Date: 18th December 2022
Location: 65nm NNE of Kahului, Maui, Hawaii
Aircraft: Airbus A330-200, registration N393HA
Operator: Hawaiian Airlines
Flight Number: HA-35
Route: Phoenix, Arizona (USA) to Honolulu, Hawaii (USA)
Occupants: 281 passengers and 10 crew
Injuries: 6 serious, 36 minor
Damage: Minor damage to the aircraft cabin
Summary of Events
On 18th December 2022, Hawaiian Airlines flight HA-35 from Phoenix to Honolulu encountered severe turbulence at FL400 about 40 minutes before landing. The turbulence caused significant injuries to 42 occupants, including six serious injuries. Despite the turbulence, the aircraft landed safely on Honolulu’s runway 04R.
The turbulence was linked to a rapidly rising cumulonimbus cloud in the vicinity of an approaching occluded frontal system. The National Weather Service had issued SIGMET warnings for thunderstorms up to FL380 in the area. Despite receiving meteorological advisories, the flight crew attempted to overfly the storm cell but encountered convectively induced turbulence.
Sequence of Events
1. Pre-flight Weather Briefing:
• The captain discussed turbulence and embedded convective activity with the flight dispatcher before departure. The crew was aware of the potential for adverse weather over the Hawaiian Islands.
2. Cruise Phase:
• The flight was in visual meteorological conditions (VMC) at FL400 above a cirrostratus cloud layer at FL370-FL380. The onboard weather radar showed no adverse weather returns.
3. Turbulence Encounter:
• The crew observed a vertically developing “plume-like” cloud ahead. Within 1 to 3 seconds, the aircraft encountered severe turbulence, resulting in vertical accelerations exceeding 2 Gs.
• Passengers and unsecured crew were thrown against the cabin interior, causing injuries.
4. Post-Turbulence Response:
• The flight crew declared Mayday, coordinated with the cabin crew, and continued to Honolulu. Injured passengers were identified using activated call lights to ensure medical teams could prioritize care upon landing.
5. Landing and Medical Assistance:
• The aircraft landed safely, and emergency medical personnel attended to the injured passengers and crew. 25 were transported to hospitals, with 6 diagnosed with serious injuries.
Initial Findings
Meteorological Conditions:
• An occluded frontal system with an upper-level trough caused unstable atmospheric conditions over Hawaii.
• SIGMETs warned of embedded thunderstorms with tops up to FL380 and moderate-to-severe clear air turbulence behind the main area of precipitation.
Flight Crew Actions:
• The crew attempted to overfly the storm cell instead of deviating around it, contrary to the operator’s guidelines.
• Weather radar sensitivity at higher altitudes failed to detect the developing turbulence.
• The captain did not make a public address announcement about the anticipated turbulence, potentially contributing to injuries.
Probable Cause
The NTSB concluded that the accident was caused by:
• The flight crew’s decision to overfly an observed storm cell instead of deviating around it, despite sufficient meteorological information indicating severe convective activity.
Contributing Factors:
• Inadequate weather radar sensitivity at higher altitudes.
• Insufficient communication of the turbulence risk to passengers and crew.
Safety Risks
1. Passenger and Crew Injuries:
• Unsecured passengers and crew were thrown against the cabin interior, causing serious injuries.
2. Operational Impact:
• Severe turbulence can compromise aircraft safety, disrupt flights, and cause delays.
3. Weather Radar Limitations:
• Reduced sensitivity at higher altitudes can prevent timely detection of rapidly forming convective activity.
Recommendations
1. Enhanced Weather Radar Technology:
• Improve weather radar systems to detect small but severe weather phenomena at high altitudes.
2. Flight Crew Training:
• Reinforce training on turbulence avoidance and decision-making regarding severe convective activity.
3. Passenger Safety Protocols:
• Ensure passengers understand the importance of seatbelt compliance during flight.
4. Meteorological Coordination:
• Provide flight crews with real-time updates on convective activity and turbulence risks.
Safety Lessons
This accident highlights the dangers of severe turbulence associated with convective activity and the importance of proactive decision-making by flight crews. Adhering to turbulence avoidance guidelines, maintaining open communication with passengers and crew, and advancing weather radar technology can mitigate such risks in the future.
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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.
