Avgeek Alert: A Look at the Cockpit’s Weather Radar


For the average person, being able to fly a commercial jetliner seems almost unthinkable. The fact is that pilots, in addition to their impressively rigorous  training, have access to various and sundry tools to help them navigate the airways. And one of those concerns an extremely important aspect of flying: dealing with weather conditions. This weather radar is right front and centre on the flight-deck instrument panel, and here’s a little more about this cruicial piece of equipment:

First of all, it’s important to note that pilots already have weather information before each takeoff (provided in Spain by the AMA (service of the State Meteorological Agency). Pilots are provided with a user name and password to access all weather-related data that will help prepare them for the flight. They also rely on information from other pilots (known as “pilot reports”), so they know in advance what they’re going to encounter. But during the flight they have the weather radar in front of them, with which they can learn in detail about any weather phenomena or any atmospheric conditions that could affect the flight, such as rain, storms or wind.  

How Does Weather Radar Work?  


The origins of radar can be traced back to the World War II-era United States. At that time, radar systems’ main function was for pilots to detect other aircraft in the area. Radar operators discovered, however, that there were signals on their monitors that were unrelated to aircraft, and it soon became clear that these signals were generated by atmospheric phenomena. At the end of the war, a number of radar systems were modified for meteorological use and immediately distributed throughout the country.   

Radar works with a system of microwaves sent from the aircraft and returned in the form of an echo when they encounter an obstacle (in weather terms, hail, snow, ice, rain, and so forth). This system is usually housed inside the nose of the aircraft and is made of a special material that allows radar waves to pass through it without any problem. With weather radar, changes in the speed and direction of water droplets can even detect turbulence.  

Interpreting the Colours on the Radar Screen


Different weather phenomena are marked with corresponding colours: green, yellow and red. In air communications between pilots and controllers, there are three levels of feedback:  Level 1 (green) means that there is light and weak precipitation, with little or no turbulence, although visibility may be reduced. Level 2 (yellow) indicates moderate precipitation; visibility can be very low while passing through the area, and turbulence is usually moderate (we know that turbulence doesn’t pose danger, but for some people it can be uncomfortable). And Level 3 (red) marks heavy and intense precipitation, thunderstorms and severe turbulence.  It’s customary to avoid Level 2 whenever possible and naturally to always avoid Level 3.  

If the aircraft encounters cloud formations which could trigger rain, thunderstorms or wind gusts, the pilot usually looks for the clear zones between them, or they either fly around or over them. It’s relatively common to fly with the autopilot engaged so that the crew can be attuned to any other weather-related issues. For example, they may request clearance from air-traffic control to deviate from the approved route to areas free of bad weather, but if a storm is in the vicinity of the airport, delaying take-off or landing may be considered until the weather improves, which enhances flight safety.  

Under Which Conditions Is Weather Radar most Useful?


Pilots can usually detect a cloud formation with potential problems visually, but weather radar is especially useful in areas of heavy cloud cover or at night. And of course not all clouds generate thunderstorms or heavy precipitation; the ones to watch out for are the storm clouds, cumulonimbus. They’re abbreviated as CB, and so in aviation lingo they’re also known as “Charlie Bravo”. These are clouds with strong vertical structure, formed by the overheating of the atmosphere and associated not only with thunderstorms or torrential rain but also with hail, snow, lightning (as well as, on the ground, tornadoes).