B737-300 captain experiences a track deviation after being cleared direct to a waypoint and selectin...

Narrative:

[I] departed on a 030 heading to avoid weather east of the field. After clearing the weather; we were cleared to our next point; forpe. I selected the point; moved it to the top of the legs page; confirmed with the first officer; and executed and then selected LNAV. The aircraft turned to forpe and was on course. During the climb; I wanted to get out the arrival for review and I was heads down for longer than usual because the arrivals were incorrect in chart manual. When I crosschecked the navigation instruments; I saw that the aircraft had passed forpe and the LNAV was no longer engaged. I immediately turned back to course and asked the first officer to inform ATC of our situation at which point ATC asked where we were going. We informed them of our system disconnect and they gave us a short vector to get back in position. We discussed the event and noted that we did a proper preflight brief and departure brief and everything was set up correctly. The aircraft simply had a hiccup and unfortunately it got us when we were distracted by another issue.

Original NASA ASRS Text

Title: B737-300 Captain experiences a track deviation after being cleared direct to a waypoint and selecting LNAV. LNAV did not engage or dropped off after selection and was not detected by the crew until after the waypoint had been passed.

Narrative: [I] departed on a 030 heading to avoid weather east of the field. After clearing the weather; we were cleared to our next point; FORPE. I selected the point; moved it to the top of the LEGS page; confirmed with the First Officer; and executed and then selected LNAV. The aircraft turned to FORPE and was on course. During the climb; I wanted to get out the arrival for review and I was heads down for longer than usual because the arrivals were incorrect in chart manual. When I crosschecked the NAV instruments; I saw that the aircraft had passed FORPE and the LNAV was no longer engaged. I immediately turned back to course and asked the First Officer to inform ATC of our situation at which point ATC asked where we were going. We informed them of our system disconnect and they gave us a short vector to get back in position. We discussed the event and noted that we did a proper preflight brief and departure brief and everything was set up correctly. The aircraft simply had a hiccup and unfortunately it got us when we were distracted by another issue.

Data retrieved from NASA's ASRS site as of July 2013 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.

Attributes
ACN	1121933
Time
Date	201310
Local Time Of Day	0601-1200
Place
Locale Reference	ZAB.ARTCC
State Reference	NM
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	Climb
Component
Aircraft Component	MCP
Person 1
Function	Captain
Experience	Flight Crew Last 90 Days 108
Events
Anomaly	Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Deviation - Track / Heading All Types

B737-300 captain experiences a track deviation after being cleared direct to a waypoint and selecting LNAV. LNAV did not engage or dropped off after selection and was not detected by the crew until after the waypoint had been passed.