4 ms·

The SFO case is interesting, because it's not just "foreign crews don't like visual approaches". It's because the US is commonly using visual approaches kind of

The SFO case is interesting, because it's not just "foreign crews don't like visual approaches". It's because the US is commonly using visual approaches kind of as a loophole to reduce separation. All major carriers require that crews use the ILS (or RNAV) as a backup to a visual approach if it's available. But by clearing for a visual approach the controller is no longer required to keep the planes on approach separated. I know a few European airlines that encourage their crews not to accept visual approaches in the US and request an ILS approach instead, because it's safer. Europe has solved the same "we need more planes per hour" problem by allowing a reduced 2.5nm separation when both planes are established in the localizer and are radar monitored by the controller. As a pilot I prefer the European way, because it's more structured and has a few more safeguards. The US method puts the problem with the pilot, who has far worse means to judge separation than the controller

nitrogen 6y ago
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)?
- dmurray 6y ago
  Yes, it's the TCAS. It sees in all directions. It's secondary radar so it only sees planes with a transponder, but that's usually all of them. https://en.wikipedia.org/wiki/Traffic_collision_avoidance_system https://en.wikipedia.org/wiki/Traffic_collision_avoidance_sy...
  - tialaramex 6y ago
    > It's secondary radar so it only sees planes with a transponder, but that's usually all of them. 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).
    - bencoder 6y ago
      Since January 1st 2020 the requirement is for ADS-B out. So they will be reporting their GPS position also, now.
- t0mas88 6y ago
  Airliners have radar in the nose, you can see the different colored part of the nosecone on some, that's where the antenna is. It points forward, scanning horizontal, with stabilization to compensate for climbing/descending and the pilots can control the tilt to scan above/below the current altitude. 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.
andybak 6y ago
> by allowing a reduced 2.5nm separation Rather alarming to read that as nano-meters briefly!
- t0mas88 6y ago
  Haha, just millimeters from crashing in that case. Aviation is terrible at any kind of SI or even any kind of sane standardization of units at all. Distance is commonly measured in nautical miles (1852 meters), but visibility in the US is in statute miles (1600ish meter?) or feet, while Europe uses km or meters for visibility. Both US and Europe use feet for altitude, but China/Russia use meters for altitude.
- navaati 6y ago
  I did, too, but I still don't get it. Is it a typo for "min" (as in minutes) ?
  - tialaramex 6y ago
    nm is "nautical miles". A "nautical mile" is a unit that feels more natural to people concerned with the globe shape of the Earth than the conventional mile (of 1609.34 metres) because it was equivalent to one minute of latitude. Today it's just defined as 1852 metres.
  - repiret 6y ago
    Nautical miles
redis_mlc 6y ago
Well, the SK airliner basically couldn't find the ILS and descended below a safe level, ultimately hitting approach light stands in the Bay, and then the pier(!), and cartwheeling, possibly twice. It was actually filmed by a dude in Oakland. I would call that uncomfortable with visual approaches. The only good news in this accident is that aeronautical structural engineers were quite impressed the plane stayed intact. For more detail, one of the SFO ILS has been out of service or shutdown for about a a decade. They cost around $2 million (max) to install, so I don't get it. Major US airports charge over $10,000 per landing, so they can afford to maintain navaids. The other notable thing was that the pilots sat stunned in the cockpit after the accident (likely knowing their careers were over), and a stewdardess took charge and ordered the evacuation after 90 seconds passed.

nitrogen 6y ago

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)?

dmurray 6y ago
Yes, it's the TCAS. It sees in all directions. It's secondary radar so it only sees planes with a transponder, but that's usually all of them. https://en.wikipedia.org/wiki/Traffic_collision_avoidance_system https://en.wikipedia.org/wiki/Traffic_collision_avoidance_sy...
- tialaramex 6y ago
  > It's secondary radar so it only sees planes with a transponder, but that's usually all of them. 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).
  - bencoder 6y ago
    Since January 1st 2020 the requirement is for ADS-B out. So they will be reporting their GPS position also, now.
t0mas88 6y ago
Airliners have radar in the nose, you can see the different colored part of the nosecone on some, that's where the antenna is. It points forward, scanning horizontal, with stabilization to compensate for climbing/descending and the pilots can control the tilt to scan above/below the current altitude. 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.

andybak 6y ago

> by allowing a reduced 2.5nm separation Rather alarming to read that as nano-meters briefly!

t0mas88 6y ago
Haha, just millimeters from crashing in that case. Aviation is terrible at any kind of SI or even any kind of sane standardization of units at all. Distance is commonly measured in nautical miles (1852 meters), but visibility in the US is in statute miles (1600ish meter?) or feet, while Europe uses km or meters for visibility. Both US and Europe use feet for altitude, but China/Russia use meters for altitude.
navaati 6y ago
I did, too, but I still don't get it. Is it a typo for "min" (as in minutes) ?
- tialaramex 6y ago
  nm is "nautical miles". A "nautical mile" is a unit that feels more natural to people concerned with the globe shape of the Earth than the conventional mile (of 1609.34 metres) because it was equivalent to one minute of latitude. Today it's just defined as 1852 metres.
- repiret 6y ago
  Nautical miles

redis_mlc 6y ago

Well, the SK airliner basically couldn't find the ILS and descended below a safe level, ultimately hitting approach light stands in the Bay, and then the pier(!), and cartwheeling, possibly twice. It was actually filmed by a dude in Oakland. I would call that uncomfortable with visual approaches. The only good news in this accident is that aeronautical structural engineers were quite impressed the plane stayed intact. For more detail, one of the SFO ILS has been out of service or shutdown for about a a decade. They cost around $2 million (max) to install, so I don't get it. Major US airports charge over $10,000 per landing, so they can afford to maintain navaids. The other notable thing was that the pilots sat stunned in the cockpit after the accident (likely knowing their careers were over), and a stewdardess took charge and ordered the evacuation after 90 seconds passed.