Flight crew of a non GPS; FMS equipped medium large transport suffer a track deviation on takeoff wh...

Attributes
ACN	819900
Time
Date	200901
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B737-400
Operating Under FAR Part	Part 121
Flight Phase	Climb
Flight Plan	IFR
Component
Aircraft Component	FMS/FMC
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 200 Flight Crew Total 22000 Flight Crew Type 5000
Person 2
Function	Local
Events
Anomaly	Aircraft Equipment Problem Critical Conflict Airborne Conflict Deviation - Procedural Published Material / Policy Deviation - Track / Heading All Types

Narrative:

I was captain and pilot flying of a flight operating out of ZZZ. We received and briefed the RNAV departure off of runway xx. At the runway end; we realigned. After takeoff at 400 ft AGL; hit LNAV and the FD indicated a slight right turn; which is unusual; but there was a strong crosswind from the right; so I thought that was it. At 1;000 ft AGL; began aircraft cleanup and activated the autopilot; at which time we became concerned about our path related to an air carrier aircraft on a parallel departure. About this time we observed the carrier aircraft begin a right turn away from us and received a left turn from the tower. First officer had the air carrier aircraft in sight the whole time and I do not believe there was a loss of separation; which the tower supervisor I talked to agreed and said he would amend the report. The bad thing is I have no idea why this happened; as we followed all the company procedures and verified the correct runway and departure.

Original NASA ASRS Text

Title: Flight crew of a non GPS; FMS equipped MLG suffer a track deviation on takeoff when the FMS fails to provide proper steering information.

Narrative: I was Captain and Pilot Flying of a flight operating out of ZZZ. We received and briefed the RNAV departure off of Runway XX. At the runway end; we realigned. After takeoff at 400 FT AGL; hit LNAV and the FD indicated a slight right turn; which is unusual; but there was a strong crosswind from the right; so I thought that was it. At 1;000 FT AGL; began aircraft cleanup and activated the autopilot; at which time we became concerned about our path related to an air carrier aircraft on a parallel departure. About this time we observed the carrier aircraft begin a right turn away from us and received a left turn from the Tower. First Officer had the air carrier aircraft in sight the whole time and I do not believe there was a loss of separation; which the Tower Supervisor I talked to agreed and said he would amend the report. The bad thing is I have no idea why this happened; as we followed all the company procedures and verified the correct runway and departure.

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.

Flight crew of a non GPS; FMS equipped medium large transport suffer a track deviation on takeoff when the FMS fails to provide proper steering information.