B737 pilot on IOE has LNAV disengage during descent resulting in heading deviation.

Attributes
ACN	334835
Time
Date	199604
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : lax
State Reference	CA
Altitude	msl bound lower : 12000 msl bound upper : 12000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : lax tower : mci
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Navigation In Use	Other
Flight Phase	descent : approach
Route In Use	arrival other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : atp
Experience	flight time last 90 days : 20 flight time total : 11100 flight time type : 20
ASRS Report	334835
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	non adherence : clearance non adherence : published procedure other anomaly other other spatial deviation
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : became reoriented
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I was on my IOE trip on the B737 after completing simulator training and 1 aircraft trip, as part of that training. So I had 17 1/2 hours in the aircraft at the start of this trip. I had spent the past 7 yrs as a flight engineer on the DC10. The instructor and I were discussing the procedures for using LNAV and VNAV coupled to fly the civet 1 arrival into lax. While I was involved with setting the VNAV altitude, I did not notice that LNAV had disengaged as we passed civet for bremr and descending from 14000 ft to 12000 ft. We were 2 dots to the left of track when lax approach control questioned our position. I made a correction back to the right and re-engaged LNAV. The correction was complete by bremr or maybe just past that point. LNAV was then closely monitored and compared with raw data. Proper ground track was then maintained and the remainder of the arrival and approach to land at lax runway 25L was completed uneventfully. This was a valuable lesson learned in the importance of monitoring the FMA to be assured that what had been selected and desired was in fact engaged. The approach controller said to review the approach arrival before a future flight to lax. Yes sir!

Original NASA ASRS Text

Title: B737 PLT ON IOE HAS LNAV DISENGAGE DURING DSCNT RESULTING IN HDG DEV.

Narrative: I WAS ON MY IOE TRIP ON THE B737 AFTER COMPLETING SIMULATOR TRAINING AND 1 ACFT TRIP, AS PART OF THAT TRAINING. SO I HAD 17 1/2 HRS IN THE ACFT AT THE START OF THIS TRIP. I HAD SPENT THE PAST 7 YRS AS A FE ON THE DC10. THE INSTRUCTOR AND I WERE DISCUSSING THE PROCS FOR USING LNAV AND VNAV COUPLED TO FLY THE CIVET 1 ARR INTO LAX. WHILE I WAS INVOLVED WITH SETTING THE VNAV ALT, I DID NOT NOTICE THAT LNAV HAD DISENGAGED AS WE PASSED CIVET FOR BREMR AND DSNDING FROM 14000 FT TO 12000 FT. WE WERE 2 DOTS TO THE L OF TRACK WHEN LAX APCH CTL QUESTIONED OUR POS. I MADE A CORRECTION BACK TO THE R AND RE-ENGAGED LNAV. THE CORRECTION WAS COMPLETE BY BREMR OR MAYBE JUST PAST THAT POINT. LNAV WAS THEN CLOSELY MONITORED AND COMPARED WITH RAW DATA. PROPER GND TRACK WAS THEN MAINTAINED AND THE REMAINDER OF THE ARR AND APCH TO LAND AT LAX RWY 25L WAS COMPLETED UNEVENTFULLY. THIS WAS A VALUABLE LESSON LEARNED IN THE IMPORTANCE OF MONITORING THE FMA TO BE ASSURED THAT WHAT HAD BEEN SELECTED AND DESIRED WAS IN FACT ENGAGED. THE APCH CTLR SAID TO REVIEW THE APCH ARR BEFORE A FUTURE FLT TO LAX. YES SIR!

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.