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T-45C TS & ADV BIFP-09
Instrument Failures
MFD Push-Button Failure: An apparent MFD problem may be caused by a
malfunctioning MFD push-button. If that happens while on the ground, initiate DSPY
MBIT (manual BIT) checking of the MFD push-buttons; DEP push-buttons can also be
checked. When in-flight, DSPY MBIT is disabled. Push-button functionality can only be
assessed by manipulating the individual push-buttons.
Data Source Failure: Some systems—such as TACAN, VOR, and ILS—are not
automatically BIT monitored and reported on the BIT status display page. If data from
an unmonitored source appears missing or incorrect, first, check the status of that
equipment. Be certain that it is properly turned ON and that it is properly set for desired
operation. Then, if the equipment incorporates a stand-alone BIT feature, activate that
BIT to check functionality.
A digital display system does not manifest a failed HSI in the same context as a flight
director or older analog system. The HSI display page can be called up in a variety of
formats and on multiple MFD units.
The HSI display page presents a lot of data; some graphically and some
alphanumerically. Different MFD/DEU system problems will result in different visible
circumstances. For example, loss of the GINA will cause a loss of aircraft attitude and
INS-based position information, but TACAN, airspeed, and altitude will remain.
Additionally, a stuck MFD push-button may disable a particular HSI function on that
particular MFD unit. Switching the display to another unit may resolve the difficulty.
As you know, there are no warning or OFF flags on the HSI display, other than AV BIT.
If a data or graphical image problem is suspected, four logical investigative steps should
be followed:
Be sure associated equipment that supplies the data in question is ON.
Be sure data has been properly entered: e.g., waypoint data, frequencies.
Perform BIT checks on suspect equipment: e.g., TACAN, VOR/ILS.
Check the DATA display page for any OPGO/DEGD alerts and react
Normally, the HSI will be selected for display on the right MFD. To assure that an HSI
problem is not really an MFD problem, call up the same HSI display on another MFD
unit and compare results.
(8-99) Original
Page 9-8

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