TCAS Limitations Below 700 Feet – Time for an Upgrade

[MD83FO]

Is the aviation industry overdue in adopting a more advanced traffic avoidance system or enhancing TCAS?



There should be no TA/RA inhibition below 700 feet. Instead, the system should still provide avoidance guidance to at least one of the conflicting aircraft, ensuring safer operations during takeoff and landing.

[neville_nobody]

How’s that going to work? You can’t send one aircraft descending at 500AGL and the other climbing. So the only other option is a lateral resolution which then opens another can of worms. So no I don’t think there will be any change as it is to difficult.

[FullWings]

There should be no TA/RA inhibition below 700 feet. Instead, the system should still provide avoidance guidance to at least one of the conflicting aircraft, ensuring safer operations during takeoff and landing.

It still shows you where the other aircraft are and their relative heights, so you have SA - it’s just up to you what you do with it. I would presume that this scenario has been investigated at great length while ACAS has been evolving and it is still thought of as the better solution to have low-level inhibits, as for one thing it would start conflicting with EGPWS (which has priority) and for another they would have to totally rethink the protected volumes otherwise a descending RA really could fly you into the ground to achieve separation from a higher conflicting aircraft. Having RAs possible that close to the surface may not ensure safer operations as the risks could outweigh the benefits.

Changing systems after one occurrence (MAC at DCA in this case) without taking into account the design rationale often leaves a worse situation than the original due to unintended consequences.