Anti-collision mechanism

On Sun, 2 Jan 2005 11:31:26 -0600, "Marty"
wrote in ::


"Larry Dighera" wrote in message
.. .

Here's the MAC that lead to mandatory TCAS:
http://www.ntsb.gov/NTSB/brief.asp?e...13X34444&key=2


Correct Larry,

The thing that gets me is that this collision would still have happened
because,

"N4891F'S X-PONDER WASN'T DISPLAYED DUE TO EQUIP CONFIGURATION."

IOW, stand-by mode.


That's not the way I read the NTSB report. Here's the pertinent part:

INV REVEALED N4891F HAD INADVERTENTLY ENTERED THE LAX TERMINAL
CONTROL AREA (TCA) & WASN'T IN RADIO CONTACT WITH ATC. LAX TRACON
WASN'T EQUIPPED WITH AN AUTO CONFLICT ALERT SYS & THE ANALOG
BEACON RESPONSE FM N4891F'S X-PONDER WASN'T DISPLAYED DUE TO EQUIP
CONFIGURATION. N4891F'S PSN WAS DISPLAYED BY AN ALPHANUMERIC
TRIANGLE, BUT THE PRIMARY TARGET WASN'T DISPLAYED DUE TO AN
ATMOSPHERIC INVERSION

What I infer from this is, that the controller's display wasn't
configured to display the Piper's transponder at the time of the
collision. That would imply that the controller reconfigured his
display between the time he noted the Piper squawking 1200 and the
time of the MAC.

As there is no mention of the Piper's altitude, I would assume it
wasn't squawking Mode C. That would be required for proper TCAS
operation if I'm not mistaken. So, I agree with your conclusion, but
for other reasons.

It would seem that the air traffic controller descended the airliner
into the path of the Piper whose alleged position at the time of the
MAC was inside the Terminal Control Area contrary to regulations,
without radio contact with ATC.

So it would appear that the NTSB found enough blame for everyone
involved, the airline PIC, the Piper PIC, the FAA, the ATC controller,
and even "OTHER/ORGANIZATION". If the Piper was eastbound and the
airliner northbound, the Piper PIC may have deviated from regulations
by failing to yield the right-of-way also.

Despite the failure of the pilots to see each other in time to alter
course, and the Pipe PIC's possible incursion into TCA airspace, it
_feels_ like the controller was in the best position to prevent this
tragedy due to the Piper's position being displayed by an
"alphanumeric triangle" on the controller's scope. I fail to
understand why the lack of display of the Piper's primary target was
significant. I know that today LAX controllers' workload can be
overwhelming at morning and evening traffic peaks during IMC. But, in
VMC just before noon, one would think the controller might have been
aware of the possible conflict.



(There's a summary he http://www.ntsb.gov/publictn/1987/AAR8707.htm
)