The main properties of the symbols depicted on the HSI are the following:
• AIRCRAFT SYMBOL
A fixed aircraft symbol helps to visualize the position of the aircraft in
relation to horizontal navigation information. In the full compass display
the aircraft symbol is in the center of the compass.
• HEADING AND DIGITAL READOUT
The aircraft heading is indicated by movement of the compass rose
with respect to the lubber mark at the top of the compass. Left turns
rotate the compass rose clockwise (CW) while right turns rotate the
compass rose counterclockwise (CCW). In the arc compass mode, the
aircraft heading is numerically displayed inside the heading indicator.
• LUBBER MARK
The aircraft heading is indicated by movement of the compass rose
with respect to a lubber mark at the top of the compass. In full compass
mode, an reversed triangle is displayed at the top of the compass to
give a lubber. In arc mode, a box with a digital readout of current
heading is displayed. The bottom of the box is notched to indicate the
lubber line. The notch and the inverted triangle are designed to fit
inside the heading bug when they are aligned.
• HEADING SOURCE
The heading source is annunciated when both pilots have the same
source selected, or when directional gyro (DG) mode is selected. When
the on-side heading source is displayed on each PFD, no source
annunciator is displayed unless the DG mode has been selected. In
this case, DG 1 annunciates the copilot PFD and DG 2 annunciates the
pilot PFD. Selecting AHRS1 with the reversion controller has MAG1 or
DG 1 displayed on each PFD. Selecting AHRS2 has MAG2 or DG 2
displayed on each PFD. Amber dashes replace the digital readout
when the selected heading source becomes unreliable. The heading
source annunciator is displayed following an AHRS failure.
• HEADING SELECT BUG
The heading bug is a rectangle with a triangular notch that move 360°
around the compass rose to select a desired aircraft heading. When
heading select is engaged, the heading bug is displayed in magenta;
while a cyan heading bug indicates the flight director is not coupled.
The heading select knob of the Remote Instrument Controller (RIC)
allows to change the position of the heading bug along the compass
rose. When the flight director is in heading (HDG) mode, commands
are generated that align and maintain the aircraft on the heading
selected by the bug.
• YAW HEADING HOLD REFERENCE BUG
The yaw heading hold reference bug is displayed on the HSI heading
scale tape when the flight director indicates that the yaw heading hold
is functional. A loss of valid heading information from the AHRS or a
loss of valid yaw heading hold reference information from the priority
autopilot causes the yaw heading hold bug to be removed.
• HEADING DIGITAL READOUT
A digital readout shows the heading currently indicated by the bug. The
heading bug and digital readout are magenta, alerting the pilot that the
flight director HDG mode is engaged and reliable. The cyan heading
bug and digital readout alert the pilot that the flight director HDG mode
is not engaged.
• DRIFT ANGLE POINTER
The white, triangular, drift angle pointer is displayed to indicate ground
track angle necessary to maintain course. A loss of reliable heading
information from the AHRS, or track angle information from the FMS
removes the drift angle pointer.
• HEADING MISCOMPARE ANNUNCIATOR
A 10° miscompare between the two AHRS displays the HDG
miscompare annunciator. The annunciator is removed when a heading
miscompare is no longer detected. A loss of reliable heading
information from the AHRS removes the HDG miscompare
annunciator.
• COURSE POINTER
The course pointer is a segmented needle that is superimposed over
the HSI compass display. It represents a selected short-range
navigation course (CRS) or FMS desired track (DTK) and the
helicopter position relative to it. The dots are always white, and the
pointer is cyan when the flight director is not coupled, magenta when
the flight director is coupled.
The course pointer pivots around a center point that corresponds to the
center of the compass card. The center position is marked by the
aircraft symbol. When the FMS is selected, the course pointer is
controlled by the FMS, and it is set to the desired track. Once a course
is selected, the needle turns with the compass card and aligns with the
lubber mark when the helicopter heading is the same as the selected
course. The course pointer can be rotated 360° clockwise and