TCAS
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TCAS
Hello everyone,
I would like to ask a question because I am not able to find the real answer to this.
I recently changed company and the type that I am flying, I used to fly A320 and now I am flying B737-800
For many years in A320 in my old company when we had TA, the first action was to look out and locate the traffic while getting ready to disconnect the AP in case RA occcurs.
About 2 years ago all of a sudden new procedures came up and we were told that when we hear TA all we have to do is to say "I have control" and get ready for RA but do not look out. The reason we were told behind this was that we do not manouver only for a TA anyway and if we have the RA we have to follow the RA manouver, so it is much better to be prepared to disconnect and follow the RA commands rather than trying to see the airplane. Because firstly there is a chance that we identify the wrong traffic and second the RA can be caused by another traffic taht we didn't see and RA manouver can be the opposite to what we expected.
Now I came to the new company and they are insisting on looking out when you have TA because it is a good airmanship. I see the points from both side of the argument but i am confused how the policy for this manouver can change from company to company or from type to type.
So my question is,
Does the procedure change from company to company or
Does the procedure change from manufacturer to manufacturer
or is there any safety agency that advises and the policy changed but my new company is not aware of it
Thanks a lot for your commments
I would like to ask a question because I am not able to find the real answer to this.
I recently changed company and the type that I am flying, I used to fly A320 and now I am flying B737-800
For many years in A320 in my old company when we had TA, the first action was to look out and locate the traffic while getting ready to disconnect the AP in case RA occcurs.
About 2 years ago all of a sudden new procedures came up and we were told that when we hear TA all we have to do is to say "I have control" and get ready for RA but do not look out. The reason we were told behind this was that we do not manouver only for a TA anyway and if we have the RA we have to follow the RA manouver, so it is much better to be prepared to disconnect and follow the RA commands rather than trying to see the airplane. Because firstly there is a chance that we identify the wrong traffic and second the RA can be caused by another traffic taht we didn't see and RA manouver can be the opposite to what we expected.
Now I came to the new company and they are insisting on looking out when you have TA because it is a good airmanship. I see the points from both side of the argument but i am confused how the policy for this manouver can change from company to company or from type to type.
So my question is,
Does the procedure change from company to company or
Does the procedure change from manufacturer to manufacturer
or is there any safety agency that advises and the policy changed but my new company is not aware of it
Thanks a lot for your commments
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From our Operations Manual Part A (EU-OPS)
8.3.6 POLICY AND PROCEDURES FOR THE USE OF TCAS / ACAS
Traffic and Collision Avoidance System (TCAS) / Airborne Collision Avoidance
System (ACAS) description is given in the FCOM Aircraft System.
Associated procedures are given in QRH/FCOM "Abnormal and Emergency
procedures" and in FCOM Supplementary Procedures".
Airborne Collision and Avoidance Systems (ACAS) provide Flight Crew with an
independent back up to visual search and the ATC system by alerting the crew to
collision hazards, independent of any ground-based aids which may be used by
air traffic control for such purposes. ACAS II (Traffic Alert and Collision Avoidance
System Type II) is the specific equipment which is currently available to meet this
requirement, as detailed in the following paragraphs.
ACAS II
Provides collision avoidance manoeuvre advice in the vertical plane, in either of
two forms:
• Traffic Advisories (TA), which indicate the approximate position relative to the
subject aircraft, either in azimuth only, or azimuth and altitude, of nearby
transponding aircraft which may become a threat;
• Resolution Advisories (RAs) which command manoeuvres or manoeuvre
restrictions in the vertical plane to resolve conflicts with aircraft transponding
SSR Mode C altitude.
If a TA or a RA is received, the following action should be taken:
Traffic Advisory; intended to alert the crew that a RA, requiring a change in flight
path, may follow. A visual search should immediately be concentrated on that
part of the sky where the TA indicates the conflicting traffic to be. If the potential
threat gives cause for concern, air traffic control assistance should be requested in
deciding whether a change of flight path is required. Do not manoeuvre based on
a TA only.
