Medium large transport descent to rdu experiences run away stabilizer trim as the first of several aircraft equipment malfunctions prior to landing.

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Attributes
ACN	457067
Time
Date	199911
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : rdu.airport
State Reference	NC
Altitude	msl single value : 23000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc.artcc
Operator	common carrier : air carrier
Make Model Name	HS 125 Series 1-600
Operating Under FAR Part	Part 121
Flight Phase	descent : vacating altitude descent : intermediate altitude
Route In Use	arrival : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : multi engine pilot : atp
Experience	flight time last 90 days : 180 flight time total : 5700 flight time type : 290
ASRS Report	457067
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : multi engine pilot : commercial
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude other anomaly other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : master caution light other flight crewa other flight crewb
Resolutory Action	controller : provided flight assist controller : issued new clearance flight crew : regained aircraft control flight crew : overrode automation flight crew : exited adverse environment
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

During descent into rdu, nose down trim was applied with trim switch (autoplt and autothrottle off) and trim runway to full nose down. The only way to stop the trim was to turn the autoplt master switch off. Field was IFR and with autoplt master off the mode control panel was lost and no navigation signals received. Once aircraft back under control autoplt master turned back on resulting in excessive right ruder (yaw damper) and the trim running full forward. Autoplt master turned back on manual trim available and restored the mode control panel. Hand flown approach flown into rdu. Digital flight guidance computer downloaded 17 errors appeared all from takeoff when a squat switch was faulty, requiring the override switch to be used to bring the gear up. No errors were detected during descent by dfgc (digital flight guidance). The DFDR (digital flight data recorder) was downloaded, but have not heard results yet.

Original NASA ASRS Text

Title: MLG DSCNT TO RDU EXPERIENCES RUN AWAY STABILIZER TRIM AS THE FIRST OF SEVERAL ACFT EQUIP MALFUNCTIONS PRIOR TO LNDG.

Narrative: DURING DSCNT INTO RDU, NOSE DOWN TRIM WAS APPLIED WITH TRIM SWITCH (AUTOPLT AND AUTOTHROTTLE OFF) AND TRIM RWY TO FULL NOSE DOWN. THE ONLY WAY TO STOP THE TRIM WAS TO TURN THE AUTOPLT MASTER SWITCH OFF. FIELD WAS IFR AND WITH AUTOPLT MASTER OFF THE MODE CTL PANEL WAS LOST AND NO NAV SIGNALS RECEIVED. ONCE ACFT BACK UNDER CTL AUTOPLT MASTER TURNED BACK ON RESULTING IN EXCESSIVE R RUDER (YAW DAMPER) AND THE TRIM RUNNING FULL FORWARD. AUTOPLT MASTER TURNED BACK ON MANUAL TRIM AVAILABLE AND RESTORED THE MODE CTL PANEL. HAND FLOWN APCH FLOWN INTO RDU. DIGITAL FLT GUIDANCE COMPUTER DOWNLOADED 17 ERRORS APPEARED ALL FROM TKOF WHEN A SQUAT SWITCH WAS FAULTY, REQUIRING THE OVERRIDE SWITCH TO BE USED TO BRING THE GEAR UP. NO ERRORS WERE DETECTED DURING DSCNT BY DFGC (DIGITAL FLT GUIDANCE). THE DFDR (DIGITAL FLT DATA RECORDER) WAS DOWNLOADED, BUT HAVE NOT HEARD RESULTS YET.

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.