A B737 flight crew flew a clearance intended for another aircraft on descent into phx.

Attributes
ACN	457720
Time
Date	199912
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : phx.vortac
State Reference	AZ
Altitude	msl single value : 12000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : p50.tracon
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	cruise : enroute altitude change
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : commercial pilot : instrument pilot : multi engine
Experience	flight time last 90 days : 125 flight time total : 6500 flight time type : 4000
ASRS Report	457720
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other controllera
Resolutory Action	none taken : detected after the fact
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

During descent on fossl 4 arrival to phx, we were given a clearance to cross tonto at 12000 ft. ATC then amended it to 14000 ft MSL, then to 13000 ft MSL, and slow to 250 KTS. The PNF checked off ATC to talk to company. The PF notified ATC that they could not make the 12000 ft restr at tonto. The PNF came back on frequency at this time and we both thought we heard a clearance to 12000 ft MSL and 250 KTS with a frequency change. The PNF responded to ATC '12000 ft at 250 KTS.' then changed frequency to approach who questioned our altitude. 1) PF did not ensure ATC did give clearance to 12000 ft MSL. 2) ATC did not catch readback of 12000 ft MSL.

Original NASA ASRS Text

Title: A B737 FLC FLEW A CLRNC INTENDED FOR ANOTHER ACFT ON DSCNT INTO PHX.

Narrative: DURING DSCNT ON FOSSL 4 ARR TO PHX, WE WERE GIVEN A CLRNC TO CROSS TONTO AT 12000 FT. ATC THEN AMENDED IT TO 14000 FT MSL, THEN TO 13000 FT MSL, AND SLOW TO 250 KTS. THE PNF CHKED OFF ATC TO TALK TO COMPANY. THE PF NOTIFIED ATC THAT THEY COULD NOT MAKE THE 12000 FT RESTR AT TONTO. THE PNF CAME BACK ON FREQ AT THIS TIME AND WE BOTH THOUGHT WE HEARD A CLRNC TO 12000 FT MSL AND 250 KTS WITH A FREQ CHANGE. THE PNF RESPONDED TO ATC '12000 FT AT 250 KTS.' THEN CHANGED FREQ TO APCH WHO QUESTIONED OUR ALT. 1) PF DID NOT ENSURE ATC DID GIVE CLRNC TO 12000 FT MSL. 2) ATC DID NOT CATCH READBACK OF 12000 FT MSL.

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.