you, and his transponder by mistake indicates same FL as you are flying in, TCAS will always see his direction in azimuth, which is independent of altitude, and his mode charley will be used to tell altitude.

There you go, an aircraft way below you triggers your TCAS, and ATC doesn't see him if he is below radar range. Two minutes after he is "gone", because his altitude encoding indicates something else, that is away from the TCAS range.

Also, some bored person might find a transponder with altitude encoder and set it to a certain flight level, just to see if he can trigger some other aircrafts TCAS. Why ? There are idiots "down there" who gives false clearences for whatever reason !

Therefore, any such ghost TCAS instance should be reported with accurate position, FL, time etc, and if it is the same place, I would send someone out to search for a ground based TCAS transponder !!!

Ground PRIMARY radar performance depends on age and condition of ground equipment and range of A/C and A/C radar reflectivity.

Ground SECONDARY radar performance depends on age and condition of ground equipment and range and strength of A/C transponder transmission.

Not all radar heads have both primary and/or secondary radar and some primary displays are fed secondary info by landline from a differently located secondary radar site. To my knowledge this happens alot at rural/regional French airports.

So it is possible for an aircraft to be outside the performance criteria for the primary radar and if ground has no secondary it would be "invisible" for all modes of transponders setting, if switched on. Or that ATC centre might be receiving a secondary feed from a site not "transponding" with the target A/C.

With 2 airborne A/C in relative close proximity they have an ideal "line of sight" transponder environment. If the primary "invisible" contact has a weak transponder strength it may not show on the ground secondary receiver approaching the limit of the ground performance envelope.

And then of course there's the military. Rumour (and I stress rumour) has it that they can vary the strength of their transponder so as not to be visible to ground radars for training and excersice but still be a good "TCAS" rule observer.

One thing that I dont know, and perhaps someone out there can supply, is is military IFF compatible with civil TCAS? Because IFF is not the same system, to my knowlegde, it's more complex and more secure.

Can anyone tell me, is the upgrade to TCAS 7.0 a software change, or a box change? And is there any way to identify one's TCAS as being 7.0 without hearing the (slightly) different verbiage on the warnings?

Thanks in advance.

ShoreGuy,

6.04->7.0 should be a software update. According to the following FAA document, it can even be done in the field:

http://www.faa.gov/AVR/AFS/FSAW/FSW0102A.DOC

The document above also shows the difference in callouts. Another way to tell software version is if you get a "traffic" TA between FL 310 and 420. Version 6.04 will give you one, 7.0 will not (RVSM).

TCAS I = TA only
TCAS II = TA/RA
TCAS III = TCAS II with azimuth advisories

Regarding TCAS III, it is not yet implemented. TCAS II only gives pitch advisory/resolutions, whereas TCAS III also can give azimuth (turning) advisories.

ADS-B and GPS-squitter are some of the terms used in the development of a system, where a GPS is added to the collosion avoidance system. This will allow especially smaller aircraft to "participate" in TCAS, as it is a lot cheaper, more precise and less space and weight consuming.

The major problem here is agreeing on a standard, because as usually there is a faster and cheaper way, and then there is a more expensive and slower path to follow, but the latter being more capable.

Read more about ADS-B, TCAS and GPS squitter implementation:

http://www.faa.gov/and/and300/datalink/navsur/gps.htm

http://www.faa.gov/and/and300/datalink/navsur/cdti1.htm

http://web.mit.edu/6.933/www/Fall200...ouilhet2a.html

http://web.mit.edu/6.933/www/Fall2000/mode-s/links.html

http://www.honeywelltcas.com/faq/whi...ointpaper.html

TCAS history/background: http://www.caasd.org/proj/tcas/

Most important,

I would still say we should take it very serious as to find out whether certain screwd individuals are setting up transponders on the ground and faking the mode charley to reply with FLXXX returns, so any aircraft crossing that FL will get a TA or RA - which ATC will not see.

Just a small correction.
For the FAA and the Mitre corporation ( designers of the software ) version 7.0 will be last one. This was announced
TCAS III was abandonned about 4 years ago and its replacement TCAS 2000 was also scrapped.