A bump in the flight – the truth about turbulence

There have been some high-profile events this year that demonstrate the extreme end of what can happen when aircraft encounter turbulence. While unsettling, turbulence isn’t normally dangerous, but it can come out of the blue and injuries can occur when passengers are not wearing their seatbelts.

So what is turbulence? One of the myths is that it’s caused by “pockets” of air, which isn’t correct. “Think of it as if you’re on a boat,” says Line Operations Manager Captain Tony Pringle. “Sometimes it’s choppy: there are currents, waves, rotations and swirls.”

Turbulence comes in many forms, and some are more predictable than others. Some are associated with weather, like storm cells, which weather radar can detect and pilots can avoid, while others correspond to geological features like mountain ranges, or even the wake from the aircraft ahead. However, the least predictable is clear air turbulence, which is hard to forecast.

But technology is helping. Cathay Pacific is a member of IATA’s Turbulence Aware programme, whereby aircraft report the wind gradient and their altitude every few minutes. This crowd-sourced data gives pilots on the same route an indication of when they might need to put the safety belt sign on or delay a meal service. “It’s like how Google Maps tells you where traffic jams are,” says Head of Line Operations Captain James Toye. 

Pilots always try to avoid areas of known turbulence, but sometimes these are too big to fly around, so there is no choice but to press on through. Despite the feeling, it is rare for altitude to deviate more than 10 feet in turbulence.

The autopilot makes corrections many times per second to counteract the changing wind gradients, in the same way that the helmsman keeps a boat on course. “You can almost never damage an aircraft with turbulence,” says Captain Pringle. “The stress from landing is significantly greater, so turbulence is more of an issue of passenger and crew safety.”

And the chance of injury from turbulence is slim, especially if everyone is buckled up – pilots always have their seatbelts fastened. So, whatever the seatbelt sign says, stay strapped in. Remember: you’re in good hands.

Predicting the severity, location and altitude of turbulence is challenging. Before each flight, pilots are equipped with weather information that lays out the position of weather systems and jet streams – high-altitude tunnels of high-speed winds – that border them. While pilots often use the tailwinds to reduce flight times in the jet stream, where it can be smooth, crossing or entering that air current is likely to be bumpy.