Anti-collision mechanism

Bob Noel wrote:

1) Reaction times are less of an issue with TCAS because normally
the system will advise the crew of traffic (called a traffic advisory
or TA)
when the conflicting aircraft is (iirc) 40 seconds out. This allows
the
crew to begin scanning for the potential conflict.

You know I'm not an aviator, but 40 secs don't appear that much. A few
secs to initially notice a warning and a few more till it properly
registers would take away much of the 40 secs. Moreover, the pilots
could easily be doing other things at the time - a loo break, chatting
up passengers while on autopilot, munching a snack, even flirting with
a hostess (hope I don't get flamed for suggesting that )...

If it isn't automatic, I think the TCAS should be. For sure.

you have far more faith in automation than I.

and why is it that you don't have faith in automation, Bob? Not having
to use brains, and doing something by rote instead, isn't necessarily a
disadvantage always. The chances of a well-programmed software
consistently doing a collision avoidance routine correctly are better
than two pilots doing so, I'd imagine.

Ramapriya

Ramapriya wrote:
Don Hammer wrote:

On 1 Jan 2005 15:17:49 -0800, "george" wrotD:

Also, since TCAS has been mandated, there has been only one mid-air
with equipped aircraft and it was because one crew ignored the
warning. (UPS and Aeroflot in Switzerland)


????? You mean the TCAS only gives a warning, with the pilots having a
say on whether or not to take action?? I was under the impression that
the TCAS sytems talk to each other and take automatic action to avoid a
collision!!

To leave it to the pilots doesn't appear to be too much of an
advantage, with a relative speed of two planes being about 1000 mph
towards each other. Also, given the small reaction time, there's also a
chance, howsoever small, that the pilots could both take action that'll
precipitate a collision instead of avoiding one; both diving, for
example.

If it isn't automatic, I think the TCAS should be. For sure.

20+ years ago I knew one of the early developers of TCAS. She told me
about some of the attempts at conflict resolution. For example, they
started off with a rule that said if two planes were heading directly at
each other, "pass with the other plane on the right". Fortunately,
they did simulations: the result is the colliding planes form a
decreasing-radius spiral about each other, always with the other plane
on the right.

20+ years ago I knew one of the early developers of TCAS. She told me
about some of the attempts at conflict resolution. For example, they
started off with a rule that said if two planes were heading directly at
each other, "pass with the other plane on the right". Fortunately,
they did simulations: the result is the colliding planes form a
decreasing-radius spiral about each other, always with the other plane
on the right.


TCAS II will only give a climb or descend command along with the rate
( shown as a line on the ROC) needed. If both have Mode S (required
if you have TCAS) then the two transponders will talk to each other
and figure out who will climb and who will descend and command the
crew to do it. If one is Mode C then the software decides if a climb
or decent would be appropriate.

TCAS I gives advisories only.

http://www.rannoch.com/tcasf.html
http://www.aerowinx.de/html/tcas.html

Some info


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