TCAS II RA while in a banking turn - wings level or continue?

[AIEXPATS]

Hallo ATC Experts.
If following a SID, STAR or even in a Radar Vectored turn (the key is the aircraft is considered to be banking for this question) and a RA climb/descent is advised by the TCAS - should we (Flight Crew) continue the turn (i.e. follow the SID/STAR/Vector) or roll out wings level and simultanously follow RA avoidance commands? Then once clear receive a new Clearance?

[Blockla]

I'd hope you'd continue the turn; if the TCAS-RA is real then vertical guidance that TCAS gives should be sufficient, ie changing flight path wouldn't assist the 'vertical resolution'... If however it's asking for something really "high rate" then maybe wings flat is the only option???

But changing the lateral flight path, may very much effect the separation with other aircraft on segregated SIDS or STARS etc.

As always with TCAS scenarios there are "grey" moments and every circumstance is different...

[Gulfstreamaviator]

The TCAS signal can be blanked by the airframe whilst in the turn.

So the logic of removing the bank is a valid one, but not perhaps the correct response in most circumstances.

So if both aircraft are banked, it is just possible that the signals could both be blanked, then I believe the TCAS logic defaults to RA mode.

One other aspect: does the data transfer rate increased whenever a TA is instigated, and then increased again between the "conflicting" RA traffic.

glf

[HEATHROW DIRECTOR]

This thread brings up something I've been curious about - how does TCAS behave in a holding pattern? I was in a BA 757 in the OCK hold a few years ago and as we banked there was an Iberia A320 above us and slightly further south in the hold. As we both banked it was exactly as if we were flying side by side 1000 ft apart...

[renard]

Our manual says that we should "If possible, the horizontal (turn) element of an ATC instruction should be followed.

As far as a/c in holds are concerned, I like to think of aircraft having a little protective bubble around them. TCAS calculates from closure rates if anopther aircraft is likely to enter your bubble. Because they are separated by 1000' and level, the "bubbles" are not touching, so no TCAS instructions issued.

What we will see on our displays in the flight deck is the other aircraft symbol will change to a filled blue diamond and we would announce it as proximate traffic.

Any aircraft within 1200' and 6.2nm will go proximate.

If the aircraft above started to descend towards my bubble, and the system thinks it may burst my bubble, then the symbol would turn to a yellow circle and the plane would say "Traffic Traffic" - it gets your attention, but you don't take any action just yet.

If the aircraft keeps descending and the system thinks it will burst my bubble, then it will issue instructions e.g CLIMB CLIMB etc, the symbol becomes a red square.

TCAS manuoevres don't have to be max G pull ups - about 1/3g and a rate of 1500fpm for about 300' should get the words we want to hear "CLEAR OF CONFLICT"

[AIEXPATS]

I found this on an ACAS Bulletin Nr. 6 published by John Law, Eurocontrol Mode S ACAS Manager of ACAS II in March 2005.

"Air traffic controllers base their actions on the comprehensive information shown on the radar display, which enables them to provide a safe and expeditious air traffic flow. The TCAS traffic display does not provide the information necessary forthe provision of separation and sequencing. Manoeuvres initiated solely on the information shown on the TCAS traffic display have often degraded flight safety. Therefore, pilots should not attempt to self-separate, nor to challenge an ATC instruction, based on the information derived solely from the TCAS traffic display. It is the controllers’ responsibility to separate aircraft."

So whether in a HOLD, SID, STAR of RV, The Controller knows what he expects you to do on horizontal scale which I assume means direction. The vertical scale is changed by the RA actions as directed by each aircraft's involved TCAS II?

[Jerricho]

Bren, I can tell you I've experienced a "4 way" in the hold at BNN. The a/c entering the hold at the top started the whole thing while the 3 aircraft in the hold were all just about to turn inbound (sods law). Avoiding action was being dealt out left right and center but TCAS certainly got involved (from memory there were 2 RA descents reported......if Hammy still reads these boards he may be able to confirm/correct). The Avoiding turns were being followed by the bottom aircraft, but I seem the remember the middle aircraft (American Operator) continue the outbound hold track for a bit.