Non adherence to an ATC clearance instruction in an airspeed altitude deviation altitude excursion.

Attributes
ACN	200480
Time
Date	199201
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : far
State Reference	ND
Altitude	msl bound lower : 25000 msl bound upper : 29000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zmp tower : bli
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 160 flight time total : 12000 flight time type : 800
ASRS Report	200480
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly
Independent Detector	other controllera
Resolutory Action	none taken : detected after the fact
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

In cruise at FL290 controller said 'air carrier flight xy, descend FL250.' a little while later the controller asked our altitude. He said he told us to slow to 250 not descend to 250. However, my first officer and I both think we clearly heard and read back a descent clearance.

Original NASA ASRS Text

Title: NON ADHERENCE TO AN ATC CLRNC INSTRUCTION IN AN AIRSPD ALTDEV ALT EXCURSION.

Narrative: IN CRUISE AT FL290 CTLR SAID 'ACR FLT XY, DSND FL250.' A LITTLE WHILE LATER THE CTLR ASKED OUR ALT. HE SAID HE TOLD US TO SLOW TO 250 NOT DSND TO 250. HOWEVER, MY FO AND I BOTH THINK WE CLRLY HEARD AND READ BACK A DSCNT CLRNC.

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.