HSI DISPLAY FAILURE
Up to this point in pilot training, you have used an analog HSI instrument. Partial or complete failure of
that instrument was signaled by OFF flags and/or freezing bars, rings, etc. By contrast, the HSI display in
the T-45C is a page of computer-generated information derived from several different electronic sources
and, then, compiled by the DEU for display on an MFD. An invalid signal from a particular source (e.g.,
GINA), results in that information not being displayed. In the case of invalid GINA-derived position
information, the HSI display will cease displaying position data as shown in Figure 47.
NORMAL DISPLAY WITH
Figure 47: HEADING INPUT FAILURE INDICATIONS
A total failure of the HSI display may be the result
of an MFD failure, rather than anything unique to
the HSI. To analyze the problem, select the HSI
display on another MFD.
System advisory legends appear simultaneously
on all four MFDs. There are nine possible
advisories; however, only two are closely related
to the HSI display.
First, the POSITION advisory legend, which
means the DEU has sensed that position data
has transitioned from valid to invalid. The exact
nature of any particular invalidity must be
determined by the pilot. It may be very obvious,
or more subtle. Data that the DEU can
recognize as invalid will be restricted from being
displayed. Nonetheless, when a POSITION
advisory appears (Figure 48), carefully cross-
check all displayed position-related data, as well
as noting what data is missing from the display.
Figure 48: POSITION ADVISORY LEGEND