Undetected Turbulence Singapore Airlines SQ321

Clear air turbulence (CAT) tends to occur in summer when weather conditions are clear.

AFP/LILLIAN SUWANRUMPHA

Singapore Airlines with flight number SQ321 from Singapore to London made an emergency landing due to severe turbulence at Suvarnabhumi International Airport in Bangkok, Thailand, on Wednesday (22/5/2024).

The plane Singapore Airlines experienced turbulence while flying over the Indian Ocean which dropped 6,000 feet or about 1,800 meters in three minutes. The flight from London, England, to Singapore resulted in the death of a British man, while 30 other passengers were injured. The Boeing 777-300ER aircraft was forced to make an emergency landing at Svarnabhumi Airport, Bangkok, Thailand, on Tuesday (21/5/2024).

The exact cause of the 73-year-old victim's death is still under investigation. Authorities say that it is possible that the victim suffered a heart attack, although this has not yet been confirmed. Ten ambulances and several fire trucks were deployed by airport management to assist in the evacuation process for the passengers.

Flight SQ321 of Singapore Airlines was carrying 211 passengers and 18 crew members. According to data from FlightRadar 24, the plane was at an altitude of 37,000 feet above sea level when turbulence occurred. Suddenly, the plane sharply plunged, dropping significantly to 31,000 feet within three minutes.

The plane managed to stay at an altitude of 31,000 feet or around 9,400 meters for less than 10 minutes, before descending quickly and landing in Bangkok in less than 30 minutes. The decline occurred when the flight over the Andaman Sea approached Myanmar's territorial territory (Kompas.id, 21/5/2024).

AP PHOTO/SAKCHAI LALIT

A number of ambulances await passengers on the London-Singapore flight which experienced heavy turbulence in Bangkok, Thailand, Tuesday (21/5/2024).

Responding to this, former pilot for commercial flights, Captain Hanafi Herlim, stated that the heavy turbulence experienced by flight SQ321 was considered extreme and very rare.

"This incident could not be detected by the pilot, by the eye or by weather radar. "Because, this incident occurred when the weather was bright, clear nothing happened," he said.

This phenomenon is called clear air turbulence (clear air turbulence/CAT). This undetectable, invisible and unidentifiable condition means that pilots cannot monitor signs of CAT.

Hanafi added that clear-air turbulence (CAT) tends to occur during the summer when the weather is sunny. Its presence cannot be detected by the naked eye or even radar equipment. On the other hand, the turbulence caused by rainy weather can be seen on radar. This is because the equipment will show bad weather conditions, with masses of red-colored clouds, allowing pilots to avoid it. Pilots can avoid turbulence 10-20 minutes before the plane enters the affected area.

In the context of Indonesia, severe turbulence such as CAT can occur at any time. The geographical conditions of an area do not affect the formation of CAT.

KOMPAS/RADITYA HELABUMI (RAD)

Illustration of sunny weather

What is turbulence?

Turbulence is unstable air that moves unpredictably. Many people associate them with large storms, but the most dangerous type is clear-air turbulence which usually occurs without warning in the sky.

Clear air turbulence most often occurs in or close to highland rivers called jet streams. The cause is wind shear, aka wind that changes suddenly in a short time. This event can occur when two large masses of air are close to each other and then move at different speeds.

If the difference is significant enough, the atmosphere cannot withstand the pressure and transforms into turbulent patterns like swirling water. This type of turbulence can occur even when the sky is clear, without clouds.

"When you experience a wind shift near the jet stream, which then triggers air overflow, it forms chaotic movements in the air," said the Chair of the Applied Aviation Science Department at Embry-Riddle Aeronautical University in Florida, Thomas Guinn.

AFP/ROSLAN RAHMAN

Passengers of Singapore Airlines flight SQ321 from London to Singapore, which made an emergency landing in Bangkok, have met their family members at Changi Airport in Singapore on May 22, 2024.

How common are injuries due to turbulence?

Identifying the number of injuries due to turbulence is difficult, but several countries publish national data.

More than a third of all airline incidents in the United States (US) from 2009-2018 were correlated with turbulence. The majority resulted in one or more serious injuries but did not cause any damage to the aircraft, as reported by the US National Transportation Safety Board.

Between 2009 and 2021, at least 163 people were seriously injured during turbulence and required hospitalization for around two days. Most of the victims were flight attendants who tended to leave their seats during the flight.

"It is not common to experience turbulence that results in minor injuries or, let's say, broken bones. However, fatal incidents are extremely rare, especially in large aircraft," said the scientist at the National Science Foundation's National Center for Atmospheric Research, Larry Cornman.

The same thing was expressed by Paul Hayes, Director of Safety Consultant of Cirium Ascend based in England. Fatal turbulence is very uncommon and rare. This incident occurred after more than 25 years since a passenger died from turbulence in a commercial aircraft.

Nowadays, standardized safety procedures have been improved to prevent more occurrences of serious injuries. This includes reviewing weather forecasts, pilots reporting when facing turbulence and delaying cabin service when the aircraft is in poor condition.

MO

Illustration. Pilots perform pre-flight checks in the cockpit of a Boeing 737 Max jet. Photo taken Wednesday (2/12/2020).

Can the pilot avoid turbulence?

Pilots use various methods to avoid turbulence, including utilizing weather radar displays. Sometimes, they are able to see and fly around thunderstorms.

Hanafi said that when turbulence occurs, pilots can immediately reduce speed, warning all passengers and cabin crew to fasten their seat belts. The pilot also activated anti-icing to prevent the engine from suddenly stopping.

Nevertheless, clear air turbulence is another issue. According to former aircraft pilot and safety consultant Doug Moss, this phenomenon can be destructive. "Because, before the incident occurs, the condition can be so calm, and people become unaware," he said.

Air traffic controllers will remind pilots after other planes have experienced clear air turbulence. Many pilots will check the upper part of the jet stream on their route to see signs of wind shifts. After that, they will fly higher, lower, or around that area.

Modern planes have now been designed to be strong enough to withstand various types of turbulence. Cabin areas, such as the overhead bins, are at risk of having their appearance damaged. However, these damages do not affect the aircraft's structure.

Is the frequency of turbulence increasing due to climate change?

A number of scientists believe that the incidence of turbulence is increasing. There are various explanations for this, but some scientists believe it is due to the impact of climate change.

According to Professor of Atmosphere Science at the University of Reading in England, Paul Williams, there is strong evidence that turbulence rates are increasing due to climate change. Research conducted with his team found that severe turbulence in clear air over the North Atlantic has increased by up to 55 percent since 1979. The team's projections indicate that severe turbulence in jet streams may increase two to three times in the coming decades if global conditions continue.

Despite this, there are also other factors that have an impact. Cornman argues that heavy turbulence can increase due to the increase in air traffic. As a result, there is a possibility that turbulence will increase along with the increase in the number of flight routes.

Indonesian aviation expert Alvin Lie stated that there is no scientific evidence linking climate change to turbulence. This is because this type of turbulence has been occurring since ancient times.

“Climate change is disrupting weather patterns, it should be the rainy season, but it's still hot. Vice versa," he said.

KOMPAS/RADITYA HELABUMI

Illustration. Cabin crew close the briefing during flight preparation (pre-flight check) by praying. Photo taken Monday (8/4/2024).

How can passengers stay safe during a flight?

Use a seat belt. Turbulence is difficult to predict, but experts emphasize that the first line of defense in the air is to always tighten the seat belt whenever possible.

“In general, airplanes are built to withstand turbulence. Put on your seat belt. That's the shortest way to prevent injury,” Guinn said. (AP/REUTERS)