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Attitude Indicatorin FLIGHT INSTRUMENTS

The attitude indicator, with its miniature aircraft and

horizon bar, displays a picture of the attitude of theaircraft. The relationship of the miniature aircraft tothe horizon bar is the same as the relationship of thereal aircraft to the actual horizon. The instrument givesan instantaneous indication of even the smallestchanges in attitude.

The gyro in the attitude indicator is mounted in a

horizontal plane and depends upon rigidity in space forits operation. The horizon bar represents the truehorizon. This bar is fixed to the gyro and remains in ahorizontal plane as the aircraft is pitched or bankedabout its lateral or longitudinal axis, indicating theattitude of the aircraft relative to the true horizon.[Figure 7-23]

Figure 7-23. Attitude indicatorThe gyro spins in the horizontal plane and resistsdeflection of the rotational path. Since the gyro relies

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on rigidity in space, the aircraft actually rotates aroundthe spinning gyro.

An adjustment knob is provided with which the pilotmay move the miniature aircraft up or down to alignthe miniature aircraft with the horizon bar to suit thepilots line of vision. Normally, the miniature aircraft isadjusted so that the wings overlap the horizon bar when the aircraft is in straight-and-level cruising flight.

The pitch and bank limits depend upon the make and

model of the instrument. Limits in the banking planeare usually from 100 to 110, and the pitch limits areusually from 60 to 70. If either limit is exceeded, theinstrument will tumble or spill and will give incorrectindications until realigned. A number of modernattitude indicators do not tumble.

Every pilot should be able to interpret the bankingscale illustrated in Figure 7-24. Most banking scaleindicators on the top of the instrument move in thesame direction from that in which the aircraft isactually banked. Some other models move in theopposite direction from that in which the aircraft isactually banked. This may confuse the pilot if theindicator is used to determine the direction of bank.

This scale should be used only to control the degree of desired bank. The relationship of the miniature aircraftto the horizon bar should be used for an indication of the direction of bank.

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Click to Enlarge - Figure 7-24. Attitude representation by theattitude indicator corresponds to the relation of the aircraft to

the real horizon.

The attitude indicator is reliable and the most realisticflight instrument on the instrument panel. Itsindications are very close approximations of the actualattitude of the aircraft.

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