TCAS before take-off

[FlyingForFun]

Hi,

I'm curious about the thoughts of current airline pilots on a recent incident which I was witness to.

I was in the visual circuit at a regional airport. An airliner was lined up on the runway, and cleared for take-off by ATC. He read back his take-off clearance, but did not move. After a moment, he informed ATC that he had a "TCAS contact" in his 11 o'clock at +100'.

ATC suggested it may be the helicoptor which was hovering in the helicoptor training area to the left of the runway. The helicoptor pilot confirmed that they were squawking 7000. ATC asked the helicoptor to switch the transponder off, and the airline pilot confirmed that his TCAS contact had gone.

From where I was looking (and my pilot passenger), it appeared to be a case of "the computer can't see the helicoptor any more, so it must be safe to take off now". Of course that isn't the case - I'm confident that the airline pilot had the helicoptor in sight (although he never said so, and ATC never asked him).

But I was just curious: what do your company's SOPs say about this kind of situation. Would the airliner have been allowed to take off by the company's SOPs with the TCAS contact there, and was the pilot being over-cautious querying it with ATC? If the SOPs prevent a take-off with a TCAS contact like this, is it sensible that simply switching off the transponder in the "offending" helicoptor would enable the take-off to go ahead?

Just to clarify, I don't have any gripe with the actions of anyone involved in this incident - I'm asking purely to satisfy my own curiosity about the way TCAS is used.

Thanks!

FFF
--------------

[False Capture]

More like an airmanship issue as opposed to an SOP. If the controller had told the crew about the helicopter, I doubt there'd have been much delay in the departure. However, when presented with a target on your TCAS display and no-one has told you about it, sounds only reasonable to question it.

I wouldn't get too carried-away with what you saw FFF, especially when you consider a TCAS Resolution Advisory is inhibited below 1000' radio altitude.

[FlyingForFun]

Thanks, FC.

Didn't realise that RAs are inhibited below 1000' (maybe I learnt it once for the written exams but have forgotten it since?)

So in this scenario, it would have been sufficient for the controller to point out the heli to the airliner, no need to actually get the heli to switch the transponder off?

Like I said, not getting carried away at all, just trying to learn more - and have learnt one thing from your reply already.

FFF
-------------

[Capt Claret]

FlyingForFun

I would imagine the question from the 'cleared to take-off' aircraft was more due to the proximity of the traffic and given it's proximity, not knowing it's intentions, rather than the fact that there was a traffic paint.

[vancouv]

Presumably getting the heli to switch his transponder off was just a way to confirm that it was really was him causing the TA? Kind of the opposite to squawking ident!

[False Capture]

FFF,

So in this scenario, it would have been sufficient for the controller to point out the heli to the airliner, no need to actually get the heli to switch the transponder off?

In short ... YES.
In most airlines you'll find the only SOP is for TCAS to be operated in TA/RA mode before take-off. Questioning the Traffic Advisory which was visible at +100' feet would amount to situation awareness/airmanship.
Dare I say, at a major international airport the controller would have alerted the crew to the position of the helicopter and in return the crew would be expected to take-off without delay.