A PC12 pilot lost aircraft control following an uncommanded autoplt disconnect in hail and turbulenc...

Attributes
ACN	639013
Time
Date	200411
Day	Tue
Place
Locale Reference	airport : iah.airport
State Reference	TX
Altitude	msl single value : 26000
Environment
Flight Conditions	IMC
Weather Elements	Turbulence
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zhu.artcc
Operator	general aviation : personal
Make Model Name	PC-12
Operating Under FAR Part	Part 91
Flight Phase	cruise : level cruise : enroute altitude change
Flight Plan	IFR
Person 1
Affiliation	other
Function	flight crew : single pilot oversight : pic
Qualification	pilot : commercial pilot : instrument
Experience	flight time last 90 days : 135 flight time total : 983 flight time type : 52
ASRS Report	639013
Person 2
Affiliation	government : faa
Function	controller : radar
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude inflight encounter : weather non adherence : clearance other anomaly
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : diverted to another airport flight crew : regained aircraft control
Supplementary
Problem Areas	Weather Aircraft Flight Crew Human Performance
Primary Problem	Aircraft

Narrative:

Aircraft was previously cleared on westerly heading direct to ZZZZ and then direct to XXXX. Conditions were VMC FL260. ATC advised that aircraft was approaching ZZZ1 arriving and departing corridors and that there was clear opening to the north for direct YYYY. We instructed ATC that we would notify of our intentions for their request for YYYY direct. Later, upon contacting ATC, we turned direct to YYYY. After turning direct to YYYY, conditions changed from VMC to IMC. The aircraft on a northwest heading, encountered moderate turbulence and hail. We contacted center and asked for heading change to the southeast. A right turn was made utilizing the autoplt. Upon entering the turn, the autoplt disconnected and left the ailerons positioned for a right roll. The aircraft proceeded to roll approximately 100-130 degrees before the crew members leveled the wings. With aircraft level, the aircraft pitched nose down and rolled left. The aircraft was leveled at FL200 and ATC was contacted for vectors to the nearest VFR airport with ILS capabilities.

Original NASA ASRS Text

Title: A PC12 PLT LOST ACFT CTL FOLLOWING AN UNCOMMANDED AUTOPLT DISCONNECT IN HAIL AND TURB.

Narrative: ACFT WAS PREVIOUSLY CLRED ON WESTERLY HDG DIRECT TO ZZZZ AND THEN DIRECT TO XXXX. CONDITIONS WERE VMC FL260. ATC ADVISED THAT ACFT WAS APCHING ZZZ1 ARRIVING AND DEPARTING CORRIDORS AND THAT THERE WAS CLR OPENING TO THE N FOR DIRECT YYYY. WE INSTRUCTED ATC THAT WE WOULD NOTIFY OF OUR INTENTIONS FOR THEIR REQUEST FOR YYYY DIRECT. LATER, UPON CONTACTING ATC, WE TURNED DIRECT TO YYYY. AFTER TURNING DIRECT TO YYYY, CONDITIONS CHANGED FROM VMC TO IMC. THE ACFT ON A NW HDG, ENCOUNTERED MODERATE TURB AND HAIL. WE CONTACTED CTR AND ASKED FOR HDG CHANGE TO THE SE. A R TURN WAS MADE UTILIZING THE AUTOPLT. UPON ENTERING THE TURN, THE AUTOPLT DISCONNECTED AND LEFT THE AILERONS POSITIONED FOR A R ROLL. THE ACFT PROCEEDED TO ROLL APPROX 100-130 DEGS BEFORE THE CREW MEMBERS LEVELED THE WINGS. WITH ACFT LEVEL, THE ACFT PITCHED NOSE DOWN AND ROLLED L. THE ACFT WAS LEVELED AT FL200 AND ATC WAS CONTACTED FOR VECTORS TO THE NEAREST VFR ARPT WITH ILS CAPABILITIES.

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.

A PC12 pilot lost aircraft control following an uncommanded autoplt disconnect in hail and turbulence.