Instrument Training

Instrument flying mandates precise skills to coordinate the controls. When you can coordinate all control inputs subconsciously, you can control the aircraft more easily, and you reduce your workload.

Aileron-Elevator Coordination: During constant airspeed climbing and descending turns, you need to coordinate pitch attitude with bank angle during entries and rollouts. Drag increases as bank angle increases, so to maintain airspeed, you have to decrease pitch as bank angle increases and increase pitch as bank angle decreases.

Throttle-Rudder Coordination: When you change power and don't coordinate the rudder properly, it's hard to maintain a constant heading. You need to anticipate rudder requirements constantly.

Instructors remind their students to keep the turn coordinator's ball centered with rudder, but two other references help you master constant heading maneuvers - a difficult instrument flying task. With the wings level, the airplane should not turn. If it does, you must use rudder and rudder trim (if available) to stop the turn. The attitude indicator (AI) and the heading gyro provide the necessary information.

Visual Versus Instrument Training

You may feel that the pitch and power rule that you learned as a private pilot contradicts two IFR pitch "requirements" - power for airspeed, pitch for altitude or vertical speed. But that's not true. The procedures you learned are directly applicable to basic instrument flying, as long as the airplane configuration (landing gear and flap position) is the same.

During slow flight and landing approaches, you learned to correct airspeed with pitch and correct altitude with power. That's correct, but remember, the landing gear and flaps were extended - a high drag configuration - and power reductions produced immediate results.

Except for the approach to landing, you fly instruments in a low drag configuration, with landing gear and flaps retracted (if possible). This low drag configuration slows an aircraft's response to power reductions, and, therefore, pitch corrections are quicker than power corrections in many situations.

You can prove this yourself. First, establish a 400 foot-per-minute (fpm) descent and trim the airplane or flight training device (FTD) for hands-off flight. Then, flying hands off, reduce power by 100 rpm or one inch of manifold pressure and count the seconds it takes for the vertical speed indicator (VSI) to indicate 600 fpm. When you finish, return to the original power setting and the 400 fpm descent.

Next, repeat the exercise with one hand on the yoke. Decrease the pitch attitude one-half bar width, and note how long it takes to establish a 600-fpm descent. The pitch correction will be quicker than the power correction, and your ability to obtain quick responses is an important instrument flying requirement.

Heavy control pressures and the ensuing rapid attitude changes are the next thing to think about. This is acceptable during visual flight because outside references allow you to keep up with the airplane. Without outside references, rapid attitude changes make the flight instruments move too fast for effective instrument scanning. When this happens, you should concentrate on the attitude indicator until the other instrument indications have stabilized. Light control pressures generate the attitude change rates required for instrument flight.

Whenever possible, you should let go of the yoke and let the aerodynamic forces do your work. Releasing the yoke also reveals whether or not your airplane is in trim - another important instrument flying requirement.

Making Corrections

When you fly instruments, attempting to make instantaneous, one-step corrections is a serious error. Two-step corrections using two-step control inputs is the proper solution.

Two-Step Instrument Correction Rule: First, stop the incorrect trend that caused the deviation. Second, you establish a new trend that will eliminate the deviation. For example, if your altitude is low and the VSI shows an undesired descent, you stop the descent first. After confirming that you're in level flight, you start a new trend that regains the lost altitude. As you acquire experience, these two-step corrections become increasingly smaller, but they never go away.

Two-Step Control Input Rule: First, put in a correction that is obviously excessive, something you know will work. Second, remove one-half of the initial input when this correction starts to work. For example, if your airspeed is low, you add power (and maintain altitude) to the point where you are certain it will accelerate the airplane to the correct speed or faster. When the airspeed begins to increase you remove half of this correction.

When you use power this way don't look at the tachometer or manifold pressure gauge. Keep your eyes on the flight instruments and "index" the throttle by keeping track of power changes, using measured increments of hand movement.

To index throttle movement in a single-engine airplane, place your extended index finger against the instrument panel and hold the throttle knob between your fourth and fifth fingers and the palm of your hand. In multiengine airplanes, you rock your hand to the right and to the left as you move it forward or backward to increase or decrease power.

The two-step control-input rule applies to both instrument and visual flying. A common error occurs when, realizing that a correction is required, you add a little, add a little more, add still more, and consequently spend too much time dealing with that problem. You are snakebitten because an "Adder" is a venomous snake.

Control Summary

When you begin instrument training and apply the basic flight control concepts in the airplane or FTD, you get the impression that instrument flying is a mechanical endeavor. This is normal, and your instructor should encourage you to think of it this way during initial training so you establish proper habit patterns quickly. If you memorize the following mechanics of aircraft control, you'll reduce instrument training time and reach a higher proficiency level.

The elevator controls pitch attitude and:

The altimeter in level flight - fine-tuned by the vertical speed indicator.

The vertical speed indicator during constant-vertical-speed climbs and descents.

The airspeed indicator when airspeed is the only pitch requirement - throttle position is fixed.

The ailerons control bank attitude and:

The heading indicator during straight flight - fine-tuned by the turn coordinator.

The turn coordinator during standard or half-standard rate turns.

The AI during specific-bank-angle turns such as steep turns.

The rudder controls yaw and:

The slip indicator (ball) during hands-on flight - and heading if the wings are level.

The AI's bank attitude or the turn coordinator's miniature airplane (zero turn rate) during hands-off flight.

The throttle controls power and:

The tachometer or the manifold pressure gauge when only one pitch requirement exists - throttle position is fixed.

The airspeed indicator when two pitch requirements exist - throttle position is variable.

The AI's pitch attitude during hands-off flight - throttle position is variable.

The final aircraft control element is trimming, which we'll discuss in February's "Instrument Training."