Resolution Advisory; pilots shall:
• respond immediately by following the RA as indicated, unless doing so would
jeopardize the safety of the aeroplane;
NOTE:
1
Stall warning, windshear, and Ground Proximity Warning System alerts
have precedence over ACAS.
2 Visually acquired traffic may not be the same traffic causing an RA. Visual
perception of an encounter may be misleading, particularly at night.
• follow the RA even if there is a conflict between the RA and an air traffic
control (ATC) instruction to manoeuvre;
• not manoeuvre in the opposite sense to a RA;
NOTE:
In the case of an ACAS-ACAS coordinated encounter, the RAs complement
each other in order to reduce the potential for collision. Manoeuvres, or lack
of manoeuvres, that result in vertical rates opposite to the sense of an RA could
result in a collision with the threat aircraft.);
• as soon as possible, as permitted by flight crew workload, notify the
appropriate ATC unit of the RA using the appropriate RT phraseology;
NOTE:
Unless informed by the pilot, ATC does not know when ACAS issues RAs. It
is possible for ATC to issue instructions that are unknowingly contrary to
ACAS RA indications. Therefore, it is important that ATC be notified when an
ATC instruction is not being followed because it conflicts with an RA.
• promptly comply with any modified RAs;
• limit the alterations of the flight path to the minimum extent necessary to
comply with the RAs;
• promptly return to the terms of the ATC instruction or clearance when the
conflict is resolved; and
• notify ATC when returning to the current clearance.
Traffic and Collision Avoidance System (TCAS) / Airborne Collision Avoidance
System (ACAS) description is given in the FCOM Aircraft System.
Associated procedures are given in QRH/FCOM "Abnormal and Emergency
procedures" and in FCOM Supplementary Procedures".
Airborne Collision and Avoidance Systems (ACAS) provide Flight Crew with an
independent back up to visual search and the ATC system by alerting the crew to
collision hazards, independent of any ground-based aids which may be used by
air traffic control for such purposes. ACAS II (Traffic Alert and Collision Avoidance
System Type II) is the specific equipment which is currently available to meet this
requirement, as detailed in the following paragraphs.
ACAS II
Provides collision avoidance manoeuvre advice in the vertical plane, in either of
two forms:
• Traffic Advisories (TA), which indicate the approximate position relative to the
subject aircraft, either in azimuth only, or azimuth and altitude, of nearby
transponding aircraft which may become a threat;
• Resolution Advisories (RAs) which command manoeuvres or manoeuvre
restrictions in the vertical plane to resolve conflicts with aircraft transponding
SSR Mode C altitude.
If a TA or a RA is received, the following action should be taken:
Traffic Advisory; intended to alert the crew that a RA, requiring a change in flight
path, may follow. A visual search should immediately be concentrated on that
part of the sky where the TA indicates the conflicting traffic to be. If the potential
threat gives cause for concern, air traffic control assistance should be requested in
deciding whether a change of flight path is required. Do not manoeuvre based on
a TA only.
Resolution Advisory; pilots shall:
• respond immediately by following the RA as indicated, unless doing so would
jeopardize the safety of the aeroplane;
NOTE:
1
Stall warning, windshear, and Ground Proximity Warning System alerts
have precedence over ACAS.
2 Visually acquired traffic may not be the same traffic causing an RA. Visual
perception of an encounter may be misleading, particularly at night.
• follow the RA even if there is a conflict between the RA and an air traffic
control (ATC) instruction to manoeuvre;
• not manoeuvre in the opposite sense to a RA;
NOTE:
In the case of an ACAS-ACAS coordinated encounter, the RAs complement
each other in order to reduce the potential for collision. Manoeuvres, or lack
of manoeuvres, that result in vertical rates opposite to the sense of an RA could
result in a collision with the threat aircraft.);
• as soon as possible, as permitted by flight crew workload, notify the
appropriate ATC unit of the RA using the appropriate RT phraseology;
NOTE:
Unless informed by the pilot, ATC does not know when ACAS issues RAs. It
is possible for ATC to issue instructions that are unknowingly contrary to
ACAS RA indications. Therefore, it is important that ATC be notified when an
ATC instruction is not being followed because it conflicts with an RA.
