Narrative:

On arrival into teterboro, we were cleared down to 4000 ft. After being at 4000 ft for some time, controller asked us why we stopped at 4000 ft and said we should be at 3000 ft. We do not remember being cleared to 3000 ft. Opposite direction traffic appeared on TCASII 200 ft below us. We descended to 3000 ft with no traffic conflict. Supplemental information from acn 468852: the leg in question was being conducted under far 135 charter operations. ATC had cleared us to descend to 4000 ft after passing the mugzy intersection. Shortly after that, we were given radar vectors for what we thought was going to be the VOR DME a approach, circle to land runway 19 at teb. I advised captain that I would be off the ATC frequency just long enough to confirm the latest ATIS. Within a couple of mins of my return to the ATC frequency, we received an urgent command from ATC to descend immediately to 3000 ft. Captain reached for the vertical speed selector on the flight guidance controller to select a descent with the autothrottles while the aircraft was still on autoplt. I immediately advised the captain to 'get rid of the automation, and get us down as soon as possible.' we had the traffic in question clearly in sight and on the TCASII about 5 or 6 mi away. When I questioned captain, 'did you receive the ATC clearance to 3000 ft while I was off the ATC frequency?' his response was something to the effect of 'I cannot remember if it was 4000 or 3000 ft.' captain's delay (attempting to use the automation for the descent) may have caused us to lose IFR separation.

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Original NASA ASRS Text

Title: A GULFSTREAM 4 CREW, FLYING UNDER PART 135, WERE INSTRUCTED TO DSND TO 3000 FT, BUT THEY STOPPED AT 4000 FT. THE N90 CTLR ADVISED THE CREW OF TFC AND REQUESTED AN IMMEDIATE DSCNT TO 3000 FT.

Narrative: ON ARR INTO TETERBORO, WE WERE CLRED DOWN TO 4000 FT. AFTER BEING AT 4000 FT FOR SOME TIME, CTLR ASKED US WHY WE STOPPED AT 4000 FT AND SAID WE SHOULD BE AT 3000 FT. WE DO NOT REMEMBER BEING CLRED TO 3000 FT. OPPOSITE DIRECTION TFC APPEARED ON TCASII 200 FT BELOW US. WE DSNDED TO 3000 FT WITH NO TFC CONFLICT. SUPPLEMENTAL INFO FROM ACN 468852: THE LEG IN QUESTION WAS BEING CONDUCTED UNDER FAR 135 CHARTER OPS. ATC HAD CLRED US TO DSND TO 4000 FT AFTER PASSING THE MUGZY INTXN. SHORTLY AFTER THAT, WE WERE GIVEN RADAR VECTORS FOR WHAT WE THOUGHT WAS GOING TO BE THE VOR DME A APCH, CIRCLE TO LAND RWY 19 AT TEB. I ADVISED CAPT THAT I WOULD BE OFF THE ATC FREQ JUST LONG ENOUGH TO CONFIRM THE LATEST ATIS. WITHIN A COUPLE OF MINS OF MY RETURN TO THE ATC FREQ, WE RECEIVED AN URGENT COMMAND FROM ATC TO DSND IMMEDIATELY TO 3000 FT. CAPT REACHED FOR THE VERT SPD SELECTOR ON THE FLT GUIDANCE CTLR TO SELECT A DSCNT WITH THE AUTOTHROTTLES WHILE THE ACFT WAS STILL ON AUTOPLT. I IMMEDIATELY ADVISED THE CAPT TO 'GET RID OF THE AUTOMATION, AND GET US DOWN AS SOON AS POSSIBLE.' WE HAD THE TFC IN QUESTION CLRLY IN SIGHT AND ON THE TCASII ABOUT 5 OR 6 MI AWAY. WHEN I QUESTIONED CAPT, 'DID YOU RECEIVE THE ATC CLRNC TO 3000 FT WHILE I WAS OFF THE ATC FREQ?' HIS RESPONSE WAS SOMETHING TO THE EFFECT OF 'I CANNOT REMEMBER IF IT WAS 4000 OR 3000 FT.' CAPT'S DELAY (ATTEMPTING TO USE THE AUTOMATION FOR THE DSCNT) MAY HAVE CAUSED US TO LOSE IFR SEPARATION.

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.