Cpr X had less than standard separation from cpr Y. System error.

Attributes
ACN	142205
Time
Date	199004
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : rka
State Reference	NY
Altitude	msl bound lower : 29700 msl bound upper : 31300
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zbw
Operator	general aviation : corporate
Make Model Name	Light Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent other
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Operator	general aviation : corporate
Make Model Name	Light Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
ASRS Report	142205
Person 2
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : unspecified
Resolutory Action	none taken : detected after the fact
Consequence	faa : investigated
Miss Distance	vertical : 1600
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Cpr X at FL370 was assigned FL310 when cpr Y was observed on radar by mode C to be leaving FL310 for FL290. Cpr X rate of descent was far greater than cpr Y's and less than standard separation occurred when cpr X was at FL313 and cpr Y was at FL297. Being company aircraft of the same make and model, I thought their respective descent rates would be close to the same. Because of my oversight and the different flying techniques of the 2 pilots, an operational error occurred.

Original NASA ASRS Text

Title: CPR X HAD LESS THAN STANDARD SEPARATION FROM CPR Y. SYSTEM ERROR.

Narrative: CPR X AT FL370 WAS ASSIGNED FL310 WHEN CPR Y WAS OBSERVED ON RADAR BY MODE C TO BE LEAVING FL310 FOR FL290. CPR X RATE OF DSNT WAS FAR GREATER THAN CPR Y'S AND LESS THAN STANDARD SEPARATION OCCURRED WHEN CPR X WAS AT FL313 AND CPR Y WAS AT FL297. BEING COMPANY ACFT OF THE SAME MAKE AND MODEL, I THOUGHT THEIR RESPECTIVE DSNT RATES WOULD BE CLOSE TO THE SAME. BECAUSE OF MY OVERSIGHT AND THE DIFFERENT FLYING TECHNIQUES OF THE 2 PLTS, AN OPERATIONAL ERROR OCCURRED.

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.