Early in flight training the student does most of the flying by reference to the outside horizon. The use of other outside references is learned when practicing maneuvers such as steep turns, turns about a point, and S-turns across a road. Having fine-tuned these outside-reference flying skills, the student should practice flying these maneuvers while dividing his or her attention inside and outside the airplane, to confirm and cross-check aircraft performance by scanning the "basic T" instrument configuration on the panel, like the one depicted on page 31. From here, the student learns the importance of each flight instrument as it relates to the view outside.
Although the flight instruments depict the view outside in a mathematical and precise fashion, they're somewhat limited in scope. But the instrument display has its own purpose and can supplement the view in a number of ways. A good scan of the flight instruments along with looking outside for visual cues will help you to precisely maneuver your aircraft in VFR conditions.
Depending on the maneuver, the cockpit flight instruments will serve either as primary or support instruments. Federal Aviation Administration Advisory Circular 61-27 (AC 61-27, the Instrument Flying Handbook) explains which flight instruments should have priority and which assume a supporting role during any maneuver. The task for the VFR student pilot is to make a real connection between the view outside and what the flight instruments inside are displaying. The two "pictures" should obviously agree, or be in harmony.
This becomes the foundation upon which flight solely by reference to instruments is constructed. These building blocks create confidence and trust for future use in instrument flying, and for VFR pilots, they translate what is happening in three dimensions outside. If you later train for the instrument rating, you will experience what is called the "transition to visual conditions" while flying an approach to the runway while still in the clouds (IMC, or instrument meteorological conditions). As you "break out" into VFR conditions on the approach, the transition from the view inside the cockpit to the view of the runway outside should be seamless, with essentially everything outside looking just as it did inside on your flight instruments just a moment ago.
Since your airplane is operating in three dimensions at once, varying any one will affect the other two in a predictable manner, and this is observed outside - and depicted inside - again, in a very predictable manner. The two pictures taken together create a synergy which leads to the realization that you are now suspended in space, the exhilaration called flying. Let the poet in you fill in the rest!
Your basic outside visual references are the relationship of the aircraft's nose to the Earth's horizon, the relationship of the left and right wingtips to the horizon, and the relative movement of references on the ground.
The horizon line outside gives the "big picture" relative to your position within the three axes of flight: pitch, roll, and yaw. The six flight instruments in front of you break this view down into separate components. Using a simple illustration, after takeoff most single-engine trainers establish a visual climb attitude with the cowl of the airplane resting on the horizon line. Let's say you want to increase your angle of climb by flying best-angle-of-climb speed, VX. This increase in pitch above the horizon line (and subsequent decrease in airspeed) would force you to use peripheral vision to maintain a constant pitch attitude, or to refer to your attitude indicator.
At any given time, except during airspeed changes, your airplane is operating in one of six states: straight and level flight, level flight with a turn, climbing flight, descending flight, climb with a turn, or descent with a turn. We will consider power/speed a variable here, as the flight regimes can be varied in speed from the stalling speed or the minimum steady flight speed at which the airplane is controllable (VS) to the never-exceed speed (VNE), depending on aircraft power capabilities. (For instance, most jet aircraft can exceed VNE while straight and level. This is virtually impossible in a piston-powered, single-engine trainer). Flight beyond VNE implies the possibility of structural damage or inflight breakup, documented in accident aircraft penetrating thunderstorms. Flight below VS will lead to a stall - and the possibility of a stall-spin scenario - unless proper recovery techniques are employed.
Straight and level flight implies that everything is in a "steady state" when viewing outside references and comparing this to cockpit flight instrument indications (we'll assume that airspeed and power are constant). Now let's identify the primary and supporting flight instruments. What will be the first indication that your pitch has changed, leading to a climb or a descent? The answer is your altitude, which shows on the altimeter as an increase or decrease, and looking outside, a change in the position of the horizon relative to the airplane's nose cowl. So, the altimeter is your primary pitch instrument for straight and level flight.
Do any other instruments support this primary indication? Your vertical speed indicator (VSI) will show a change in rate of climb or descent and is therefore called a supporting pitch instrument. Your attitude indicator will show a symbolic airplane climbing or descending against an artificial horizon, and therefore it also is a supporting instrument. Your straight and level scan of the flight instruments should consist of quick glances of first the altimeter, VSI, and artificial horizon (to verify level), then DG, turn coordinator, and artificial horizon (to verify straight). Looking outside will confirm straight and level, but the flight instruments show the details and your trend.