• promptly comply with any modified RAs;
• limit the alterations of the flight path to the minimum extent necessary to
comply with the RAs;
• promptly return to the terms of the ATC instruction or clearance when the
conflict is resolved; and
• notify ATC when returning to the current clearance.
The whole point of a TA is to bring traffic to your attention to help you visually find it before the possible RA.
Never maneuver in response to a TA, always follow the RA even if you have the traffic visual, but you should already be looking out for traffic even without a TA.
During a TA or RA the crew should be doing their best to visually locate the traffic. The idea that you would purposefully not look out is ridiculous at best and shows a complete lack of understanding of basic airmanship.
Never maneuver in response to a TA, always follow the RA even if you have the traffic visual, but you should already be looking out for traffic even without a TA.
During a TA or RA the crew should be doing their best to visually locate the traffic. The idea that you would purposefully not look out is ridiculous at best and shows a complete lack of understanding of basic airmanship.
Last edited by ahramin; 17th Jan 2013 at 03:01.
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During a TA or RA the crew should be doing their best to visually locate the traffic.
BTW what's happened to the "In VMC if two aircraft are head on at the same
level, both will alter heading to the right" rule?
I disagree with the notion you must respond to a RA even if you have the other aircraft in sight. Not in sight, absolutely, but in sight means just that. I've sat and watched departures climbing out of airports while on downwind for another runway. I had them in sight before the traffic call, had them in sight before the TA and had them in sight before the RA. If the course looks like it might converge, act accordingly. If however you receive one because of the large threat envelope of the TCAS when clearly there's no threat, as in the other aircraft couldn't hit you if he wanted to, then you are making the situation worse.
I've heard the counter arguments of those who propose acting ALL the time, I don't buy it.
Yes, my companies sop's allow us to disregard the RA if the threat aircraft is in sight, it also says we must follow it if the flight paths appear to merge.
I've heard the counter arguments of those who propose acting ALL the time, I don't buy it.
Yes, my companies sop's allow us to disregard the RA if the threat aircraft is in sight, it also says we must follow it if the flight paths appear to merge.
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West Coast,
This assumes you are looking at the aircraft that is the threat.
I am truly amazed that your company SOP permits non compliance based on a visual spot. It harks back to the early days of TCAS. Later versions (especially change 7 onwards) don't generate anywhere near as many nuisance RAs, and even then *Accurate* compliance should only deviate your flight path by a few hundred feet.
I remembar a particular incident, reported in the FAA TCAS transition Program back in about '98. The crew got a TA, had visual, were happy they were separated. Then they got an RA, the skipper didn't think it was needed but flew it anyway, at which point a second aircraft missed them vertically by 300'. It had been co-altitude.
There are situations where non compliance can be justified, I've talked about them here many times over the years, but a visual spot is not one of them.
It is staggering to me, 15 years later, that such SOPs still exist.
Even more so it staggers me that this far down the road guys keep turning up in this forum who quite clearly do not know how TCAS works nor the internationally agreed best practice for how to use it. I'm not having a go at the individuals - good for them for asking - but it is a damning indictment of their training and standards department that they have to come here to fill the cracks in their training.
I recently took a break from flying my desk and refreshed on a medium passenger jet, as it happened I had the opportunity to do the entire course alongside some new entrants at a company I do some consulting for. TCAS barely got a mention. I guess we need some more mid-airs before regulators will actually check that the required theoretical and practical training is actually being done.
This assumes you are looking at the aircraft that is the threat.
I am truly amazed that your company SOP permits non compliance based on a visual spot. It harks back to the early days of TCAS. Later versions (especially change 7 onwards) don't generate anywhere near as many nuisance RAs, and even then *Accurate* compliance should only deviate your flight path by a few hundred feet.
