Altitude deviation.

Attributes
ACN	296930
Time
Date	199502
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : atl
State Reference	GA
Altitude	msl bound lower : 28000 msl bound upper : 28400
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : ztl
Operator	common carrier : air carrier
Make Model Name	F28 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : cfi pilot : flight engineer pilot : instrument pilot : commercial
Experience	flight time last 90 days : 200 flight time total : 8000 flight time type : 200
ASRS Report	296930
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
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

While autoplt on, cleared by ZTL to FL280. Leveled off at FL280. Selected altitude hold on autoplt. Aircraft, after short period of time (less than 5 mins), went back into pitch mode. Unknown to us, aircraft started slow climb. Altitude alert sounded approximately 400 ft above assigned altitude. At this time ATC called to verify FL280. I immediately disconnected the autoplt and went back to FL280. We also got a TCASII TA for traffic at FL290 (approximately 6 mi). We leveled off at FL280. No further action.

Original NASA ASRS Text

Title: ALTDEV.

Narrative: WHILE AUTOPLT ON, CLRED BY ZTL TO FL280. LEVELED OFF AT FL280. SELECTED ALT HOLD ON AUTOPLT. ACFT, AFTER SHORT PERIOD OF TIME (LESS THAN 5 MINS), WENT BACK INTO PITCH MODE. UNKNOWN TO US, ACFT STARTED SLOW CLB. ALT ALERT SOUNDED APPROX 400 FT ABOVE ASSIGNED ALT. AT THIS TIME ATC CALLED TO VERIFY FL280. I IMMEDIATELY DISCONNECTED THE AUTOPLT AND WENT BACK TO FL280. WE ALSO GOT A TCASII TA FOR TFC AT FL290 (APPROX 6 MI). WE LEVELED OFF AT FL280. NO FURTHER ACTION.

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.