Narrative:

On departure from lax on the holtz RNAV departure from runway 24L; both pilots checked and confirmed navigation waypoints and the FMC were set up for an RNAV departure. The takeoff was uneventful. At approximately 600 ft; I engaged the LNAV and at 1000 ft; called for flaps 1 degree climb thrust. At about 1200 ft; I called for flaps up and shortly after; the CDI and command bars commanded a right turn. I expected the right turn at dlrey and followed the command bars. I had already begun the turn when the captain pointed out that the FMC showed we had not yet reached dlrey. About that time ATC asked about our course and directed a left turn to 180 degrees. I was in the turn back when they asked us to copy down a number for a possible pilot deviation. The captain asked them to stand by. Before reaching the 180 degree heading; we were cleared direct pevee and 250 KTS. The captain said direct pevee and updated the FMC. He then asked ATC to go ahead with the number. I continued the turn and climb while looking down to confirm the FMC was directing us to pevee; LNAV was engaged; and the command bars were pointing the right way. About that time; ATC directed an immediate descent to 5000 ft. I saw 5700 ft on the altimeter and began the descent as the captain took the aircraft and continued to 5000 ft. We were given a short vector to the right then cleared on course to pevee. I put in direct pevee and executed our new course. The captain gave me back the aircraft and we continued the leg uneventfully. We never determined the cause of the turn indication; however; there are some things we could have done better. We should have waited until a safer point to write down the phone number from ATC. I should have ensured the autoplt was engaged before being distraction by the other events that were occurring. I should have also confirmed that the captain had his head up while I went head down to confirm our course and navigation setup. The captain and I discussed the issue and agreed that using the automation could have prevented the altitude deviation. Supplemental information from acn 788222: we were on the holtz RNAV SID off of runway 24L. FMC points were checked and displayed properly. Takeoff occurred uneventfully; first officer was the PF and captain was the pilot monitoring. At approximately 600 ft; LNAV was selected and continued to display a course aligned with the runway to dlrey. At 1000 ft; the first officer called for flaps 1 degree and climb thrust. As the first officer called for flaps up; the command bars in LNAV commanded a right turn. CDI still showed us centered on course. As the bars continued to command a turn to a heading of approximately 270 degrees (CDI centered and now reflecting a 270 degree course); I checked the FMC and realized dlrey still showed as the next point; not enney which would have required a slight right turn (about 254 degrees). I realized the FMC was providing erroneous information; but before I was able to direct the first officer to turn left and contact ATC; socal instructed us to make a left turn to 180 degrees and that we were off course. They then asked me to take down a phone number in order to respond to a possible deviation. I told them to stand by. Socal then gave us direct pevee and 250 KTS. The first officer was still hand flying the aircraft; so I selected pevee in the FMC and executed stating pevee is in and executed. We were in a left turn and climbing smoothly so I told ATC to go ahead with the phone number. I should not have done this. In the middle of passing the number; ATC instructed us to begin an immediate descent and return to 5000 ft. I realized that we were still climbing and instructed the first officer to immediately return to 5000 ft. I was not comfortable with the rate of our correction so I took the aircraft; stopped the climb; and began a descent to 5000 ft. The maximum altitude reached was 5700 ft.

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Original NASA ASRS Text

Title: B737 FLT CREW DEPARTING LAX ON HOLTZ9 RNAV HAS COURSE DEV APPROACHING DLREY AND AN ALT DEV WHILE COPYING A PHONE NUMBER FROM SCT.

