Flight crew of P180 divert to an en route airport due to recurring roll trim problems and stiff manu...

Attributes
ACN	683034
Time
Date	200601
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : las.airport
State Reference	NV
Altitude	msl single value : 33000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zla.artcc
Make Model Name	Small Transport Low Wing 2 Turboprop Eng
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 215 flight time total : 5370 flight time type : 435
ASRS Report	683034
Person 2
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical other spatial deviation
Independent Detector	other flight crewa
Resolutory Action	flight crew : diverted to another airport flight crew : overcame equipment problem
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

We had leveled off at FL330; en route from lax to jac and were northeast of las; cleared direct to mlf. Throughout the climb; we had been experiencing excessive autoplt trim roll commands. Periodically; I would disengage the autoplt; trim manually; re-engage the autoplt and things would be fine for several mins. Lots of wind shifts on climb and I thought perhaps this was behind the roll trim. For several mins after leveloff; the autoplt seemed to be functioning fine. Then; once again; excessive roll trim began and then the aircraft started an uncommanded turn to the left (west). I let it go for a moment to see if it would connect and then it went the other way (east) -- up to 45 degrees off to begin. I disconnected the autoplt; retrimmed but the yoke would barely move -- enough to maintain control; but definitely not 'normal.' I engaged autoplt which I discussed the issue with my copilot. Given the WX at destination and our plans for the day (cross country to teb eventually with minimum WX the whole way); we elected to divert. We requested las and center vectored us. On descent; hand flew and controls seemed normal once at lower altitudes.

Original NASA ASRS Text

Title: FLT CREW OF P180 DIVERT TO AN ENRTE ARPT DUE TO RECURRING ROLL TRIM PROBS AND STIFF MANUAL ROLL INPUTS.

Narrative: WE HAD LEVELED OFF AT FL330; ENRTE FROM LAX TO JAC AND WERE NE OF LAS; CLRED DIRECT TO MLF. THROUGHOUT THE CLB; WE HAD BEEN EXPERIENCING EXCESSIVE AUTOPLT TRIM ROLL COMMANDS. PERIODICALLY; I WOULD DISENGAGE THE AUTOPLT; TRIM MANUALLY; RE-ENGAGE THE AUTOPLT AND THINGS WOULD BE FINE FOR SEVERAL MINS. LOTS OF WIND SHIFTS ON CLB AND I THOUGHT PERHAPS THIS WAS BEHIND THE ROLL TRIM. FOR SEVERAL MINS AFTER LEVELOFF; THE AUTOPLT SEEMED TO BE FUNCTIONING FINE. THEN; ONCE AGAIN; EXCESSIVE ROLL TRIM BEGAN AND THEN THE ACFT STARTED AN UNCOMMANDED TURN TO THE L (W). I LET IT GO FOR A MOMENT TO SEE IF IT WOULD CONNECT AND THEN IT WENT THE OTHER WAY (E) -- UP TO 45 DEGS OFF TO BEGIN. I DISCONNECTED THE AUTOPLT; RETRIMMED BUT THE YOKE WOULD BARELY MOVE -- ENOUGH TO MAINTAIN CTL; BUT DEFINITELY NOT 'NORMAL.' I ENGAGED AUTOPLT WHICH I DISCUSSED THE ISSUE WITH MY COPLT. GIVEN THE WX AT DEST AND OUR PLANS FOR THE DAY (XCOUNTRY TO TEB EVENTUALLY WITH MINIMUM WX THE WHOLE WAY); WE ELECTED TO DIVERT. WE REQUESTED LAS AND CTR VECTORED US. ON DSCNT; HAND FLEW AND CTLS SEEMED NORMAL ONCE AT LOWER ALTS.

Data retrieved from NASA's ASRS site as of January 2009 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.

Flight crew of P180 divert to an en route airport due to recurring roll trim problems and stiff manual roll inputs.