Flight crew rejected the takeoff after experiencing a pronounced yaw.

Attributes
ACN	434527
Time
Date	199904
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : las.airport
State Reference	NV
Altitude	agl single value : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : las.tower
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	ground : takeoff roll
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : cfi pilot : commercial pilot : instrument pilot : multi engine
Experience	flight time last 90 days : 250 flight time total : 6800 flight time type : 1500
ASRS Report	434527
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : rejected takeoff
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

The takeoff roll was smooth and uneventful until at approximately 120-125 KIAS there was a pronounced yaw. It was quick, from one direction then the other. I believe it was right then left. Then it stopped. I do recall a slight variation in the green speed trend arrow on the speed tape prior to the yaw. All other monitored indications in the cockpit were normal. The winds were reported as variable at 5 KTS. The captain initiated the abort at 130 KIAS, 8 KTS prior to V1. Autobrakes engaged, and as the airplane decelerated, the captain asked for the autobrakes to be disengaged. The captain used reverse thrust and manual braking for the remainder of the roll. I advised the tower of the reject. I also instructed the passenger to remain seated with their seatbelts fastened. We exited runway 25R at taxiway A6, advised ground control and operations that we were returning to the gate.

Original NASA ASRS Text

Title: FLC REJECTED THE TKOF AFTER EXPERIENCING A PRONOUNCED YAW.

Narrative: THE TKOF ROLL WAS SMOOTH AND UNEVENTFUL UNTIL AT APPROX 120-125 KIAS THERE WAS A PRONOUNCED YAW. IT WAS QUICK, FROM ONE DIRECTION THEN THE OTHER. I BELIEVE IT WAS R THEN L. THEN IT STOPPED. I DO RECALL A SLIGHT VARIATION IN THE GREEN SPD TREND ARROW ON THE SPD TAPE PRIOR TO THE YAW. ALL OTHER MONITORED INDICATIONS IN THE COCKPIT WERE NORMAL. THE WINDS WERE RPTED AS VARIABLE AT 5 KTS. THE CAPT INITIATED THE ABORT AT 130 KIAS, 8 KTS PRIOR TO V1. AUTOBRAKES ENGAGED, AND AS THE AIRPLANE DECELERATED, THE CAPT ASKED FOR THE AUTOBRAKES TO BE DISENGAGED. THE CAPT USED REVERSE THRUST AND MANUAL BRAKING FOR THE REMAINDER OF THE ROLL. I ADVISED THE TWR OF THE REJECT. I ALSO INSTRUCTED THE PAX TO REMAIN SEATED WITH THEIR SEATBELTS FASTENED. WE EXITED RWY 25R AT TXWY A6, ADVISED GND CTL AND OPS THAT WE WERE RETURNING TO THE GATE.

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.