Altitude deviation. Autoplt commenced uncommanded climb, captain disconnected and used alternate aut...

Attributes
ACN	299710
Time
Date	199503
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : gls
State Reference	TX
Altitude	msl bound lower : 35000 msl bound upper : 35400
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zhu
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : cfi pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 207 flight time total : 10036 flight time type : 2610
ASRS Report	299710
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I usually fly a B-767. On this flight I was in a B-757. Just after being cleared direct marte from A766 southeast of gls our altitude alert sounded. The aircraft was FL353 and climbing. Vertical velocity was 500 ft up and increasing. The captain disengaged the autoplt and leveled off 350-400 ft above our assigned FL350, he re-engaged the same autoplt, and the aircraft did not descend. When an alternate autoplt was selected, the aircraft descended to the proper altitude. Duration of deviation was 30-45 seconds. I did not feel the aircraft start the climb, I had been leaning to the right, preoccupied with adjusting items in my kit bag on the floor to the right of my seat. Apparently the captain did not feel the climb either. I am not sure where he was looking at the time. Autoplt malfunction and distraction appear to be the causes. The altitude warning system worked as it should, and the captain corrected the situation.

Original NASA ASRS Text

Title: ALTDEV. AUTOPLT COMMENCED UNCOMMANDED CLB, CAPT DISCONNECTED AND USED ALTERNATE AUTOPLT.

Narrative: I USUALLY FLY A B-767. ON THIS FLT I WAS IN A B-757. JUST AFTER BEING CLRED DIRECT MARTE FROM A766 SE OF GLS OUR ALT ALERT SOUNDED. THE ACFT WAS FL353 AND CLBING. VERT VELOCITY WAS 500 FT UP AND INCREASING. THE CAPT DISENGAGED THE AUTOPLT AND LEVELED OFF 350-400 FT ABOVE OUR ASSIGNED FL350, HE RE-ENGAGED THE SAME AUTOPLT, AND THE ACFT DID NOT DSND. WHEN AN ALTERNATE AUTOPLT WAS SELECTED, THE ACFT DSNDED TO THE PROPER ALT. DURATION OF DEV WAS 30-45 SECONDS. I DID NOT FEEL THE ACFT START THE CLB, I HAD BEEN LEANING TO THE R, PREOCCUPIED WITH ADJUSTING ITEMS IN MY KIT BAG ON THE FLOOR TO THE R OF MY SEAT. APPARENTLY THE CAPT DID NOT FEEL THE CLB EITHER. I AM NOT SURE WHERE HE WAS LOOKING AT THE TIME. AUTOPLT MALFUNCTION AND DISTR APPEAR TO BE THE CAUSES. THE ALT WARNING SYS WORKED AS IT SHOULD, AND THE CAPT CORRECTED THE SIT.

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.

Altitude deviation. Autoplt commenced uncommanded climb, captain disconnected and used alternate autoplt.