Abnormal procedures
In the event of TAWS system or component failure, the appropriate annunciators will indicate
which function or component has failed.
Failure condition Effect on aircraft and crew
Loss of GPS Position
Source
Loss of the necessary input for Terrain Advisory alerts. Loss of
graphic display. No loss of basic GPWS functions.
Loss of Radio Altimeter Loss of basic GPWS modes. No loss of Terrain advisory alerts.
Loss of air data computer Loss of basic GPWS modes.
Loss of No. 1 ILS Receiver Loss of basic GPWS Mode 5. (Glideslope Alerting)
Loss of Aural Alerts Crew will still have visual alerts.
Loss of visual alerts Crew will still have aural alerts
Failure of Terrain Inhibit
Switch
a. If failed to the inhibit state, all Terrain Alerts will be
inhibited.
b. If failed to perform function, crew cannot inhibit Terrain
Alerts
Failure of G/S Inhibit
Switch
a. If failed to the inhibit state, all GPWS mode 5 alerts will be
inhibited.
b. If failed to perform function, crew cannot inhibit GPWS
mode 5 alerts.
Failure of Flap Override
Switch
a. If failed to perform function, the “Too Low Flaps” caution
will be inhibited.
b. If failed to the “Normal State”, the crew cannot inhibit flap
related alerts, if flaps are not in the landing position.
Fokker 50 - Flight Navigation Instruments
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