CNA explains: How often does turbulence occur and how did it affect flight SQ321?

What causes turbulence?

Turbulence occurs when an aircraft is caught in a sudden change in airflow caused by changes in wind speed and direction.

They can be created by atmospheric pressure, thunderstorms, mountain ranges, or strong air currents called jet streams.

Airplanes can shake or shake when they encounter turbulence, as can ships in rough waters.

Does it make planes crash?

Flight tracking data showed that SQ321 experienced a 1.8 km (6,000 ft) drop in four minutes.

While turbulence can cause planes to lose altitude quickly, experts said the sudden plunge of a plane the size of the Boeing 777-300ER was highly abnormal. Instead, the reaction of the pilots would have been more likely, analysts said.

“That amount of descent time (relative to) may not be subject to a downdraft, it could be more indicative of the pilots’ reaction to the situation,” Michael Daniel, CEO of consulting firm Aviation Insight, told the show. CNA’s Singapore Tonight.

Can turbulence be avoided?

Turbulence can be detected on an airplane’s weather radar if it contains water particles.

“Normally, in the event of turbulence caused by cloud movement, pilots will be alerted so they can avoid it or notify crew and passengers to wear their seat belts,” Shantanu Gangakhedkar, senior aviation consultant, told CNA938. from market research firm Frost and Sullivan.

Pilots also receive pre-flight weather briefing that includes information on potential turbulence, allowing them to make adjustments to route, altitude or speed to minimize the impact.

However, the least predictable type of disturbance is clear-sky turbulence, which can appear without visible signs.

What is clear air turbulence?

These invisible air pockets can occur at high altitudes above 30,000 feet in clear skies.

Clear-sky turbulence is often the cause of injuries as it can occur without warning, and the flight crew may not have time to instruct passengers to fasten their seat belts.

Currently, there is no technology to detect the phenomenon.

NASA says it is developing an early warning system, but experts warn it could take years.

Several analysts CNA spoke to believe SQ321 was hit by clear-air turbulence due to the sudden nature of the incident.

“Looking at the number of injuries, SQ321 (probably) encountered extreme clear-air turbulence, where an aircraft can be shaken violently (and without warning),” said independent aviation analyst Alvin Lie.

“Clear-air turbulence can occur anytime, anywhere, without prior knowledge. I believe there were many other planes flying in that area at the same time (but they were not affected). “It was just bad luck (for SQ321).”

How often does extreme turbulence occur?

The SIA plane was hit by “sudden extreme turbulence,” an intensity that experts say planes rarely encounter.

The intensity of turbulence is classified as light, moderate, severe and extreme, according to the National Weather Service of the National Oceanic and Atmospheric Administration of the United States (NOAA).

During light turbulence, which occurs quite frequently, passengers may experience slight bumps.

During extreme turbulence, which occurs very rarely, an airplane can be shaken violently and become momentarily uncontrollable. It can also cause structural damage.

Experts say commercial airliners are designed to fly in difficult weather conditions.

Deaths or serious injuries related to turbulence also remain extremely rare.

Are some roads bumpier than others?

Some regions are more prone to turbulence, particularly areas with more weather activities.

“Southeast Asia is a region that is known to have more storm activity and is therefore likely to experience more turbulence,” said Leithen Francis, managing director of Francis & Low, a specialist aviation marketing agency.

The SIA flight was flying over the Irrawaddy basin in Myanmar when it encountered the sudden and extreme turbulence.

Scientists have warned that severe turbulence has increased by 55 percent over the past 40 years and is expected to increase further due to the impact of climate change.

How do people get hurt during turbulence?

Most turbulence-related injuries occur because passengers and crew members are not wearing seat belts.

Sudden, severe movements of an airplane during turbulence can cause people to be thrown around the cabin.

In the case of SQ321, witnesses said those not wearing seat belts were thrown against the roof, hitting the luggage compartments above.

Even with seat belts fastened, passengers can be hit by flying objects or falling luggage if the overhead compartments are suddenly opened.

Experts highlight that crew members are the most at risk for injuries since they are not buckled up most of the time, including having to check passengers’ seat belts when the signals come on.

What can passengers do to stay safe?

Be diligent, experts say.

Fasten your seat belt when seated, even at cruising altitude when the “fasten seat belt” sign is not on.

Attendants also advise passengers to pay attention to safety instructions before takeoff and to listen to crew and pilot announcements during the flight.

“We cannot anticipate sudden turbulence, which could cause serious injuries when people are not buckled up. So, when you are in the seat, be diligent and buckle up whether there is a fasten seat belt sign or not,” said Mr. Daniel. .