The National Transportation Safety Board (NTSB) is sending an accredited representative along with four technical advisors to support the Singapore Transport Safety Investigation Bureau’s (TSIB) inquiry into the turbulence incident involving Singapore Airlines Flight 321. This collaboration is in accordance with the International Civil Aviation Organization’s (ICAO) Annex 13 guidelines.
Flight Diversion and Incident Details
A Singapore-bound Boeing 777-300ER, operating as Flight SQ 321, was diverted to Bangkok, where it landed at 15:45 local time (08:00 GMT). According to a statement from the airline, the flight was carrying 211 passengers and 18 crew members. Tragically, one passenger was killed as a result of a heart attack, and more than 30 others were injured after the flight from London to Singapore encountered severe turbulence. The airline later reported, “As of 1950hrs Singapore time on 21 May 2024, 18 individuals have been hospitalized. Another 12 are being treated in hospitals.” According to ADS-B data, the aircraft’s ground speed rapidly decreased by approximately 20 knots just before it began a controlled descent from FL370 to FL310. The data also indicate that about 15 minutes earlier, while en route at FL370 over Myanmar, approximately 350 nautical miles west-northwest of Bangkok, the aircraft experienced an altitude deviation of -100 to +300 feet.
NTSB’s Focus on Turbulence-Related Incidents
The NTSB has a longstanding concern regarding turbulence-related accidents and incidents. In 2021, the NTSB published a comprehensive Safety Research Report focused on preventing injuries caused by turbulence. The report delves into the frequency and risk factors associated with turbulence in Part 121 air carrier operations, evaluates the effectiveness of current safety measures, and proposes improvements for avoiding turbulence and mitigating injuries.
To compile the report, the NTSB employed both quantitative and qualitative research methods, including a thorough literature review, analysis of aviation accident data, and interviews with various stakeholders from government and industry sectors. Additionally, the NTSB conducted in-depth investigations into 10 turbulence-related Part 121 accidents.
The research identified several critical safety issues:
- Insufficient reporting and sharing of turbulence observations.
- A lack of collective awareness about turbulence risks.
- The need for better mitigation of common injury scenarios related to turbulence.
- The necessity for updated turbulence guidelines.
Based on these findings, the NTSB issued 18 new recommendations to the Federal Aviation Administration (FAA), two to the National Weather Service, and one to industry associations including Airlines for America, the National Air Carrier Association, and the Regional Airline Association. The NTSB also reiterated three recommendations to the FAA and classified one additional recommendation as reiterated.
The report revealed that turbulence contributed to more than one-third (38%) of Part 121 air carrier accidents from 2009 to 2018.
Importance of Seat Belts for Passengers
One key takeaway for passengers is the importance of wearing seat belts, which significantly reduces the risk of injury during turbulence. The research found that passengers constituted only 21 percent of those seriously injured by turbulence, with nearly all being unbelted at the time of the incident.
However, flight attendants are more frequently injured during turbulence, accounting for 79 percent of serious injuries in the incidents studied. These injuries often occur as flight attendants prepare the cabin for landing, a phase when the seat belt sign is usually illuminated for passengers. The NTSB concluded that having flight attendants seated and buckled earlier in the descent phase could reduce their injury rates and overall turbulence-related accidents.
Despite the NTSB’s recommendations, the FAA has yet to revise its turbulence guidance for airlines. The recommendation to secure flight attendants at higher altitudes during descent was also made more than 20 years ago by the Commercial Aviation Safety Team but has not been widely adopted. Since the 2021 NTSB report, there have been 30 turbulence-related air carrier accidents, with reports completed and available for 11 of them. More than half of these accidents involved flight attendants seriously injured at or below 20,000 feet.
The NTSB continues to advocate for updated safety measures to protect both passengers and crew from turbulence-related injuries.