Message Name:

AMBER RAD FLAG ON PILOT AND COPILOT PFDS

The Priority Fault Warning Computer (in normal confirmation Integrated Avionics Computer (IAC)/Symbol Generator (SG) 3) has detected that the radio altitude data displayed on the Pilot and Copilot Primary Flight Display (PFD) are miscompare by more then the following threshold:

• RAD (Amber)=10 + 0.0625 (Pilot Radio Altitude + Copilot Radio altitude). Example: On the ground (0) altitude, this would be 10 feet

NOTE: that the Priority Fault Warning Computer is the Integrated Avionics Computer (IAC) Symbol Generator (SG) that controls the CAS message display information on the Display Unit (DU 3)

• Radio Altimeter 1 (A67)
• Radio Altimeter 2 (A68)
• Radio Altimeter Transmit Antenna 1 (E19)
• Radio Altimeter Transmit Antenna 2 (E17)
• Radio Altimeter Receive Antenna 1 (E20)
• Radio Altimeter Receive Antenna 2 (E18)
• Integrated Avionics Computer (IAC) 1 (A11)
• Integrated Avionics Computer (IAC) 2 (A10)
• Integrated Avionics Computer (IAC) 3 (A12)

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.

• CAIMS Message(s) may be associated to this failure for the fault warning computer(s) reporting the condition.

  ATA	Fault Code	Fault Code	Type	LRU	Definition
  31	3141006FW1	FWC 1 - EXTERNAL MONITOR FAULT	External Fault	Integrated Avionics Computer (FWC)#1	Sensor miscompare messages, config module miscompare, clock interface. (for any EDS IMT fault type 3100-3199) Select fault to view data/detailsIMT code 3109: Rad Alt Miscompare. Fault Warning Processor detected a data difference between the left and right displayed Radio Alt sources.
  31	3141006FW2	FWC 2 - EXTERNAL MONITOR FAULT	External Fault	Integrated Avionics Computer (FWC)#2	Sensor miscompare messages, config module miscompare, clock interface. (for any EDS IMT fault type 3100-3199) Select fault to view data/detailsIMT code 3109: Rad Alt Miscompare. Fault Warning Processor detected a data difference between the left and right displayed Radio Alt sources.
  31	3141006FW3	FWC 3 - EXTERNAL MONITOR FAULT	External Fault	Integrated Avionics Computer (FWC)#3	Sensor miscompare messages, config module miscompare, clock interface. (for any EDS IMT fault type 3100-3199) Select fault to view data/detailsIMT code 3109: Rad Alt Miscompare. Fault Warning Processor detected a data difference between the left and right displayed Radio Alt sources.

• CAIMS Message may be associated to this failure for the HUD computer (COM/MON Channels) reporting the condition.

  ATA	Fault Code	Fault Code	Type	LRU	Definition
  34	3430020HUD	RAD/HUDC CONS FAULT	External Fault	HUD Computer	Discrepancy between Radio altitude data RA1 and RA2. May be associated with HUD MISCOMPARE message when no HUD annunciation. Detection threshold is 10 feet (if RA less then 200 feet) and 20 feet (if 200< RA <1500 ft)

1. Record the Radio altitude values on the Pilot and Copilot PFDs.

   1. If the difference is within the threshold (problem is related to the Priority IAC/SG fault warning computer), go to step 3.
   2. If the difference is equal to or greater than the threshold (miscompare condition), continue with next step.

2. Based on current aircraft altitude to determine either the pilot's radio altitude or the copilot's altitude is incorrect. Perform troubleshooting to the side (Pilot or Copilot) that gives incorrect or erratic radio altitude value on PFD.

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

3. Replace IAC that generate the amber RA flag (Use SG reversion to select an alternate IAC/SG as the Priority FWC to determine affected IAC).
   NOTE:

   • Normal configuration (no SG reversion), IAC/SG 3 is the Priority FWC
   • Select SG3 to ALTN. IAC/SG 2 is the Priority FWC
   • Select SG3 and SG2 to ALTN. IAC/SG 1 is the Priority FWC

4. Do close out.