A C414A in descent at 7600 ft had an uncommanded flap extension from '0' units to '15' units causing...

Attributes
ACN	644043
Time
Date	200501
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl bound lower : 7600 msl bound upper : 8000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zzz.artcc
Operator	common carrier : air taxi
Make Model Name	Chancellor 414A & C414
Operating Under FAR Part	Part 135
Flight Phase	descent : intermediate altitude
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	flight crew : single pilot
Qualification	pilot : cfi pilot : atp
Experience	flight time last 90 days : 90 flight time total : 6000 flight time type : 1300
ASRS Report	644043
Person 2
Affiliation	government : faa
Function	controller : radar
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	aircraft equipment other aircraft equipment : trim indication other flight crewa other flight crewb
Resolutory Action	controller : provided flight assist flight crew : overcame equipment problem flight crew : regained aircraft control flight crew : diverted to another airport flight crew : landed in emergency condition
Consequence	other
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Aircraft

Narrative:

We initiated a descent from 8000 ft. The airspeed was about 185 KTS. The air was relatively smooth with just a few occasional bumps. The autoplt was engaged. At 7600 ft the aircraft began to pitch up suddenly. This caused the autoplt to rapidly put in nose down trim. I immediately disengaged the autoplt and felt significantly heavy pressure in the control yoke. I reduced power immediately and re-trimmed the aircraft. The cause of the problem was the uncommanded activation of the flap switch. The flap switch moved by itself from 0 degrees to 15 degrees. I immediately retracted the flaps and pulled out the circuit breaker. We informed ATC and received an IFR clearance back to ZZZ. The no-flap landing was uneventful. The maintenance a & P determined that a 'set screw' within the flap switch controller had gotten loose. This made the flap switch very susceptible to vibration; which caused it to move on its own. The flap switch was so sensitive that it would engage by itself on the ground simply by softly tapping it on its right; exposed side. Callback conversation with reporter revealed the following information: the reporter stated on taxi out the procedure is to taxi out with flaps up; prior to takeoff. On the controls check the reporter noted the flaps were out of full up detent. The reporter was not sure if he failed to check the flap setting prior to taxi. The flaps operated normally until descent began at 8000 ft and at 7600 ft the airplane suddenly pitched up causing the autoplt to immediately trim nose down. Found flaps had gone from full up '0' units to '15' units extended uncommanded. On the ground a technician found a loose screw that adjusted the tension of the handle. Rptdly any slight vibration allowed the handle to move. The reporter has time exceeding 3000 hours in this type of airplane and claims he/she has never encountered this type of flap failure.

Original NASA ASRS Text

Title: A C414A IN DSCNT AT 7600 FT HAD AN UNCOMMANDED FLAP EXTENSION FROM '0' UNITS TO '15' UNITS CAUSING THE ACFT TO SUDDENLY PITCH UP AND THE AUTOPLT TO RAPIDLY TRIM NOSE DOWN.

Narrative: WE INITIATED A DSCNT FROM 8000 FT. THE AIRSPD WAS ABOUT 185 KTS. THE AIR WAS RELATIVELY SMOOTH WITH JUST A FEW OCCASIONAL BUMPS. THE AUTOPLT WAS ENGAGED. AT 7600 FT THE ACFT BEGAN TO PITCH UP SUDDENLY. THIS CAUSED THE AUTOPLT TO RAPIDLY PUT IN NOSE DOWN TRIM. I IMMEDIATELY DISENGAGED THE AUTOPLT AND FELT SIGNIFICANTLY HEAVY PRESSURE IN THE CTL YOKE. I REDUCED POWER IMMEDIATELY AND RE-TRIMMED THE ACFT. THE CAUSE OF THE PROB WAS THE UNCOMMANDED ACTIVATION OF THE FLAP SWITCH. THE FLAP SWITCH MOVED BY ITSELF FROM 0 DEGS TO 15 DEGS. I IMMEDIATELY RETRACTED THE FLAPS AND PULLED OUT THE CIRCUIT BREAKER. WE INFORMED ATC AND RECEIVED AN IFR CLRNC BACK TO ZZZ. THE NO-FLAP LNDG WAS UNEVENTFUL. THE MAINT A & P DETERMINED THAT A 'SET SCREW' WITHIN THE FLAP SWITCH CTLR HAD GOTTEN LOOSE. THIS MADE THE FLAP SWITCH VERY SUSCEPTIBLE TO VIBRATION; WHICH CAUSED IT TO MOVE ON ITS OWN. THE FLAP SWITCH WAS SO SENSITIVE THAT IT WOULD ENGAGE BY ITSELF ON THE GND SIMPLY BY SOFTLY TAPPING IT ON ITS R; EXPOSED SIDE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED ON TAXI OUT THE PROC IS TO TAXI OUT WITH FLAPS UP; PRIOR TO TKOF. ON THE CTLS CHK THE RPTR NOTED THE FLAPS WERE OUT OF FULL UP DETENT. THE RPTR WAS NOT SURE IF HE FAILED TO CHK THE FLAP SETTING PRIOR TO TAXI. THE FLAPS OPERATED NORMALLY UNTIL DSCNT BEGAN AT 8000 FT AND AT 7600 FT THE AIRPLANE SUDDENLY PITCHED UP CAUSING THE AUTOPLT TO IMMEDIATELY TRIM NOSE DOWN. FOUND FLAPS HAD GONE FROM FULL UP '0' UNITS TO '15' UNITS EXTENDED UNCOMMANDED. ON THE GND A TECHNICIAN FOUND A LOOSE SCREW THAT ADJUSTED THE TENSION OF THE HANDLE. RPTDLY ANY SLIGHT VIBRATION ALLOWED THE HANDLE TO MOVE. THE RPTR HAS TIME EXCEEDING 3000 HRS IN THIS TYPE OF AIRPLANE AND CLAIMS HE/SHE HAS NEVER ENCOUNTERED THIS TYPE OF FLAP FAILURE.

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.

A C414A in descent at 7600 ft had an uncommanded flap extension from '0' units to '15' units causing the aircraft to suddenly pitch up and the autoplt to rapidly trim nose down.