1)At least the pilots managed to go around bottoming out at 200ft vertical after the ground proximity warning went off.
10 km vis, and they needed the GPWS to tell them something was wrong. Not really all that different to Asiana. Also a 787, and if I’m not mistaken (I’ll check with a friend who flies them), the HUD projects a synthetic runway onto the display. Zero excuse.
2)Sounds like VMC (visual meteorological conditions) at HKG (edited from PVG)
ILS glideslope reported to be “fluctuating” but aircraft cleared for ILS landing.
They quite regularly fluctuate, which is why movements on the ground are restricted when low vis conditions are in force. Aircraft landing or taking off in front of you will also distort the beams. You just need to be watching for it.
3) Rule of thumb of 300 ft vertical per 1nm from runway threshold suggests they should have been approx 800ft at 2.6nm
Yes. And the sink rate should never really change much from 650 feet per minute. If it goes above, or below that, there should be an obvious reason.
What would be the reason for not turning off the GS which then would result in VFR only approach?
We don’t know that it was VMC, only the wind and visibility at ground level. What was the cloud base?
You can turn the G/S off, and do a localiser only approach. In the A380, that was almost as precise (and used the same procedures) as an ILS. I haven’t been to HK for a few years, so I don’t know what GPS approaches are available.
What alternatives are there to the ILS glideslope?
Well, if the cloud lets you you, looking out the window has always worked for me. Being aware of ILS issues, is obviously what everyone else was doing. You could do a localiser only approach. You could query the issue with ATC, and do another approach or go to another runway. To be honest though, the aircraft registration tells me all I need to know.