A B757 flight crew has a malfunctioning FMS which leads them off course.

Attributes
ACN	526240
Time
Date	200110
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : bos.airport
State Reference	MA
Altitude	msl single value : 400
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tower : bos.tower
Operator	common carrier : air carrier
Make Model Name	B757-200
Flight Phase	climbout : takeoff climbout : initial
Route In Use	departure sid : wylie
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	526240
Events
Anomaly	aircraft equipment problem : less severe other spatial deviation non adherence : company policies
Resolutory Action	controller : issued new clearance flight crew : returned to intended or assigned course
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Aircraft

Narrative:

Wylie FMS departure from bos. B757/runway 27. First officer's leg. Upon reaching the hold short, the aircraft symbol was touching the runway. Did not accomplish quick align. Per procedure, called for LNAV at 400 ft RA. The ADI commanded a right turn, first officer began a right turn and then immediately came back left when it was obviously wrong. Captain was busy bringing up flaps and switching from tower to departure frequency. Departure gave us vectors to get us back on proper course. Lesson learned: one of us should have been in full VOR mode to back up the FMS.

Original NASA ASRS Text

Title: A B757 FLT CREW HAS A MALFUNCTIONING FMS WHICH LEADS THEM OFF COURSE.

Narrative: WYLIE FMS DEP FROM BOS. B757/RWY 27. FO'S LEG. UPON REACHING THE HOLD SHORT, THE ACFT SYMBOL WAS TOUCHING THE RWY. DID NOT ACCOMPLISH QUICK ALIGN. PER PROC, CALLED FOR LNAV AT 400 FT RA. THE ADI COMMANDED A R TURN, FO BEGAN A R TURN AND THEN IMMEDIATELY CAME BACK L WHEN IT WAS OBVIOUSLY WRONG. CAPT WAS BUSY BRINGING UP FLAPS AND SWITCHING FROM TWR TO DEP FREQ. DEP GAVE US VECTORS TO GET US BACK ON PROPER COURSE. LESSON LEARNED: ONE OF US SHOULD HAVE BEEN IN FULL VOR MODE TO BACK UP THE FMS.

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.