Boeing 757 flight crew reported an uncommanded roll during descent with the autopilot engaged. The r...

Attributes
ACN	1439165
Time
Date	201704
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.TRACON
State Reference	US
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Flight Plan	IFR
Component
Aircraft Component	Rudder Control System
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 240 Flight Crew Total 30500 Flight Crew Type 10686
Person 2
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Less Severe Inflight Event / Encounter Unstabilized Approach

Narrative:

On descent on STAR into ZZZ; we were told to slow down to accommodate traffic ahead. As I was decelerating the aircraft through 270 to 250 (assigned) knots; the aircraft started a substantial roll. Autopilot and autothrottle were on. I disengaged the autopilot to hand fly; and fully stowed the speed brakes. Despite speed brakes stowed; the aircraft rolling moment was quite different. Rudder ratio light came on a few seconds later. Ran the checklist; simultaneously we further reviewed the situation. Rudder and roll moment had a peculiar (bungee) feel to it. Configured early and landed uneventfully. Had crash fire rescue equipment equipment inspect the aircraft on landing; condition and fluids issues of at all. None found visually by crash fire rescue equipment crews. Jump seater was put to use and was great assistance.

Original NASA ASRS Text

Title: Boeing 757 flight crew reported an uncommanded roll during descent with the autopilot engaged. The Rudder Ratio light illuminated a few seconds later.

Narrative: On descent on STAR into ZZZ; we were told to slow down to accommodate traffic ahead. As I was decelerating the aircraft through 270 to 250 (assigned) knots; the aircraft started a substantial roll. AUTOPILOT AND AUTOTHROTTLE WERE ON. I disengaged the autopilot to hand fly; and fully stowed the speed brakes. Despite speed brakes stowed; the aircraft rolling moment was quite different. Rudder ratio light came on a few seconds later. Ran the checklist; simultaneously we further reviewed the situation. Rudder and roll moment had a peculiar (bungee) feel to it. Configured early and landed uneventfully. Had CFR equipment inspect the aircraft on landing; condition and fluids issues of at all. None found visually by CFR CREWS. Jump seater was put to use and was great assistance.

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.

Boeing 757 flight crew reported an uncommanded roll during descent with the autopilot engaged. The rudder ratio light illuminated a few seconds later.