Message Name:

UNEXPECTED AT RETARDING

Unexpected Retarding of Both Thrust Levers with Auto Throttle engaged.

• Flight Management System (FMS)
• Landing Gear Electronic Control Unit (LGECU) (A52)

Advisory Wire/Service Bulletin:

• AW700-22-0423 - Unexpected Retarding of Both Thrust Levers with Auto Throttle engaged
• Service Bulletins (SB) 700-31-034 / 700-1A11-31-017, Modification - Central Processing System - Batch 3.3 Software Upgrade (initial released Jul/16) Revision 2 released 23 Jan 2017

Forum Articles/Infoservice/Newsletter: None

• Honeywell Service Information Letter (SIL) D201502000055 - Bombardier Global Express/5000/XRS FMZ-2000 - Flight Management System (FMS) Resets May Retard the Throttle Levers or Cause Auto-Throttle (AT) System Disconnects
• ELDEC Service Bulletin 8-879-32-01 - Landing Gear System - Landing Gear Electronic Control Unit Modification of 8-879-03 Units to 8-879-05

NOTES:
FMS Failure: There is an FMS software issue that causes an incorrect speed target to be provided to the AT following an FMS reset. It is applicable to the Bombardier Global Express/5000/XRS FMZ-2000 NZ5.8 and earlier and NZ6.1 Bombardier Batch 3.

Momentary Nuisance 'GEAR DISAGREE' message: It was noted that the fault message 'PROX_REFERENCE_ VOLTAGE_FAIL' was present in the Landing Gear Electronic Control Unit (LGECU) NVM, at the exact same time as the 'GEAR DISAGREE' EICAS message and then the AT retard event occurred. It is applicable to the Bombardier Global aircraft equipped with LGECU P/N 8-879001-03.

1. If the AT is observed to retard in a flight configuration in similar conditions, follow the appropriate troubleshooting action.

   1. If the AT retard occurred after an FMS failure, continue with next step.
   2. If the AT retard occurred after a "GEAR DISAGREE" CAS message, go to step 3.
   3. If the condition that applies cannot be identified, go to step 4.

2. To address this condition, operators are required to upgrade their IACs software to Batch 3.3 which introduces a corrective software into the changes to the FMS. This software upgrade is now available through Free of Charge (FOC) SB to operators who previously incorporated the Batch 3 software upgrade SB.
3. In LGECU P/N 8-879-05, this anomaly is resolved. The LGECU manufacturer ELDEC recommendation is to upgrade the LGECU P/N 8-879-03 to 8-879-05 via ELDEC Service Bulletin 8-879-32-01.
4. If the operator cannot identify or confirm which condition applies to his case, he can request Bombardier assistance by contacting Customer Response Support (CRC), and attach the following information and data:

   • Download DFDR data for the associated flight per AMM Task 31-31-00-970-801, Download of the Flight Data Recorder Data.
   • Download the IAC (FWC) EICAS message NVM per AMM Task 45-45-00-970-822, Access to Non-Volatile Memory (NVM) Management.
   • Download the LGECU NVMs per AMM Task 45-45-00-970-822, Access to Non-Volatile Memory (NVM) Management.
     NOTE: When downloading the LGECU NVM, two (2) files are required. After downloading the first channel it is necessary to rename the file before downloading the 2nd channel
   • Fill out the attached questionnaire Form (Questionnaire Unexpected AT Retarding.doc)

5. Do close out.