Phl approach misjudged climb performance and lost separation.

Attributes
ACN	583499
Time
Date	200306
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : phl.airport
State Reference	PA
Altitude	msl single value : 7000
Environment
Flight Conditions	IMC
Light	Dusk
Aircraft 1
Controlling Facilities	tracon : phl.tracon
Operator	common carrier : air carrier
Make Model Name	A321
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	climbout : intermediate altitude
Route In Use	departure : on vectors
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : phl.tracon
Operator	common carrier : air carrier
Make Model Name	A320
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Route In Use	departure : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : departure
Qualification	controller : radar
Experience	controller radar : 14
ASRS Report	583499
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : radar mode c other controllera
Resolutory Action	controller : issued new clearance controller : separated traffic
Consequence	faa : investigated
Miss Distance	vertical : 700
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance Aircraft
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Aircraft #1 was climbing wbound toward mxe, climbing to 10000 ft. Aircraft #2 was climbing to 9000 ft and turning northbound. When I observed aircraft #1 climbing slowly, I instructed aircraft #2 to maintain 7000 ft to stay under the first aircraft. Aircraft #2 seemed to have a higher then normal climb rate, and leveled off at 7000 ft sooner than I expected.

Original NASA ASRS Text

Title: PHL APCH MISJUDGED CLB PERFORMANCE AND LOST SEPARATION.

Narrative: ACFT #1 WAS CLBING WBOUND TOWARD MXE, CLBING TO 10000 FT. ACFT #2 WAS CLBING TO 9000 FT AND TURNING NBOUND. WHEN I OBSERVED ACFT #1 CLBING SLOWLY, I INSTRUCTED ACFT #2 TO MAINTAIN 7000 FT TO STAY UNDER THE FIRST ACFT. ACFT #2 SEEMED TO HAVE A HIGHER THEN NORMAL CLB RATE, AND LEVELED OFF AT 7000 FT SOONER THAN I EXPECTED.

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.