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Landing in Fog: How Pilots Find the Runway

2 min read

The short answer

In fog, pilots follow radio beams from the runway that guide them precisely left and right, up and down. Many planes can even land themselves. Strict rules set what the pilots must see, and when. If they can't see enough in time, they simply climb away and try again, or land elsewhere.

Radio Beams Lead the Way

Most large airports have an instrument landing system. Two radio beams shine out from the runway. One shows the pilots whether they're left or right of the centre line. The other shows whether they're too high or too low.

Instruments in the cockpit show the plane's exact position, even when nothing can be seen outside.

The Plane Can Land Itself

In thick fog, many airliners use autoland. The autopilot follows the radio beams all the way down. It raises the nose just before touchdown and lands on the centre line. It can even steer the plane along the runway afterwards.

The pilots watch every step, ready to take over. Read more about autopilot.

Strict Rules on What Pilots Must See

Every approach has a decision point. By then, the pilots must see the runway or its lights — otherwise they climb away.

  • In normal low cloud, that point is usually 200 feet above the ground.
  • In the thickest fog, with autoland, it can be much lower. In Europe, some landings need only about 75 metres of visibility along the runway.

These special landings need three things: an approved plane, specially trained pilots and an airport with extra protections. All three must be in place.

The Airport Plays Its Part

When fog rolls in, the airport switches to low-visibility procedures. Vehicles and planes are kept clear of the radio beams, arrivals are spaced further apart, and extra lights guide the way.

That's why foggy days can bring delays. There are fewer landings per hour, purely for safety's sake. You might circle for a while before landing.

If the Runway Doesn't Appear

If the pilots can't see what they need by the decision point, they climb away. This is a routine go-around. They may try again or fly to a backup airport with clearer weather. The fuel for this is always on board.

What You'll Notice

  • Grey outside the window until the last moments, then the runway lights appear.
  • Often a very smooth, precise touchdown — autoland is famously exact.
  • Perhaps a short wait or a slower taxi to the gate.

Sources

Keep reading

Autopilot: What It Does and What It Doesn't

What autopilot really does — and why the pilots are always in charge.

Go-Arounds Explained

Why a plane sometimes climbs away instead of landing — what a go-around is, why pilots choose it, and what you'll hear and feel.

How Pilots Navigate Weather

How pilots plan around rain, storms, turbulence and ice — and why weather is never a surprise.

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