Aerodrome forecasts

A study focused on the production and dissemination of aerodrome forecasts (TAFs) indicates that improvements in the forecast accuracy may yield a significant benefit to airline customers. Aerodrome forecasts represent a critical component of airline flight operations.

Improvements in TAF accuracy lower an airline’s cost of operations. Knowledge of the future weather conditions at the destination and alternates directly affect the decisions made about the conduct of the flight. Aerodrome forecasts represent one of many pieces of information that assist dispatches and pilots in determining the amount of fuel to load, the best alternate aerodrome to use and deciding whether or not to cancel or delay the flight. Annual savings can be attributed to three key aspects of airline operations: fuel burn or payload substitution, number of diversions and number of fuel stops.

The avoidance of flight cancellations and delays, reduction in the number of missed approaches and diversions can be the result of accurate aerodrome forecasts.

 36 Exercise 3.

Flying forecast

Pilots are keenly aware of weather conditions at all times, and they won't even take off if it isn't safe. Besides, there are strict rules regarding what pilots may and may not do in every sort of weather condition.

During a flight, pilots constantly monitor the onboard weather radar so they can avoid areas of heavy precipitation or anything that even looks like a thunder­storm. Each airline also employs a team of meteorologists who forecast the weath­er around the clock in order to minimize flight delays and other problems.

One of the trickiest conditions to forecast is fog which is just very low cloud cover. Today, flying through fog isn't a problem, but when it comes to taking off and landing, each airport and each airplane are rated for a low allowable visibil­ity (the distance you can see the runway and other objects clearly). Some airports also impose a minimum ceiling (the distance of clear air from ground to clouds), often about 200 feet.

Some newer aircraft (like the Boeing 777) and pilots are even rated to land in zero visibility conditions based on electronic instru­ments that are installed at some airports and on the airplane. In these cases, the autopilot can do everything from land to taxi to park outside the gate.

 37 Exercise 4.

Meteorological hazards

Weather phenomena can be considered as potential hazards for flights.

Thunderstorms and cumulonimbus clouds in the vicinity of the airport are dangerous for taking off and landing.

Fog, haze, smoke, dust, torrential rain and low cloud are all approach and landing hazards. Such conditions have the potential to reduce conditions below the required landing minima. If this occurs, the pilot must not hesitate to abort the approach and proceed to an alternate destination.

During flight, the pilot can see and avoid many hazardous weather phenomena, such as thunderstorms and areas of forecast severe turbulence. There is one meteorological hazard known as clear аir turbulence (CAT) that occurs at cruise altitude and which is very difficult to detect. CAT can cause sudden and severe turbulence. It is often encountered in areas where there is jet-stream activity.

Lightning strikes can occur as a result of having to fly in areas where cumulonimbus clouds are present. Damage to the airframe, instruments, radio communications and even the pilot’s vision can occur.

When the aircraft flies through super-cooled rain, sleet or snow, ice may form.

Ice may be ingested into the engine causing damage and possibly requiring engines to be shutdown.

The best opportunity for pilots to avoid meteorological hazards comes with careful planning of the flight. Planning a route to avoid severe weather, the consideration of alternate destinations and rigidly following correct procedures all give maximum safety margins.

 38 Exercise 5.