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.  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).  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.  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.  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.  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.  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]  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.  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.  Figure 8-13.  Multi-function display (MFD).  8-13  Attitude Indicator  Turn Indicator  Tachometer  Slip/Skid Indicator  Turn Rate Indicator  Vertical Speed Indicator (VSI)  Altimeter  Heading Indicator 