There are six flight instruments whose indications are so coordinated as to create a “Picture” of an aircraft’s flight condition and required control movements. These instruments are:
i. Airspeed Indicator.
ii. Altimeter.
iii. Gyro Horizon Indicator.
iv. Direction Indicator
v. Vertical Speed Indicator.
vi. Turn & Bank Indicator.
The first real attempt at establishing a standard method of grouping was the “Blind Flying Panel” or “Basic Six”. The “Gyro Horizon Unit (HGU) occupies the top centre position, and since it provides positive and direct indications of the aircraft’s attitude, it is utilized as the “Master Instrument”. As control of airspeed and altitude is directly related to attitude, the “Indicated Air-Speed (IAS), Indicator, Altimeter and Vertical Speed Indicator (VSI) flank the HGU.
Changes in direction are initiated by banking the aircraft, and the degree of heading change is obtained from the “Direction Indicator” (DI). The DI supports the interpretation of the roll attitude and is positioned directly below the HGU. The “Turn & Bank Indicator” serves as a secondary reference instrument for heading changes, so it also supports the interpretation of roll attitude.
With the development and introduction of new types of aircraft with more comprehensive display presentation, afforded by the indicators of flight director systems, a review of the functions of certain instruments and their relative positions within the group resulted in the adoption of the “Basic T” arrangement as the current standard.
There are now four key indicators:
i. Attitude Director Indicator.
ii. Horizontal Situation Indicator.
iii. Combined Speed indicator.
iv. Altimeter.
