How Airline Pilots Use Radar to Avoid Bad Weather


Weather radar is a pilot’s best friend, and there’s one under the domed nose of every AC aircraft.

Whether in the air or not, I’m always on the lookout for inclement weather. It’s amazing what you can see from a few hundred feet up or at cruising altitude – and for what I don’t catch I’m glad to have my aircraft’s onboard weather radar. Radar detects precipitation, which, if significant, implies turbulence because the air is unstable and moving about and can cause a bumpy ride.

The radar is housed in the nose of an airliner – it’s called a radome (radar dome), and it can be hinged open for servicing. Weather radar was derived from World War II technology (just like its cousin, the microwave oven). Radar sends out pulses of microwave energy, and precipitation reflects it back to the receiver. It is a great detector of rain, but other types of precipitation reflect less energy so a pilot must challenge these “returns.”

August 18, 2020
Air Canada B787 Flight deck Christmas tree

Generally, what’s painted on the radar screen looks a lot like what you see in your phone’s weather app: Light precipitation is green, medium intensity is yellow with red as heavy to extremely heavy. (Some radars paint magenta for the extreme category.) Pilots avoid those red returns.

My Boeing 787 radar incorporates multi–scan technology where only threat weather is displayed. An airliner’s radar range is typically 320 nautical miles and, like our radios and our line of sight, is limited due to the curvature of the earth. Now that we have Internet access in the flight deck, we can download radar data in near real–time – the Internet’s slight lag means our onboard radar takes precedence.

To this day, another great method for avoiding heavy showers and turbulent cloud (and an important complement to radar technology) is using a pair of eyeballs. You’ll find me scanning the sky, and – at night with the flight deck lighting turned down – acutely looking outside.

A close up of a screen using weather radar on an Air Canada plane

More About Radar

  • RADAR stands for radio detection and ranging.

  • Weather radar came about haphazardly from radar surveillance during World War II. Radar operators, tasked to monitor enemy activity, discovered certain weather caused echoes on their screens that potentially masked enemy targets. After the war, further research on this “radar noise” gave rise to weather radar.

  • Procedures require that weather radar is switched on during flight but must be turned off while we are parked or approaching the gate.

  • Every Air Canada aircraft has weather radar. Smaller airplanes do not.

  • Usually, weather radar itself is not able to detect turbulence. The strong returns from heavy precipitation within a thunderstorm are directly related to the powerful updrafts and downdrafts necessary to produce water drops of significant size and density. The 787 I fly can depict turbulence from shearing winds out to 40 miles and is colour coded magenta.

  • The “painting on the weather radar” is aviation lingo for what is currently depicted on the radar screen.

  • Experienced pilots reference radar returns as: “cell,” “build up,” “convective build up,” or just “weather” (as in…“Denver Center, we have some “weather” up ahead, request a ten degree turn to the left,”); they may also say “painting weather,” and “good returns” (weather radar is seeing cells).

  • We international pilots scrutinize weather radar as we traverse the ITCZ – Intertropical Converge Zone – near the equator where thunderstorms lurk daily.

  • Precipitation, from the most reflective to the least: wet hail, rain, wet snow, dry hail, ice crystals, snow, and drizzle.

Portrait of Air Canada's Captain Doug Morris
Photo: Reynard Li

Doug Morris is an author, meteorologist, instructor and Air Canada captain on the Boeing 787.