Originally Posted by
PukinDog
Those motives (to shift responsibility) don't apply to this case. The issuance of a visual approach by ATC if traffic ahead is reported in sight is true if that traffic is on approach to the same runway as you are. The controller can't assign a visual approach to a runway based only on having traffic in sight that's on approach to another, which was the situation here; UAL was on approach for 28R. You'll notice that ATC didn't clear Cathay for a visual approach when he confirmed he had visual contact with UAL. Cathay's clearance remained to fly a 310 heading to intercept the LOC for 28L and was never amended until much later when the offer for a visual approach came after the intercept was blown and it had all gone pear-shaped. The controller retained responsibility for the in-trail separation for the aircraft to their respective runways.
After confirming they had the traffic in sight, the "maintain visual separation" instruction Cathay received and acknowledged is an instruction that reiterates the US regulation that applies to both IFR and VFR traffic in VMC conditions, even under positive control, to see and avoid other traffic at all times, critical at SFO with converging vectors to intercept the final courses conducting simultaneous approaches in close proximity, separated laterally by only 750'. Cathay's burden of responsibility was to intercept the LOC and to maintain visual separation from the parallel traffic. By regulation, even if that traffic hadn't been pointed out or Cathay hadn't spotted them and confirmed, in those VMC conditions and despite being on an IFR flight plan under positive control, "See and Avoid" is a pilot responsibility that can't be shifted to the controller.
If in U.S. it's a mistake to believe that just because one is on an IFR flight plan and/or equipped with TCAS there is no burden of responsibility to maintain a visual traffic watch when prevailing conditions permit. It rested with Cathay as they were blowing through the LOC, one they had previously acknowledged with regards to specific traffic pointed out for them, and not linked in any way to the the issuance of visual approach. The visual approach clearance came later in an effort to salvage their arrival and only after Cathay was asked if they could proceed using one, they weren't assigned one as you describe or for the reason you've stated. The motive behind ATC's visual approach offer to Cathay was to allow them to sidestep back over to the runway 28L if they were able, at that point the only approach option left.
While all traffic has a duty to see and avoid when able to do so, a "maintain visual separation" clearance is a specific one where the pilots are required to do so if accepting it, and advise ATC if unable. It deletes the responsibility of the controller to provide separation IFR to IFR (or in some cases IFR to VFR) and places the responsibility wholly on the pilot.
To the other bloviators about miscellaneous stuff, I think the point was concern over the deterioration of basic piloting skills of people to the point they can't safely execute visual approaches anymore. This is a training and proficiency issue; the problem is that when playing in the US, this is a skill that pilots are expected to have--due largely to the extreme business of the airports and that the controllers use a variety of techniques (which are plenty safe when folks do what they're supposed to) to make it the most efficient ATC system in the world. To the extent of clearing airplanes for takeoff and landing when there is reasonable belief deconfliction has been achieved. So if you want to play there, you have to be up to the rules of the game there.
Perhaps rather than concentrating on stump the chump esoteric questions about minutia, or constructing scenarios of low probability failures, this training time would be better served by doing a bazillion visuals (with traffic and at airports we use) — with and without the magic (especially without) — to hone basic flying skills that might be needed.