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RADIO ALTITUDE LOW ALTITUDE AWARENESS NOT ON THE ALTITUDE TAPE ON COPILOT PFD

Radio Altitude Low Altitude Awareness (brown shading as the ground) not on the Altitude Tape on Copilot Primary Flight Display (PFD). Low Altitude Awareness will be displayed when Radio (RA) Altitude of 550 feet or less, is shown on Copilot PFD. If the Radio Altitude value display is in view and that only the Low Altitude Awareness would be missing, it would be indicative of an Electronic Flight Instrument System (EFIS) issue. If Radio Altitude value is also missing refer to RAD ALT Display Not Shown on Copilot PFD.

• Integrated Avionics Computer (IAC) 2 (A10)
• Display Unit (DU) 2 (M8)
• Radio Altimeter 2 (A68)

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Before proceeding with troubleshooting, remember that while on ground radio altitude displayed values may be affected by the ground surface material or surrounding equipment near the antennas. If the condition is only present on ground, the aircraft may me moved to another location to monitor the effect.

NOTE: It is very unlikely that the Radio Altitude value display would be in view and that only the Low Altitude Awareness would be missing, in the case where Low Altitude Awareness only is missing it is likely related to PFD 2 (DU) or IAC 2 failure, which can be isolated by doing a PFD/SG reversions.

1. Perform a PFD 2 Reversion to ALTN.

   1. If radio altitude is not displayed on selected DU, go to step 4.
   2. If radio altitude is displayed on selected DU, continue with next step.

2. Return PFD 2 Reversion to normal (NORM).
3. Replace DU 2.

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

4. Perform a IAC, SG 2 Reversion to ALTN.

   1. If radio altitude is not displayed on PFD 2, go to step 7.
   2. If radio altitude is displayed on PFD 2, continue with next step.

5. Return IAC, SG 2 Reversion to normal (NORM).
6. Replace IAC 2 (SG).

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

7. Check for Radio Altimeter 2 correctly computes an altitude of 2500 feet or higher, there will be displayed altitude digits and Low Altitude Awareness.

   1. If YES, do close out.
   2. If NO, continue with next step.

8. Perform troubleshooting of Radio Altimeter 2 and associated antenna/coax system in accordance with Observed Fault: Incorrect or Erratic Radio Altitude Value on Co-Pilot PFD.
9. Do close out.