There’s nothing like a bit of bad weather in the UK to get everyone fretting. Perhaps we have nothing better to talk about and it’s certainly uncontroversial.
Let’s consider fog. On the ground it causes problems primarily because drivers don’t take enough account of the problems it is likely to cause. The density of traffic on the roads and the fact that there are lots of intersections junctions and alternative routes means that regulating the traffic is very difficult. If all the traffic on a particular road were going to one destination and all travelling at the same speed and all accelerating and decelerating at the same rate then driving on those roads would be very much safer.
It is regulation of air transport that makes flying much safer than being on the roads in that bad weather. On an average day a pilot will takeoff and at some stage be in cloud during the flight. The plane and the crew are equipped to do this as a matter of routine. As far as the pilot is concerned a foggy day is one where the cloud is on the ground and so it doesn’t represent any particular difficulty or danger.
To take off a pilot needs a minimum visibility along the runway. This visibility is measured by very accurate instruments on the ground. If the visibility is at or above that level of the aircraft can take off, if less than that value and aircraft cannot take off. Similarly on landing the visibility must be at a particular level before an aircraft can make an approach or land. Compared with the road conditions the visibility levels for aircraft are very low. It is quite possible to land an aircraft in thick fog in greater safety than the road traffic trying to reach or leave the airport.
Air traffic control will ensure that the runway is clear and nothing is obstructing the broadcast of the radio signals needed for the auto pilot to land the aircraft.
Before making an approach to land the pilots will check the minimum height and the minimum visibility that their company require for that aircraft to land. These conditionsare worked out between the aircraft manufacturer, the licensing authorities, the civil aviation authorities and the airlines when an aircraft is brought into service.
In a very low visibility the pilot are required to use the auto pilot to land the aircraft. You will be pleased to know that it is not one single autopilot but two or three depending upon the circumstances.
I was part of the crew that made the first totally blind landing in a jumbo sized aircraft. I was the First Officer on a Tri-Star flying from London to Paris.
In Paris (Charles de Gaulle airport) the visibility was zero and the cloudbase was at airport level. At the time this was a significant event and yet within a few years landing in such conditions was routine.
If you are flying on a day when you think the weather is bad please remember that it is much easier to fly an aeroplane than it is to drive your car.