BA46 at FL290 descends below assigned altitude in ZOB airspace.

Attributes
ACN	593639
Time
Date	200309
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : djb.vortac
State Reference	OH
Altitude	msl bound lower : 28500 msl bound upper : 29000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob.artcc
Operator	common carrier : air carrier
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : intermediate altitude descent : vacating altitude
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zob.artcc
Make Model Name	Commercial Fixed Wing
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : commercial pilot : cfi pilot : instrument
Experience	flight time last 90 days : 90 flight time total : 3500 flight time type : 350
ASRS Report	593639
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : required legal separation non adherence : clearance
Independent Detector	aircraft equipment : tcas other controllera other flight crewa
Resolutory Action	controller : issued new clearance flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 6000 vertical : 800
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

During cruise at FL290, we were given instructions by ZOB to turn right 20 degrees. As the PNF, I heard to turn right 20 degrees and descend to FL280. I read back the clearance, 'turn right 20 degrees and descend to FL280.' the captain (PF) turned right 20 degrees. When I noticed that he was not descending, I told him that the controller wanted us to descend to FL280. During our descent, I called ZOB back and asked if he wanted us to descend to FL280. The first time he did not reply. After the second inquiry, the controller said, 'negative aircraft X, there is an aircraft under you climbing to FL280.' during the second inquiry to ATC, the captain and I noticed the other aircraft on the TCASII. The TCASII went off with 'monitor vertical speed,' followed a few seconds later by 'climb, climb now.' by this time we were between FL286 and FL285. The captain immediately climbed back to FL290. The controller told the other aircraft to stop their climb, and then continued the climb when we were back to FL280. Flight to dtw was the last leg of the 4TH day of a continuous duty overnight. I admit that I was tired from only receiving 4 hours of sleep at the hotel that morning. Fatigue played a major role in this situation.

Original NASA ASRS Text

Title: BA46 AT FL290 DSNDS BELOW ASSIGNED ALT IN ZOB AIRSPACE.

Narrative: DURING CRUISE AT FL290, WE WERE GIVEN INSTRUCTIONS BY ZOB TO TURN R 20 DEGS. AS THE PNF, I HEARD TO TURN R 20 DEGS AND DSND TO FL280. I READ BACK THE CLRNC, 'TURN R 20 DEGS AND DSND TO FL280.' THE CAPT (PF) TURNED R 20 DEGS. WHEN I NOTICED THAT HE WAS NOT DSNDING, I TOLD HIM THAT THE CTLR WANTED US TO DSND TO FL280. DURING OUR DSCNT, I CALLED ZOB BACK AND ASKED IF HE WANTED US TO DSND TO FL280. THE FIRST TIME HE DID NOT REPLY. AFTER THE SECOND INQUIRY, THE CTLR SAID, 'NEGATIVE ACFT X, THERE IS AN ACFT UNDER YOU CLBING TO FL280.' DURING THE SECOND INQUIRY TO ATC, THE CAPT AND I NOTICED THE OTHER ACFT ON THE TCASII. THE TCASII WENT OFF WITH 'MONITOR VERT SPD,' FOLLOWED A FEW SECONDS LATER BY 'CLB, CLB NOW.' BY THIS TIME WE WERE BTWN FL286 AND FL285. THE CAPT IMMEDIATELY CLBED BACK TO FL290. THE CTLR TOLD THE OTHER ACFT TO STOP THEIR CLB, AND THEN CONTINUED THE CLB WHEN WE WERE BACK TO FL280. FLT TO DTW WAS THE LAST LEG OF THE 4TH DAY OF A CONTINUOUS DUTY OVERNIGHT. I ADMIT THAT I WAS TIRED FROM ONLY RECEIVING 4 HRS OF SLEEP AT THE HOTEL THAT MORNING. FATIGUE PLAYED A MAJOR ROLE IN THIS SIT.

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.