If you read much about instrument flying, you will encounter many complex treatises on the subject of the instrument scan. The FAA espouses what has come to be known as the primary and secondary method of instrument scan; you will also encounter what is usually known as the control and performance method of instrument scan. You must learn the rudiments of this method for the Instrument Rating Knowledge exam, but I submit that it is a needlessly complicated scheme for actually controlling the airplane. In fact, it is tantamount to full-time partial panel and is a vestige of the era when gyroscopic instruments and their power sources were unreliable, but that is another topic. It seems that every instructor, examiner, or aviation writer has his own variation on the instrument scan, often with clever names such as “inverted V scan,” or “around the clock scan” or “triangles of confirmation scan.” It gets a more than a little ridiculous. Controlling the airplane on instruments is not that complicated. To say it is not complicated is not, however, to say that it is easy. It requires adherence to a very few basic principles, which are not immediately intuitive and which are easy to abandon under the stress of actual instrument operations.

In teaching instruments to a number of pilots, I’ve tried to discern the irreducible basics of consistent aircraft control. If you will begin with just these few basic fundamentals, make them a habit early in your instrument training, and return to them any time aircraft control seems to be a struggle, you will be well served. There is nothing intrinsically difficult about any aspect of instrument flying. The total workload is the problem – it overwhelms some instrument pilots and it challenges most of us at least some of the time. The only way to master the total workload is to make aircraft control so natural that it occupies very little of our attention, freeing up what marginal mental faculties we possess for the myriad other tasks that constitute instrument flying.

Basic aircraft control on instrument in three easy principles

Yes, I know that seems simplistic, but there are subtleties to each of those statements that require some thought to appreciate and practice to apply and you will find that it requires discipline to adhere to even such apparently simple principles.

Number 1

Know what the instruments do and do not indicate. VFR flight can be managed with a very general comprehension of the flight instruments and will in fact survive their misunderstanding. Instrument flight, because it relies on the flight instruments totally for control of the airplane, will not tolerate anything less than a thorough understanding of their function. Understand that the attitude indicator does not depict the performance of the airplane. While it shows a bank, the airplane is not necessarily turning. It can show a pitch up and the airplane is not necessarily climbing. Understand that the turn coordinator shows the performance of the airplane – whether it is rolling or turning – but nothing about its attitude, except by inference. Most VFR pilots misunderstand something about each of the six flight instruments; as an instrument pilot you cannot afford such misunderstanding.

Number 2

Understand the folly of chasing the performance instruments, either because of momentum lag such as in the airspeed indicator or actual instrument lag such as in the VSI. Most of the difficulty I observe instrument pilots suffering in their control of the airplane is a result of the natural human tendency to watch what is moving rather than what is still. It’s an instinct shared by all predators but it does not serve the instrument pilot well. The more difficult the conditions, the faster the airplane, the more futile it becomes to attempt to establish an airspeed or a vertical speed or a turn rate by watching the airspeed indicator, the VSI, or the turn coordinator. Attitude and power are the keys to achieving stability in any mode of flight. One must know what attitude and power setting will achieve a given airspeed or vertical speed or turn rate, establish and stabilize those settings, and wait for them to take full effect before making incremental adjustments. Repeat after me: STABILITY BEFORE PRECISION.

Number 3

When changing the attitude of the airplane, keep your eyes on the Attitude Indicator. Do not look away from the Attitude Indicator until the pitch and bank of the airplane are stabilized. Take, for instance, the process of executing a turn. First, stabilize the pitch and bank on the AI. Then, while still looking at the AI, establish the bank required for a standard rate turn, using the bank reference at the top of the AI for bank angle and the pip in the center of the wings for pitch reference. Do not look away from the AI until the airplane has ceased rolling and is stable in both pitch and bank. Once stabilized in the intended bank, the ATTITUDE of the airplane is no longer changing. Yes, its heading is changing as it turns, but its attitude is stable (no change in pitch, bank or yaw). At this point, you can continue your scan of the other instruments. Check the turn coordinator to verify standard rate, check the altimeter to verify altitude, check the heading indicator to verify the turn, check the VSI to note any incipient altitude deviation, check the airspeed indicator as a crosscheck on pitch attitude – but return to the Attitude Indicator between each other instrument, or at least frequently, to verify that the ATTITUDE has not changed, ie., that the airplane remains in the intended bank with the intended pitch.

During the turn, do not fool with other things—look at charts, tune radios, start timers, or twist a heading bug. Why? Because, repeat after me . . . “When your wings are banked in the clouds, your life is hanging by a thread.” The principal reason for limiting turns to standard rate—and one of the reasons why you will hear me say, “Standard rate, please,” when we exceed standard rate — is that in a standard rate turn the airplane is nicely balanced and is not subject to the over-banking tendency that leads to spirals. When you are turning in the clouds, you cannot sense the bank angle and if the bank gets excessive, the over-banking tendency kicks in, the bank increases, a spiral develops, and unless you are scanning the instruments diligently you will fail to notice until an unusual attitude develops. So, eyes on the AI while you are rolling into the bank (changing the attitude of the airplane). Once established in the bank/turn, continue the scan to the other instruments, continuing to refer to the AI for any evidence of a change in bank or pitch. When it comes time to roll out (change the attitude of the airplane), again, eyes on the AI. Look nowhere else until the wings are again level and the pitch is stabilized. Then continue the scan to verify heading, altitude, and airspeed. Then, and only then, concern yourself with other things—timers, heading bugs, radios, etc. I would further suggest that whenever you must look away from the six basic flight instruments, whether to tune a radio, find a chart, or find your sandwich – that the Attitude Indicator should be the last thing you look at before you look away and it should be the first thing you look at when you return to the instruments. This is one of those concepts that seems so simple as to be trivial, and it may be difficult to appreciate the importance of it, but if you will bear it in mind and practice it, you will find that airplane control will smooth out. You’ll still have to work hard to maintain altitude and heading on bumpy days or when you are busy. We all do. But you will not suffer the feeling that the airplane is alive and temperamental and you’re along for the ride. You will also find that the stability you achieve will make instrument flight much less fatiguing. One caveat: The principal argument against this reliance on the attitude indicator is the danger of a vacuum or instrument failure. Reliance on the attitude indicator is efficient, practical, and effective. Fixation on the attitude indicator can be fatal. I was long puzzled by the FAA’s insistence on what it calls the primary and secondary system of instrument scan and control until I realized that it is nothing more than full-time partial panel. The attitude indicator is never the primary instrument in this scheme, which does somewhat inoculate the pilot against a failure of the vacuum system or attitude indicator itself. Accident statistics do suggest that most of us will not handle an instrument failure nearly so well as we imagine. By no means neglect your responsibility to crosscheck the attitude indicator information with corroborating instruments. Practice partial panel flying regularly and regularly practice recognition of and recovery from unusual attitudes. If you are flying general aviation airplanes in IMC you should do so regardless of how you see the instruments.

IN THREE EASY PRINCIPLES:

This article was written by George Scheer (george.scheer@gmail.com) and is reproduced here with his permission.