Narrative:

I; the pilot not flying/monitoring; noticed a message that said TRU2 on my pfd and on my mfd. I looked over to my captain's side and saw his said TRU1. I knew this was not normal to see so I asked him about it. Both the captain and I thought that it was referring to the transformer rectifier units (tru) in the electrical system. We brought up the electrical page to monitor TRU1 and TRU2 both looked fine. We got out our aom (aircraft operating manual) and contacted dispatch and maintenance control to see if we could find out what it meant as neither of us had seen that displayed before. The plane seemed to be acting fine so we continued to our destination. While on approach we noticed the TRU1 and the TRU2 message was blinking. When we switched from the FMS to ILS; we noticed a difference in course and also in heading. So we went missed. After being vectored around we noticed that our heading indicator was about 12 degrees off of the magnetic compass. We were in IMC conditions and in mountainous terrain. Our localizer did not match the runway heading so the captain decided to go missed again. On the climb out he made the decision to go to our published alternate which was VFR. After landing I finally figured out that the FMS was set to display true instead of magnetic data which was the reason that our heading and ILS course did not match up. That's when we realized that TRU1 and TRU2 were referring to true heading/course not transformer rectifier unit.

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Original NASA ASRS Text

Title: The Flight Crew of a CRJ900; as well as their Maintenance and Dispatch resources; failed to recognize the TRU messages displayed on their MFDs meant a previous user had selected True instead of Magnetic data to be displayed. The resulting uncertainty caused them to divert from their IMC destination in mountainous terrain to a VMC alternate.

Narrative: I; the Pilot Not Flying/Monitoring; noticed a message that said TRU2 on my PFD and on my MFD. I looked over to my Captain's side and saw his said TRU1. I knew this was not normal to see so I asked him about it. Both the Captain and I thought that it was referring to the Transformer Rectifier Units (TRU) in the electrical system. We brought up the electrical page to monitor TRU1 and TRU2 both looked fine. We got out our AOM (Aircraft Operating Manual) and contacted Dispatch and Maintenance Control to see if we could find out what it meant as neither of us had seen that displayed before. The plane seemed to be acting fine so we continued to our destination. While on approach we noticed the TRU1 and the TRU2 message was blinking. When we switched from the FMS to ILS; We noticed a difference in course and also in heading. So we went missed. After being vectored around we noticed that our heading indicator was about 12 degrees off of the magnetic compass. We were in IMC conditions and in mountainous terrain. Our localizer did not match the runway heading so the Captain decided to go missed again. On the climb out he made the decision to go to our published alternate which was VFR. After landing I finally figured out that the FMS was set to display True instead of Magnetic data which was the reason that our heading and ILS course did not match up. That's when we realized that TRU1 and TRU2 were referring to true heading/course not Transformer Rectifier Unit.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.