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It's going to be a bumpy rideIt's going to be a bumpy ride

Don’t fight turbulence—slow down and ride it out

Rodman Gomez, 46, of Jasper, Alabama, was introduced to strong turbulence on his long cross-country flight for the private pilot certificate in February 2017. The powered-paraglider instructor was flying the Cessna 150 he bought in November for training and, in the future, to commute between his two powered-paraglider schools—one in Jasper and one at Lake Wales, Florida. 
Turbulence

Causes of turbulence

Advisory Circular 00-6B, Aviation Weather, lists three causes of turbulence:

  1. Convective currents and the subsequent rising and sinking of air cause convective turbulence.
  2. Obstructions in wind flow such as trees, buildings, and mountains cause mechanical turbulence. Mountain waves are a type of mechanical turbulence.
  3. Wind shear is a change in wind speed or direction over a short distance.
Illustration by Kevin Hand

Illustration by Oliver BurstonReturning from Tupelo, Mississippi, Gomez said he encountered turbulence for more than 100 nautical miles associated with a storm system 130 miles away in Tennessee.

“It was so turbulent it was just picking the airplane up, setting it down, thrashing my wing up and down,” Gomez recalled. “I went through this for 110 miles.” He changed altitudes beneath the overcast cloud deck at 4,500 feet, hoping to find smoother air. “I was just not sure if it was going to flip me upside down, or break a wing off. You never know what could happen,” Gomez said. When Memphis Center told him to change frequency, he had a hard time getting his fingers to the radio controls on the bouncing panel. He slowed to maneuvering speed, which allows a full deflection of the controls without causing structural damage. “It was a long ride,” Gomez said of the slower speed.

It was exactly the right thing for Gomez to do. Airplanes are designed to be safe in turbulence, especially when slowed to maneuvering speed (see “VA or VAs?”). Compare it to hitting a pothole with your car: The car will wallow through the hole at very slow speeds without damage, but may require wheel realignment after banging through at high speeds. Staying at or below the maneuvering speed protects the airframe from the stresses imposed by gusts.

Bryan Adamez of Hagerstown, Maryland, is a flight instructor and founder of V1 Aeronautics, a flight school and testing center. He suggests never fighting turbulence with the flight controls. “Slow the aircraft to maneuvering speed and accept altitude changes,” he said. He encourages his students to stay relaxed and apply only enough pressure on the flight controls to keep the wings level and the nose in the level-flight attitude. “Overcorrecting can make turbulence feel worse than it is,” he said.

On the afternoon he spoke to Flight Training, Gomez had just completed another cross-country flight, and once again there was turbulence. He said this time he was much more comfortable, having had the previous experience.

Many flavors

Turbulence, like Baskin-Robbins ice cream, comes in many flavors. Unlike Baskin-Robbins, the exact number is in dispute; it varies from four to eight kinds of turbulence.

What Gomez experienced was thermal turbulence, also known as convective turbulence. It is caused by a difference in temperatures and is usually associated with weather fronts—especially fast-moving cold fronts.

Thunderstorms also have convective turbulence. You can avoid them because they are visible, but what you don’t know is that there may be associated turbulence 15 to 30 miles away.

A temperature inversion with warm air trapped above cold air offers a difference in temperatures, and where they meet there is likely to be turbulence.

Clear air turbulence or CAT is associated with clear weather involving winds of varying speeds and directions, including up and down. Entering and leaving the jet stream can offer a rough boundary layer of turbulence.

Mountains are associated with mountain waves, rotors, and general turbulence.

All aircraft cause wake turbulence. The turbulence off your trainer aircraft would be dangerous for a drone, while turbulence from a Boeing 747 is equally scary for single-engine trainer aircraft. Swirls of air off the wing tips, called wingtip vortices, are the most challenging since they can cause an unwanted banking of your aircraft.

Are there buildings at your airport with a reputation for sending swirling winds across the runway hundreds of yards away? That’s mechanical turbulence that can generate rotating air to make your touchdown more interesting.

It is rare for an aircraft to come apart in turbulence. After some digging into accident statistics, here’s what David Jack Kenny of the AOPA Air Safety Institute found: In the 20 years from 1996 to 2015, 10 general aviation aircraft weighing less than 12,500 pounds broke up in flight caused by nonconvective (non-thunderstorm) turbulence, and 30 broke up during thunderstorm encounters.

Cues to bumps

Aside from thunderstorms, turbulence is invisible, but there are indications at your local airport that may give mechanical turbulence away.

Buildings, trees, and terrain can channel and tumble the wind into rotors to harass aircraft. Wind is like a river. Water may pass over a submerged boulder that creates waves on the surface to rock your boat—but this time in a bad way. Turbulence can be created by airport buildings hundreds of yards from the runway, or nearby hills and especially mountains.

It makes reading the FAA chart supplements (formerly the airport/facility directory) or the “Additional Remarks” section of AOPA’s airport directory (www.aopa.org/airports) more important. At Sierra Vista Municipal-Libby Army Airfield, a public and U.S. Army airport in southern Arizona, you should expect wind shear when “approaching all runways.” At Oscoda-Wurtsmith Airport at Oscoda, Michigan, the remarks indicate that during daylight hours tailwinds may simultaneously exist over both ends of Runway 6/24.

It may be helpful to call the destination airport before your trip. Locals at California’s Santa Monica Municipal Airport can warn you of the “Santa Monica Swirl,” while locals at Santa Paula, California, tell of a “Santa Paula Swirl” off the former hangar of the late actor Steve McQueen.

Airports known as “aircraft carriers” because they sit on a high mesa with steep sides have special problems on windy days. Winds can’t go through the mountain, so they go up one side—across the runway—and down the other. If the wind is 90 degrees to the mesa, expect tumbling, swirling air across the runway. Such mesas include California’s popular Catalina Airport offshore of Los Angeles; Sedona Airport in Arizona (see “Road Trip: Mesa Landing,” p. 22); and North Fork Valley Airport at Paonia, Colorado, 50 miles southwest of Aspen, Colorado.

Want to visit the spot where aviation began? First Flight Airport at Kill Devil Hills, North Carolina, is the place to do that, but a turbulence tumbles to the runway through a gap in the pine trees. Airport remarks for Gnoss Field at Novato, California, 25 miles north of San Francisco, indicate it is a windy airport with turbulence “all summer.”

So how do you land in that stuff? Your training may have already provided a few clues, such as adding half the gust factor to the approach speed for better aircraft control. Is it blowing at 20 and gusting to 30 knots? That’s a 10-knot gust, so add 5 knots to the approach speed. I like to use partial flaps because full flaps give me the sensation of bobbing like a cork on the ocean in turbulent conditions

Your flight instructor ensures you don’t encounter high winds and turbulence often. When you arrive at the airport for solo practice, there may be a sign on the counter stating, “No student solo.” Even after you earn your certificate, you may want to approach flying on turbulent days with caution until you gain more experience, and a tougher stomach. Your passengers not only have limited experience with flying, they have limited experience flying in turbulence. Putting it delicately, they will enjoy it more on a calm day—and your airplane will stay cleaner, if you get my drift.

Start your certificated days with flights in light winds and gradually test your tolerance for rougher conditions. When you know what you can tolerate, set that wind condition as your personal standard. Soon you’ll laugh (silently) at pilots who complain about turbulence, because you’ll be on the ground the day they went flying. And you’ll have repeat passengers.

Alton Marsh

Alton K. Marsh

Freelance journalist
Alton K. Marsh is a former senior editor of AOPA Pilot and is now a freelance journalist specializing in aviation topics.

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