Narrative:

Issue: the flight director on the captain's side did not properly command the roll bar to maintain LNAV course. The aircraft did not navigation on the magenta line and had to be manually flown back to the proper course. Backgnd: during preflight; the holtz departure was loaded into the FMC. It was verified loaded on the route pages and was stepped through on the legs pages with no apparent errors. The first point (hiipr) was verified as the active waypoint. There was a magenta line from the approach end of runway 25R to the last point of the cleared route; a fix near iad. The LNAV button on the MCP was pressed and was lit. The roll bar on the captain's pfd appeared and was centered. LNAV was annunciated on the FMA. During taxi out to the runway; when MCP was challenged on the before takeoff checklist; the LNAV button was verified illuminated. The takeoff was performed normally. However; approaching hiipr; the first officer noticed that his flight director was commanding a left turn. He glanced at the captain's flight director and noticed that the bars were commanding straight ahead climbing flight. He called out this difference and the captain turned back to the left to intercept the course. Tower then gave a vector of 190 degrees to reintercept the departure. I believe controller gave us direct pevee; which we loaded and executed. Both flight directors then operated normally for the remainder of the flight. The #1 radio altimeter was placarded inoperative; which also affected the HUD; which was also placarded inoperative. It is not known if this affected the performance of the captain's flight director. The first officer was encouraged to also file a safety report; which he has stated will be accomplished later on this morning (friday).

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Original NASA ASRS Text

Title: B737-800 FLT CREW HAS A TRACK HDG DEV DURING HOLTZ 7 DEP FROM LAX.

Narrative: ISSUE: THE FLT DIRECTOR ON THE CAPT'S SIDE DID NOT PROPERLY COMMAND THE ROLL BAR TO MAINTAIN LNAV COURSE. THE ACFT DID NOT NAV ON THE MAGENTA LINE AND HAD TO BE MANUALLY FLOWN BACK TO THE PROPER COURSE. BACKGND: DURING PREFLT; THE HOLTZ DEP WAS LOADED INTO THE FMC. IT WAS VERIFIED LOADED ON THE RTE PAGES AND WAS STEPPED THROUGH ON THE LEGS PAGES WITH NO APPARENT ERRORS. THE FIRST POINT (HIIPR) WAS VERIFIED AS THE ACTIVE WAYPOINT. THERE WAS A MAGENTA LINE FROM THE APCH END OF RWY 25R TO THE LAST POINT OF THE CLRED RTE; A FIX NEAR IAD. THE LNAV BUTTON ON THE MCP WAS PRESSED AND WAS LIT. THE ROLL BAR ON THE CAPT'S PFD APPEARED AND WAS CTRED. LNAV WAS ANNUNCIATED ON THE FMA. DURING TAXI OUT TO THE RWY; WHEN MCP WAS CHALLENGED ON THE BEFORE TKOF CHKLIST; THE LNAV BUTTON WAS VERIFIED ILLUMINATED. THE TKOF WAS PERFORMED NORMALLY. HOWEVER; APCHING HIIPR; THE FO NOTICED THAT HIS FLT DIRECTOR WAS COMMANDING A L TURN. HE GLANCED AT THE CAPT'S FLT DIRECTOR AND NOTICED THAT THE BARS WERE COMMANDING STRAIGHT AHEAD CLBING FLT. HE CALLED OUT THIS DIFFERENCE AND THE CAPT TURNED BACK TO THE L TO INTERCEPT THE COURSE. TWR THEN GAVE A VECTOR OF 190 DEGS TO REINTERCEPT THE DEP. I BELIEVE CTLR GAVE US DIRECT PEVEE; WHICH WE LOADED AND EXECUTED. BOTH FLT DIRECTORS THEN OPERATED NORMALLY FOR THE REMAINDER OF THE FLT. THE #1 RADIO ALTIMETER WAS PLACARDED INOP; WHICH ALSO AFFECTED THE HUD; WHICH WAS ALSO PLACARDED INOP. IT IS NOT KNOWN IF THIS AFFECTED THE PERFORMANCE OF THE CAPT'S FLT DIRECTOR. THE FO WAS ENCOURAGED TO ALSO FILE A SAFETY RPT; WHICH HE HAS STATED WILL BE ACCOMPLISHED LATER ON THIS MORNING (FRIDAY).

Data retrieved from NASA's ASRS site as of January 2009 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.