An mdt crew responded to another aircraft's clearance deviating from assigned altitude.

Attributes
ACN	529732
Time
Date	200111
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : atw.airport
State Reference	WI
Altitude	msl bound lower : 33000 msl bound upper : 30000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zmp.artcc artcc : zme.artcc
Operator	common carrier : air carrier
Make Model Name	Medium Transport, Low Wing, 2 Turbojet Eng
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : enroute altitude change
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : private pilot : multi engine pilot : instrument pilot : commercial pilot : cfi pilot : atp
Experience	flight time last 90 days : 250 flight time total : 3871 flight time type : 531
ASRS Report	529732
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance Airspace Structure ATC Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

On nov/xa/01 on flight abcd, myself and my captain were the PNF and PF respectively on a flight from msp to apw. The flight progressed normally until we were at cruise flight at FL350 approximately 105 NM southwest of the outagamie county regional airport. At about XA30, we became concerned because we were kept too high too close in, so we queried the controller for lower anticipating lower or a slow descent clearance. The controller made us aware of crossing traffic, which we had a visual on. At about XA37, we were still at FL350 and 70 mi out from the airport. We also were aware of similar sounding company aircraft in the area going to the same airport, which had an air carrier call sign. The controller's workload seemed to be increasing. We heard a clearance from the msp high altitude controller saying 'air carrier abcd turn right to heading 090 degrees and descend to FL240.' I then read back 'heading 090 degrees down to FL240 from FL350, air carrier abcd.' at approximately FL330 we heard from the controller saying 'air carrier abcd say altitude.' then I responded 'somewhere around FL330.' then the controller said the descent for air carrier bcde. At that point we slowed our descent. I told the controller we must have misunderstood his clearance that we read back. He then said we were cleared to heading 090 degrees only. We were then cleared to continue down to FL240 with vector changes that followed. Then we were given to the lower altitude controller down to the approach control, then the atw tower for landing clearance.

Original NASA ASRS Text

Title: AN MDT CREW RESPONDED TO ANOTHER ACFT'S CLRNC DEVIATING FROM ASSIGNED ALT.

Narrative: ON NOV/XA/01 ON FLT ABCD, MYSELF AND MY CAPT WERE THE PNF AND PF RESPECTIVELY ON A FLT FROM MSP TO APW. THE FLT PROGRESSED NORMALLY UNTIL WE WERE AT CRUISE FLT AT FL350 APPROX 105 NM SW OF THE OUTAGAMIE COUNTY REGIONAL ARPT. AT ABOUT XA30, WE BECAME CONCERNED BECAUSE WE WERE KEPT TOO HIGH TOO CLOSE IN, SO WE QUERIED THE CTLR FOR LOWER ANTICIPATING LOWER OR A SLOW DSCNT CLRNC. THE CTLR MADE US AWARE OF XING TFC, WHICH WE HAD A VISUAL ON. AT ABOUT XA37, WE WERE STILL AT FL350 AND 70 MI OUT FROM THE ARPT. WE ALSO WERE AWARE OF SIMILAR SOUNDING COMPANY ACFT IN THE AREA GOING TO THE SAME ARPT, WHICH HAD AN ACR CALL SIGN. THE CTLR'S WORKLOAD SEEMED TO BE INCREASING. WE HEARD A CLRNC FROM THE MSP HIGH ALT CTLR SAYING 'ACR ABCD TURN R TO HDG 090 DEGS AND DSND TO FL240.' I THEN READ BACK 'HDG 090 DEGS DOWN TO FL240 FROM FL350, ACR ABCD.' AT APPROX FL330 WE HEARD FROM THE CTLR SAYING 'ACR ABCD SAY ALT.' THEN I RESPONDED 'SOMEWHERE AROUND FL330.' THEN THE CTLR SAID THE DSCNT FOR ACR BCDE. AT THAT POINT WE SLOWED OUR DSCNT. I TOLD THE CTLR WE MUST HAVE MISUNDERSTOOD HIS CLRNC THAT WE READ BACK. HE THEN SAID WE WERE CLRED TO HDG 090 DEGS ONLY. WE WERE THEN CLRED TO CONTINUE DOWN TO FL240 WITH VECTOR CHANGES THAT FOLLOWED. THEN WE WERE GIVEN TO THE LOWER ALT CTLR DOWN TO THE APCH CTL, THEN THE ATW TWR FOR LNDG 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.