Airborne weather radar
This tool is your first line of defense against dangerous meteorological conditions.
By David Ison
Contributing Writer
Radar systems like the Garmin GWX 8000 StormOptix enable pilots to see a “slice” of a storm’s interior, where color codes represent rain intensity. Green indicates lighter rain, yellow shows moderate to heavy rain, and magenta suggests intense precipitation.
Encounters with bad weather continue to make headlines in the aviation world, serving as stark reminders of nature’s power and the critical importance of proper weather radar usage. As examples, we have the IndiGo Airbus A321 that sustained significant radome damage after encountering a hailstorm near Srinagar, India in May 2025, and a Ryanair flight the following month that had to make an emergency landing in Germany due to violent turbulence that injured 9 passengers. These 2 cases highlight the importance of every pilot being fully proficient in operating their weather radar system.
For pilots unfamiliar with weather radar operations, these systems are your primary tool for detecting and avoiding dangerous precipitation. Unlike ground-based weather services that provide broad regional pictures, your airborne radar shows real-time conditions directly ahead of your flight path.
Understanding how to use this equipment properly can mean the difference between a routine flight and a life-threatening encounter. Even people with extensive experience in radar need refreshers from time to time. Let’s revisit this essential tool and explore how to use it.
Life-saving color code
Most airborne weather radar systems display precipitation intensity using a simple color scheme that every pilot should be familiar with. Green indicates light precipitation, yellow shows moderate intensity, and red represents heavy precipitation.
For light aircraft, the rule is straightforward – green means proceed with caution, yellow means the ride won’t be pleasant, and red means don’t go there. For larger aircraft, red may be penetrable if confirmed as non-convective heavy rain, but this requires advanced evaluation skills that most pilots shouldn’t attempt without extensive training.
The key insight from recent weather encounters is that storms developing rapidly can catch even experienced crews off guard. During the IndiGo incident, the crew requested deviations, which were denied due to airspace restrictions, forcing them to penetrate the weather system. This highlights why early detection and planning are crucial.
Master the CAST technique
Professional pilots rely on 4 essential radar skills, easily remembered by the acronym CAST – contouring, attenuation, sensitivity, and tilt. These techniques work together to provide a complete picture of the weather ahead.
Contouring refers to analyzing storm shapes and patterns. Smooth, rounded, uniformly colored echoes typically indicate stratiform precipitation, while closely spaced, intense cores suggest dangerous convective activity. The IndiGo flight encountered what authorities described as a cumulonimbus system – precisely the type of aggressive, towering storm that radar contouring helps identify.
Attenuation occurs when heavy precipitation absorbs or reflects radar energy, creating “shadows” behind intense cells.
This can hide additional dangerous weather, making a treacherous path look safe. Always assume that areas immediately behind intense red returns may contain hidden threats. Never fly the plane into a location where you cannot paint behind it.
Sensitivity (or gain) controls how much weak precipitation is displayed on your screen. Too little sensitivity and you might miss developing weather. On the other hand, with too much sensitivity, your screen becomes cluttered with ground clutter and light returns that obscure real threats.
A rule of thumb is to turn down gain by 50%. If you still see precipitation, avoid it. Another often-used estimate is to turn down the gain fully. If anything still paints, avoid it like the plague. And don’t forget to turn the gain back up when you’re down.
Tilt management is perhaps the most critical skill. Between the aircraft flying at high altitude and the curvature of the Earth, an improperly tilted beam can shoot over storm tops, making dangerous weather invisible. The general rule is to use a slight down tilt of zero for weather detection, adjusting based on your altitude and the distance to the weather. More on this later.
Trust but verify
Understanding radar limitations is crucial for flight safety, as these systems can mask dangerous weather conditions that pose significant threats to aircraft operations.
Pilots must remain vigilant about dry hail and snow, which reflect radar energy poorly and may appear as light precipitation. They may also disappear entirely from the display, creating a false sense of security when flying through what appears to be benign weather.
Thunderstorms that develop rapidly present another critical challenge, as these cells can intensify from moderate to severe conditions within minutes – faster than most radar systems can update their sweep cycles. This means that the weather ahead may be significantly worse than what appears on your screen.
