TCAS inhibited
 

A question on TCAS from an ATCO. I understand that below certain altitudes TCAS gets inhibited to prevent warnings on short final etc. against a/c on the ground (I may have misunderstood this so please correct me). If it does inhibit or disable itself on short final (ie 200ft) and the a/c goes around will it become re-activated?

In short: yes!

The input source for RA inhibit is the RadAlt, usually kicks in between 1000-800 ft RH (depending on type). Once the RH increases above this value again, everything is back to normal TA/RA.

Brgds,
Empty

Ok so if an a/c went around and upon passing 1500ft was in potential conflict with an outbound at 2000ft how would TCAS react? A descend instruction would be a little un-nerving I would guess. Can TCAS get one climb and one stop instruction?

Interesting question GT3, I was just thinking along the same lines......

It is very possible for the climbing aircraft to get a descend RA. Increase Descent RA's are inhibited at around 1500'. But that is the only limitation. Untill you get down to 900' where all RA's are inhibited. In any case GPWS has priority over TCAS.

Hi all

My 757 manual infront of me states that all TCAS RAs are inhibited in the climb until 1100 ft Rad alt. Descend RAs are inhibited in the climb until 1200 ft rad alt. and also inhibited from 1000 ft rad alt in the descent.

Also, if given a descend RA at just above 1200ft in the climb, it will be inhibited as soon as the EGPWS alert activates due to terrain floor closure!

So although you need to descend to avoid colliding with another aircraft, you may have to climb to avoid hitting the ground! Assuming that the other aircraft is TCAS equipped with RA capability, it should work out that you are not descending and tell it to increase climb! In technology we trust!!!

ACA