Altitude deviation altitude excursion. Clearance interpretation expected.

Attributes
ACN	298886
Time
Date	199503
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : msp
State Reference	MN
Altitude	msl bound lower : 10500 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Dawn
Aircraft 1
Controlling Facilities	tracon : msp
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other
Route In Use	arrival other arrival star : star
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 250 flight time total : 18000 flight time type : 250
ASRS Report	298886
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : flight engineer pilot : atp pilot : commercial
Experience	flight time last 90 days : 120 flight time total : 9000 flight time type : 600
ASRS Report	298899
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : became reoriented flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

PF mistakenly thought we were cleared bunkr 7 arrival and changed altitude warning indicator from cleared altitude (11000 ft) to 9000 ft and descended to 10500 ft while PF attention diverted and without confirming with PNF. Aircraft descended to 10500 ft before PNF called deviation and altitude was returned to 11000 ft. Contributing factors: non compliance with SOP's. This flight pattern does not allow for adequate rest as it is impossible to expect a person to sleep in the middle of the day to be rested for flying all night long. Supplemental information from acn 298899: PF understood cleared for the arrival, cross cedar at 9000 ft (expected crossing altitude). PF reset MCP altitude to 9000 ft to stay on vertical path. Asked for confirmation from PNF at approximately 10500 ft. PNF stated clearance was 11000 ft. Immediately returned to 11000 ft. Note: we asked for a confirmation of assigned altitude as we were getting extremely high on the vertical path for a landing at msp and the controller immediately cleared us to 6000 ft, as though he had forgotten to issue us a clearance for a lower altitude (at XA20 local very little traffic).

Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION. CLRNC INTERP EXPECTED.

Narrative: PF MISTAKENLY THOUGHT WE WERE CLRED BUNKR 7 ARR AND CHANGED ALT WARNING INDICATOR FROM CLRED ALT (11000 FT) TO 9000 FT AND DSNDED TO 10500 FT WHILE PF ATTN DIVERTED AND WITHOUT CONFIRMING WITH PNF. ACFT DSNDED TO 10500 FT BEFORE PNF CALLED DEV AND ALT WAS RETURNED TO 11000 FT. CONTRIBUTING FACTORS: NON COMPLIANCE WITH SOP'S. THIS FLT PATTERN DOES NOT ALLOW FOR ADEQUATE REST AS IT IS IMPOSSIBLE TO EXPECT A PERSON TO SLEEP IN THE MIDDLE OF THE DAY TO BE RESTED FOR FLYING ALL NIGHT LONG. SUPPLEMENTAL INFO FROM ACN 298899: PF UNDERSTOOD CLRED FOR THE ARR, CROSS CEDAR AT 9000 FT (EXPECTED XING ALT). PF RESET MCP ALT TO 9000 FT TO STAY ON VERT PATH. ASKED FOR CONFIRMATION FROM PNF AT APPROX 10500 FT. PNF STATED CLRNC WAS 11000 FT. IMMEDIATELY RETURNED TO 11000 FT. NOTE: WE ASKED FOR A CONFIRMATION OF ASSIGNED ALT AS WE WERE GETTING EXTREMELY HIGH ON THE VERT PATH FOR A LNDG AT MSP AND THE CTLR IMMEDIATELY CLRED US TO 6000 FT, AS THOUGH HE HAD FORGOTTEN TO ISSUE US A CLRNC FOR A LOWER ALT (AT XA20 LCL VERY LITTLE TFC).

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.