ELi5 Why are planes grounded when there is fog but they can fly through fog and clouds.

Question

I dont understand when they have control towers and such advanced technology why fog can ground planes. Not much is done by eyesight now surely?

In: Technology

Answer 1

Instrument rated pilot here. It is possible to land a plane in “zero zero” conditions, meaning clouds are to the ground and you can’t see anything ahead of you. Doing so requires the aircraft and runway to have special equipment and the aircrew to have special training. Check out Cat III Autoland, there are plenty of videos on YouTube. Any instrument approach will have “minimums”, a required vertical visibility to land. This is typically 200 feet, or 100 feet with certain lighting systems.

Approaches are flown with GPS, ground based radio beacons (instrument landing system), or a combination of the two (GLS).

Visual approaches are quite common in good weather. Planes can land closer together in visual conditions.