The aircraft pitch attitude is controlled by changing the  deflection of the elevator. As the pilot pulls back on the  control yoke causing the elevator to rise, the yellow chevron  begins to show a displacement up from the artificial horizon  line. This is caused by the AHRS unit sensing the changing  angle between the longitudinal plane of the earth and the  longitudinal axis of the aircraft.  The attitude indicator displayed on the PFD screen is a  representation of outside visual cues. Rather than rely on the  natural horizon visible during visual flight rules (VFR) flight,  the pilot must rely on the artificial horizon of the PFD screen. During normal cruise airspeed, the point of the yellow  chevron (aircraft symbol) is positioned on the artificial  horizon. Unlike conventional attitude indicators, the EFD  attitude indicator does not allow for manipulating the position  of the chevron in relationship to the artificial horizon. The  position is fixed and therefore always display the pitch angle  as calculated by the AHRS unit. The attitude indicator only shows pitch attitude and does  not indicate altitude. A pilot should not attempt to maintain  level flight using the attitude indicator alone. It is important  for the pilot to understand how small displacements both up  and down can affect the altitude of the aircraft. To achieve  this, the pilot should practice increasing the pitch attitude  incrementally to become familiar with how each degree of  pitch changes the altitude.  [Figures 7-50  and  7-51]  In both  cases, the aircraft will slow and gain altitude. To master the ability to smoothly control the elevator, a pilot  must develop a very light touch on the control yoke. The  thumb and two fingers are normally sufficient to move the  control yoke. The pilot should avoid griping the yoke with  a full fist. When a pilot grips the yoke with a full fist, there  is a tendency to apply excess pressures, thus changing the  aircraft attitude. Practice making smooth, small pitch changes both up and  down until precise corrections can be made. With practice,  a pilot is able to make pitch changes in 1 degree increments,  smoothly controlling the attitude of the aircraft.  The last step in mastering elevator control is trim. Trimming  the aircraft to relieve any control pressures is essential  for smooth attitude instrument flight. To accomplish this,  momentarily release the control yoke. Note which way the  aircraft pitch attitude wants to move. Grasp the control yoke  again and then reapply the pressure to return the attitude to the  previous position. Apply trim in the direction of the control  pressure. Small applications of trim make large changes in  the pitch attitude. Be patient and make multiple changes to  trim, if necessary. Once the aircraft is in trim, relax on the control yoke as  much as practicable. When pressure is held on the yoke,  unconscious pressures are applied to the elevator and ailerons,  which displaces the aircraft from its desired flightpath. If the  aircraft is in trim, in calm, non-turbulent air, a pilot should be  able to release the control yoke and maintain level flight for  extended periods of time. This is one of the hardest skills to  learn prior to successfully flying in instrument meteorological  conditions (IMC).  The full height of the chevron is approximately 5 degrees  and provides an accurate reference for pitch adjustment. It is  imperative that the pilot make the desired changes to pitch by  referencing the attitude indicator and then trimming off any  excess control pressures. Relieving these pressures allow for  a more stabilized flight and reduces pilot work load. Once the  aircraft is trimmed for level flight, the pilot must smoothly  and precisely manipulate the elevator control forces in order  to change the pitch attitude.  Figure 5-51. Pitch Correction for Level Flight, three-bar width.  Figure 7-51.  Pitch illustrated at 10 ° . Figure 7-50.  Pitch indications for various attitudes (1° through 5°). 7-35 XPDR 5537 IDNT LCL23:00:34  VOR 1  270 ° 2  1  1  2  400 4500  4400  4300  3900  4100  4000  3900  3600  3500  3440000  3300  3200  3100  20 80 4200 4000  150  140 130 110 100 90  1 120 9 TAS 120KT  OAT 7°C  ALERTS  5 338  $_{1}$1652  200  46  13.7  1800  18.0  NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1 123.800 118.000 COM2 $_{WPT }$_ _ _ _ _ _$_{ DIS }$_ _ ._ $_{NM}$ $_{DTK }$_ _ _$_{°}$ TRK 360° XPDR 5537 IDNT L CL23:00: 3 4 VOR 1  270 ° 2  1  1  2  400 4500  4400  4300  3900  4100  4000  3900  3600  3500  3440000  3300  3200  3100  20 80 4200 4000  150  140 130 110 100 90  1 120 9 TAS 120KT  OAT 7°C  ALERT S  5 338  $_{1}$1652  200  46  13.7  1800  18.0  NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1 123.800 118.000 COM2 $_{WPT }$_ _ _ _ _ _$_{ DIS }$_ _ ._ $_{NM}$ $_{DTK }$_ _ _$_{°}$ TRK 360° 4100  3000  3 900  20 80 4 000 4100  4100  3 900  40 00 4 020 100 4200  4200  4 000  70 30 4 100 200 4200  4100  4 000  45 05 4 150 300 4°  3°  2°  1° 