Helicopter Rotor Wash Can Spoil All Your Plans

How close can you come and stay safe?

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Bell 407Bell Helicopter

Most pilots are aware of the danger of wingtip vortices from heavy fixed-wing aircraft. And they understand the wisdom of avoiding the mini-tornadoes that flow invisibly outward and down. And intuitively, we all can easily imagine that a helicopter's rotor wash stirs up the air in the immediate vicinity — picture a turbine-powered ceiling fan. But how close is too close, when it comes to takeoffs, landings and taxiing nearby a helicopter? The Aeronautical Information Manual (AIM) has some guidelines. Section 7-3-7 reads: "Pilots of small aircraft should avoid operating within three rotor diameters of any helicopter in a slow hover taxi or stationary hover." For reference, that translates to giving a Bell 407 at least 105 feet of clearance (35-foot rotor diameter); and a Sikorsky S76 at least 132 feet (44-foot rotor diameter). Think about half a football field (150 feet) and you should have plenty of buffer. In addition, the AIM recommends caution when operating in the vicinity of a landing or departing helicopter, and by extension, even getting uncomfortably close at altitude: "In forward flight, departing or landing helicopters produce a pair of strong, high-speed trailing vortices similar to wing tip vortices of larger fixed-wing aircraft. Pilots of small aircraft should use caution when operating behind or crossing behind landing and departing helicopters."

A recent news item indicated that the helicopter market has been less adversely affected by the economic downturn than the fixed-wing segment. That could mean that those of us still flying fixed-wings might be seeing more helicopter activity on average. I've seen it at my home-base airport, for sure. There's no reason helicopters and fixed-wing aircraft can't coexist pleasantly, as long as pilots of both types show courtesy and respect for each other. For example, helicopter pilots should be conscious of hovering for extended periods of time too close to an active runway, where their rotor vortices could render the runway unsafe to use. And fixed-wing pilots should become familiar with how helicopters operate in the landing pattern, on the runway and around the ramp area. At a non-tower airport, communicating over the Unicom frequency can often clear up just what the other guy is up to, and what's going to happen next.

Call to action: If you have any tips of your own you'd like to share, or have any questions about flying technique you'd like answered, send me a note at enewsletter@flyingmagazine.com. We'd love to hear from you.