IRS and instrument failure on medium large transport.

Attributes
ACN	290388
Time
Date	199412
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : dca airport : bwi
State Reference	DC
Altitude	msl bound lower : 31000 msl bound upper : 31000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc tower : las
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other other other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 300 flight time total : 11500 flight time type : 4000
ASRS Report	290388
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : declared emergency none taken : unable other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

While en route from pbi to lga both CDU's announced, 'FMC fail,' followed by #1 attitude indicator flag. Transfer switch selected to attitude indicator -- both on 2. Then #2 attitude indicator failed after approximately 1 min. All AC and dc system checked normal. Both IRS units announced 'IRS fault.' both system were placed from 'navigation' to 'attitude indicator' position. After flying straight and level, steady speed for 1-2 mins, we were still unable to get attitude indicators back. With only standby attitude indicator and magnetic compass available, the flight diverted to bwi. At 10000-12000 ft MSL, attitude indicator flags disappeared, FMC faults remained. Normal landing at bwi followed by logbook maintenance entry.

Original NASA ASRS Text

Title: IRS AND INST FAILURE ON MLG.

Narrative: WHILE ENRTE FROM PBI TO LGA BOTH CDU'S ANNOUNCED, 'FMC FAIL,' FOLLOWED BY #1 ATTITUDE INDICATOR FLAG. TRANSFER SWITCH SELECTED TO ATTITUDE INDICATOR -- BOTH ON 2. THEN #2 ATTITUDE INDICATOR FAILED AFTER APPROX 1 MIN. ALL AC AND DC SYS CHKED NORMAL. BOTH IRS UNITS ANNOUNCED 'IRS FAULT.' BOTH SYS WERE PLACED FROM 'NAV' TO 'ATTITUDE INDICATOR' POS. AFTER FLYING STRAIGHT AND LEVEL, STEADY SPD FOR 1-2 MINS, WE WERE STILL UNABLE TO GET ATTITUDE INDICATORS BACK. WITH ONLY STANDBY ATTITUDE INDICATOR AND MAGNETIC COMPASS AVAILABLE, THE FLT DIVERTED TO BWI. AT 10000-12000 FT MSL, ATTITUDE INDICATOR FLAGS DISAPPEARED, FMC FAULTS REMAINED. NORMAL LNDG AT BWI FOLLOWED BY LOGBOOK MAINT ENTRY.

Data retrieved from NASA's ASRS site as of July 2007 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.