TCAS reliability
Thread Starter
SpaceRanger
Joined: May 1999
Posts: 213
Likes: 0
From: Samsonite
TCAS reliability
How reliable is TCAS?
Just as GPWS/EGPWS, it is a last resort system, when all else fails.
But what if ... it does not work? How often do you see other traffic, which is not on the traffic screen, though it should have been? Some times I notice how traffic, getting closer, suddenly disappears. Temporarily, usually, but sometimes it just goes away. Or passing civil traffic, which never appears on the display, though it is radar environment requiring TCAS operational.
Even with two antennas, there must be times where the antennae of two aircraft cannot see each other, even when close.
I have seen this i different aircraft, from small bizjets to wide body airline.
I could not find any other information on the subject but hope that others could join in with what they experienced, or know about it.
I am not talking about faulty equipment, or transponders switched off or to the wrong setting, but normally working Mode S / TCAS. How great is the reliability?
The closer traffic gets, the more important the function of TCAS, so I would hope that when it really counts, TCAS can be trusted.
Just as GPWS/EGPWS, it is a last resort system, when all else fails.
But what if ... it does not work? How often do you see other traffic, which is not on the traffic screen, though it should have been? Some times I notice how traffic, getting closer, suddenly disappears. Temporarily, usually, but sometimes it just goes away. Or passing civil traffic, which never appears on the display, though it is radar environment requiring TCAS operational.
Even with two antennas, there must be times where the antennae of two aircraft cannot see each other, even when close.
I have seen this i different aircraft, from small bizjets to wide body airline.
I could not find any other information on the subject but hope that others could join in with what they experienced, or know about it.
I am not talking about faulty equipment, or transponders switched off or to the wrong setting, but normally working Mode S / TCAS. How great is the reliability?
The closer traffic gets, the more important the function of TCAS, so I would hope that when it really counts, TCAS can be trusted.
Joined: Aug 1999
Posts: 1,050
Likes: 4
From: England
Don't confuse being tracked with being displayed. There are a bunch of reasons why a blip may not be showing, even with fully serviceable equipment.
e.g. No bearing 'other' traffic, Interference limiting mode, TA or RA underway. Or if its not as close as you think it is and isn't actually in the display volume.
As a result it is quite routine to see blips appearing and disappearing and should not be taken as the TCAS being unreliable or used as a justification for ignoring an RA.
pb
e.g. No bearing 'other' traffic, Interference limiting mode, TA or RA underway. Or if its not as close as you think it is and isn't actually in the display volume.
As a result it is quite routine to see blips appearing and disappearing and should not be taken as the TCAS being unreliable or used as a justification for ignoring an RA.
pb
Joined: Mar 2006
Posts: 1,115
Likes: 86
From: England
Do I detect the suggestion that pilots now depend on TCAS, on EGPWS, and other 'last-ditch' systems ?
Conceptually these are error detectors, either yours or someone else’s. What has happened to the need to avoid the situations where the system may be required, the multitude of error avoiding, trapping, and mitigating strategies?
If TCAS (EGPWS) fails after all of those, then perhaps it’s just not your day – or conversely it is your day.
Reliability … it’s as good as any other aviation electronic system, but an accident … including a human failure; presumably the system has a failure alert.
“ looking out the window … so always do that when responding to an RA.”
I don’t think so. The advice I have seen is to follow the RA; use the head down instruments. This avoids possible errors from misidentification and visual illusion – mistaken altitude differences, relative bearing, etc.
Don’t invent a new procedure to cover extreme ‘hypothetical’ probabilities of failure including an encounter. It’s far more likely that you have made the error in the first instance – guard against that first of all.
“Two TCAS North of Darwin” … I think that that implied an attitude to safety, opposed to the reality of serviceability.
Conceptually these are error detectors, either yours or someone else’s. What has happened to the need to avoid the situations where the system may be required, the multitude of error avoiding, trapping, and mitigating strategies?
If TCAS (EGPWS) fails after all of those, then perhaps it’s just not your day – or conversely it is your day.
Reliability … it’s as good as any other aviation electronic system, but an accident … including a human failure; presumably the system has a failure alert.
“ looking out the window … so always do that when responding to an RA.”
I don’t think so. The advice I have seen is to follow the RA; use the head down instruments. This avoids possible errors from misidentification and visual illusion – mistaken altitude differences, relative bearing, etc.
Don’t invent a new procedure to cover extreme ‘hypothetical’ probabilities of failure including an encounter. It’s far more likely that you have made the error in the first instance – guard against that first of all.
“Two TCAS North of Darwin” … I think that that implied an attitude to safety, opposed to the reality of serviceability.
Joined: Aug 1999
Posts: 1,050
Likes: 4
From: England
NEVER use a visual spot as a reason to ignore an RA.
Here is why.
However you may consider turning for additional separation, depending on the situation and your company SOPs. General guidance is that one an RA is underway, the handling pilot should be head in on instruments. However the non handling pilot can lookout depending on the other tasks underway.
However, be advised that a late turn actually increases the collision risk if the aircraft do overlap laterally. But a prompt turn early in the encounter might be helpful.
pb
Here is why.
However you may consider turning for additional separation, depending on the situation and your company SOPs. General guidance is that one an RA is underway, the handling pilot should be head in on instruments. However the non handling pilot can lookout depending on the other tasks underway.
However, be advised that a late turn actually increases the collision risk if the aircraft do overlap laterally. But a prompt turn early in the encounter might be helpful.
pb
