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
)

In article . com,
"Ramapriya" wrote:

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?

because I've seen how avionics software systems are developed

because I've seen the state-of-the-art wrt safety-critical software.

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.

1) the chances of actually having that "well-programmed" software
is pretty

2) I suggest you check out the accuracy of the TCAS II system wrt
azimuth for conflicting traffic. I'm just a software guy, but my hardware
guys tell me that the 4 element (4 pole?) antenna used doesn't give
an azimuth accuracy of even +/- 15 degrees.

--
Bob Noel
looking for a sig the lawyers will like

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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"AnthonyQ" wrote in message It does not give any terrain warning.

In the US, starting this quarter, all turbine powered equipment with six
passenger seats or more will be required to have Terrain Awareness Warning
Systems (TAWS) installed. This equipment is required on private as well as
commercial equipment, freight or passenger, jet or turboprop. TAWS uses GPS
positioning compared against topographic mapping to determine if a threat
exists. A screen shows the mountains near you. Red is bad. Green is okay.
This equipment would have been helpful in the incident Ram is asking about.

D.

"Ramapriya" wrote in message
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.

For a crew that is trained to respond to a TCAS alert by instinct, 40
seconds is plenty.

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 )...

With a professional crew, only one pilot is chatting up the hosties. The
other is flying. A professional crew always has one of the pilots placing
his/her attention on the plane, even with the auto-pilot on.

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.

Bob understands the limitation of the equipment. It is great stuff. TCAS is
a huge inprovement in safety. However, it isn't infallible. I was on the
jumpseat last week when a fellow crew received a TCAS warning even though a
real threat did not exist. Well-trained pilots who are supplied with good
information will always be the best safety equipment.

For example- the A-320 you have experienced was designed so that idiots can
fly it. The idiots still manage to crash the A-320.

D.

AnthonyQ opined

Ram, if I recall that incident correctly, ATC had repeatedly requested a
heading change and direction of turn (don't recall actual numbers) but the
flight crew repeatedly read back incorrectly. In the end the controller
deferred to the "obviously" more experienced and knowledgeable captain - and
gave in...

With respect to the capability of TCAS - it only interrogates the
transponders of nearby airplanes. It then figures out their distance away,
bearing and delta altitude (assuming a mode C or S transponder). It will
give a Resolution Advisory (Climb or Descend) instruction. It does not give
any terrain warning.

Maybe if we put mode C Transponders on every mountain top... And radio tower
for that matter.

"Ramapriya" wrote in message
oups.com...
Bob, guess I didn't frame the Q properly enough.
While I knew about the GPWS and TCAS individually, I wasn't sure
whether TCAS was equipped to deal with purely traffic or whether
accidental straying into terrain would also be taken care of.
I'm asking this because I remember an incident of many years ago where
an idiot in the ATC asked an Indonesian aircraft to turn 'left' when he
had to say 'right' and the unsuspecting blokes ran into a mountain. I
was wondering if that kinduva incident can be avoided with the TCAS...

Cheers,

Ramapriya


Bob Moore wrote:
"Ramapriya" wrote

Does this get activated only when there's an aircraft in the
dangerous
vicinity or will it also trigger if the aircraft is hurtling
towards
some terrain such as a hill?

In my generation of aircraft, (B-727) they are two different systems.
First came the GPWS (Ground Proximity Warning System) and then some
time later came the TCAS (Traffic Alert and Collision Advoidance
System).

And does every aircraft have this system these days, regardless of
size?

No, only passenger jets are required to have them.

Bob Moore





-ash
Cthulhu in 2005!
Why wait for nature?

"Ash Wyllie" wrote in message
...
AnthonyQ opined

Ram, if I recall that incident correctly, ATC had repeatedly requested a
heading change and direction of turn (don't recall actual numbers) but
the
flight crew repeatedly read back incorrectly. In the end the controller
deferred to the "obviously" more experienced and knowledgeable captain -
and
gave in...

With respect to the capability of TCAS - it only interrogates the
transponders of nearby airplanes. It then figures out their distance
away,
bearing and delta altitude (assuming a mode C or S transponder). It will
give a Resolution Advisory (Climb or Descend) instruction. It does not
give
any terrain warning.

Maybe if we put mode C Transponders on every mountain top... And radio
tower
for that matter.


Ummm...doesn't TAWS read a map database that holds such obstructions?


--
Matt
---------------------
Matthew W. Barrow
Site-Fill Homes, LLC.
Montrose, CO

In article ,
"Matt Barrow" wrote:

Ummm...doesn't TAWS read a map database that holds such obstructions?

DTED (terrain data) is pretty constant. Vertical obstructions are quite
the challenge in that it is almost impossible for the various database
providers to keep up with every tower that is out there.

--
Bob Noel
looking for a sig the lawyers will like

"Larry Dighera" wrote in message
...
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.


IIRC it is (or was) common practice to eliminate "1200s" from displays in
high traffic areas for clarity purposes. I don't know if the Piper was
equipped with Mode C at the time or not.
My statement about the X-Ponder being in stand-by was distant memory of a
report that I can't cite where from. Maybe a news report? I dunno, I wish I
could remember.
I can only agree with your reasoning on the issue.

Marty

"Bob Noel" wrote in message
...
In article ,
"Matt Barrow" wrote:

Ummm...doesn't TAWS read a map database that holds such obstructions?

DTED (terrain data) is pretty constant. Vertical obstructions are quite
the challenge in that it is almost impossible for the various database
providers to keep up with every tower that is out there.

They use the same data that the NACO/FAA provides, with the same frequency.


Matt
---------------------
Matthew W. Barrow
Site-Fill Homes, LLC.
Montrose, CO