<< >> NASA ASRS Report 558357, August 2002

A B757-200 crew, on final to sfo, encountered an autoplt uncommanded roll input requiring autoplt disconnect.

Attributes
ACN	558357
Time
Date	200208
Day	Thu
Place
Locale Reference	airport : sfo.airport
State Reference	CA
Altitude	msl single value : 3700
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : o90.tracon
Operator	common carrier : air carrier
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : approach
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : o90.tracon
Operator	common carrier : air carrier
Make Model Name	B747 Undifferentiated or Other Model
Flight Phase	descent : approach
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : flight engineer pilot : commercial pilot : atp pilot : multi engine
Experience	flight time last 90 days : 180 flight time total : 13000 flight time type : 5700
ASRS Report	558357
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : less severe other anomaly other other spatial deviation
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : overrode automation flight crew : regained aircraft control flight crew : overcame equipment problem
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

On FMS bridge visual runway 28R into sfo international at 3700 ft MSL, descending -900 FPM, speed 180 KTS, flaps set at 15 degrees, right autoplt command, VNAV, LNAV, on left navigation track, above VNAV path, gear down, smooth air, above heavy traffic (B747) ahead flight path and at least 5 mi behind this B747. Autoplt seemed to malfunction because airplane did a rapid smooth roll to right to 30-40 degree angle of bank. First officer disconnected autoplt (he was PF) and manually leveled plane. I, the captain, immediately took control of plane, became PF, and landed manually with flaps 30 degrees. After autoplt disconnected, plane flew normally. We had no EICAS messages, advisories, cautions, or warnings. No autoplt warnings -- probably an autoplt malfunction with uncommanded roll. If we had not acted promptly, plane would have rolled right on over.

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Original NASA ASRS Text

Title: A B757-200 CREW, ON FINAL TO SFO, ENCOUNTERED AN AUTOPLT UNCOMMANDED ROLL INPUT REQUIRING AUTOPLT DISCONNECT.

Narrative: ON FMS BRIDGE VISUAL RWY 28R INTO SFO INTL AT 3700 FT MSL, DSNDING -900 FPM, SPD 180 KTS, FLAPS SET AT 15 DEGS, R AUTOPLT COMMAND, VNAV, LNAV, ON L NAV TRACK, ABOVE VNAV PATH, GEAR DOWN, SMOOTH AIR, ABOVE HVY TFC (B747) AHEAD FLT PATH AND AT LEAST 5 MI BEHIND THIS B747. AUTOPLT SEEMED TO MALFUNCTION BECAUSE AIRPLANE DID A RAPID SMOOTH ROLL TO R TO 30-40 DEG ANGLE OF BANK. FO DISCONNECTED AUTOPLT (HE WAS PF) AND MANUALLY LEVELED PLANE. I, THE CAPT, IMMEDIATELY TOOK CTL OF PLANE, BECAME PF, AND LANDED MANUALLY WITH FLAPS 30 DEGS. AFTER AUTOPLT DISCONNECTED, PLANE FLEW NORMALLY. WE HAD NO EICAS MESSAGES, ADVISORIES, CAUTIONS, OR WARNINGS. NO AUTOPLT WARNINGS -- PROBABLY AN AUTOPLT MALFUNCTION WITH UNCOMMANDED ROLL. IF WE HAD NOT ACTED PROMPTLY, PLANE WOULD HAVE ROLLED RIGHT ON OVER.

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.