DC9 crew had altitude deviation.

Attributes
ACN	462450
Time
Date	200002
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : gdm.vortac
State Reference	MA
Altitude	msl bound lower : 25000 msl bound upper : 29000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zbw.artcc tower : zzz.tower
Operator	common carrier : air carrier
Make Model Name	DC-9 30
Operating Under FAR Part	Part 121
Flight Phase	descent : vacating altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : multi engine pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 250 flight time total : 19000 flight time type : 2300
ASRS Report	462450
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : multi engine
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance non adherence : far non adherence : published procedure other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance controller : issued alert
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

During cruise flight from buf to bos at FL290, I responded to and read back a clearance to FL250. The first officer and I pointed to the altitude setting and verbally confirmed the altitude change. While descending, the ZBW controller asked us to say assigned altitude, and we responded 'passing through FL275 for FL250.' he said the clearance we had acknowledged on readback was for another aircraft, but he said that he understood the confusion involved and 'no harm was done.' soon after, further clearance was issued to FL210. No separation errors resulted and no traffic was observed on TCASII within 20 NM. I think the new ATC procedures that allow a controller to ignore an incorrect readback was the main factor in this misunderstanding. Also there was a lot of backgnd noise on ZBW frequency 135.32.

Original NASA ASRS Text

Title: DC9 CREW HAD ALTDEV.

Narrative: DURING CRUISE FLT FROM BUF TO BOS AT FL290, I RESPONDED TO AND READ BACK A CLRNC TO FL250. THE FO AND I POINTED TO THE ALT SETTING AND VERBALLY CONFIRMED THE ALT CHANGE. WHILE DSNDING, THE ZBW CTLR ASKED US TO SAY ASSIGNED ALT, AND WE RESPONDED 'PASSING THROUGH FL275 FOR FL250.' HE SAID THE CLRNC WE HAD ACKNOWLEDGED ON READBACK WAS FOR ANOTHER ACFT, BUT HE SAID THAT HE UNDERSTOOD THE CONFUSION INVOLVED AND 'NO HARM WAS DONE.' SOON AFTER, FURTHER CLRNC WAS ISSUED TO FL210. NO SEPARATION ERRORS RESULTED AND NO TFC WAS OBSERVED ON TCASII WITHIN 20 NM. I THINK THE NEW ATC PROCS THAT ALLOW A CTLR TO IGNORE AN INCORRECT READBACK WAS THE MAIN FACTOR IN THIS MISUNDERSTANDING. ALSO THERE WAS A LOT OF BACKGND NOISE ON ZBW FREQ 135.32.

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.