ILS Localizer Failure

T-45C TS & ADV BIFP-09

Instrument Failures

Loss of a valid ILS glideslope is signaled by appearance of the GLIDESLOPE advisory

box, and the glideslope needle on the ADI and HUD will become blanked. In that

circumstance, the pilot may elect to continue flying an ILS, but to a localizer-only; totally

discontinue the ILS approach; or transition to another type approach (VOR, TACAN,

PAR, ASR, VFR) depending upon the situation, availability, and location. If you change

to another type IFR approach, the approach minimums will probably change.

ILS LOCALIZER FAILURE 1.8.1.9.10.2

The FWD/AFT selection made on the HSI MFD determines which NAV control head is

active. The frequency entered by the pilot automatically determines whether the HSI

MFD displays an ILS or VOR legend.

Like VOR, ILS is only available and can only be selected in the HSI CDI mode. Once

ILS steering has been selected in the CDI mode, changing to HSI PLAN mode will

cause removal of the ILS course line and ILS CDI bar, but ILS steering needles will

continue to be displayed on both the HUD and ADI.

Loss of a valid ILS localizer is signaled by appearance of the LOCALIZER advisory box

and disappearance of the glideslope and localizer needles on the ADI and HUD. In that

circumstance, the pilot must abort the ILS and transition to another type approach

(VOR, TACAN, PAR, ASR, VFR). If the type IFR approach changes, the IFR approach

minimums will probably change.

ILS MARKER BEACON FAILURE 1.8.1.9.11.2

If an outer marker is incorporated in an approach, which is not always the case, the ILS

final approach fix (FAF) will be coincidental with that OM. If you lose the OM, you may

still be able to complete an ILS approach. It is allowable if the ILS approach plate also

gives TACAN/DME, radar, or TACAN crossing radials for determining the FAF from

which descent to MDA and missed approach timing are commenced, or missed

approached is also denoted with a DME.

According to the FAA, middle marker (MM) beacons are no longer required for ILS or

localizer-only approaches. Nonetheless, many MM beacons are still indicated on ILS

plates. The FAA says that they should be considered information-only assets. The MM

may––or may not––be positioned coincidentally with the published missed approach

point: ILS or localizer-only.

(8-99) Original

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