Global 7500 fly-by-wire system – How to identify failed REU(s)

Effectivity:  Global 7500 aircraft 

ATA: 27 

By: Daniel Genois - Technical Engineering 

Bombardier has observed occurrences in production and in-service where the 27 FLT CTRL – PRIM REU INOP (INFO) EICAS message is posted at power up. The reported occurrences show when the aircraft is powered by the batteries as a single source and the battery voltage drops to about 17 V-DC. 

This condition is well described in Advisory Wire (AW) AW700-27-0873. 

The AW refers to the document called “FBW FAULTS - TIPS AND RESETTING METHODS”, section 8 in SmartFix Plus (SFP), and provides detailed explanations and resetting methods. 

It has been observed that even when guided by the document “FBW FAULTS - TIPS AND RESETTING METHODS”, some customers are challenged to identify the faulty REU(s). 

For this reason, Bombardier has performed testing on a test rig to find an easier way to identify the REUs that need to be reset. 

Our testing has shown that the best way of identifying the REUs that are locked in Integrity Fail state is by accessing the OMS IIM1, IIM2 and IIM 3 STATUS/FAULTS 1 data pages. The REU(s) at fault will show TTP STALE FAULT = YES. 

The next SmartFix Plus Technical Publication update will include the above changes. 

Example of OMS IIM1 STATUS/FAULTS 1 data page.