A certain accident over Germany a few years back got me thinking on this issue.
Imagine you are flying in cruise, and there isn't much traffic around.
ATC doesn't pointout any conflicting traffic to you, but then suddenly TCAS jumps in, showing a converging traffic, and giving out the RA, for example let's say it tells you to climb to avoid that traffic.
Momentarily after the RA, ATC contacts you and tells you to descend immediately to avoid collision, and the poor guy tells you that a few times in a rather desperate tone.
Let's say it is in Canada where you are allowed to deviate from your last ATC clx or instruction to follow GPWS or TCAS instruction.
Who would you trust, the human being or the computer (TCAS)?
TCAS RA vs. ATC Resolution - Your actions?
Moderators: Sulako, lilfssister, North Shore, sky's the limit, sepia, I WAS Birddog
TCAS RA vs. ATC Resolution - Your actions?
"Then from 1000 ft AGL until the final capture altitude, the A/C accelerates backwards up along the altitude profile with idle thrust"
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Canus Chinookus
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complexintentions
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ALWAYS, ALWAYS, follow the RA's solution! ATC DOES NOT know what resolution was arrived at by two TCAs-equipped a/c! If that Russian skipper had followed his, I wouldn't have lost a friend who was the FO on the DHL -57! What blows is that the DHL crew did everything right! FOLLOW YOUR RA LIKE YOU WERE TRAINED FOR G$%DA$$IT!!
Incidentally, in the last few days, the Russian who blamed the Swiss air traffic controller for the deaths of his wife and children on board the Russian airliner in this incident, and murdered the controller, was sentenced to eight years in prison.
http://www.mosnews.com/news/2005/10/26/ ... dict.shtml
Incidentally, in the last few days, the Russian who blamed the Swiss air traffic controller for the deaths of his wife and children on board the Russian airliner in this incident, and murdered the controller, was sentenced to eight years in prison.
http://www.mosnews.com/news/2005/10/26/ ... dict.shtml
I’m still waiting for my white male privilege membership card. Must have gotten lost in the mail.
Even the controllers in Canada are trained and EXPECTING you to follow the RA. They should never give conflicting directions IF you say its a ACAS RA.
ALWAYS FOLLOW THE RA!!!!
However, procedures aside, and soley as a matter of intellectual debate, I'd trust a human loooong before I'd trust a computer....garbage in - garbage out.
The number of inflight at cruise ATC caused mid-airs compared to the number of flights = a pretty well proven record. Airport runway incursions and The German one aside, the last ATC caused mid-air I recall was Zagreb. Pls correct me if there are others....
As well if I recall correctly, the impetus for ACAS wasn't to correct ATC IFR issues, it was a result of the El Ceritos accident in the States between an IFR and unknown VFR and a major recomendation from the TSB.
ALWAYS FOLLOW THE RA!!!!
However, procedures aside, and soley as a matter of intellectual debate, I'd trust a human loooong before I'd trust a computer....garbage in - garbage out.
The number of inflight at cruise ATC caused mid-airs compared to the number of flights = a pretty well proven record. Airport runway incursions and The German one aside, the last ATC caused mid-air I recall was Zagreb. Pls correct me if there are others....
As well if I recall correctly, the impetus for ACAS wasn't to correct ATC IFR issues, it was a result of the El Ceritos accident in the States between an IFR and unknown VFR and a major recomendation from the TSB.
Familyguy, I'll buy you a beer if you can successfully determine if the jet that's about to hit you is above or below or whatever. If you spend time second-guessing an RA you will not survive. Period.
TA, maybe.
ACAS is most of a company; TCAS is the thingy in your a/c.
TA, maybe.
ACAS is most of a company; TCAS is the thingy in your a/c.
"What's it doing now?"
"Fly low and slow and throttle back in the turns."
"Fly low and slow and throttle back in the turns."
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bizjet_mania
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I'd go for the TCAS as well (although I'm not quite there in terms of aircraft), there is always the possibility of an incident like this one:
http://www.tsb.gc.ca/en/reports/air/20 ... 1q0122.asp
(Long story short, wrong RA instructions caused by a faulty mode-C transponder in the conflicting aircraft, disaster avoided because one aircraft saw the other...)
Goodbye,
Louis
http://www.tsb.gc.ca/en/reports/air/20 ... 1q0122.asp
(Long story short, wrong RA instructions caused by a faulty mode-C transponder in the conflicting aircraft, disaster avoided because one aircraft saw the other...)
Goodbye,
Louis
ACAS, TCAS, sorry its the same thing essentially. Airborne vs Traffic...
The problem for any individual pilot making a judgement on the effectiveness of TCAS is you would need to fly thousands of hours to experience even a slight smattering of the issues. ATC on the other hand, deals with thousands of those issues yearly.
I've seen my fair share of "false" RA's and reported appropriately. I've seen real RA's "pick up the slack" even though really unwarranted. I have seen very few RAs that "may" have saved the day.
Bottom line is its a relatively good system...now. Nothing is 100% foolproof - not humans and not any system designed by humans.
Following the prescribed procedures increases your chances of coming out the other side...period.
The problem for any individual pilot making a judgement on the effectiveness of TCAS is you would need to fly thousands of hours to experience even a slight smattering of the issues. ATC on the other hand, deals with thousands of those issues yearly.
