You're probably familiar with the dangers of wake turbulence. It's powerful, invisible, and can linger in the air for several minutes.

But what you may not know is that wake turbulence caused by the rotor wash of a helicopter is something to be equally aware of. Watch the video below to see the result of a pilot encountering the wake turbulence caused by a UH-60 Blackhawk helicopter at 27 seconds into the video...

How It Happens

Wake turbulence caused by helicopters follows the same basic principles as wake created by fixed wing airplanes. The production of lift by the rotor blades creates vortices which swirl down, out, and subsequently back up when deflected by the ground. And with light winds at 3 knots from 110 degrees, the rotor wash lingered over the runway for more than 30 seconds following the departure of the UH-60 Blackhawk.

In this specific accident in Fort Collins, Colorado, the pilot was flying his second solo in a Cirrus SR-20. In the NTSB report, the student stated that "he was aware of the helicopter and that he attempted to land long. However, just before touchdown, the airplane encountered the wake turbulence of the helicopter and then entered an un-commanded steep left bank." The student attempted to counter the left bank and go-around, but he was unable to maintain control.

The following dust-storm, created by this CH-47 Chinook, is a good visual indication of the direction, speed, and strength of rotor wash:

What You Can Do

Unfortunately, there is no information provided by the FAA in the Aeronautical Information Manual as to recommended separation criteria between light aircraft and helicopters for wake turbulence avoidance. So we recommend you follow similar procedures for wake turbulence avoidance following large aircraft. That is, stay above rotor wash, know the direction wake turbulence travels due to wind and stay upwind, and give it several minutes to fully dissipate.

Encounters like this between light aircraft and helicopters are rare, but pose a very real threat to pilots landing and departing.

The next time you see a helicopter departing or arriving ahead of you, know the risks, and be prepared to give yourself a little extra room.

Have you ever had an encounter with wake turbulence? Tell us about it in the comments.