737 IRS Fault codes

[Jwscud]

I had a strange IRS issue today - one of the IRS units would align, with no caution lights, but the MAP flag was displayed on the affected ND, and status code 09 was displayed with HDG/STS selected.

Eventually, after several realignments, it came to life of its own accord, but would be interested to know if anyone has a list of the IRS status messages for future rerence as both the FCOM and the MRG are silent on the matter.

[Skyjob]

You need to ask engineers in company.
They hold manuals such as AMM which can describe for your configuration

[de facto]

Code 09 means "enter heading". serious:E

[Jwscud]

"09" Makes sense as it was operating in ATT mode for some reason and the "ENTER IRS HDG" prompt was present on POS REF 1/3 on the FMC. I was wondering if anyone knew why it was stuck in ATT mode with no fault flags on the IRS itself.

There was no wind, or shaking of the aircraft before anyone asks.

[flying apple]

If you move the IRS mode selector to att by accident and turn immediatly back to nav it will be stuck in att mode.

[Golden Rivet]

I've seen the 737NG enter ATT mode on numerous occasions when NAV had been selected.

Never did get to the bottom of it as the a/c moved base, but I suspect it was a fault with the selector switch itself.

If you go into the MAINT index and select <ADIRS and then <ADIRS MAINT CODES, it will give you a full list of Maintenance codes on the CDU with their description. According to the Maintenance Manual, there are 38 available codes.

[Jwscud]

Thanks - a faulty switch and going straight into ATT seems like the most likely explanation.

Always more strange quirks to discover!

[CaptainSandL]

Try http://www.b737.org.uk/navigation.htm#IRS_Malfunction_Codes