TCAS RA without receiving TA beforehand?

[dcoded]

Hi,

Like the title says, is it possible a flight could get an RA issued without being issued a TA before?

On aircraft such as A320 which has automatic TCAS BLUE, how would such a system cope with the RA if "TCAS BLUE" wasnt armed by triggering the TA?

[First.officer]

Most likely you won't get an arming of the "TCAS BLUE" (no TA to 'trigger') - hence no FMA, hence - back to basics in a manner of speaking, and fly in accordance with either your company SOP's, or in absence - Airbus guidance material. The trigger for you as a crew member is the absence (or not) of the "TCAS BLUE" and this then makes the difference as to how you'll handle the event.

[Tu.114]

Normally, the protected areas are staggered so that an intruder crosses the yellow TA area first before he has a chance to enter the red RA area. Here is a FAA-provided introductory pdf, in case You are interested.

If a resolution advisory is generated, it is to be followed within 5 seconds. Airbus has provided memory items for that case that have been changed a little bit with the advent of Auto-TCAS, find them in OM-B - PRO - ABN - SURV - [MEM] TCAS WARNING - RESOLUTION ADVISORY.

In a nutshell - if the auto TCAS works as intended and as required, that is fine and acceptable. But if it does not, it is the classic memory item that has been around for ages. Autopilot/Flight Director off (to achieve SPEED or MACH in the FMA), then fly the required vertical speed and have the PM announce the RA to ATC. Or, with a CLIMB RA in final approach in Config 3 or Full - go around.

Overreliance on the automatics has often caused a headache lateron...

[PENKO]

Originally Posted by dcoded

Hi,

Like the title says, is it possible a flight could get an RA issued without being issued a TA before?

On aircraft such as A320 which has automatic TCAS BLUE, how would such a system cope with the RA if "TCAS BLUE" wasnt armed by triggering the TA?

As far as FCOM goes I see no relationship between TA and RA or TCAS blue and green. From experience, you do not need a prior TA to get an RA, I have experienced and instantaneous RA. And looking at the wording in FCOM, TCAS blue is not an arming requirement for TCAS green.

[maui]

My experience is as with PENKO.
No TA. Straight to RA.
Overflying a military base (F4) at the time. Possibly someone hot dogging on take-off.
Didn't eyeball the offender.
Circumstance never revealed. Possibly because of security implications,

Maui

[Flying Wild]

I've had a TCAS RA with no TA when descending rapidly through London airspace. Had someone climbing right below us and as we approached our level, the closure rate triggered the RA. Was in a 737.

[ATC Watcher]

Not aware on Airbus " Blue" set up but I know how TACA works., and yes you can and will get RAs without prior TAs. in some situations. Think a level bust by you or the other one, or with an aircrfat cleared 1000 ft below or above you and increasing its rate of climb or descent in the last moment before leveling off . No incident here but you'll get a sudden RA.

[dcoded]

Thank you everyone!

I think this is something which needs to be trained in the simulator. We have always trained for the classic "TRAFFIC TRAFFIC" which get you alerted.
But I have never trained for a direct RA.

Thanks