far worse means to judge separation than the controller
Those cockpit windows don't seem like they provide the best view... Out of curiosity, do civilian aircraft have onboard radar? If so, what directions can it see (up/down/front/back/sides)?
Those cockpit windows don't seem like they provide the best view... Out of curiosity, do civilian aircraft have onboard radar? If so, what directions can it see (up/down/front/back/sides)?
But it's weather radar, so it mostly sees water droplets (rainshowers, thunderstorms etc), not other planes.
The TCAS system scans for transponders from other planes in all directions, checks their path and altitude and will play audible alerts (it shouts "traffic, traffic!") when there is a potential collision risk. You can use it to see other planes on the navigation display, but you cannot legally call that "visual separation".
If a controller asks you whether you have traffic in sight (they must ask that before they can tell you to follow it for example), you cannot say you have it on the screen. That doesn't count, you have to see it out the window.
https://en.wikipedia.org/wiki/Traffic_collision_avoidance_sy...
In particular we're talking here about aeroplanes on an approach to a major airport (if they aren't on approach then by definition they aren't choosing between ILS and a visual clearance, and if it isn't a major airport why are we trying to bunch them up more?).
All US major airports have a "Mode C veil" which means there's a regulation requiring aircraft near those airports to have transponders ("Mode C" is a transponder mode in which the aircraft reports its own assessment of its altitude based on air pressure as well as a four octal identifier).