Confusion over clearance interpretation was increased by a radio communication problem.

Attributes
ACN	359900
Time
Date	199701
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : pxr
State Reference	AZ
Altitude	msl bound lower : 11000 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zab
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise other descent other
Route In Use	arrival other arrival star : star enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 220 flight time total : 17000 flight time type : 11000
ASRS Report	359900
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other
Situations
ATC Facility	other physical facility

Narrative:

Captain and first officer were assigned 11000 ft altitude at plesant intersection on arrival to phx. Upon reaching 11000 ft, ZAB asked our altitude, and began to alter our heading several times. Radio xmissions with ZAB became erratic. We were then cleared to continue arrival. The tone of voice at ZAB started us to question our assigned altitude. No response from ZAB.

Original NASA ASRS Text

Title: CONFUSION OVER CLRNC INTERP WAS INCREASED BY A RADIO COM PROB.

Narrative: CAPT AND FO WERE ASSIGNED 11000 FT ALT AT PLESANT INTXN ON ARR TO PHX. UPON REACHING 11000 FT, ZAB ASKED OUR ALT, AND BEGAN TO ALTER OUR HDG SEVERAL TIMES. RADIO XMISSIONS WITH ZAB BECAME ERRATIC. WE WERE THEN CLRED TO CONTINUE ARR. THE TONE OF VOICE AT ZAB STARTED US TO QUESTION OUR ASSIGNED ALT. NO RESPONSE FROM ZAB.

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.