Date: 9th June 2024
Location: Hartberg, Styria, Austria, near Vienna Airport
Aircraft: Airbus A320-200, registration OE-LBM
Operator: Austrian Airlines
Flight Number: OS-434
Route: Palma Mallorca, Spain, to Vienna, Austria
Occupants: 173 passengers and 6 crew
Injuries: None reported
Damage: Severe hail damage to the windshields, nose/radome, and several panels
Summary of Events
On 9th June 2024, Austrian Airlines flight OS-434 from Palma Mallorca to Vienna encountered severe hail while descending through FL200, approximately 60 nautical miles south-southwest of Vienna. The aircraft suffered extensive damage, including cracked windshields and a damaged nose radome. Despite the adverse conditions, the crew declared a Mayday and successfully landed the aircraft on Vienna’s runway 11. All passengers and crew remained uninjured.
Sequence of Events
1. Descent and Weather Encounter:
• During descent through FL227, the aircraft entered a thunderstorm cell near Hartberg, Styria.
• The weather radar failed to display the storm, and the crew reported no adverse weather indications on their primary or navigation displays.
2. Hail Strike and System Failures:
• The aircraft experienced moderate turbulence (1.75G) and severe hail damage.
• The right-hand airspeed indicator dropped significantly, triggering a master warning.
• Autopilot systems 1 and 2, as well as autothrust, deactivated. Flight controls transitioned to alternate law.
3. Crew Actions and Mayday Declaration:
• The first officer levelled the aircraft at FL190. The captain, returning from a break, assumed control and declared Mayday.
• The crew donned oxygen masks and worked the unreliable airspeed checklist but did not complete the checklist for cracked windshields.
4. Landing in Direct Law:
• During the ILS approach, the captain maintained limited visibility through small clear areas of the cracked windshield.
• Upon lowering the landing gear, the flight controls transitioned to direct law, and an overspeed warning was triggered due to unreliable speed readings.
• The crew safely landed on runway 11 and vacated the runway as instructed. The aircraft was towed to the apron.
Damage and Investigation Findings
1. Aircraft Damage:
• Severe damage to the nose radome, both windshields, and several panels caused by hail.
• Flight control systems were affected, transitioning to alternate and direct law during the flight.
2. Weather Information Limitations:
• The thunderstorm was not visible on the weather radar, and Austria’s air traffic control systems lack weather depiction capabilities.
• Pilots are informed via the AIP Austria that ATC cannot provide weather advisories or guidance on storm avoidance.
3. Crew and System Responses:
• The first officer managed the aircraft during the initial encounter, followed by the captain’s assumption of control.
• The unreliable airspeed checklist was followed, but the cracked windshield checklist was not executed.
4. Incident Classification:
• The Austrian Sicherheitsuntersuchungsstelle (SUB) rated the occurrence as an incident and launched an investigation.
Safety Risks
1. Inadequate Weather Avoidance Information:
• The absence of weather depiction capabilities in ATC systems limited the crew’s ability to avoid hazardous conditions.
2. System Failures During Critical Phases:
• Failures of the autopilot and autothrust systems, combined with unreliable airspeed indications, increased workload and operational risk.
3. Hail Damage to Aircraft Structure:
• Structural damage to the nose, radome, and windshields posed significant challenges for navigation and safe operation.
Recommendations
1. Enhanced Weather Radar Systems:
• Review and improve onboard weather radar capabilities to detect and display adverse weather conditions more effectively.
2. ATC Weather Information Integration:
• Implement weather depiction capabilities in air traffic control systems to provide real-time storm advisories.
3. Crew Training:
• Enhance crew training on managing hail encounters, system failures, and handling unreliable airspeed indications.
4. Aircraft Maintenance and Inspection:
• Conduct thorough inspections and repairs of hail-damaged components, with special attention to structural integrity and flight systems.
Safety Lessons
This incident underscores the critical importance of reliable weather radar systems and the need for robust ATC weather advisory capabilities. The crew’s prompt decision-making and adherence to emergency protocols ensured a safe outcome despite significant challenges.
Disclaimer
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Our investigation reports are based on all the evidence and facts we have at the time of writing and posting. We apologise if any details are missed or are not fully accurate.
