TCAS RA vs visual on traffic
Join Date: Aug 1999
Location: England
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Grounded27,
In the OPs scenario his equipment was not capable of having an RA.
With the numbers given the 737 should have received an RA. However it would have been Preventative (to stop the 737 from climbing) rather than requiring the 737 to descend. This would occur if the aircraft were predicted to be vertically within 300' to 600' at the closest point of approach (CPA).
However, if the aircraft were predicted to be <300' apart at the CPA the 737 would have got a descent. 2,000' is not low enough to inhibit that.
The vertical inhibitions are:
DESCEND inhibited below 1,100'
INCREASE DESCENT inhibited below 1,550'
So we can see that at 2,000' the 737's TCAS would initially have had all options open to it as the encounter progressed.
Yes, I take your point that the terrain floor may well have come into play if the 737 flight path had altered downwards, and that depending on the local terrain that could even generated a terrain pull up. Perversely, that would direct the 737 back up at the conflicting traffic, which in itself is a great example of how following an RA can cause a decrease in safety. However, as we've scene, in this situation the 737 would not have been directed to descend so its a moot point.
regards,
pb
In the OPs scenario his equipment was not capable of having an RA.
With the numbers given the 737 should have received an RA. However it would have been Preventative (to stop the 737 from climbing) rather than requiring the 737 to descend. This would occur if the aircraft were predicted to be vertically within 300' to 600' at the closest point of approach (CPA).
However, if the aircraft were predicted to be <300' apart at the CPA the 737 would have got a descent. 2,000' is not low enough to inhibit that.
The vertical inhibitions are:
DESCEND inhibited below 1,100'
INCREASE DESCENT inhibited below 1,550'
So we can see that at 2,000' the 737's TCAS would initially have had all options open to it as the encounter progressed.
Yes, I take your point that the terrain floor may well have come into play if the 737 flight path had altered downwards, and that depending on the local terrain that could even generated a terrain pull up. Perversely, that would direct the 737 back up at the conflicting traffic, which in itself is a great example of how following an RA can cause a decrease in safety. However, as we've scene, in this situation the 737 would not have been directed to descend so its a moot point.
regards,
pb
