Instructor Report

In the sometimes-mysterious process of becoming a proficient instrument pilot, improper sequencing of data is at the heart of most common errors.

Less mysterious is why so many instrument students get snookered into flying with an incorrect scan. Students tend to focus on the parameters emphasized most by their instructors: altitude, heading, and airspeed. If a student is repeatedly told to maintain altitude as the airplane drifts away from level flight, he or she will focus more attention on the altimeter. The instrument scan turns into a game of Whack-A-Mole. Here is why.

The altimeter, heading indicator, and airspeed indicator all are lagging indicators that show deviations well after they are visible elsewhere on the panel. The pilot who flies predominantly by scanning these three instruments—or worse, fixating on one of them—will spend precious time and energy correcting for one deviation after another. Consuming mental bandwidth with these corrections makes it more difficult to maintain aircraft control, while also accomplishing the many other tasks associated with flight in the instrument environment. By learning a proper way of thinking about instrument flying, with a scan to match, we can eliminate this constant chase, free up bandwidth, and make instrument flight easier and more enjoyable.

Many pilots have heard of the “inverted V” scan. To fully utilize this tool we must rewire our brains to focus primarily on the three flight instruments we tend to look at the least. Here’s an exercise that will transform our instrument flying, and might help transform our entire concept of aircraft control: Attitude control is aircraft control.

In level flight and after clearing the practice area, ensure that the airplane is trimmed for a typical cruise airspeed. The airplane should have enough energy that frequent power changes are not necessary.

With the student flying with a view-limiting device, the flight instructor or safety pilot covers the airspeed and heading indicators, as well as the altimeter. In a conventional six-pack instrument panel, this leaves the inverted V: the attitude indicator at the top, vertical speed indicator on the lower right, and turn coordinator at the lower left.

The scan goes from the attitude indicator to the VSI, back to the attitude indicator, then to the turn coordinator, and repeat. Initially focus on the relationship between the attitude indicator and the VSI. To fly a heading, wings should be level on the attitude indicator.

The scan between attitude indicator and the VSI is the key. Many pilots ignore the VSI because they’ve heard the instrument lags and is inaccurate. Maybe we collectively missed the part about instantaneous trend information, i.e., climb or descent. If we see the VSI increase—as might happen when entering a thermal—we scan back to the attitude indicator and lower pitch to return the VSI to zero. If the VSI shows a descent, we refer to the attitude indicator, increasing pitch enough to keep the VSI at zero. Power adjustment is reserved for situations extreme enough to induce an airspeed increase or decrease of more than 10 percent, or when we add climbs and descents to our practice.

In a well-trimmed aircraft, this practice quickly turns into a gentle massage of pitch attitude with reference to the attitude indicator. Guard against a tendency to omit attitude from the equation and control directly with reference to the VSI. It might take a short time to get the hang of this, so be patient. In bumpy air, a fairly rapid scan between attitude indicator and VSI may be required. It is OK, even preferable, to do this in the kind of thermal-induced turbulence that normally would provide an excuse for altitude deviation.

After practicing this skill, we introduce two new components: zero tolerance and time. The challenge is to maintain perfection for a limited period of time. After covering the noninverted-V instruments, commit to keeping the VSI perfectly level for one minute. At the end of one minute, remove the cover from the altimeter. We should be rewarded with an indication that is very close to the initial value—say, within 50 feet. If not, calibrate the VSI by experimenting with pitch for slightly higher- or lower-than-level indications.

When it’s possible to keep the VSI level for one minute, increase the time. If I can attain perfection for one minute, I probably can do it for two minutes. When I can do it for two minutes, I probably can do it for five. If I can do it for five, I probably can do it continuously.

It does not take long for this to become habitual. Perceive VSI deflection, process attitude, apply control pressure to change attitude to remove VSI deflection, and repeat. This exercise can change the quality of a pilot’s flying in the first lesson. Where we may have been accepting altitude deviations of 200 to 300 feet, it is quite satisfying to see these deviations largely disappear.

The modern turn coordinator has a gyro canted 30 degrees from horizontal, which has the effect of making the instrument hypersensitive during level flight. To maintain a heading, keep the wings level on the attitude indicator, checking that the turn coordinator shows the ball centered, and that the airplane symbol also is level. Working with this relationship shows that a pilot can maintain a more precise heading by scanning between the turn coordinator and the attitude indicator than by looking directly at the directional gyro or magnetic compass.

This exercise can be expanded to include standard-rate and timed turns, rate climbs and descents, and combinations of these. Later when we teach the ILS approach, we incorporate pitch attitude showing 400 to 600 fpm on the VSI as necessary for groundspeed, to keep the glideslope needle centered.

When we practice this scan as described above, we will quickly develop the ability to control the airplane to tight tolerances with relative ease. When we add the other three flight instruments back into the scan, we merely confirm that our pitch/VSI work is maintaining altitude. If slight deviations in altitude do occur, we just fine-tune the scan a little.

The inverted V is not the only way to scan an instrument panel, although it is very effective for new students, high-workload situations, and whenever we find ourselves straining to maintain the desired flight path. Working too hard on an ILS approach and getting a lousy result? Go back to the inverted V.

While the same concept works in a glass-panel airplane, the scan will be different. Post-It notes or some easy-to-remove tape on strategic parts of the PFD should remove the distraction of altitude, heading, and airspeed indications.

If introduced, understood, and practiced in the early stages of instrument training, the inverted V—combined with the timed zero-tolerance exercise—can revolutionize instrument flight. This scan teaches us a great deal about what it is we really are doing with those flight controls: controlling the airplane by changing or maintaining attitude.