<< >> NASA ASRS Report 322630, December 1995

Jumpseat rider reported air carrier B737-400 uncommanded roll to the right. Reporter saw 'cws roll' illuminated on first officer's flight mode annunciator. Captain overcame equipment problem by moving yoke back to left.

Attributes
ACN	322630
Time
Date	199512
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : den
State Reference	CO
Altitude	msl bound lower : 14000 msl bound upper : 14000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : den tower : pit
Operator	common carrier : air carrier
Make Model Name	B737-400
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent : approach other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	observation : observer
Qualification	controller : non radar
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	other anomaly other other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	other

Narrative:

During approach to den, on a left downwind to runway 16, at 14000 ft, the B737-400 made an uncommanded roll to the right. Alarms sounded. I noticed on the copilot's monitor the letters cws roll. The pilot turned the yoke to the left and grabbed the throttle. There were no other aircraft flying above us or even close, according to the traffic on the TCASII. It was never explained what caused the 20-30 degree roll. It was my first unpleasurable flight. I could tell by the pilot's and first officer's reaction, that they were just as surprised and unhappy about what happened as I was.

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Original NASA ASRS Text

Title: JUMPSEAT RIDER RPTED ACR B737-400 UNCOMMANDED ROLL TO THE R. RPTR SAW 'CWS ROLL' ILLUMINATED ON FO'S FLT MODE ANNUNCIATOR. CAPT OVERCAME EQUIP PROB BY MOVING YOKE BACK TO L.

Narrative: DURING APCH TO DEN, ON A L DOWNWIND TO RWY 16, AT 14000 FT, THE B737-400 MADE AN UNCOMMANDED ROLL TO THE R. ALARMS SOUNDED. I NOTICED ON THE COPLT'S MONITOR THE LETTERS CWS ROLL. THE PLT TURNED THE YOKE TO THE L AND GRABBED THE THROTTLE. THERE WERE NO OTHER ACFT FLYING ABOVE US OR EVEN CLOSE, ACCORDING TO THE TFC ON THE TCASII. IT WAS NEVER EXPLAINED WHAT CAUSED THE 20-30 DEG ROLL. IT WAS MY FIRST UNPLEASURABLE FLT. I COULD TELL BY THE PLT'S AND FO'S REACTION, THAT THEY WERE JUST AS SURPRISED AND UNHAPPY ABOUT WHAT HAPPENED AS I WAS.

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.