Waypoints: Riding the wake

The wind was out of about 310 degrees at 12 knots—a quartering headwind. “We might get some wake,” Hirschman advised. I watched carefully where the Legacy lifted off and planned my touchdown well before that, but knew the headwind might blow some wake back down the runway. In anticipation of a thump, I added a few knots to the airspeed, wanting a bit more roll control on short final.

At the same time I thought of the article by CFII, designated pilot examiner, and mathematician Catherine Cavagnaro in the December 2018 issue of AOPA Pilot (“Proficiency: In the Vortex”). In it—and in convincing videos she has created—Cavagnaro says the FAA guidance in the Aeronautical Information Manual and other publications is wrong when it says that a wing begins to generate wake turbulence at liftoff. She contends that wake vortices begin as soon as the wing begins to generate lift, which is well before the airplane actually gets into the air.

Given that and the quartering headwind blowing any vortices my way, I could expect to feel some turbulence over the numbers or even before. Another swipe of the throttle for an extra knot or two. With more than 7,000 feet of runway available I was not worried about rolling off the end.

Sure enough, right over the runway and just before I started to flare, the airplane rolled right and the bottom fell out. I tugged on the yoke and rolled in opposite aileron just as the right main landing gear touched down and then the left and with a solid thump we were on the ground.

While it all turned out fine, I should have gone around. It was already a tight approach, given the late takeoff clearance to the Legacy. In my mind, I was following a “business jet.” Sure, it’s bigger than the Beechcraft Bonanza A36, but, I thought, not that much bigger. Later I reminded myself that the Legacy is almost as large as the Embraer ERJ 145 regional airliner. I take no consolation in the fact that the tower controller never issued a wake turbulence warning. As pilot in command I’m responsible for my airplane and its safety, and I should have been more proactive in responding to the dynamic situation.

Perhaps it was experience that led me to not respond aggressively enough to the threat of wake turbulence. Having participated in hundreds of air-to-air photo missions over the years, I’ve often encountered wake turbulence. As the lead photo platform, the Bonanza often gets caught up in wake turbulence from the two aircraft in the formation as we fly circles on a calm evening. With no wind to break them up, the vortices hang in the air and we hit them on the next circuit. It’s usually just a little bounce and not much more. But the photo missions are usually of airplanes of similar size, although the size does vary a lot.

When flying as the subject in the photo mission—in the trailing position—there’s the same possible wake encounter when flying in circles, but also the chance encounter when drifting a little too far to the 6 o’clock position behind the lead airplane. There, the intensity of the experience can vary greatly. One of the worst encounters I have had was flying behind a Piper Lance. On another occasion, I got a strong rolling moment off of a Commander 114.

In either case and in others, the initial aileron input to counteract the rolling moment of the vortices is ineffective. The airplane will continue to roll for a second, which seems much longer as it unfolds, but then as you drift out of the vortices, the airplane snaps back.

Although I take some comfort that these encounters occur at altitude with lots of time to recover, I am also reminded of the Bombardier CL604 Challenger flying along at 34,000 feet over the Arabian Sea when an Airbus A380 passed overhead at 35,000 feet. Forty-five seconds later the Challenger rolled over several times and plummeted 8,700 feet, causing injuries to the passengers and crew. It landed safely but was deemed unrepairable because of the structural damage.

Wake turbulence: hard to spot, but easier to predict. Plan to stay away.

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