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|
Attributes | |
ACN | 1312996 |
Time | |
Date | 201511 |
Local Time Of Day | 0001-0600 |
Place | |
Locale Reference | SEA.Airport |
State Reference | WA |
Aircraft 1 | |
Make Model Name | B737 Undifferentiated or Other Model |
Operating Under FAR Part | Part 121 |
Flight Phase | Initial Approach |
Route In Use | Vectors |
Flight Plan | IFR |
Person 1 | |
Function | Captain Pilot Flying |
Qualification | Flight Crew Air Transport Pilot (ATP) |
Events | |
Anomaly | Aircraft Equipment Problem Less Severe Deviation - Procedural Clearance Deviation - Track / Heading All Types |
Narrative:
Just off the STAR; we were being vectored by ATC for an anticipated approach to runway 16R sea from the east. We received a clearance to proceed direct agane. We programmed the FMC; exec; LNAV and direct we went. About 3 NM from agane we queried ATC whether they wanted us to proceed inbound on the localizer; or hold at agane...they replied 'standby.' LNAV just began turning the aircraft toward the next waypoint inbound on the approach; 'celak' when ATC gave us the approach clearance 'turn left 190; cross celak at or above 4;000; cleared for the ILS 16R'. We complied; pushed heading sel on the MCP; set heading 190; armed the appch mode and also armed the second [autopilot] 'B' for the CAT III ILS as requested and cleared.reading the FMA on the pfd; VOR/localizer was captured immediately and we proceeded inbound...but something looked wrong. On the map display we noticed we were tracking east of course; approaching bugne we were about 0.3 east of course; raw data confirmed this; as well as a visual to the airport ahead. I recognized this as a 'standoff' and disengaged automation; turned off the flight directors...then back on; rebuilt the approach and automation just outside bugne. The glide slope captured at this point and our descent rate slowed...so did our approach speed; the autothrottles did not get re-engaged during the 'rebuild' of the approach and automation. Speed got down to 127 knots referencing a target speed set at what I believe was 139 knots. Power was manually set; autothrottles were re-engaged. We were stabilized by the glideslope intercept altitude (gsia) 'finka' and had a successful CAT III autoland rollout.this was a training flight with a new first officer.ATC's late approach clearance combined with FMC LNAV functions (and interface with appch mode/immediate capture) caused a control wheel position that I believe put the aircraft into an automated 'standoff mode.' the recognition and subsequent rebuilding of the automation and timing of all the above resulted in the autothrottles not being re-engaged.
Original NASA ASRS Text
Title: A B737 Captain reported deviating from cleared track when the aircraft entered a 'standoff' condition.
Narrative: Just off the STAR; we were being vectored by ATC for an anticipated approach to RWY 16R SEA from the east. We received a clearance to proceed direct AGANE. We programmed the FMC; EXEC; LNAV and direct we went. About 3 NM from AGANE we queried ATC whether they wanted us to proceed inbound on the localizer; or hold at AGANE...they replied 'standby.' LNAV just began turning the aircraft toward the next waypoint inbound on the approach; 'CELAK' when ATC gave us the approach clearance 'turn left 190; cross CELAK at or above 4;000; cleared for the ILS 16R'. We complied; pushed HDG SEL on the MCP; set heading 190; armed the APPCH mode and also armed the second [autopilot] 'B' for the CAT III ILS as requested and cleared.Reading the FMA on the PFD; VOR/LOC was captured immediately and we proceeded inbound...but something looked wrong. On the MAP display we noticed we were tracking east of course; approaching BUGNE we were about 0.3 east of course; raw data confirmed this; as well as a visual to the airport ahead. I recognized this as a 'Standoff' and disengaged automation; turned off the Flight Directors...then back on; rebuilt the approach and automation just outside BUGNE. The Glide Slope captured at this point and our descent rate slowed...so did our approach speed; the Autothrottles did not get re-engaged during the 'rebuild' of the approach and automation. Speed got down to 127 knots referencing a target speed set at what I believe was 139 knots. Power was manually set; Autothrottles were re-engaged. We were stabilized by the Glideslope Intercept Altitude (GSIA) 'FINKA' and had a successful CAT III Autoland rollout.This was a training flight with a new First Officer.ATC's late approach clearance combined with FMC LNAV functions (and interface with APPCH mode/immediate capture) caused a control wheel position that I believe put the aircraft into an automated 'Standoff Mode.' The recognition and subsequent rebuilding of the automation and timing of all the above resulted in the Autothrottles not being re-engaged.
Data retrieved from NASA's ASRS site 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.