HSI Failure - P-12850091

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.

HSI FAILURE 1.8.1.7.12.2

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

accordingly.

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