I remembar a particular incident, reported in the FAA TCAS transition Program back in about '98. The crew got a TA, had visual, were happy they were separated. Then they got an RA, the skipper didn't think it was needed but flew it anyway, at which point a second aircraft missed them vertically by 300'. It had been co-altitude.
There are situations where non compliance can be justified, I've talked about them here many times over the years, but a visual spot is not one of them.
It is staggering to me, 15 years later, that such SOPs still exist.
Even more so it staggers me that this far down the road guys keep turning up in this forum who quite clearly do not know how TCAS works nor the internationally agreed best practice for how to use it. I'm not having a go at the individuals - good for them for asking - but it is a damning indictment of their training and standards department that they have to come here to fill the cracks in their training.
I recently took a break from flying my desk and refreshed on a medium passenger jet, as it happened I had the opportunity to do the entire course alongside some new entrants at a company I do some consulting for. TCAS barely got a mention. I guess we need some more mid-airs before regulators will actually check that the required theoretical and practical training is actually being done.
Last edited by Capt Pit Bull; 17th Jan 2013 at 10:34.
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WC don't forget the intruder will likely be responding to an RA on you,
which means the target trajectory - even if you've got the right target
- will be visually unpredictable.
which means the target trajectory - even if you've got the right target
- will be visually unpredictable.
The big problem with responding visually is that although the altitude representation of the contact is going to be accurate, due to the way the azimuth representation works, the contact bearing can be as much as 30 degrees out. This can mean the target which is visually aquired is the wrong one!
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From FAA AC120-55c:
Capt Pit Bull is truly amazed at a company's SOPs allowing pilots to disregard an RA. Personally, I am absolutely stunned.
That is dangerous bulls**t, which demonstrates an ignorance of the system. West Coast, you need to find someone with a brain to write your SOPs.
When an RA occurs, the PF should respond immediately by direct attention to RA displays and maneuver as indicated, unless doing so would jeopardize the safe operation of the flight or the flightcrew can assure separation with the help of definitive visual acquisition of the aircraft causing the RA. By not responding to an RA, the flightcrew effectively takes responsibility for achieving safe separation. In so choosing, consider the following cautions:
(a)
The traffic may also be equipped with TCAS and it may maneuver in response to an RA coordinated with your own TCAS.
(b)
The traffic acquired visually may not be the same traffic causing the RA.
(c)
Visual perception of the encounter may be misleading. Unless it is unequivocally clear that the target acquired visually is the one generating the RA and there are no complicating circumstances, the pilot’s instinctive reaction
(a)
The traffic may also be equipped with TCAS and it may maneuver in response to an RA coordinated with your own TCAS.
(b)
The traffic acquired visually may not be the same traffic causing the RA.
(c)
Visual perception of the encounter may be misleading. Unless it is unequivocally clear that the target acquired visually is the one generating the RA and there are no complicating circumstances, the pilot’s instinctive reaction
.... it also says we must follow it if the flight paths appear to merge.
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Two jets approaching each other (opposite direction) are doing 900 knots. Thats one quarter mile per second. Think you will see it before the crash? Good luck.
Looking out is not the answer. Follow the RA instructions.
Looking out is not the answer. Follow the RA instructions.
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Capt Pit Bull, I completely agree with what you have said ,and wished I could add more weight to it.
I am also very frustrated to see that after so many well publizied incidents and one accident , people ( i.e pilots and controllers) still do not understand how TCAS works and what it takes to make it efficient ( i.e prevent metal from touching) .
If it was to me I would print thousands of stickers and glue one in every cocpkit saying : "Follow the RA , discuss debate about it afterwards !"
and put the other in every Radar display at every ATC console : "TCAS is not there to ensure radar separation ! "
If those 2 basics were understood and followed , we would ALL be much safer..
As to visual aquisition , forget it, read the JAL/JAL accident report if you need convincing, add to this that TCAS is very poor in azimuth , and that there is anyway no time for this .
