Flying on the Boeing 777
Tuesday, 11 December 2007 21:29
If the weather is foggy, what are the chances of the plane being diverted?
The airline regulatory authorities such as the Civil Aviation Authority and FAA ensure that airlines are operated safely. They have rules and regulations encompassing the conduct of a safe flight in all sort of environment. To ensure compliance, they do spot checks once in a while unannounced.
So all flights are carefully planned and pilots are given weather forecasts notifying them whether they can expect good or foggy weather on arrival at the destination. In most cases, the detailed weather forecast are extremely accurate. More attention are usually paid by pilots when fog is expected. Sufficient fuel on board would be carried to cover all contingencies and an alternate airport with good weather would be nominated in the event of a diversion.
Having taken care of all the eventualities of the flight planning, the crew would proceed to the destination airfield, confident on what to expect. A well trained pilot knows his limitations when landing in poor weather condition. If the landing criteria is beyond his legal limits he would divert or answer for any infringements.
Today, most major airfields are equipped with Instrument Landing Systems (ILS) that allow landing in foggy conditions that would have shut many airports in the past. Modern airplanes, like the Boeing 777 have been designed to land even with zero visibility but the ground equipment must be maintained to a very high standard. Consequently, the maintenance costs are expensive and so most major airports in the world would only install an ILS up to Category 3B, a level lower that the Category that permits landing at zero visibility. A Category 3B approach allows an airplane to land in poor and foggy weather conditions that has a minimum visibility of 100 meters and a cloud ceiling of 20 feet.
To land in these foggy airports, pilots must be certified, qualified and current to do so. This means that they have to undertake special courses in simulators before being certified to perform automatic landings in foggy or adverse weather. To maintain currency, a pilot must perform at least 3 such automatic landings, either actual or practice landings in the last 180 days.
Therefore, if the airplane you are flying is manned by qualified and current aircrew, the chances of you being diverted from a foggy airport are very slim. Further, during an automatic landing, you can expect a smooth flight in the approach because in foggy condition, the air mass is usually very stable and the wind tends to be very light.
Landing is executed by the automatic pilot under the supervision of the Captain. On the landing roll, the aircraft will maintain center line and will come to a safe stop by means of the automatic brake. Thereafter, the Captain takes over the control and if the visibility is very poor, a "Follow Me" truck will lead the aircraft to the parking bay. You have arrived safely!