Serious incident ATR 42-300 N266AT, Saturday 4 March 1995

You can contribute by submitting additional or updated information.

Date:	Saturday 4 March 1995
Time:	23:29 LT
Type:	ATR 42-300
Owner/operator:	Simmons Airlines
Registration:	N266AT
MSN:	266
Year of manufacture:	1991
Engine model:	P&W PW120
Fatalities:	Fatalities: 0 / Occupants: 25
Other fatalities:	0
Aircraft damage:	None
Category:	Serious incident
Location:	Las Vegas, NV - United States of America
Phase:	Unknown
Nature:	Passenger - Scheduled
Departure airport:	Los Angeles International Airport, CA (LAX/KLAX)
Destination airport:	(KLVS)
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
THE CREW REPORTED HEAVY MIXED ICING CONDITIONS ON THE WINDSCREEN AND SOME ICE AFT OF THE DE-ICE BOOTS DURING A DESCENT THROUGH 15,500 FEET, FOLLOWED BY TWO UNCOMMANDED LATERAL CONTROL MOVEMENTS. THE PILOTS SAID THE CONTROLS WERE STIFF AND THEY FELT A 'BUZZING' SENSATION IN THE AILERON AND RUDDER CONTROLS. THE AUTOPILOT WAS NOT ENGAGED AT THE TIME AND THE AIRCRAFT WAS IN A CLEAN CONFIGURATION. THE CREW DID NOT REPORT ANY TURBULENCE UNTIL REACHING LOWER ALTITUDES. SOME PASSENGERS REPORTED NO SIGNIFICANT TURBULENCE OR NOTHING EXCESSIVE, WHILE OTHER PASSENGERS DESCRIBED THE TURBULENCE AS 'SCARY' OR 'TOO MUCH'. EXAMINATION OF THE FLIGHT CONTROLS, ASSOCIATED SYSTEMS AND EQUIPMENT REVEALED NO MALFUNCTIONS. THE FLIGHT DATA RECORDER WAS ANALYZED AND THE DATA REVEALED SOME LATERAL CONTROL MOVEMENT THAT IS USUALLY ASSOCIATED WITH TURBULENCE.

Probable Cause: an unexpected lateral control movement associated with in-flight turbulence.

Accident investigation: