ILS Glideslope Failure

T-45C TS & ADV BIFP-09

Instrument Failures

steering mode, a TACAN course line, CDI or Planimetric, will also be displayed.

The T-45C display system is designed so that a TACAN channel may be tuned

anytime, and the TACAN kept in the ON position without causing a cockpit distraction.

When within range, the system will lock-on. If a properly tuned TACAN fails, the aural

identification tone will be lost. Unlike many analog systems, no TACAN warning “flags”

will appear on the HSI display.

If the bearing information fails after lock-on, the TACAN digital bearing readout, the

bearing pointer, and TACAN symbol will be removed. If the TACAN has only lost its

lock-on, the digital bearing readout and TACAN symbol will still disappear, but the

TACAN bearing pointer will rotate in a search mode. If a valid DME signal is lost or the

DME fails, all digital DME and the TACAN symbol will be removed until return of a valid

signal, and the CDI will go away.

(NOTE: For computation of digital TACAN time-to-go, the system uses whatever GS is

being computed at that precise moment on the existing aircraft heading. That resulting

GS will not necessarily be the same GS that would result after turning the aircraft to

proceed directly to the TACAN station. Depending on relative bearing of the TACAN

station and the actual wind direction/velocity, the GS and time-to-go computation may

be significantly different than those that are correct for a direct flight to the TACAN

station.)

The procedure for dealing with TACAN bearing/DME failure is:

1. Reset the desired channel.

2. Cycle the TACAN control panel to OFF and back to ON.

3. Check with ATC to determine if the subject TACAN is in operation, or select another

TACAN that is known to be in operation and within range.

4. Use VOR (if available), waypoints (non-IFR conditions), or request radar vectors.

ILS GLIDESLOPE FAILURE 1.8.1.9.9.2

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

head is active. The frequency entered by the pilot will automatically direct the HSI MFD

to display 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.

(8-99) Original

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