Why can't airplanes land in fog?

Question

If airplanes have such sophisticated equipment that measure location and distances in such precise ways, why can't pilots land airplanes in fog?

Answer 1

Do you completely trust a computer? no? well neither do pilots. especially on landings. Pilots have a little light on their Attitude Direction Indicator that says "DH" on it. DH stands for decision height. Decision Height is determined by a preset absolute altitude from within the Radio, or Radar Altimiter... (hereon referred to as RADALT) which is usually around 200 feet but can be adjusted to any altitude right down to the ground. When the plane reaches decision height above the ground, the light comes on, indicating as such, and if the pilot CANNOT see the runway, they will go around and try again or fly to another airport. If a pilot does not go around at decision height, he is usually commited to land and keep in mind... 200 feet may seem like a lot, but when you're flying at 135-140 knots just to keep your plane from falling out of the air, 200 feet is nothing!

Answer 2

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Answer 3

Auto-land systems are reliable and safe and have been in use for many years. the 0-0 landing mentioned earlier is a possibilty, as long as both the pilots and the aircraft are certified to what is known as Category 3c landing minimums. Category 3 equipment and training is VERY expensive, and not generally used. Imagine spening $500,000 in order to prevent a 4 gour delay that might happen 10 times a year...it's just not worth it. Some airlines use it at places that fog in frequently (Hawaii...also because there's really nowhere else to go if the weather drops on you enroute), but it is not very common.

The reason that pilots can't land otherwise is because if those systems are not installed, the pilots have to see the runway and land the airplane themselves. And its really hard to land on something you can't see.

Answer 4

Yes they can, in fog, heavy rain, smoke.. But it depends how much visibility there is at the runway. When an airplane is on a final approach course to land, they descend to the MDA (minimum descent altitude) a this point they have to continue flying a this altitude until they have enough runway in sight. If they have enough runway in sight they can keep descending and land. If they dont see enough runway they fly at MDA until the missed approach point. Now when I say enough runway in sight its because every instrument approach has its visibility minimums or RVR (runway visual range). For example rwy 12L at San Antonio International requires the pilot to have at least 1800 of runway in sight to be able to land. Even if the pilot sees the runway, runway lights and identifies the runways number, they can not land if they dont have the required runway visual range. And they can determine how much runway they can see because of all of the markings on the runway are seperated in 1000 or 500 feet intervals, from the threshold to the touchdown zone markers. If they dont have the required runway visual range they can not land no matter what, even if they have autoland bla bla... bla..

Now other people said some stuff about categories, for example a normal ILS approach (instrument landing system) and a ILS CAT II (category two) the diference is that the approach minimums are reduced in aircrafts altitude and visibilty, but not all aircraft can do a Category II ILS special aircrew and aicraft certification is required.

Answer 5

Aircraft can land in fog- there is very sophisticated navigation equipment available to even general aviation aircraft that allows guidance to the ground. What you may question is why would an airport be closed due to fog if the planes can land? The problem is navigation on the taxi-ways. There have been aircraft and other vehicle incursions during low visibility which makes it wiser and safer to close the airport to all traffic until conditions improve.

Answer 6

"Category III B - A precision instrument approach and landing with: a) a decision height lower than 15 m (50 ft) above touchdown zone elevation, or no decision height; and b) a runway visual range less than 200 m but not less than 50 m."

If you can see a bout 150 feet in front of the craft you can land if you are Cat II B certified..


"Category III C - A precision instrument approach and landing with no decision height and no runway visual range limitations. A Category III C system is capable of using an aircraft's autopilot to land and guide the aircraft to the terminal if required."

As of 12/18/2003 no Cat III C aproaches are authorized. I couldn't find a newer reference.

Answer 7

They can land in fog. But depending on the plane, if it's not cat 3 (I think), doing a 0-0 landing might not be possible. Now that's for big jets. If we're talking GA (general aviation), then the rules are slightly different. If the pilot can't see the runway, it's simply not safe to land.

Answer 8

They can, the aiplane does not know if it is foggy, with out cat 3 equipment and trained pilots if they cannot see the runway, the plane will land....just might n ot be exactly where it is supposed to.

Answer 9

They can land in fog (zero visbility) in category 3 airports (which are most large commercial airports). For category 1 or 2, the pilot must be able to see the runway 200 ft (I believe) before touchdown.

Answer 10

a jet liner pilot must be able to see the runway..if he does not then no go...private on the other hand is dofferent..with tools such as thermal imageing you can see as if it were a clear day. but in eather case...dont fly in the fog...bad things can happen