Interpretation of Attitude by the Means of the Attitude Indicator

Chapter 19.1

The Horizon and Flight Attitude

The term «flight attitude» refers to the orientation of an aircraft with respect to a reference line, which is the natural horizon in visual flight. If the latter is difficult to discern or invisible, a technical representation of the horizon as a reference must be used.

This representation is the artificial horizon. It is a highly simplified image of the Earth and the sky. The artificial horizon is the basis of the ATTITUDE INDICATOR, AI.

The Natural Horizon

At sea level, the real horizon and the apparent horizon are identical. When the flight altitude increases, the real horizon is lower. Therefore we need a parallel line, the APPARENT HORIZON.

Orientation Limits Using the Natural Horizon

In visual flight we determine the position of the aircraft in space by reference lines and landscape points. As long as the eye has fixed landmarks, the position is unconsciously adjusted. This allows us to ignore the importance of the accelerations that occur in turns and the changes in attitude. The sense of sight dominates the sensation of the attitude. Without references to the horizon however, we get a false impression of the attitude during accelerations, and then we intuitively execute erroneous movements on the flight controls, trying to adopt an attitude that corresponds to our illusions.

Possible Misinterpretation of the Horizon Due to Optical Illusions

Another danger of misinterpretation of the attitude comes from optical illusions that simulate a false horizon. In the absence of a visible natural horizon, we construct an image dependent on available structures. The attitude of the aircraft is intuitively adapted to, for example, layers of clouds or lines of terrain.

The Natural Sense of the Attitude

You should never trust your innate sense of attitude in the event of loss of the natural horizon. The balancing organ in your ear gets deceived and confused by apparent forces. Quickly you will adjust the attitude erroneously. It is quite possible that you think you are flying straight and level when you are actually making a turn!

Spatial DISORIENTATION, VERTIGO

By continuing to follow your innate sense of attitude without visual references, it will lead to dangerous SPATIAL DISORIENTATION or VERTIGO. This is often linked to unpleasant physiological reactions such as dizziness, malaise, sweating, chills, hyperventilation etc.

Attitude Flying

When you need to maintain an attitude using instruments, a systematic methodology is absolutely necessary.

ATTITUDE FLYING is the active establishment of a combination of such attitude and power.

Flight PERFORMANCE is the result of the following combination:

• ATTITUDE
• ENGINE POWER
• aerodynamic resistances (Flaps, Gear, ..)

LOOKOUT when using attitude indicators

Under visual flight conditions /VMC, even if the flight is in accordance with the instrument flight rules, airspace shall be actively monitored.