Airliner pilot and controller extend the discussion of flight-levels separation from UCAP239.

Listener Biggles71, an “airline captain (Airbus A330/A340)”:

At high altitude it is very difficult to estimate vertical separation. I recall cruising at Fl390 over central Europe (Prague FIR to be precise) in an A320 about 10 years ago, when all of a sudden we noticed opposite traffic on TCAS at the same level. A controller had the opposite traffic on a non semi-circular level and had forgotten about him. Exactly as you guys discussed on the podcast.

With a closing speed of close to 1200mph there was no time to even question ATC, our TCAS gave us a brief TA (Traffic advisory) immediately followed by a RA (resolution advisory) “Climb, Climb message”. We later learnt that the opposite traffic, a SwissAir MD11, correctly followed his RA, Descend, Descend.

In the maneuver we stayed visual all the way. But what was even more amazing was the visual illusion; as we were climbing and the other one descending, we still thought that the MD11 would overfly us. Obviously this was not the case and he flew below us…

and from listener ATC_Ben:

TCAS has the floor if it produces an RA, our phraseology has the simple response to ATC of “Unable, TCAS RA” and that’s it… at that point you have to just sit and watch… some praying wouldn’t hurt. Although TCAS only resolves in the vertical, so don’t ignore the ATC, as they’ll likely also be trying to give you a hard turn as well which will help the situation!

Our training for such a situation is to identify the situation (responding to a STCA [Short Term Conflict Alert] normally), pick an aircraft and a resolution rapidly and start talking! We don’t worry about finesse obviously and we are advised to pick a large heading change out of the conflict (normally at least 60+ degrees)… it may sound strange but we may even (pending the situation) turn you ‘through’ the other aircraft as this is the safer of the two turns.

But we are trained to make these ‘snapshot’ decisions and actions as normally you won’t make such an error it’s more commonly when you are either overloaded or dead quiet (boredom), so the first you’ll know about it is the STCA!

Great stuff. Thanks. And there’s more, read it all here.

(Paragraph breaks in the quotes added by Jack)

One Comment

  1. You are welcome Jack!
    Regards from Dubai