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Why can't planes land in fog?

Newcastle, Australia
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Why can't planes land in fog?

My flight got diverted earlier this week when fog prevented it landing at Sydney airport. Not really what I wanted coming from LAX via AKL with 4 young kids but at least Brisbane was sunny.

So I have been wondering why, with all the technology available to airlines and airports, fog prevents planes from landing?

Amsterdam, The...
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1. Re: Why can't planes land in fog?

Because the pilot can't see and it's dangerous.

Sydney, Australia
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2. Re: Why can't planes land in fog?

If the pilots can't see the ground, they can't know where to land.

Some airports, such as Heathrow, have automatic systems that will allow a plane to land in fog, but these systems require expensive equipment at the airport and on the planes. Sydney does not often have a problem with fog, so it is not worth the expense of installing the systems.

Fredericia, Denmark
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3. Re: Why can't planes land in fog?

It is possible to land a plane with ILS, but for security reasons a minimum sight is required.

Hitchin, United...
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4. Re: Why can't planes land in fog?

Aircraft can theoretically land in fog with no problems and sometimes have to in the most dire emergency situations. As you rightly say the aircraft and the airports (in general) have the systems to allow that, and in most cases these days the aircraft wouldn't need any input from the pilot either. The trouble comes on the ground where an aircraft just becomes a really big, fast moving ground vehicle (steered by a human after touchdown and roll out), if there is an obstruction (a vehicle, another aircraft etc) on a taxiway or stuck on a runway, no amount of avionics technology will stop you stuffing into it, or clipping the wing on a pier while taxying.

For those reasons of ground visibility, at a few hundred feet the aircraft computer calls out "minimums" which is the pilot's decision height. If he can't see the runway at that point, he goes around to try again or he goes elsewhere.

Banbury
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5. Re: Why can't planes land in fog?

>>>It is possible to land a plane with ILS, but for security reasons a minimum sight is required

I think you mean safety

A good example of you can go wrong when a plane tries to land or take off in fog at an airport without the proper facilities can be found here …wikipedia.org/wiki/Tenerife_airport_disaster

6. Re: Why can't planes land in fog?

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London, United...
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7. Re: Why can't planes land in fog?

Yep, it's as others have said, it's simply common sense, if you can't see the ground well enough in advance, it's not really a good idea to try to land it,,,would be a little bit like the childrens game of pin the tail on the donkey.:-))

Amsterdam, The...
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8. Re: Why can't planes land in fog?

I read that no airports in Oz have Cat II or Cat III ILS capabilty (or they may have but CASA don't authorise them for ALS (automatic landing systems)) simply because they don't get that much fog.

Kinda like putting snowploughs on Hawai.

Is that the case??

UK
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9. Re: Why can't planes land in fog?

Add to all that, even when they can and do land in fog, for example at Heathrow, the minimum landing times between successive planes is lengthened considerably, so there likely isn't enough time at congested airpots operating to the max, to land all planes, so some have to be diverted.

Italy
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10. Re: Why can't planes land in fog?

Better to land in Brisbane than not be here to tell the tale but seriously it's a question of safety, if the pilot can't see the runway then he will usually cruise around to wait if it clears a bit but no pilot will risk landing when he can't see.