Attenuation creates perhaps the most insidious threat, where heavy precipitation absorbs radar energy and creates “shadow zones” behind intense cells, hiding completely additional dangerous weather that could include embedded thunderstorms, hail cores, or severe turbulence.
Given these inherent radar limitations, pilots must adjust continuously tilt settings, range selections, and gain controls throughout different phases of flight, using higher tilt angles during climb to detect weather above, zero or slightly negative tilt during cruise for optimal detection, and careful low-tilt scanning during descent to capture ground-level threats.
Operational strategy
The most essential lesson about radar isn’t technical, but rather philosophical. Weather radar should be used defensively, not as a tool to thread between cells. Professional pilots must maintain generous separation from any weather return, understanding that radar shows where precipitation is, but doesn’t detect turbulence, windshear, or hail.
Consider altitude in your planning. The IndiGo crew was cruising at FL360 when they encountered the storm, yet still experienced “warnings of angle of attack fault, alternate law protection lost, and backup speed scale unreliable” with descent rates reaching 8500 fpm. Even at high altitudes, severe weather can overwhelm aircraft systems and challenge the most experienced crews.
Pre-flight weather intelligence
Effective weather avoidance begins long before you turn on the radar. Monitor weather briefings for:
• Convective SIGMETs indicating thunderstorm activity.
• Lifted Index values below zero, suggesting atmospheric instability.
• Windshear reports or rapid wind direction changes.
• Temperature-dewpoint spreads exceeding 15–30° C, indicating potential microburst activity.
• How other aircraft are handling the situation. Are they deviating from their planned routes? Are they turning around? Going to their alternate?
Both the IndiGo and Ryanair incidents occurred during periods of known severe weather activity. The Indian Meteorological Department had issued a red alert for Delhi-NCR warning of heavy rainfall, hailstorms, and gusty winds up to 80 kph. Similarly, severe storms were affecting southern Germany when the Ryanair flight encountered its difficulties.
One thing to note, however, is that when viewing ground-based radar imagery, it is essential to determine whether you are looking at a composite image or a single-site image. Since composite images show overlapping areas of coverage, the intensity of storms displayed on composite versions tends to be over-exaggerated. Regardless, the proper technique of airborne radar use will eliminate any misinformation.
In addition to using your radar’s maximum effective range (typically 200 to 300 nm) for tactical avoidance, you could also use it for strategic planning. Long-range detection allows time to plan alternative routes, request different altitudes, or even delay departure.
At closer ranges (80 miles or less), focus on specific cell characteristics and gaps. Remember that apparent gaps between cells may close rapidly, and areas of light precipitation can intensify within minutes during active weather periods.
The human factor
The IndiGo and Ryanair incidents highlight how even modern aircraft and well-trained crews can be challenged by severe weather. The IndiGo crew flew the aircraft manually till they exited the hailstorm after multiple system warnings.
Meanwhile, the Ryanair captain requested medical assistance ahead of landing due to passenger injuries from turbulence. These scenarios underscore that weather radar, while essential, is just one tool in a comprehensive weather avoidance strategy. The goal isn’t to defeat the weather – it’s to avoid it entirely.
Weather radar proficiency should be a basic survival skill. The recent IndiGo and Ryanair incidents demonstrate that even brief encounters with severe weather can cause significant damage to aircraft, result in injuries to passengers, and pose a challenge to even the most experienced crews.
Master your radar’s controls, understand its limitations, and always err on the side of caution. Remember that passengers trust you to keep them safe, and no schedule pressure is worth flying into conditions that could compromise that trust. When the weather looks questionable, it probably is, and your radar is there to help you stay clear of nature’s most dangerous moods. The best weather penetration technique remains the same as it’s always been – don’t penetrate the weather at all.
David Ison, PhD is an aviation researcher, educator, and planner with the Washington State Department of Transportation (WSDOT). He has authored numerous publications on aviation operations, technology, and safety, and his expertise spans both academic and applied domains of the industry. Dr Ison is also the author of the book titled Navigating Weather: A Pilot’s Guide to Airborne and Ground-Based Weather Radar.