Background
The flight crew, properly certificated and qualified, received flight release documents from airline dispatch that were incomplete and lacked pertinent Convective SIGMETs and a tornado watch bulletin. Despite this, the crew observed a computerized weather display before departure and noted a line of adverse weather along their intended route.
Flight and Weather Encounter
During initial climb after takeoff, the crew noticed they were approaching a line of thunderstorms. The captain initially planned to fly around the line but observed a 10-mile gap depicted on the aircraft's onboard weather radar display. The captain decided to fly through this gap, which was also visible looking outside. The first officer did not challenge the decision. Both crewmembers stated the weather radar was functioning normally, though it remains unknown exactly what was depicted on the radar.
Radar and weather data indicate that the airplane penetrated an extreme weather echo classified as VIP level 6, which likely contained a severe thunderstorm, hail, and severe to extreme turbulence. The thunderstorm top was above 45,000 feet.
Injuries and Damage
Neither the flight attendants nor the passengers received an adequate or timely briefing to remain seated and prepare for potential turbulence. During the encounter, the aft flight attendant and a passenger sustained serious injuries. Hail shattered the front windshield and damaged the pitot system, radome, wings, tail, and engines. The flight crew successfully performed an emergency landing at a nearby airport.
Investigation Findings
The investigation revealed that the captain had been involved in two prior air carrier incidents involving adverse weather conditions. The airline lacked adequate training and guidance regarding hazardous weather interpretation and avoidance, as well as adequate procedures to notify flight attendants about potential turbulence. According to FAA guidance, flight crews should avoid intense or extreme level radar echoes by at least 20 miles, and such echoes should be separated by at least 40 miles before attempting to fly between them.