A B767-300's three IRU's shifted about 12 NM as the aircraft approached brv causing a map shift and ...

Attributes
ACN	949438
Time
Date	201105
Local Time Of Day	0601-1200
Place
Locale Reference	DCA.Airport
State Reference	DC
Environment
Light	Daylight
Aircraft 1
Make Model Name	B767-300 and 300 ER
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Route In Use	STAR BARIN ONE
Flight Plan	IFR
Component
Aircraft Component	INS / IRS / IRU
Person 1
Function	First Officer Pilot Not Flying
Experience	Flight Crew Last 90 Days 150 Flight Crew Total 9000 Flight Crew Type 5000
Person 2
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 240 Flight Crew Total 16000 Flight Crew Type 11000
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Procedural Clearance Deviation - Track / Heading All Types

Narrative:

We were on the barin arrival when we thought we were 10 NM prior to brv. About that time the map started shifting and the pilot flying started turning. Soon after; ATC called and mentioned something about us being 'off the arrival.' we told them that we were experiencing map shift. We tried to use raw data off the arrival plate; but there is no frequency for brv. The captain looked it up on the chart and we tuned it and confirmed that we were off course by about 3 NM. Captain checked all 3 irus in the box and they were all showing 12+ miles in error. We armed the manual update and hit 'now.' by this time we were on vectors. The rest of the approach went without any problems to a successful landing. After landing; we rechecked the IRU errors and they were all in the normal range. Prior to the problem; we had been in radar contact with multiple centers for at least 2-3 hours with no idea that we had any problem.

Original NASA ASRS Text

Title: A B767-300's three IRU's shifted about 12 NM as the aircraft approached BRV causing a map shift and tract deviation. ATC began vectors for a normal approach and at gate arrival the IRU positions were normal.

Narrative: We were on the BARIN Arrival when we thought we were 10 NM prior to BRV. About that time the map started shifting and the pilot flying started turning. Soon after; ATC called and mentioned something about us being 'off the Arrival.' We told them that we were experiencing map shift. We tried to use raw data off the Arrival plate; but there is no frequency for BRV. The Captain looked it up on the chart and we tuned it and confirmed that we were off course by about 3 NM. Captain checked all 3 IRUs in the box and they were all showing 12+ miles in error. We armed the manual update and hit 'now.' By this time we were on vectors. The rest of the approach went without any problems to a successful landing. After landing; we rechecked the IRU errors and they were all in the normal range. Prior to the problem; we had been in radar contact with multiple centers for at least 2-3 hours with no idea that we had any problem.

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.

A B767-300's three IRU's shifted about 12 NM as the aircraft approached brv causing a map shift and tract deviation. ATC began vectors for a normal approach and at gate arrival the IRU positions were normal.