Examiners know that wake turbulence lies in wait like a Hollywood villain, with ambush skills that are equally well-honed and results that are just as final. Your pilot privileges will allow you to fly yourself and your passengers into wake turbulence situations, so the FAA has addressed the issue in the "examiner responsibility" section of the practical test standards (PTS). The PTS says, "Examiners shall test, to the greatest extent practicable, the applicant's correlative abilities rather than mere rote enumeration of facts throughout the practical test." Using this statement as a guide, many examiners thoroughly test applicants on wake turbulence awareness.
Even if your examiner doesn't emphasize this topic, the vicissitudes of chance and air traffic control (ATC) may thrust it into your flight. When you are faced with a real wake turbulence situation on the checkride, your objective becomes not scaring the examiner.
During the ground, or oral, phase of your testing, you might reasonably expect anything from brief to in-depth questioning regarding wake turbulence. Some examiners ask direct questions like "What is wake turbulence?" Others use stealthier strategies to sample your knowledge, insinuating wake turbulence considerations into questions that seem to focus on other issues. My personal favorite involves giving the applicant a scenario wherein a two-way-radio communications failure occurs after the tower has issued downwind instructions that place the applicant's airplane behind a C-130 or similar large aircraft on a long final approach. I expect the student to know how to avoid the rolling shakes of wake turbulence and keep the aircraft out of danger.
Common misconceptions about wake turbulence include just when it begins. Occasionally applicants announce that danger first appears when the generating airplane begins the takeoff roll. (It actually begins the moment the airplane leaves the ground.) Others state that wingtip vortices aloft somehow remain level for a significant time (they actually fall toward the ground and may linger just above the runway depending on wind conditions), and a few report that heavy, fast, and clean airplanes beget the strongest slipstream upheavals (it's the heavy, slow, and clean aircraft that are the most dangerous). Few examiners would fail an applicant for these mistakes alone. But if you make such an error, expect more questions.
Applicants who don't realize that the primary hazard from wake turbulence is the loss of control that results from the roll that wingtip vortices produce raise doubts in examiners' minds. Examiners want your first goal to be that of avoiding wake turbulence. If your examiner sees that avoidance is your urgent desire, questioning will likely move to other subjects.
Another common series of misconceptions includes the idea that a light crosswind weakens and rapidly dissipates wingtip vortices on the runway behind a departing airplane. The fact is that a light wind from the side can trap the upwind vortex in the takeoff zone for longer than one might imagine. You can read about this if you have the FAA advisory circular Aircraft Wake Turbulence (AC 90-23E). It's available free on the Internet (http://nasdac.faa.gov/ safety-products/WakeAC.html). This booklet can help you to avoid another misconception: Wake turbulence is always the harbinger of disaster.
Most pilots have experienced wake turbulence at some point. My first encounter with it was as a student pilot in the 1960s. I knew I had made a good 360-degree steep turn by the way my little airplane skipped timidly through its own propwash. (At the time, I quietly wondered about invisible potholes of my own making and never once connected that experience with the thought of trailing behind a bigger airplane.) But wingtip vortices can create a similar jolting effect of varying severity, depending on how close you are to the larger airplane and a variety of other factors. The fact that these wingtip vortices are invisible multiplies their danger to pilots.
Asked about avoiding wake turbulence behind a jet, some applicants say that they would notice the jet's rotation point and plan to lift off before that point, climbing above the jet's flight path. That's the correct book response, but a pilot who tries to do this could still find himself in trouble. The logical follow-up question involves the airplane's ability to climb as steeply as the jet. Some jets can climb as if they forgot something on Mars. Taking off behind one in a typical training airplane and hoping to climb more steeply than a jet shows a certain lack of awareness and judgment. Too many good pilots have challenged the horizontal tornado of wingtip vortices and lost.
Some examiners pose their question in this way: "If you wanted to refresh your knowledge on wake turbulence, in which FAA publication would you look?" The answer is the Aeronautical Information Manual (AIM). Such a query is an open invitation to open the book and look. The AIM now includes accounts of an actual wake turbulence incident in which a DC-9 flew less than two miles in trail of a DC-10, rolled, and struck the ground with a wingtip.
You may know that, under certain circumstances, ATC advises pilots of potential wake turbulence. You should also know that acknowledging a wake turbulence advisory means that you, the pilot in command (PIC), accept the responsibility for providing wake turbulence separation. As PIC, you have the authority to request additional separation, for example, two minutes instead of four or five miles, depending on the type of airplane that you must trail. Incidentally, this is precisely why ATC specifies the use of the word "heavy" in certain radio transmissions. Of course, some airplanes that weigh less than a "heavy" can produce wingtip vortices equivalent to a larger plane. The AIM notes that the Boeing 757 is such an airplane and lists separation criteria for wake turbulence avoidance. It further states that controllers may not reduce or waive this interval. Your examiner may not ask, but it's a good idea to know where to find this information.
Be sure you know the terms wake turbulence, vortices, thrust stream turbulence, jet blast, jet wash, propeller wash, and rotor wash and how they relate to your operations both on the ground and in the air. You must understand that wake turbulence avoidance is every bit as much a part of safe ground operations as it is a part of safe flying.
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