I've seen my fair share of "false" RA's and reported appropriately. I've seen real RA's "pick up the slack" even though really unwarranted. I have seen very few RAs that "may" have saved the day.
Bottom line is its a relatively good system...now. Nothing is 100% foolproof - not humans and not any system designed by humans.
Following the prescribed procedures increases your chances of coming out the other side...period.
My understanding that it was the case with the Dash-8 case. From the TSB report Louis was referring to:
So far we have examples of the crew following ATC and killing themselves, and those who followed RA and almost killed themselves.
It appers as if in case of RA, you only depend one one instrument and can't verify its indication in anyway rather than seeing the conflicting traffic, and if you can't, is it only fortune you're depending on?
They were commanded to descend when the conflicting aircraft was at a lower altitude.Findings as to Causes and Contributing Factors
3. The Cessna's Mode C transmitted an incorrect altitude to the DHC-8 traffic alert and collision-avoidance (TCAS). As a result, the DHC-8 crew followed a resolution advisory (RA) that brought their aircraft closer to the Cessna instead of farther away
So far we have examples of the crew following ATC and killing themselves, and those who followed RA and almost killed themselves.
It appers as if in case of RA, you only depend one one instrument and can't verify its indication in anyway rather than seeing the conflicting traffic, and if you can't, is it only fortune you're depending on?
"Then from 1000 ft AGL until the final capture altitude, the A/C accelerates backwards up along the altitude profile with idle thrust"
Sorry - I didn't see Louis post 
Garbage in, garbage out. The TCAS system worked perfectly, but it assumes that all mode C altitudes are golden. Hm.
In this case, I guess the Cessna with the malfunctioning encoder should have been squawking mode A (ie ON instead of ALT) and I presume the TCAS system would have performed differently?
Garbage in, garbage out. The TCAS system worked perfectly, but it assumes that all mode C altitudes are golden. Hm.
In this case, I guess the Cessna with the malfunctioning encoder should have been squawking mode A (ie ON instead of ALT) and I presume the TCAS system would have performed differently?
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captain_v1.0
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In that situation RA no question. But I'd rather use TCAS as a tool to help eyeball traffic than let it get to the point where I'm gambling on a little box of electrons.
If it gets to the point where TCAS butts in I'll follow the RA over some guy 100 miles away fueled by caffine and adrenaline any day. In fact I'd let the passengers vote on what to do rather than follow ATC. He or she had their chance to resolve the conflict long before there was a problem and blew it.
Remember the weakest link in aviation is the human element.
If it gets to the point where TCAS butts in I'll follow the RA over some guy 100 miles away fueled by caffine and adrenaline any day. In fact I'd let the passengers vote on what to do rather than follow ATC. He or she had their chance to resolve the conflict long before there was a problem and blew it.
Remember the weakest link in aviation is the human element.
"So far we have examples of the crew following ATC and killing themselves, and those who followed RA and almost killed themselves."
Hands up those would rather be killed or who would rather be almost killed?
I had an RA over Orly and we never saw them - both of us crew were very busy getting ready for the approach and following a very busy controller - it was a fully loaded BAE 146, they said, and he dove while we climbed. Interesting for their passengers...
Next time you are in RVSM airspace, like down the east coast, practice calling if the various jets you encounter are above or below you. You won't get them all right.
In that Dash 8 example it was still a near hit.
Hands up those would rather be killed or who would rather be almost killed?
I had an RA over Orly and we never saw them - both of us crew were very busy getting ready for the approach and following a very busy controller - it was a fully loaded BAE 146, they said, and he dove while we climbed. Interesting for their passengers...
Next time you are in RVSM airspace, like down the east coast, practice calling if the various jets you encounter are above or below you. You won't get them all right.
In that Dash 8 example it was still a near hit.
"What's it doing now?"
"Fly low and slow and throttle back in the turns."
"Fly low and slow and throttle back in the turns."
Follow the RA...ALWAYS!
Discuss it later if it's false.
TCAS II systems talk to each other to ensure each conflicting airplane maneuvers AWAY from the other. If you don't do what it says you are maneuvering TOWARD the other.
Do not hesitate (1/4 g in 5 seconds), if you do and get an "increase climb" or descent, it's 1/2 g in 3 seconds and you had better get to it.
On the other side of the coin, if you get a TA and you are in IMC conditions, you are PROHIBITED from maneuvering without a clearance from ATC. You are not permitted to maneuver based on a TA only even if you see the guy on the TCAS coming right down the pipe toward you.
If you actually see him then do whatever you have to do to miss him. See and avoid is primary whether IMC or VMC.
Discuss it later if it's false.
TCAS II systems talk to each other to ensure each conflicting airplane maneuvers AWAY from the other. If you don't do what it says you are maneuvering TOWARD the other.
Do not hesitate (1/4 g in 5 seconds), if you do and get an "increase climb" or descent, it's 1/2 g in 3 seconds and you had better get to it.
On the other side of the coin, if you get a TA and you are in IMC conditions, you are PROHIBITED from maneuvering without a clearance from ATC. You are not permitted to maneuver based on a TA only even if you see the guy on the TCAS coming right down the pipe toward you.
If you actually see him then do whatever you have to do to miss him. See and avoid is primary whether IMC or VMC.
