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normal range, and caution range. [Figure 8-12] The number value changes color to red when the airspeed exceeds V$_{NE}$ to warn the pilot of exceeding the maximum speed limitation. 

## Attitude Indicator 

One improvement over analogue instrumentation is the larger attitude indicator on EFD. The artificial horizon spans the entire width of the PFD. [Figure 8-12]  This expanded instrumentation offers better reference through all phases of flight and all flight maneuvers. The attitude indicator receives its information from the Attitude Heading and Reference System (AHRS). 

## Altimeter 

The altimeter is located on the right side of the PFD. [Figure 8-12]  As the altitude increases, the larger numbers descend from the top of the display tape, with the current altitude being displayed in the black box in the center of the display tape. The altitude is displayed in increments of 20 feet. 

## Vertical Speed Indicator (VSI) 

The VSI is displayed to the right of the altimeter tape and can take the form of an arced indicator or a vertical speed tape. [Figure 8-12]  Both are equipped with a vertical speed bug. 

## Heading Indicator 

The heading indicator is located below the artificial horizon and is normally modeled after a Horizontal Situation Indicator (HSI). [Figure 8-12] As in the case of the attitude indicator, the heading indicator receives its information from the magnetometer, which feeds information to the AHRS unit and then out to the PFD. 

## Turn Indicator 

The turn indicator takes a slightly different form than the traditional instrumentation. A sliding bar moves left and right below the triangle to indicate deflection from coordinated flight. [Figure 8-12]  Reference for coordinated flight comes from accelerometers contained in the AHRS unit. 

## Tachometer 

The sixth instrument normally associated with the “six pack” package is the tachometer. This is the only instrument that is not located on the PFD. The tachometer is normally located on the multi-function display (MFD). In the event of a display screen failure, it is displayed on the remaining screen with the PFD flight instrumentation. [Figure 8-13] 

## Slip/Skid Indicator 

The slip/skid indicator is the horizontal line below the roll pointer. [Figure 8-12] Like a ball in a turn-and-slip indicator, a bar width off center is equal to one ball width displacement. 

## Turn Rate Indicator 

The turn rate indicator, illustrated in Figure 8-12 , is typically found directly above the rotating compass card. Tick marks to the left and right of the lub b er line denote the turn (standard­rate versus half standard-rate). Typically denoted by a trend line, if the trend vector is extended to the second tick mark the aircraft is in a standard-rate turn. 

Individual panel displays can be configured for a variety of aircraft by installing different software packages. [Figure 8-14] Manufacturers are also able to upgrade existing instrument displays in a similar manner, eliminating the need to replace individual gauges in order to upgrade. 

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