Serious incident with the aircraft SE-RYC in connection with turbulence before landing in Helsinki

Summary

On August 11, 2024, a Boeing 737-Max 8 airliner operated by Norwegian on a service from Rhodes, Greece, encountered severe turbulence during approach to Helsinki, Finland. The event was classified as a serious incident. The onboard weather radar showed a rain shower or thunderstorm to the left of the airplane’s track. Despite the captain’s intention to avoid the developing cloud by deviating to the east, the airplane penetrated the top of the cloud in an area where it was battered by violent vertical currents and became subject to severe oscillations.

Two cabin members who were preparing the aft galley and cabin for landing became repeatedly weightless and sustained injuries on hitting aircraft structures. Both were prescribed several weeks of sick leave.

The en-route forecast that the pilots had received at Rhodes showed isolated rain-bearing or thunderstorm clouds moving slowly to the east over Estonia among other cloud formations, but no turbulence was to be expected. Because Norwegian's Boeing 737-Max 8 airplanes do not have provisions for updating an en-route weather forecast received at the departure aerodrome, only on-board weather radar picture and meteorological information from the aircraft communication addressing and reporting system (ACARS) are available to the pilots. Therefore, the incident pilots’ weather-related situational awareness regarding thunderstorms and the weather front was based on information received at the departure aerodrome several hours earlier and was deficient. The continuous use and monitoring of the weather radar combined with information from other sources, such as the ACARS, will improve pilots’ situational awareness and their preparedness to assess the effects of weather conditions along the route.

Turbulence can be avoided by keeping an adequate distance from a thunderstorm during deviation. However, Norwegian’s procedures do not prescribe a clearance to the clouds during avoidance. The probability of encounters with thunderstorm-triggered turbulence can be reduced by issuing a specific clearance to a thunderstorm during avoidance.

Norwegian’s training syllabi give insufficient attention to communications between pilots and cabin crew during turbulence-related events. The company had already experienced similar turbulence-related occurrences that had taken the cabin crew by surprise. It is essential from the viewpoint of safety that the pilots have update information of any weather-related changes along the route of flight. With this information available, they can notify the cabin crew, who can then adjust cabin service accordingly. Research indicates that climate changes are increasing the prevalence of turbulence and other extreme weather conditions, which in turn will increase the importance of intra-crew communications in the future.

The Safety Investigation Authority of Finland issued three safety recommendations with the aim of avoiding similar incidents and mitigating resulting damage.

• Norwegian improves crew training on communication between the pilots and cabin crew.
• Norwegian defines minimum clearances and procedures for thunderstorm avoidance.
• Norwegian puts more emphasis on proactive and continuous use of the weather radar during pilot training.