I am also very frustrated to see that after so many well publizied incidents and one accident , people ( i.e pilots and controllers) still do not understand how TCAS works and what it takes to make it efficient ( i.e prevent metal from touching) .
If it was to me I would print thousands of stickers and glue one in every cocpkit saying : "Follow the RA , discuss debate about it afterwards !"
and put the other in every Radar display at every ATC console : "TCAS is not there to ensure radar separation ! "
If those 2 basics were understood and followed , we would ALL be much safer..
As to visual aquisition , forget it, read the JAL/JAL accident report if you need convincing, add to this that TCAS is very poor in azimuth , and that there is anyway no time for this .
How ever did we survive under see and avoid?
Angling for RWY 28L In KSFO, ATC has long since pointed out traffic for the charted visual to 28R that I'm to pair up with. Long before it was ever a TA or RA the aircraft was in sight. No other TCAS targets around to be confused with, RA clearly based off the aircraft that corresponds visually to where the box is saying, tell ya what, I'm comfortable not blindly responding based simply because the SOP says I have to.
If there's any doubt, then there's no question, immediately comply, if it's an out of the blue unexpected RA, immediately comply, if after visually acquiring the target the situation isnt acceptable, comply. I imagine the blindly follow the command crowd and I would agree on 99% of TCAS protocal, there are however scenarios where I comfortable that I am visually looking at the TCAS target beyond doubt and to respond might introduce a greater threat (botched response at a low energy, high drag configuration) than to monitor the traffic you've seen for 20 miles.
As far as making sure it's the right aircraft I'm looking at, what before TCAS or when its deferred? In the above situation, the analogy would be for me to climb or descend away from an aircraft I visually acquired many miles out from the join up simply because there might be another aircraft out there. Wouldn't make sense to do that if you were minus TCAS, just as it doesn't make sense to do it with TCAS if by various means you're sure it's the threat aircraft. At an altitude where the RA is suppressed, the same aircraft represents the same threat, but now it's merely a TA, yet you don't respond to it. There are so many inconsistencies with the logic of blindly following the TCAS (or any other) protocal. I don't sign away my PIC authority to the TCAS, though chances are I am going to follow it's commands the vast majority of the time.
I know I'm not going to convince anyone, and chances are no one of the blindly follow the TCAS command mindset is going to sway me, just understand there are other interpretations out there.
Angling for RWY 28L In KSFO, ATC has long since pointed out traffic for the charted visual to 28R that I'm to pair up with. Long before it was ever a TA or RA the aircraft was in sight. No other TCAS targets around to be confused with, RA clearly based off the aircraft that corresponds visually to where the box is saying, tell ya what, I'm comfortable not blindly responding based simply because the SOP says I have to.
If there's any doubt, then there's no question, immediately comply, if it's an out of the blue unexpected RA, immediately comply, if after visually acquiring the target the situation isnt acceptable, comply. I imagine the blindly follow the command crowd and I would agree on 99% of TCAS protocal, there are however scenarios where I comfortable that I am visually looking at the TCAS target beyond doubt and to respond might introduce a greater threat (botched response at a low energy, high drag configuration) than to monitor the traffic you've seen for 20 miles.
As far as making sure it's the right aircraft I'm looking at, what before TCAS or when its deferred? In the above situation, the analogy would be for me to climb or descend away from an aircraft I visually acquired many miles out from the join up simply because there might be another aircraft out there. Wouldn't make sense to do that if you were minus TCAS, just as it doesn't make sense to do it with TCAS if by various means you're sure it's the threat aircraft. At an altitude where the RA is suppressed, the same aircraft represents the same threat, but now it's merely a TA, yet you don't respond to it. There are so many inconsistencies with the logic of blindly following the TCAS (or any other) protocal. I don't sign away my PIC authority to the TCAS, though chances are I am going to follow it's commands the vast majority of the time.
I know I'm not going to convince anyone, and chances are no one of the blindly follow the TCAS command mindset is going to sway me, just understand there are other interpretations out there.
Last edited by West Coast; 20th Jan 2013 at 08:09.