You may have thought that the artificial horizon was your primary pitch instrument here. This is not true, because if you reduced your airspeed but held your altitude, the artificial horizon airplane would indicate a slight pitch-up or climb, even though you are not climbing. This indication is a function of aircraft attitude.
A good example of this point is when you practice slow flight while maintaining altitude. As you approach the slow target airspeed, your pitch increases and a power increase is required to maintain altitude. Adding more power and increasing speed will necessitate lowering pitch to maintain altitude, otherwise you'll climb. You will be very busy with elevator trim changes and rudder during this demonstration, and your scan inside and out will be working overtime.
Now let's start a stabilized climb at a constant rate. Rate implies altitude gain or loss per unit of time, generally feet per minute. So, you guessed it, once you're established in the climb, the VSI is the primary pitch instrument - the attitude indicator is primary as you start the climb - and the DG becomes the primary bank instrument, because any change in heading implies a deviation from wings level - you've entered a bank. The primary power instrument is logically the airspeed indicator, because any deviation in airspeed means a throttle adjustment has occurred, given that your pitch (rate of climb) is constant. The turn coordinator is the supporting bank instrument, and the artificial horizon becomes supporting in pitch and bank.
Now modify your scan so that your attention is drawn to the primary instruments first, then the supporting instruments for verification. Remember, depending on what maneuvers you perform, the primary and supporting instruments may change roles, and therefore you will have to modify your scan accordingly. The same hierarchy of instruments applies to a constant-rate descent, but remember the VNE value enters the picture now, so reduce power.
Now let's look at what instruments the primary and supporting labels are assigned to for a standard-rate turn at a constant airspeed. Here again the altimeter and VSI are primary and supporting pitch informants, but the artificial horizon assumes the role of primary bank initially, then supporting pitch. Consequently, the turn coordinator becomes the primary bank instrument as the turn is established. As you look outside and scan what's happening relative to the real horizon, scan these instruments to make a connection and tie it all together.
Now you are gaining the absolute greatest amount of information from your flight instruments for any given state of the aircraft. The understanding of this relationship between your flight instruments and the real world outside the window will enhance your proficiency during training using view-limiting devices, and later your training for the instrument rating.
You will rarely hear an instructor during a VFR training session say that you are spending too much time looking outside; in fact, you probably hear the opposite, perhaps with an admonition not to fixate on the instrument panel during VFR flight. The definition of scan (from Webster's Collegiate Dictionary) is "to examine by point-by-point observation or checking, and to investigate thoroughly by checking point-by-point and often repeatedly." As it applies to VFR flying, the observation would be outside, the checking inside, and the often repeatedly would be a smooth transition between the two. A good scan is essential in any flying you do in order to grasp "the big picture."
Don't overlook other cues of aircraft performance. Did you hear engine rpm increase while you were attending to some- thing else? If you didn't touch the throttle, you're probably descending, or climbing if you hear a decrease in rpm. Check your attitude relative to the horizon and check your altimeter (primary pitch).
I like to use, and recommend that you develop, a "final scan" while on final approach to landing. With the before-landing checklist complete and your aircraft stabilized nicely on final, keep a scan going on "Airspeed/Runway" all the way down to the flare. Airspeed control (primary power) and runway alignment are critical in the last 500 feet of the approach. You may consider the visual approach slope indicator (VASI) or precision approach path indicator (PAPI), if the runway offers one, as a supporting instrument that you should integrate into your scan. On a clear VFR day, your visual sense and processing of this information will take priority over your scan of the instruments.
Plan the "big picture" while you are flying. Look outside. Look inside. While inside during your scan of the flight instruments, do not fixate on any one instrument for more than a few seconds. Remember to scan outside for other aircraft, as well. A little control input goes a long way. Relax on the controls and make smooth and appropriate elevator, aileron, and rudder inputs. Make small pitch corrections and bank corrections to effect the desired change. A pitch change of 2 or 3 degrees, or bank angle of 15 degrees with a little rudder, is all that is needed to begin the process of climbing, descending, or turning. Increase or decrease as necessary while noting changes both outside on the horizon and inside during your scan. Scan your primary and supporting flight instruments in order of importance.
Now go fly. And completely enjoy the scan.
Joel Stoller is a Douglas DC-9 captain for Midwest Airlines. He is also a part-time CFI who has more than 16,000 flying hours, including more than 600 hours of dual instruction.
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