Narrative: ON DEP FROM LAX ON THE HOLTZ RNAV DEP FROM RWY 24L; BOTH PLTS CHKED AND CONFIRMED NAV WAYPOINTS AND THE FMC WERE SET UP FOR AN RNAV DEP. THE TKOF WAS UNEVENTFUL. AT APPROX 600 FT; I ENGAGED THE LNAV AND AT 1000 FT; CALLED FOR FLAPS 1 DEG CLB THRUST. AT ABOUT 1200 FT; I CALLED FOR FLAPS UP AND SHORTLY AFTER; THE CDI AND COMMAND BARS COMMANDED A R TURN. I EXPECTED THE R TURN AT DLREY AND FOLLOWED THE COMMAND BARS. I HAD ALREADY BEGUN THE TURN WHEN THE CAPT POINTED OUT THAT THE FMC SHOWED WE HAD NOT YET REACHED DLREY. ABOUT THAT TIME ATC ASKED ABOUT OUR COURSE AND DIRECTED A L TURN TO 180 DEGS. I WAS IN THE TURN BACK WHEN THEY ASKED US TO COPY DOWN A NUMBER FOR A POSSIBLE PLTDEV. THE CAPT ASKED THEM TO STAND BY. BEFORE REACHING THE 180 DEG HDG; WE WERE CLRED DIRECT PEVEE AND 250 KTS. THE CAPT SAID DIRECT PEVEE AND UPDATED THE FMC. HE THEN ASKED ATC TO GO AHEAD WITH THE NUMBER. I CONTINUED THE TURN AND CLB WHILE LOOKING DOWN TO CONFIRM THE FMC WAS DIRECTING US TO PEVEE; LNAV WAS ENGAGED; AND THE COMMAND BARS WERE POINTING THE RIGHT WAY. ABOUT THAT TIME; ATC DIRECTED AN IMMEDIATE DSCNT TO 5000 FT. I SAW 5700 FT ON THE ALTIMETER AND BEGAN THE DSCNT AS THE CAPT TOOK THE ACFT AND CONTINUED TO 5000 FT. WE WERE GIVEN A SHORT VECTOR TO THE R THEN CLRED ON COURSE TO PEVEE. I PUT IN DIRECT PEVEE AND EXECUTED OUR NEW COURSE. THE CAPT GAVE ME BACK THE ACFT AND WE CONTINUED THE LEG UNEVENTFULLY. WE NEVER DETERMINED THE CAUSE OF THE TURN INDICATION; HOWEVER; THERE ARE SOME THINGS WE COULD HAVE DONE BETTER. WE SHOULD HAVE WAITED UNTIL A SAFER POINT TO WRITE DOWN THE PHONE NUMBER FROM ATC. I SHOULD HAVE ENSURED THE AUTOPLT WAS ENGAGED BEFORE BEING DISTR BY THE OTHER EVENTS THAT WERE OCCURRING. I SHOULD HAVE ALSO CONFIRMED THAT THE CAPT HAD HIS HEAD UP WHILE I WENT HEAD DOWN TO CONFIRM OUR COURSE AND NAV SETUP. THE CAPT AND I DISCUSSED THE ISSUE AND AGREED THAT USING THE AUTOMATION COULD HAVE PREVENTED THE ALTDEV. SUPPLEMENTAL INFO FROM ACN 788222: WE WERE ON THE HOLTZ RNAV SID OFF OF RWY 24L. FMC POINTS WERE CHKED AND DISPLAYED PROPERLY. TKOF OCCURRED UNEVENTFULLY; FO WAS THE PF AND CAPT WAS THE PLT MONITORING. AT APPROX 600 FT; LNAV WAS SELECTED AND CONTINUED TO DISPLAY A COURSE ALIGNED WITH THE RWY TO DLREY. AT 1000 FT; THE FO CALLED FOR FLAPS 1 DEG AND CLB THRUST. AS THE FO CALLED FOR FLAPS UP; THE COMMAND BARS IN LNAV COMMANDED A R TURN. CDI STILL SHOWED US CTRED ON COURSE. AS THE BARS CONTINUED TO COMMAND A TURN TO A HDG OF APPROX 270 DEGS (CDI CTRED AND NOW REFLECTING A 270 DEG COURSE); I CHKED THE FMC AND REALIZED DLREY STILL SHOWED AS THE NEXT POINT; NOT ENNEY WHICH WOULD HAVE REQUIRED A SLIGHT R TURN (ABOUT 254 DEGS). I REALIZED THE FMC WAS PROVIDING ERRONEOUS INFO; BUT BEFORE I WAS ABLE TO DIRECT THE FO TO TURN L AND CONTACT ATC; SOCAL INSTRUCTED US TO MAKE A L TURN TO 180 DEGS AND THAT WE WERE OFF COURSE. THEY THEN ASKED ME TO TAKE DOWN A PHONE NUMBER IN ORDER TO RESPOND TO A POSSIBLE DEV. I TOLD THEM TO STAND BY. SOCAL THEN GAVE US DIRECT PEVEE AND 250 KTS. THE FO WAS STILL HAND FLYING THE ACFT; SO I SELECTED PEVEE IN THE FMC AND EXECUTED STATING PEVEE IS IN AND EXECUTED. WE WERE IN A L TURN AND CLBING SMOOTHLY SO I TOLD ATC TO GO AHEAD WITH THE PHONE NUMBER. I SHOULD NOT HAVE DONE THIS. IN THE MIDDLE OF PASSING THE NUMBER; ATC INSTRUCTED US TO BEGIN AN IMMEDIATE DSCNT AND RETURN TO 5000 FT. I REALIZED THAT WE WERE STILL CLBING AND INSTRUCTED THE FO TO IMMEDIATELY RETURN TO 5000 FT. I WAS NOT COMFORTABLE WITH THE RATE OF OUR CORRECTION SO I TOOK THE ACFT; STOPPED THE CLB; AND BEGAN A DSCNT TO 5000 FT. THE MAX ALT REACHED WAS 5700 FT.

Data retrieved from NASA's ASRS site as of May 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.