ZBW controller described a conflict event when an A330 descent rate instruction was read back incorr...

Attributes
ACN	903847
Time
Date	201008
Local Time Of Day	1201-1800
Place
Locale Reference	ZBW.ARTCC
State Reference	NH
Aircraft 1
Make Model Name	A330
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	Vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Challenger CL604
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Route In Use	Direct
Flight Plan	IFR
Person 1
Function	Enroute
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy
Miss Distance	Horizontal 25519 Vertical 700

Narrative:

A330 was on a vector towards the holding pattern at rka at FL260 at 250K due to ZNY not taking any more phl arrivals. ZNY called to say send phl traffic on course they will hold him. A330 cleared to resume normal speed. A330 replied where do you want me to go. A330 cleared direct dny speed your discretion expect to hold with the next controller. A330 was cleared to FL190. A corporate jet was eastbound deviating south of dny cleared to FL230 direct peter when able. A330 was told to maintain at least 1;500 ft per minute; A330 read back 600 ft per minute. Nobody at the sector heard the erroneous read back. As the aircraft were getting closer; A330 was told to maintain 2;000 ft per minute. Corporate jet responded to a TCAS-RA and climbed and was then cleared to FL240. A330 later said he received a TCAS-RA as well. Recommendation: issue crossing restriction/s instead of descent rate.

Original NASA ASRS Text

Title: ZBW Controller described a conflict event when an A330 descent rate instruction was read back incorrectly; but not noted by the reporter; setting the stage for the loss of separation.

Narrative: A330 was on a vector towards the holding pattern at RKA at FL260 at 250K due to ZNY not taking any more PHL arrivals. ZNY called to say send PHL traffic on course they will hold him. A330 cleared to resume normal speed. A330 replied where do you want me to go. A330 cleared direct DNY speed your discretion expect to hold with the next controller. A330 was cleared to FL190. A Corporate Jet was eastbound deviating south of DNY cleared to FL230 direct PETER when able. A330 was told to maintain at least 1;500 FT per minute; A330 read back 600 FT per minute. Nobody at the sector heard the erroneous read back. As the aircraft were getting closer; A330 was told to maintain 2;000 FT per minute. Corporate Jet responded to a TCAS-RA and climbed and was then cleared to FL240. A330 later said he received a TCAS-RA as well. Recommendation: issue crossing restriction/s instead of descent rate.

Data retrieved from NASA's ASRS site as of April 2012 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.

ZBW controller described a conflict event when an A330 descent rate instruction was read back incorrectly; but not noted by the reporter; setting the stage for the loss of separation.