A B737-400 in climb at 2000 ft; flaps retracting from 5 to 1 units; experienced uncommanded nose dow...

Attributes
ACN	676549
Time
Date	200510
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 2000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tower : zzz.tower
Operator	common carrier : air carrier
Make Model Name	B737-400
Operating Under FAR Part	Part 121
Flight Phase	climbout : initial
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 230 flight time type : 3670
ASRS Report	676549
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 250
ASRS Report	676550
Events
Anomaly	aircraft equipment problem : critical other anomaly
Independent Detector	other flight crewa other flight crewb
Resolutory Action	aircraft : equipment problem dissipated flight crew : overcame equipment problem flight crew : overrode automation
Consequence	other other
Supplementary
Problem Areas	Flight Crew Human Performance Environmental Factor Aircraft
Primary Problem	Aircraft

Narrative:

On climb out at approximately 2000 ft MSL; flaps 5 being retracted to flaps 1; aircraft accelerating; the aircraft went into an uncommanded nose down attitude with climb power selected. Nose up trim selected but slow to respond with a heavy control yoke to bring aircraft to level and climb attitude. As the aircraft began gradual descent; airspeed increased rapidly before PF could disengage autothrottles; flaps 1 overspd occurred by approximately 8 KTS (258 KTS indicated). Once airspeed decreased and flaps retracted; no other flight control problems were evident and no other abnormal indications were present. Flight continued to ZZZ with normal descent approach and landing. Callback conversation with reporter revealed the following information: the reporter stated the uncommanded nose down attitude change was caused by the autoplt stabilizer trim. The flight recorder was removed and established that a 700 ft per min descent was initiated. The reporter stated the autoplt and autothrottle systems were switched off; but a flap overspd occurred by 8 KTS. Once airspeed was decreased and flaps retracted; all flight controls were normal. Maintenance action was replacement of stabilizer trim switch and the low speed jackscrew actuator.

Original NASA ASRS Text

Title: A B737-400 IN CLB AT 2000 FT; FLAPS RETRACTING FROM 5 TO 1 UNITS; EXPERIENCED UNCOMMANDED NOSE DOWN ATTITUDE WITH CLB POWER. A FLAP OVERSPD OF 8 KTS WAS EXPERIENCED.

Narrative: ON CLBOUT AT APPROX 2000 FT MSL; FLAPS 5 BEING RETRACTED TO FLAPS 1; ACFT ACCELERATING; THE ACFT WENT INTO AN UNCOMMANDED NOSE DOWN ATTITUDE WITH CLB POWER SELECTED. NOSE UP TRIM SELECTED BUT SLOW TO RESPOND WITH A HVY CTL YOKE TO BRING ACFT TO LEVEL AND CLB ATTITUDE. AS THE ACFT BEGAN GRADUAL DSCNT; AIRSPD INCREASED RAPIDLY BEFORE PF COULD DISENGAGE AUTOTHROTTLES; FLAPS 1 OVERSPD OCCURRED BY APPROX 8 KTS (258 KTS INDICATED). ONCE AIRSPD DECREASED AND FLAPS RETRACTED; NO OTHER FLT CTL PROBS WERE EVIDENT AND NO OTHER ABNORMAL INDICATIONS WERE PRESENT. FLT CONTINUED TO ZZZ WITH NORMAL DSCNT APCH AND LNDG. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE UNCOMMANDED NOSE DOWN ATTITUDE CHANGE WAS CAUSED BY THE AUTOPLT STABILIZER TRIM. THE FLT RECORDER WAS REMOVED AND ESTABLISHED THAT A 700 FT PER MIN DSCNT WAS INITIATED. THE RPTR STATED THE AUTOPLT AND AUTOTHROTTLE SYSTEMS WERE SWITCHED OFF; BUT A FLAP OVERSPD OCCURRED BY 8 KTS. ONCE AIRSPD WAS DECREASED AND FLAPS RETRACTED; ALL FLT CTLS WERE NORMAL. MAINT ACTION WAS REPLACEMENT OF STABILIZER TRIM SWITCH AND THE LOW SPD JACKSCREW ACTUATOR.

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 B737-400 in climb at 2000 ft; flaps retracting from 5 to 1 units; experienced uncommanded nose down attitude with climb power. A flap overspd of 8 KTS was experienced.