B737-300 crew deviates from track during initial phase of holtz RNAV departure from lax.

Attributes
ACN	727728
Time
Date	200702
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : lax.airport
State Reference	CA
Altitude	msl single value : 400
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : sct.tracon
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	climbout : takeoff
Route In Use	departure sid : holtz
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 73 flight time type : 4500
ASRS Report	727728
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : less severe non adherence : clearance non adherence : published procedure non adherence : required legal separation other spatial deviation
Independent Detector	other controllera
Resolutory Action	controller : issued alert controller : issued new clearance flight crew : returned to intended or assigned course
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

Captain takeoff using HUD with toga armed LNAV switches down for the holtz 7 RNAV departure. At 400 ft LNAV mode engaged (per fom) aircraft guidance showing a left turn to course. Initially following guidance knowing this is incorrect; I turned back to a 250 degree heading and at the same time ATC inquired and instructed an immediate right turn to 250 degrees to avoid conflict. Looked at the XXX page and it showed the actual rnp at 3.52 well above the 2.0 threshold required for navigation performance. Told ATC we need vectors RNAV unreliable. Upon further climb out rnp; went back down to normal reading of about .5. Accepted direct to next fix and resumed the departure. FMC was verified prior to push with the correct holtz 7 departure and runway 24L. RNAV departure procedures were reviewed in the takeoff briefing. In the B-300 aircraft if RNAV departures are required; a second FMC must be installed to monitor the legs page and rnp. Our fom directs us to display the takeoff reference page during takeoff. Make the system reliable -- dual GPS should also be installed.

Original NASA ASRS Text

Title: B737-300 CREW DEVIATES FROM TRACK DURING INITIAL PHASE OF HOLTZ RNAV DEPARTURE FROM LAX.

Narrative: CAPT TKOF USING HUD WITH TOGA ARMED LNAV SWITCHES DOWN FOR THE HOLTZ 7 RNAV DEP. AT 400 FT LNAV MODE ENGAGED (PER FOM) ACFT GUIDANCE SHOWING A L TURN TO COURSE. INITIALLY FOLLOWING GUIDANCE KNOWING THIS IS INCORRECT; I TURNED BACK TO A 250 DEG HDG AND AT THE SAME TIME ATC INQUIRED AND INSTRUCTED AN IMMEDIATE R TURN TO 250 DEGS TO AVOID CONFLICT. LOOKED AT THE XXX PAGE AND IT SHOWED THE ACTUAL RNP AT 3.52 WELL ABOVE THE 2.0 THRESHOLD REQUIRED FOR NAV PERFORMANCE. TOLD ATC WE NEED VECTORS RNAV UNRELIABLE. UPON FURTHER CLBOUT RNP; WENT BACK DOWN TO NORMAL READING OF ABOUT .5. ACCEPTED DIRECT TO NEXT FIX AND RESUMED THE DEP. FMC WAS VERIFIED PRIOR TO PUSH WITH THE CORRECT HOLTZ 7 DEP AND RWY 24L. RNAV DEP PROCS WERE REVIEWED IN THE TKOF BRIEFING. IN THE B-300 ACFT IF RNAV DEPS ARE REQUIRED; A SECOND FMC MUST BE INSTALLED TO MONITOR THE LEGS PAGE AND RNP. OUR FOM DIRECTS US TO DISPLAY THE TKOF REF PAGE DURING TKOF. MAKE THE SYS RELIABLE -- DUAL GPS SHOULD ALSO BE INSTALLED.

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.