The second fundamental skill, instrument interpretation, requires the most thorough study and analysis. It begins with your understanding of each instrument's construction and operating principles. Then you must apply this knowledge to the performance of the airplane you are flying, the particular maneuvers to be executed, the cross-check and control techniques applicable to that airplane, and the flight conditions in which you are operating. For example, (Fig. 5-2), using full power in a light airplane for a 5-minute climb from near sea level, the attitude indicator shows the miniature aircraft two bar widths (twice the thickness of the miniature aircraft wings) above the artificial horizon. The airplane is climbing at 500 feet per minute as shown on the vertical-speed indicator, and at an airspeed of 90 knots, as shown on the airspeed indicator. With the power available in this particular airplane and the attitude selected by the pilot, the performance is shown on the instruments.
Now set up the identical picture on the attitude indicator in a modern jet executive airplane. With the same airplane attitude as shown in the first example, the vertical-speed indicator in the jet reads 2,000 feet per minute, and the airspeed indicates 300 knots. As you learn the performance capabilities of the airplane in which you are training, you will interpret the instrument indications appropriately in terms of the attitude of the airplane. If the pitch attitude is to be determined, the airspeed indicator, altimeter, vertical-speed indicator, and attitude indicator provide the necessary information. If the bank attitude is to be determined, the heading indicator, turn coordinator, and attitude indicator must be interpreted.
For each maneuver, you will learn what performance to expect and the combination of instruments that you must interpret in order to control airplane attitude during the maneuver.
The third fundamental instrument flying skill is aircraft control. With the instruments substituted for outside references, the necessary control responses and thought processes are the same as those for controlling airplane performance by means of outside references. Knowing the desired attitude of the airplane with respect to the natural and artificial horizon, you maintain the attitude or change it by movement of the appropriate controls.
Aircraft control is composed of three components: pitch control, bank control, and power control.
1. Pitch control is controlling the rotation of the airplane about the lateral axis by movement of the elevators. After interpreting the pitch attitude from the proper flight instruments, you exert control pressures to effect the desired pitch attitude with reference to the horizon.
2. Bank control is controlling the angle made by the wing and the horizon. After interpreting the bank attitude from the appropriate instruments, you exert the necessary pressures to move the ailerons and roll the airplane about the longitudinal axis.
3. Power control is used when interpretation of the flight instruments indicates a need for a change in thrust.
Figure 5-2. Power and attitude equal performance.
Trim is used to relieve all possible control pressures held after a desired attitude has been attained. An improperly trimmed airplane requires constant control pressures, produces tension, distracts your attention from cross-checking, and contributes to abrupt and erratic attitude control. The pressures you feel on the controls must be those you apply while controlling a planned change in airplane attitude, not pressures held because you let the airplane control you.