B757-200
Flight Crew Flight Instructor; Flight Crew Flight Engineer; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 100; Flight Crew Total 20000; Flight Crew Type 10000
Human-Machine Interface; Confusion
Aircraft Equipment Problem Critical
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; General Maintenance Action
Aircraft; Human Factors
During taxi; take-off; climb and cruise; FMC function was normal; but just passing RAVNN Intersection on the RAVNN3 arrival at BWI; with no alert messages; both ADI maps shifted approximately 5 miles to the northwest; and remained 5 miles displaced from our visually confirmed position for the remainder of the flight including during final approach; and while parked at the gate at BWI. IRS monitor showed over 5 miles drift for all three IRS's. The in flight NAV deviation occurred when map shift first occurred after passing RAVNN waypoint. ATC queried us at that time about out track on the STAR; and we were given radar vectors for a visual approach to Runway 15R. There were no traffic conflicts or altitude deviations. Throughout the visual approach; both ADI maps continued to depict the airport as 5 miles northwest of its actual position; and at gate all indications (fix page; latitude/longitude. and drift) continued to show our gate position five miles from actual. Maintenance Control issued an MEL for subsequent flight under Non-RNAV restrictions.
[No Additional information]
B757 flight crew descending into BWI experiences a sudden 5 NM map shift and resultant track deviation that is questioned by ATC. The error is verified visually during approach and again at the gate using the map display; fix page; and the IRS latitude and longitude. The system is MEL'd for the return flight.