B737 Next Generation Undifferentiated
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 283; Flight Crew Type 12000
Situational Awareness
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Human Factors; Aircraft
On the HAWKZ 7 arrival into SEA; in LNAV and VNAV. Just before COFAY Intersection; we changed the approach for Runway 16R from the RNAV Z to the ILS. We then looked up and noticed the aircraft in heading mode. A slight course deviation east of intended flight path occurred before direct to BREVE was entered and LNAV re-engaged. Proceeded on arrival to landing. Loss of LNAV was unexpected; and a small period of time elapsed before we noticed. Better attention in my role of Pilot Monitoring next time.
B737 Captain reported a track deviation occurred on the HAWKZ 7 arrival into SEA when the aircraft dropped out of LNAV into HDG SEL.