Turbulence: Interesting Facts and Safety Tips

Every pilot knows that turbulence is, at times, unavoidable, and can be potentially dangerous. According to the FAA, in-flight turbulence is the leading cause of injuries to airline passengers and flight attendants, in nonfatal accidents. Understanding the facts and science behind turbulence can help improve safety for both pilots and passengers. Here are some interesting facts about turbulence and safety reminders from the FAA and Executive Travel.

Let’s start out with some turbulence statistics from the FAA:

• About two-thirds of turbulence-related accidents happen at or above 30,000 feet.
• Every year in the U.S., almost 60 people are injured by turbulence due to not wearing their seat belts.
• U.S. air carriers reported 234 turbulence accidents, which resulted in 298 serious injuries and three fatalities, between 1980 and 2008.
• Of the 298 serious injuries, 184 involved flight attendants and 114 involved passengers.
• At least two of the three fatalities involved passengers who were not wearing their seat belts while the seat belt sign was illuminated.

Defining and understanding turbulence

Merriam-Webster defines turbulence as irregular atmospheric motion especially when characterized by up-and-down currents. It is created by the convergence of air at the jet stream. To classify as a jet stream, winds must be greater than 50 knots. Winds are usually stronger in the winter (mid-latitude) than in the summer (lower-latitude).

Why turbulence is an issue in the U.S.

North America, and the U.S, in particular, has many natural phenomena that contributes to atmospheric instability and high turbulence rates, including a convergence of jet streams, the mountain wave over the Rocky Mountains, and a high incidence of convective activity over the contiguous U.S.

More about mountain waves

Mountain waves are oscillations of air that blow over mountain ranges. Mountain waves can cause clear-air turbulence at up to 50,000 feet, and can reach as far as 100 miles downwind from a mountain. If you fly past a large mountain range, expect a mountain wave and/or related turbulence.

Detecting clear-air turbulence

Nearly 40 percent of all turbulence-related accidents are caused by clear-air turbulence, which cannot be detected by conventional aircraft radar systems. But technology called LIDAR (Light Detection and Ranging), usually located under the nose of a plane, uses radar and lasers to detect the movement of atmospheric dust particles. The reflection of light and radar energy back to the aircraft gives pilots an early warning of clear-air turbulence.

In addition to LIDAR, advancements in meteorological science and satellites have greatly improved the accuracy of forecasts related to air turbulence. Additionally, pilot reports (PIREPs) are always included in preflight plans, providing pilots with feedback from other pilots, and the latest information from airborne aircraft.

Avoiding turbulence

Jet aircraft typically fly higher than most convective activity when possible.

As a rule, the higher an aircraft flies, the smoother the ride will be. The exception to this rule is flying near or through the tropopause — the thin layer separating the lower atmosphere from the stratosphere. This is where most weather phenomena occur. The tropopause is lower at the poles and higher at the equator.

Beware of wake turbulence

Like a wake created by a large boat, wake turbulence is turbulence created behind a plane. Large and heavy aircraft create the largest wake at slow speeds. The best way to avoid wake turbulence is to avoid it by not following other aircraft on approach too closely. Also practice on simulators on how to recognize wake turbulence.

How planes react to turbulence

Aircraft reacts to turbulence much the same way a boat reacts to hitting rough water at high speed. Turbulence can damage a plane, though it is rare. Planes today are built to withstand substantial turbulence. Since the late 1970s, all aircraft manufacturers use Boeing-designed damage tolerance engineering methods to determine airframe inspection thresholds and intervals. These give mechanics an idea of how well an aircraft will hold up under stress. These techniques have increased the life of aircraft and reduced catastrophic failures to near zero.

Turbulence takeaways and tips

• Take advantage of the latest meteorological data available to pilots—before any flight, make sure you know areas of turbulence, and their severity, and plan flight paths accordingly to avoid bad areas.
• When planning a flight, determine if the flight path passes through the tropopause, and be aware of the likelihood of turbulence.
• Keep your seatbelt fastened. It’s common sense advice, but pilots and passengers should always keep their seatbelts securely fastened, even if turbulence isn’t an issue and the seat belt sign is turned off.
• When flying west to east, consider routing in or near the jet stream to take advantage of tailwinds. When flying from east to west, avoid the jet stream, if possible.
• If flying near mountains, seek out information from other pilots PIREPs (Pilot Reports) regarding mountain waves and turbulence.
• If you encounter turbulence, slow the aircraft to turbulence penetration speed. Slowing will reduce the chance of damage to the aircraft and create a smoother ride through the turbulence.
• Avoid wake turbulence by not following larger aircraft on final approach too closely.

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