Weather Radar Cannot Detect Bad Decisions

When pilots first learn to fly, they are taught how to understand weather characteristics so they can learn when and how to avoid anything that might put their aircraft in danger. As pilots progress in their career, their perspective on weather must shift. They must learn how to operate in and near adverse weather while keeping their aircraft and passengers safe.

With each level of aircraft system sophistication comes added confidence in being able to endure weather challenges. Aircraft anti-/de-ice systems, cabin pressurization, intricate navigation, and weather radar all add layers of safety when trying to navigate over or around hazardous weather. All these components allow pilots to make decisions in challenging conditions, but they can also lure a pilot into a weather system's trap.

Pilot Lure

On February 22, 2023, a King Air 200 was destroyed, killing four passengers and the pilot, when it was involved in an accident near Little Rock (LIT), Arkansas. Despite Low-Level Wind Shear (LLWS) advisory alerts transmitted by both tower and ground control during the taxi, the pilot requested takeoff clearance and departed. Low-Level Wind Shear refers to a sudden change in wind velocity and/or direction that can be hazardous to aircraft during takeoff, landing, or while flying at low altitudes.

A video surveillance camera shows the airplane take off normally and begin an initial climb to the south. Just as the airplane goes out of sight, about one mile from the airport, the camera records a rising plume of smoke. Shortly after, the camera appears to shake from the wind and records blowing debris and heavy rain on the ramp where the camera is located.

Weather reports from Little Rock show that what the camera recorded was consistent with rapidly changing/deteriorating weather conditions shown on the radar.

• Prior to departure, winds were: 210° at 19 gusting to 27 kts
• Moments after the departure, winds were: 300° at 22 gusting to 40 kts

The conditions at the accident site were Visual Meteorological Condition (VMC) and 4700 ft overcast ceiling, but the radar imagery at the time of the accident shows a fast-moving convective line speeding from west to east.

We all think it won't happen to us, but how many times have YOU looked at the radar one last time before departure and thought, If I don't get out of here now, we'll be stuck for hours…I've got to get out of here before this weather arrives…If I can just get airborne, I can use the radar to pick my way through this weather? So let's take a closer look at weather radar and some of its limitations.

R.A.D.A.R. Basics

RADAR is the acronym that comes from Radio Detection and Ranging. As the name implies, radars use radio waves to determine the distance and velocity of the targets they hit. A radar system usually consists of a transmitter to send out radio signals and a receiver to catch any reflected energy from targets. In most cases, the transmitting and receiving antenna is the same.

The width of the radar beam is like that of a flashlight shown on a distant wall. The radar beam spreads out as it gets further away from the transmitting antenna, resulting in less reflected energy back to us and our radar display.

The takeaway is that even intense precipitation far from us may produce weak or no returns at all due to beam spread. The closer we get, especially under 50 miles, the better the picture. But that also means your aircraft is that much closer to the storm and the dangers which are not necessarily in it but surrounding it.

NEXRAD

Weather reporting still has infinite variables, but with emerging technologies, those variables are now better tracked with the Next Generation Weather Radar (NEXRAD). With new data-linked systems in aircraft and data-linked NEXRAD radar, pilots can see radar returns hundreds of miles ahead because it is not limited to a narrow horizontal and vertical beam directly in front the aircraft. This has created a revolution in the way pilots approach thunderstorm avoidance, but one of the biggest limitations of NEXRAD is also the biggest lure into bad weather—a time delay.

NEXRAD radars take multiple vertical and horizontal scans, which are then collated with other stations prior to broadcast. As a result, the radar picture is at least 10 minutes old prior to reaching your aircraft. Because of this time delay, you should not use data-linked NEXRAD imagery for making departure decisions, tactical weather avoidance like weaving around cells, or navigating your way through a storm complex.

Instead, NEXRAD should be used as a strategic tool to give strong storm cells a wide berth. Your NEXRAD cockpit display is something that happened in the past, so that "clear" path ahead of you may just be a lure into the storm. This is where your onboard weather radar becomes the most valuable tool in the aircraft for weather avoidance, but onboard weather radar does not work on the ground and, once airborne, has its own limitations like shadowing and attenuations (which is described in detail in the Weather Radar training module).

Not on the Radar

Blending an understanding of the limitations of radar and the common characteristics of weather AROUND thunderstorms is the key for safety. Radar returns shows the storm in that moment, but not necessarily the environment around it and the stage of the storm. Pilots must learn to interpret the trend of the storm; is it still growing, topped out, collapsing, and which way is the system moving? Each phase and movement have different surrounding characteristics, but they're all hazardous to aircraft. In addition to hail and lighting, it's the unpredictable airflow surrounding and ahead of the storm which was the key element in the sequence of an incoming storm that brought down the King Air.

Outflow from the movement of a thunderstorm (not just within the storm itself) is the air that flows away from a storm system. It can contain a wedge of rain-cooled air that radiates from the storm. This wedge is called an outflow boundary, or gust front, and it's created when a thunderstorm's downdraft of air hits the ground and spreads out.

This rain-cooled air is denser than the surrounding air, so it falls and creates an outflow boundary. Outflow boundaries create low-level wind shear like in the King Air crash that is sudden, unpredictable, and severe. Both an understanding of radar and the characteristics of weather near thunderstorms is needed to make safe decisions.

How do YOU Change Plan Continuation Bias

Now, let's take your knowledge of NEXRAD, overlay it on the King Air crash at LIT, and help create risk mitigation for your own flight department. Every situation requires an individual assessment, but you can use this conversation for discussion at your next pilot safety briefing.

Scenario

ATIS included a Low-Level Wind Shear (LLWS) alert, and both ground and tower transmitted LLWS advisory alerts within two minutes prior to the aircraft being cleared for takeoff.

• If an LLWS alert is issued while you taxi out or on approach to land with convective activity in the area, what criteria do you or your company use to decide to continue or change your plan?
• Do you update takeoff or landing performance numbers based on any adjustments you make to aircraft speeds?
• Considering the delay of datalink weather radar, how close can a thunderstorm be displayed to the airport before you delay departure or arrival?
• What techniques do you use with your onboard weather radar to evaluate storms when you are near or on the ground?
• Do you have limits on how close to the airport a certain intensity level of precipitation may be before you delay departure or arrival?

Reminders

• Just because another aircraft landed a few minutes ahead of you doesn't mean that conditions didn't drastically change.
• Stay alert and be on the lookout for planned continuation bias and use this time during training to review company rules or come up with personal limits on operating near convective activity.
• Having limits established and well-ingrained will improve your decision-making during high workload phases of flight.

The King Air accident, several case studies, and more in-depth radar information are included in Advanced Aircrew Academy's updated Weather Radar module that is designed to provide the required understanding and knowledge for flight crews to assess summertime weather conditions that may be potentially hazardous to flight.

The module includes a detailed operational perspective on using onboard airborne and data-uplinked NEXRAD weather radar. We also present specific scenarios and incidents about weather-related accidents in turbine business aircraft flown by professional flight crews.

This module also includes information on the following documents:

• FAA Advisory Circular (AC) 00-24C Thunderstorms and (AC) 00-54 Aviation Weather Services
• NTSB Safety Alert 11 Thunderstorm Encounters and Safety Alert 17 In-Cockpit NEXRAD Mosaic Imagery

For more information about how Advanced Aircrew Academy can provide customized eLearning for your entire flight department, email info@aircrewacademy.com or visit our website.