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If a pilot is asked to confirm traffic in sight, but they have hard time locating the traffic visually, however, they can see it on the TCAS display.

Can they confirm they have the traffic in sight and are able to maintain visual separation based solely on TCAS?

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    $\begingroup$ No, its see and avoid, you need to make visual contact before you report "traffic in sight". If you can only see it on your TCAS or ADS-B, you can report that, but clarify that you do not have visual contact. 91.113 pretty much says you need to see and avoid, meaning visual contact. $\endgroup$ – Ron Beyer Oct 17 '16 at 1:49
  • $\begingroup$ @RonBeyer Interesting that you bring up ADS-B. The CAVS procedure allows you to use ADS-B for maintaining visual separation on approach after you have visually confirmed that the ADS-B target is there. You are still responsible for see and avoid other aircraft. See AC 91.114A $\endgroup$ – DeltaLima Oct 17 '16 at 6:53
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    $\begingroup$ @ymb1 Exactly; TCAS traffic cannot be used in lieu of actual visual separation. ADS-B traffic can be used but only under very specific circumstance. That has not only to do with identification, but with the system design, the safety cases, position integrity and a whole lot more. TCAS was never designed a replacement for visual separation. For one thing, the position accuracy of displayed traffic is very poor. $\endgroup$ – DeltaLima Oct 17 '16 at 13:01
  • $\begingroup$ @DeltaLima Yes, for approved equipment only, only on approach, and only for traffic-to-follow. You can't use CAVS for conflicting traffic. $\endgroup$ – Ron Beyer Oct 17 '16 at 13:44
  • $\begingroup$ @RonBeyer exactly. Note that there is an ADS-B application for conficting traffic as well, called TSAA (Traffic Situation Awareness including Alerts). This is basically TCAS of small aircraft. It is not a replacement of, or alternative to see & avoid / visual separation. $\endgroup$ – DeltaLima Oct 17 '16 at 14:01
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No, "in sight" or "visual contact" means seeing the actual traffic visually, with your eyes. When you report "traffic in sight," then the controllers are allowed to issue a clearance such as "maintain visual separation" or "follow that traffic, cleared visual approach...". They can't issue those clearances when you only see the traffic on TCAS. In fact, having the traffic on your TCAS display doesn't really help them.

The only time that I'll even mention that I have the called traffic on TCAS is in a situation where it may save the controller extra transmissions pointing out the traffic "now at 2 oclock moving to 1 oclock" etc. If he knows that I'm getting bearing from TCAS & will call it when I see it, that may save some radio congestion, but until I see the traffic and report it in sight, he can't clear me for anything based on visual contact.

TCAS is a great tool for collision avoidance & for awareness, but it isn't designed as a "follow that traffic" tool.

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