MD80 crew was informed by the controller they had descended lower than he had intended.

Attributes
ACN	516370
Time
Date	200106
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : a90.tracon
State Reference	MA
Altitude	msl bound lower : 6000 msl bound upper : 7000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : lfrr.artcc
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
ASRS Report	516370
Events
Anomaly	non adherence : far non adherence : company policies non adherence : clearance non adherence : published procedure
Resolutory Action	controller : issued new clearance controller : issued alert
Consequence	other
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	Ambiguous

Narrative:

Altitude deviation. Captain armed and set and pointed 6000 ft in FMA as has been our practice. Passing 6500 ft in descent, controller questioned altitude, then said we should be at 7000 ft but to continue to 6000 ft, as this was his airspace also. No conflicts. We continued and inquired about conflicts -- none generated. How or what caused problem neither of us know. We set preselect and both acknowledged the FMA. Maybe he gave it to us in error. Maybe we misunderstood '6' instead of '7.' maybe we set it in error. Maybe.... Will try to be more vigilant in the future and hope it does not happen again.

Original NASA ASRS Text

Title: MD80 CREW WAS INFORMED BY THE CTLR THEY HAD DSNDED LOWER THAN HE HAD INTENDED.

Narrative: ALTDEV. CAPT ARMED AND SET AND POINTED 6000 FT IN FMA AS HAS BEEN OUR PRACTICE. PASSING 6500 FT IN DSCNT, CTLR QUESTIONED ALT, THEN SAID WE SHOULD BE AT 7000 FT BUT TO CONTINUE TO 6000 FT, AS THIS WAS HIS AIRSPACE ALSO. NO CONFLICTS. WE CONTINUED AND INQUIRED ABOUT CONFLICTS -- NONE GENERATED. HOW OR WHAT CAUSED PROB NEITHER OF US KNOW. WE SET PRESELECT AND BOTH ACKNOWLEDGED THE FMA. MAYBE HE GAVE IT TO US IN ERROR. MAYBE WE MISUNDERSTOOD '6' INSTEAD OF '7.' MAYBE WE SET IT IN ERROR. MAYBE.... WILL TRY TO BE MORE VIGILANT IN THE FUTURE AND HOPE IT DOES NOT HAPPEN AGAIN.

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.