It’s a fair bet that among pilots, if not aerodynamic theorists, wake turbulence is one of the least understood hazards of flight. It’s not experienced very often—pilots may fly for years without encountering significant wake turbulence—you can’t see it, and there’s no safe way to simulate it convincingly in the cockpit.
The avoidance techniques taught to general aviation pilots require us to try to monitor another aircraft’s flight path and take off or touch down point while simultaneously attempting to visualize how wind drift is pushing invisible vortices across the landscape, all while we’re pretty busy managing our own airplanes in close proximity to both terra firma and the critical angle of attack. Merely to make the effort, we need to be aware that there’s another aircraft nearby whose wake could affect us. It’s easy to ignore traffic that no longer poses any collision threat, and even at a towered field, ATC might not warn us in time.
It doesn’t help that the most common rules of thumb, while useful, are decidedly incomplete. Yes, wingtip vortices are most powerful when the aircraft generating them is heavy, clean, and slow, but in 2003 a pressurized Beechcraft Baron was rolled inverted on short final by the wake of an Embraer 145 regional jet that had landed about two minutes earlier on a parallel runway. The pilot and front-seat passenger were both killed, and the other two passengers were badly injured. At that time, FAA guidance suggested that the wake could be expected to “dissipate or move away from the runway” within two minutes; the controller warned the pilot of possible wake turbulence nevertheless. The pilot, who’d accumulated more than 3,000 hours in more than 30 years of flying, acknowledged the warning just four minutes before the accident.
An ERJ 145 is certainly bigger than a Baron, but most pilots wouldn’t consider it a “heavy” aircraft in the same sense as a Boeing 757, and its landing configuration probably wasn’t clean. It didn’t matter. Nor is it safe to ignore a small airplane if it’s still bigger than yours. A little over a year ago, a single-seat Mini-Max homebuilt was “slammed down hard” by the wake of a Cessna that had taken off just before it arrived. The model of Cessna wasn’t specified, but even a Cessna 150 would have weighed more than double the Mini-Max’s maximum gross of 560 pounds.
Another pilot who’d been warned by a tower controller of “possible wake turbulence from a departing Cessna” barely recovered in time to avoid crashing; afterward, he suggested that it would have been helpful if the controller had specified that departing traffic was a fully loaded FedEx Caravan. And it’s not just airplanes, either.
Helicopter rotor wash has upset a number of other aircraft, including a Piper Cherokee 140 that was passed on short final by a helicopter landing on a parallel taxiway. The pilot attempted to go around but the Cherokee was unable to climb through the helicopter’s wake; it struck a wingtip and cartwheeled.
With all the potential for mayhem posed by nontowered fields, intersection departures, and parallel runways, it’s a relief (and maybe also a surprise) that these things don’t happen more often. About three dozen accidents have been attributed to wake turbulence over the past 10 years; the Baron was among the five that were fatal. Another 16 pilots chose to report incidents involving wake turbulence, most of which resulted in minor damage to their aircraft. The fact that wake turbulence upsets are so rare is probably a tribute to the care exercised by controllers, the lower density of operations most of the time at most nontowered fields, and perhaps, just a bit, to the wariness and skill of the pilots who operate in high-density traffic. But their very rarity also makes them more insidious. Most of the pilots who’ve survived them admit that they hadn’t expected the sudden loss of control in circumstances leaving little altitude or airspeed in which to recover.