Not assigning blame or leveling criticism at anybody, Im new to the Avro having spent 15 years on glass Boeings and FBW airbus, and before that heave turboprops that make that DC-9 pictured above look like the 787, and can't for the life of me understand how the Avro crew failed to identify this failure as an IR fault...the abnormal/emergency checklist has PICTURES of the failure along with the checklist...