A B737-800 pilot reports a return to departure airport following an IRU failure and the loss of asso...

Attributes
ACN	761603
Time
Date	200711
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : zzzz.artcc
State Reference	FO
Altitude	msl single value : 37000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zzzz.artcc
Operator	common carrier : air carrier
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
ASRS Report	761603
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : landed as precaution other
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

During cruise; the left IRS faulted with associated lights; master cautions and autoplt disconnecting. I gave control of the aircraft to first officer as I initially had no usable instrumentation on my side. I ran the abnormal IRS fault checklist and restored most of the instrumentation to my side. I called dispatch to advise and see if we might be better served by returning to ZZZ1. Once we viewed the MEL restrs (to re-dispatch from ZZZZ required day VMC; non-rvsm; no autoplts; lmp restrs; etc) we agreed to turn back. I did not declare an emergency with center but; in hindsight; I probably should have. I am not sure if dispatch declared an emergency. Having just declared an emergency a week prior due to a medical emergency this just didn't feel like one. However; hand flying using raw data (my flight director never restored) is not something I get to do very often. I advised my flight attendants; my passenger; center; ZZZ1 operations; ZZZ1 maintenance of our situation. We landed without incident; replaced the IRU and re-dispatched to ZZZZ.

Original NASA ASRS Text

Title: A B737-800 PILOT RPTS A RETURN TO DEP ARPT FOLLOWING AN IRU FAILURE AND THE LOSS OF ASSOCIATED EQUIP AND FUNCTIONS. ACFT WAS HAND FLOWN WITH RAW DATA.

Narrative: DURING CRUISE; THE L IRS FAULTED WITH ASSOCIATED LIGHTS; MASTER CAUTIONS AND AUTOPLT DISCONNECTING. I GAVE CTL OF THE ACFT TO FO AS I INITIALLY HAD NO USABLE INSTRUMENTATION ON MY SIDE. I RAN THE ABNORMAL IRS FAULT CHKLIST AND RESTORED MOST OF THE INSTRUMENTATION TO MY SIDE. I CALLED DISPATCH TO ADVISE AND SEE IF WE MIGHT BE BETTER SERVED BY RETURNING TO ZZZ1. ONCE WE VIEWED THE MEL RESTRS (TO RE-DISPATCH FROM ZZZZ REQUIRED DAY VMC; NON-RVSM; NO AUTOPLTS; LMP RESTRS; ETC) WE AGREED TO TURN BACK. I DID NOT DECLARE AN EMER WITH CTR BUT; IN HINDSIGHT; I PROBABLY SHOULD HAVE. I AM NOT SURE IF DISPATCH DECLARED AN EMER. HAVING JUST DECLARED AN EMER A WK PRIOR DUE TO A MEDICAL EMER THIS JUST DIDN'T FEEL LIKE ONE. HOWEVER; HAND FLYING USING RAW DATA (MY FLT DIRECTOR NEVER RESTORED) IS NOT SOMETHING I GET TO DO VERY OFTEN. I ADVISED MY FLT ATTENDANTS; MY PAX; CTR; ZZZ1 OPS; ZZZ1 MAINT OF OUR SITUATION. WE LANDED WITHOUT INCIDENT; REPLACED THE IRU AND RE-DISPATCHED TO ZZZZ.

Data retrieved from NASA's ASRS site as of January 2009 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.

A B737-800 pilot reports a return to departure airport following an IRU failure and the loss of associated equipment and functions. Aircraft was hand flown with raw data.