Narrative:

Prior to departure, we were issued the wylyy 3 departure. It was entered in the FMS as was the runway 27. We had ample time to review the departure. After takeoff, at approximately 400 ft AGL, we engaged the lateral navigation mode as required in the departure procedure. The flight director initially indicated that a slight left turn was required. Upon contacting departure, they instructed us to turn to 260 degrees after wylyy. A few seconds later, the flight director commanded a left turn (as would be expected passing garve intersection). A few seconds later, the flight director commanded a right turn. After about 30 degrees of turn (to approximately a 260 degree heading), I stopped the turn since this command did not seem appropriate. The flight director continued to command a right turn. A glance at the map on the FMS showed a departure far different from the wylyy 3. The map indicated a left turn slightly before garve followed by a right turn to approximately 030 degrees. Departure then commanded a turn and this was complied with. The remainder of the flight was normal. The database was current.

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Original NASA ASRS Text

Title: A B737-300 FLC EXPERIENCES AN UNEXPECTED TURN COMMAND FROM THEIR FMS DURING THE WYLYY 3 DEP PROC W OF BOS, MA.

Narrative: PRIOR TO DEP, WE WERE ISSUED THE WYLYY 3 DEP. IT WAS ENTERED IN THE FMS AS WAS THE RWY 27. WE HAD AMPLE TIME TO REVIEW THE DEP. AFTER TKOF, AT APPROX 400 FT AGL, WE ENGAGED THE LATERAL NAV MODE AS REQUIRED IN THE DEP PROC. THE FLT DIRECTOR INITIALLY INDICATED THAT A SLIGHT L TURN WAS REQUIRED. UPON CONTACTING DEP, THEY INSTRUCTED US TO TURN TO 260 DEGS AFTER WYLYY. A FEW SECONDS LATER, THE FLT DIRECTOR COMMANDED A L TURN (AS WOULD BE EXPECTED PASSING GARVE INTXN). A FEW SECONDS LATER, THE FLT DIRECTOR COMMANDED A R TURN. AFTER ABOUT 30 DEGS OF TURN (TO APPROX A 260 DEG HDG), I STOPPED THE TURN SINCE THIS COMMAND DID NOT SEEM APPROPRIATE. THE FLT DIRECTOR CONTINUED TO COMMAND A R TURN. A GLANCE AT THE MAP ON THE FMS SHOWED A DEP FAR DIFFERENT FROM THE WYLYY 3. THE MAP INDICATED A L TURN SLIGHTLY BEFORE GARVE FOLLOWED BY A R TURN TO APPROX 030 DEGS. DEP THEN COMMANDED A TURN AND THIS WAS COMPLIED WITH. THE REMAINDER OF THE FLT WAS NORMAL. THE DATABASE WAS CURRENT.

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.