Why would a plane start to land in the fog then pull out at the last second?

Question

I live right next to the airport in San Diego. When it's foggy the planes will come very close to landing but (what seems like) at the last second fly right over and circle. Is this because the pilot decided at the last second not to land or because he is being instructed not to by the airport?

Answer 1

San Diego does  have an ILS first of all, but they almost never land on runway 9.  The winds usually favor runway 27 and they only have a LOC runway 27.

What you are seeing is the pilots following the approach system down to the lowest point they are authorized to reach without seeing the runway.  There are a bunch of different types of instrument approaches, but for the most part, they all rely on the pilots to see the runway and land on it at some point.

The approach gets them down to a safe altitude that is hopefully below the clouds.  If they see the runway at that point, they land.  In not they execute the "missed approach" described above.  After a missed approach, they can come back and try it again or divert to an alternate airport.

There is not "last second" decision not to land.  Pilots are trained and prepared to do a missed approach.  We know exactly what to do when reaching the missed approach point (MAP) and the procedure is even charted so all we have to do is follow the direction on our approach plates (essentially little maps that tell us all we need to know about each different approach)

Here's an approach plate:  http://204.108.4.16/d-tpp/0801/00373L27....

We know how to read those and  what to do.  Rest assured that a missed approach is not exactly "abnormal" we are well-trained and we do them with some level of regularity.

Answer 2

Couple of possibilities.

1. His approach was too high and he would be landing too far down the runway.

2. He flew an Instrument approach for one runway but intended to land on another. He uses the instrument approach to get down to the airport, once in site, the pilot maneuvers to land on the other. (The other runway may not have a published Instrument Approach).

3. He decided his visibility was not good enough to attempt to land. His visibility may not be as good as yours.

4. He was shooting a practice approach in real IFR conditions and did not intend to land. He was just getting some valuable training.

5. The tower instructed the pilot not to land. Perhaps another plane was somewhere on the runway.

6. He looked down at the airport and said "OH c**p, WRONG AIRPORT!" and flew away before anyone noticed:)

Answer 3

Actually, a commercially flown airplane cannot even begin an approach to land if the ceiling and / or visibility are not reported to be above the prescribed "minimums". If they begin an approach while the ceiling and visibility are at or above those values, but then the airport goes "below minimums", they may continue all the way to the "decision height" or "missed approach point", depending on the type of approach being flown. These points are quite low and quite close to the runway (typically 200-500 feet high and 1/2 mile out) although some airlines with specially equipped airplanes and specially trained pilots are authorized for even lower minimums. .In either case, if they cannot see the runway well enough at that point to make a safe landing, they MUST execute a missed approach.  

A non-commercial (private) aircraft does not have quite the same restrictions. Even if the ceiling and visibility are reported below minimums, the pilot may still make an instrument approach for a "look see". If they get to the MAP or DH and the runway is in sight, they may land, if not, they go around.

Quite often in foggy conditions in southern California you can see down through the fog if it is thin but you cannot see horizontally through it at all, particularly when flying toward the sun. I used to fly freight into Burbank every morning very early, 5 days a week, and it was often foggy there. If I could make it in before sunrise, I could see the runway lights and land, no problem, but after sunrise the glare off the fog was so great I couldn't see anything, so I'd have to circle until the sun got higher, and / or the fog burned off, or I'd have to go to another airport.

Answer 4

He can't see the ground.

Answer 5

They could be cleared for an ILS approach with a circle to land instruction.

Answer 6

It's called a Missed Approach, and they are quite common in certain types of weather conditions.  If the crew are flying an ILS (Instrument Landing System) approach, they must be able to see the runway environment at a certain distance and altitude if they are to complete the landing safely.

If they reach the specified position and altitude (called the Missed Approach Point) and cannot see the runway environment, they must initiate a Missed Approach.  Typically they go back to the airways navigation point and try again, under the control of ATC.  If they can't see it on the second try, and unless conditions are improving, then the usual procedure is to go to the designated alternate airport.

Answer 7

When visibility is impaired, planes use the ILS to land. They do not need to see the field until just prior to touchdown. If they are told to go around by the controller, they do.

Answer 8

AIRCRAFT HAVE MINIMUM VISIBILITY AND ALTITUDE REQUIREMENTS. IF CERTAIN CONDITIONS ARE NOT MET THE PILOT MUST ABORT THE LANDING AND EITHER GO AROUND FOR ANOTHER APPROACH OR FLY TO AN ALTERNATE AIRPORT. CONDITIONS  REQUIRED  WILL VARY WITH THE EQUIPMENT AT THE AIRPORT AND EQUIPMENT ON THE PLANE.

Answer 9

Having shot ENDLESS approaches into NAS North Island... it is simply because he HAS to see the ground before he can land... EVEN if he is doing a GCA / ILS approach.

WE used to CHEAT constantly at NAS North Island (prior to thermal imaging)... the CREWMAN would turn on the radar so the pilots could see the physical land features, and then lean out the door of the helicopter and look DOWN so he could call the points on the approach.

MANY a time I would be the ONLY one who could see the threshold as we passed over.

Answer 10

Actually the pilot can still land the plane in the fog, ILS (Instrument Landing System) helps to guide the plane down to a safe landing whether it be fog a white out or even heavy rain. The tower also helps, if the pilots have any questions. But in this case if the plane was coming down it may have had a warning that it was to fast  or descending to rapidly, also called sink rate, It could have also been another aircraft on the runway so he avoided a collision but that hasn't happened since the 70's (on the ground anyway)