Crew had an altitude deviation.

Attributes
ACN	436060
Time
Date	199905
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : lit.airport
State Reference	AR
Altitude	msl bound lower : 30700 msl bound upper : 31000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zme.artcc
Operator	common carrier : air carrier
Make Model Name	B737-500
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 225 flight time total : 15000 flight time type : 2200
ASRS Report	436060
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : multi engine
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : turbulence
Independent Detector	other controllera other flight crewa
Resolutory Action	controller : issued alert flight crew : returned to original clearance
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance Weather
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

First officer flying with autoplt off due to turbulence. We requested FL280 and were told we had traffic at 12 O'clock at FL290 and we would be cleared to FL280 when clear of traffic. Shortly after this transmission, the aircraft descended approximately 300 ft. The first officer corrected back to FL310 and was there when center asked us if we were at FL310 and that we should maintain FL310. Traffic passed underneath us. A call to ARTCC after we landed, talked to an ATC controller X at ZME, revealed no traffic conflict occurred and, according to him, there was no problem.

Original NASA ASRS Text

Title: CREW HAD AN ALTDEV.

Narrative: FO FLYING WITH AUTOPLT OFF DUE TO TURB. WE REQUESTED FL280 AND WERE TOLD WE HAD TFC AT 12 O'CLOCK AT FL290 AND WE WOULD BE CLRED TO FL280 WHEN CLR OF TFC. SHORTLY AFTER THIS XMISSION, THE ACFT DSNDED APPROX 300 FT. THE FO CORRECTED BACK TO FL310 AND WAS THERE WHEN CTR ASKED US IF WE WERE AT FL310 AND THAT WE SHOULD MAINTAIN FL310. TFC PASSED UNDERNEATH US. A CALL TO ARTCC AFTER WE LANDED, TALKED TO AN ATC CTLR X AT ZME, REVEALED NO TFC CONFLICT OCCURRED AND, ACCORDING TO HIM, THERE WAS NO PROB.

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.