Pilot's tip of the week

When Thermals Turn Turbulent

Featuring Scott Dennstaedt

Subscriber question:

"I know thermals form in the afternoon, but sometimes they only create minor bumps and other times my fillings are getting rattled out. It's not consistently worse on hotter days. What makes thermal turbulence turn nasty?" — Art B.

Scott:

“Perhaps one of the most common forms of turbulence we experience is called thermal turbulence. This is the turbulence that we feel during the midday when we’re flying near the surface during late spring, summer and early fall.

The heating of the day causes convective thermals to rise—but the turbulence is not typically caused by the rising thermals alone. It is the interaction between the thermals and the prevailing winds aloft that really make the bumps.

These thermals act as obstructions to the normal air flow similar to mountainous terrain. The prevailing wind must deviate around the convective thermals resulting in turbulent eddies. These turbulent eddies are then carried downwind some distance before dissipating. The turbulent eddies are what we feel as bumps. Therefore, the intensity of the turbulence is related to the intensity of the thermals and the wind velocity.

Light prevailing winds (aloft) generally result in light thermal turbulence. Stronger prevailing winds (aloft) mean that you should tighten your seat belt.”

What is the strongest turbulence you're comfortable flying through?

(NEW) VFR Mastery scenario #97 “Keeping Your Cool at Hot Springs” is now available. Two years ago, you bought a 172M with a 180 HP conversion a bit past TBO. After 100 hours you decided to overhaul, and added an engine monitor. That revealed consistently high CHTs, often hitting 430°F in the climb. Today you’re at Hot Springs, SD, with the family. It’s 85°F with density altitude near 6000′. You know that if you lean for best power the engine will get super hot. Maybe that’s fine for a short time. Or maybe keeping things cool matters more, and a full rich takeoff is safer as long as performance is adequate. Or is there a middle ground? If you wait for cooler weather, it’ll be awhile. Watch the Intro video.

Get the Pilot’s Tip of the Week

Sign up here to receive tips like this every week along with videos, quizzes and more.

  • This field is for validation purposes and should be left unchanged.