Tcas

[PushingTin111]

Are there any pilots out there who might be able to answer me this question?

I am an Air Traffic Controller and would like to know if TCAS can be completely disabled on the B737-800 series?

I do not know a whole lot about TCAS, only the basics. I would like to know that if you get a TA (Traffic Alert), is it mandatory for the pilots to tell ATC? Secondly, if an RA (Resolution Advisory) is subsequently issued, must the pilots follow the RA regardless of the instructions given by ATC? (Due regard for the incident in Germany!)

Would any pilots be able to explain TCAS II and it's functions more accurately, ie. when and what time before possible collision are TA's and RA's issued?

Thank You.

[savechip55]

If it is any help, our rules at LATCC state that if a pilot is responding to a RA then he/she will follow that and not ATC instructions. You as a controller therefore, just have to inform any other ATC agencies this might affect, as you obviously wont be able to carry out any co-ordination whilst the RA is happening.

Any help???
regards. :)

[PushingTin111]

Thanks savechip55. :ok:

Wonder is that an international rule?

[604guy]

Our training on this side of the pond is that crews will follow an RA, advise ATC that they are doing that but the action is already in progress by then. The folks on your side of the mike are keeping others out of the way at that point.

I can't offer any concrete answer re 737-800 or any other series 37 for that matter.

[Thunderbug]

PushingTin111

Hi, I'm not a 737 pilot, but the 747 / 757 / 767 that I have flown have a selector on the transponder panel that controls the TCAS functions.

STBY - Off , No Transponder nor TCAS function
TXDR - Transponder and some Mode S functions - No TCAS
TA Only - Transponder & TCAS, but whilst you get Traffic alerts and traffic displays, you get no resolution advisory. The clever bit is that TCAS tells other TCAS units that you cannot manouever and so they calculate on resolving the situation on their own. We use this setting when we have an engine failure and have less performance to enable aerobatic avoidance manouevers. It is also the automatic default below 1000'AAL.
RA/TA - All Transponder & TCAS operation

So to answer your question - I reckon a 737-800 can inhibit its TCAS - Not a good idea, but can be done.

If you get a TA - you don't have to tell anyone. In fact if you get a RA that does NOT require manouevering or a change from your clearance (e.g. MONITOR VERTICAL SPEED) you don't have to tell anyone either - although you might want to discuss how the situation arose.

Always, Always, Always, No excuses, follow TCAS. Southern Germany (and a very near miss in Japan) shows the dire consequenses of one aircraft following TCAS and the other not. It is not an international rule, except that the training package that comes when you buy a TCAS set will stress the importance of following the RA. Some countries though had exemptions that allowed pilots to manouver against TCAS if they were visual. That led to the Japan incident.

The technical bit....... Do an internet search for more comprehensive description!

TCAS II works by calculating the closest point at which the aircraft will pass. If it calculates that this point will infringe the protection envelope within 30-40 seconds. It gives the heads up warning "Traffic, Traffic" and the traffic display changes the intruders symbol from a white diamond to a yellow circle.

If the intruder is going to conflict within 15-20 seconds, you get the intruder displayed as a red box, a voice says "Climb, Climb (or descend, descend)" and your Primary Flying Display or VSI will display the manouever required to achieve the avoidance. It both aircraft are TCAS equiped, the manouver is co-ordinated, with one aircraft climbing,the other descending.

Note that the manouvers are all in the vertical plane as horizontal resolution is not accurate enough to calculate avoidance manouvers. Note also that the warning is done on time to conflict, therefore a "head to head" encounter will get a warning a number of miles out, but an approch from behind, could get quite close before a warning occurs. It is very clever and can resolve conflicts between several aircraft all at the same time.

Clear as mud......:ok:

T'Bug

[PushingTin111]

Many, many thanks T'Bug. That was everything I was lookin for.

More or less answers my questions. I'll do a little bit of searching on the net for related issues.

Oh, by the way, does anyone know where I could find info orreports on AIRPROX's around the world? I'm kinda interested in this area and the whole reason why AIRPROX's occur and ways to avoid them. I looked at the UKAB site but I can't seem to download the reports.

Thanks for the help again.

Regards.....

PushingTin111:ok:

[Thunderbug]

PushingTin111

Try This (http://aviation-safety.net/events/midair/links.html)

T'Bug ;)

[PushingTin111]

Cheers Man!

That just about does it.:cool: