Altitude deviation. Excursion from assigned. Momentary loss of aircraft control.

Attributes
ACN	131977
Time
Date	198912
Day	Sat
Local Time Of Day	0001 To 0600
Place
Locale Reference	atc facility : irw
State Reference	OK
Altitude	msl bound lower : 21000 msl bound upper : 22000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zfw tower : bis
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport
Flight Phase	cruise other
Route In Use	enroute airway : j14
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : instrument pilot : commercial
Experience	flight time last 90 days : 186 flight time total : 29500 flight time type : 2850
ASRS Report	131977
Person 2
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly
Independent Detector	other flight crewa
Resolutory Action	flight crew : regained aircraft control flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Ambiguous
Air Traffic Incident	other

Narrative:

After climbing to FL210 and leveling off, aircraft was trimmed and autoplt was engaged. At this time the altitude hold was engaged. In approximately 3-4 mins, the nose pitched up. I tried to disengage the autoplt with the switch on the right control wheel. At the same time I applied forward pressure on the yoke. The autoplt did not disengage and the aircraft continued to climb. At this time the pilot got on the controls and was applying forward pressure on the controls and disconnected the autoplt with switch on left control wheel. He assumed control and reduced power and descended back down to FL210. The autoplt was emergency disconnected and flight was continued to destination airport west/O further incident.

Original NASA ASRS Text

Title: ALT DEVIATION. EXCURSION FROM ASSIGNED. MOMENTARY LOSS OF ACFT CONTROL.

Narrative: AFTER CLBING TO FL210 AND LEVELING OFF, ACFT WAS TRIMMED AND AUTOPLT WAS ENGAGED. AT THIS TIME THE ALT HOLD WAS ENGAGED. IN APPROX 3-4 MINS, THE NOSE PITCHED UP. I TRIED TO DISENGAGE THE AUTOPLT WITH THE SWITCH ON THE RIGHT CONTROL WHEEL. AT THE SAME TIME I APPLIED FORWARD PRESSURE ON THE YOKE. THE AUTOPLT DID NOT DISENGAGE AND THE ACFT CONTINUED TO CLB. AT THIS TIME THE PLT GOT ON THE CONTROLS AND WAS APPLYING FORWARD PRESSURE ON THE CONTROLS AND DISCONNECTED THE AUTOPLT WITH SWITCH ON LEFT CONTROL WHEEL. HE ASSUMED CONTROL AND REDUCED PWR AND DSNDED BACK DOWN TO FL210. THE AUTOPLT WAS EMER DISCONNECTED AND FLT WAS CONTINUED TO DEST ARPT W/O FURTHER INCIDENT.

Data retrieved from NASA's ASRS site as of August 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.