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Slow Flight

Because this is critical to a safe landing, you'll be tested on it

By Dave Wilkerson

We often hear that aviation's value to society is speed; but first, pilots must learn how to fly at very low airspeeds. The FAA's Flight Training Handbook (Advisory Circular 61-21) discusses minimum controllable airspeed (MCA), but the current private pilot practical test standards (PTS) calls it what it is — slow flight.

Slow flight training's purest objective is to cultivate a pilot's sense of feel when flying the airplane near the edge of a stall. It's vital for a pilot to know and understand an airplane's slow-flight characteristics because airplanes fly at slow airspeeds when they take off, climb, and land — and examiners do not take this subject lightly.

Examiners typically question applicants about stall speeds during the oral portion of a checkride. The examiner will likely ask for the airplane's VS1 speed. The Pilot's Handbook of Aeronautical Knowledge (FAA Advisory Circular 61-23) describes VS1 as the airplane's stalling speed or minimum steady flight speed in a specified configuration. Therefore, the examiner might ask, "The airplane's flaps are up, so what's its VS1?"

After hearing the answer, the examiner might ask, "Okay, and with full flaps, VS1 is?"

The examiner may then open the PTS to area of operation eight, "Slow Flight and Stalls," Task A, "Maneuvering During Slow Flight," point to objective three, and say, "Now let's see what the airspeeds at 1.2 VS1 would be for both the flaps-up and full-flaps configurations." The figures you quote will be the airspeeds the examiner expects you to fly, plus 10 or minus 0 knots, when you demonstrate slow flight.

During training you practiced slow flight for two distinct flight situations. The first is establishing and maintaining the specified airspeed — 1.2 VS1 — and a constant heading. This airspeed is close to what most aircraft manufacturer's recommend for approach to landing and go-arounds. The second situation mirrors the first, but it adds turns.

During the checkride, if you enter slow flight at more than 1,500 feet above ground level (AGL), you meet a requirement of objective two in the PTS, selecting an appropriate entry altitude. The examiner might ask you to enter slow flight when the aircraft is lower than 1,500 feet AGL. Because you are the pilot in command during a checkride, politely decline and say you will begin slow flight after climbing to an appropriate altitude.

All examiners should insist on clearing turns before starting maneuvers. In "Flight Instructor Responsibility," the PTS emphasizes effective visual scanning and collision avoidance, and it directs CFIs to use AC 90-48, "Pilots' Role in Collision Avoidance." Examiners must abide by this, and AC 90-48 tells them to "direct attention to the applicant's vigilance of other air traffic and an adequate clearance of the area." Annual examiner training sessions reinforce the emphasis on collision avoidance.

Once you're in slow flight, the examiner may ask for a demonstration of straight-and-level flight and level turns. He may also specify a bank angle and aircraft configuration. If the aircraft has the power, the examiner may also ask to see both straight-and-level and turning climbs and descents. Adjust the power as necessary and use coordinated control inputs.

The PTS tolerances for slow-flight maneuvering call for staying within 100 feet of the specified altitude and 10 degrees of the specified heading in straight and level flight. Maintaining heading is easy if you use ground references near the horizon, but it can be laborious if you fixate on the heading indicator. As noted earlier, airspeed has to be within the range of 10 knots faster or 0 knots slower than VS1.

If the examiner specifies a bank angle for a level turn, it must be plus or minus 0 degrees and minus 10 degrees. When the examiner asks you to roll out on a specified heading and/or level off at a specified altitude, you must be with 10 degrees and 100 feet.

Maintaining the specified airspeed, altitude, and heading tolerances, and meeting the PTS requirement to divide your attention between airplane control and orientation, seems simple enough. (Orientation includes collision avoidance as well as knowing where you are.) But these requirements harbor a hidden gremlin — distractions.

NASA's Aviation Safety Reporting System reports that cockpit conversation is far more distracting than the industry once believed. The more personal the conversation, the more distracting. Beware. The PTS directs examiners to provide realistic distraction during the flight. Many examiners launch an innocuous conversation during slow flight specifically to test your handling of distractions.

While the examiner is talking to you, he's also evaluating how you divide your attention inside and outside the cockpit. The Aeronautical Information Manual recommends during that a 20-second span you should spend four to five seconds with your eyes in the cockpit, and the remainder looking outside, looking for traffic.

Finally, Federal Aviation Regulation (FAR) 61.43, "Practical Tests: General Procedures," requires good judgment, application of aeronautical knowledge, and mastery of the aircraft, with the successful outcome of a procedure or a maneuver never seriously in doubt. When it comes to slow flight, which is among flying's most necessary skills, the PTS requirements should be the starting point of every pilot's career-long operational standard.