Aircraft in slow descent caused less than standard separation with another aircraft also descending.

Attributes
ACN	134713
Time
Date	199001
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : bgm
State Reference	NY
Altitude	msl bound lower : 29400 msl bound upper : 31000
Environment
Light	Night
Aircraft 1
Controlling Facilities	artcc : zob
Operator	general aviation : corporate
Make Model Name	Light Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller military : 5 controller radar : 8
ASRS Report	134713
Person 2
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	non adherence : far non adherence : clearance non adherence : required legal separation other anomaly other
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	other
Consequence	faa : investigated
Miss Distance	horizontal : 24000 vertical : 1600
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Cga X checked onto my frequency descending to FL330. At that time I saw air carrier Y being handed off to me from ZNY at FL310 nwbnd towards buf. I cleared cga X to FL270 with no delay, expecting to get him under air carrier Y. When air carrier Y checked in, he was complaining of chop and requested a ride report at FL280. I advised that FL280 was smooth. At that time, I determined that I had 2 mins to get cga X, who was still descending out of FL335, out of FL290 or descend air carrier Y down and take cga X over the top. I issued air carrier Y a descent to FL280, with no delay in descent. He reported out of FL310 and I stopped cga X at FL310. On my scope cga X mode C at that time showed FL332. When I saw air carrier Y, mode C, I determined that his descent rate was over 2000 FPM and that he was no factor with cga X. After doing some coordination, handoffs and some higher priority duties, I looked back at air carrier Y and saw he was 7 mi from cga X and his mode C indicated FL297. I told air carrier Y I needed him out of FL290 in 10 seconds or less for traffic. He responded with, 'we're going down now.' after listening to the tapes and looking at the computer readout, it showed air carrier Y descended to FL298 in 30 seconds, climbed back up to FL300 and stayed there for approximately 35 seconds. He then started back down and that is when I asked him to be out of FL290 in 10 seconds or less. That is where separation was lost at FL294 and 4 mi.

Original NASA ASRS Text

Title: ACFT IN SLOW DESCENT CAUSED LESS THAN STANDARD SEPARATION WITH ANOTHER ACFT ALSO DESCENDING.

Narrative: CGA X CHECKED ONTO MY FREQ DESCENDING TO FL330. AT THAT TIME I SAW ACR Y BEING HANDED OFF TO ME FROM ZNY AT FL310 NWBND TOWARDS BUF. I CLRED CGA X TO FL270 WITH NO DELAY, EXPECTING TO GET HIM UNDER ACR Y. WHEN ACR Y CHECKED IN, HE WAS COMPLAINING OF CHOP AND REQUESTED A RIDE REPORT AT FL280. I ADVISED THAT FL280 WAS SMOOTH. AT THAT TIME, I DETERMINED THAT I HAD 2 MINS TO GET CGA X, WHO WAS STILL DESCENDING OUT OF FL335, OUT OF FL290 OR DSND ACR Y DOWN AND TAKE CGA X OVER THE TOP. I ISSUED ACR Y A DSCNT TO FL280, WITH NO DELAY IN DSCNT. HE REPORTED OUT OF FL310 AND I STOPPED CGA X AT FL310. ON MY SCOPE CGA X MODE C AT THAT TIME SHOWED FL332. WHEN I SAW ACR Y, MODE C, I DETERMINED THAT HIS DSCNT RATE WAS OVER 2000 FPM AND THAT HE WAS NO FACTOR WITH CGA X. AFTER DOING SOME COORDINATION, HANDOFFS AND SOME HIGHER PRIORITY DUTIES, I LOOKED BACK AT ACR Y AND SAW HE WAS 7 MI FROM CGA X AND HIS MODE C INDICATED FL297. I TOLD ACR Y I NEEDED HIM OUT OF FL290 IN 10 SECONDS OR LESS FOR TFC. HE RESPONDED WITH, 'WE'RE GOING DOWN NOW.' AFTER LISTENING TO THE TAPES AND LOOKING AT THE COMPUTER READOUT, IT SHOWED ACR Y DESCENDED TO FL298 IN 30 SECONDS, CLIMBED BACK UP TO FL300 AND STAYED THERE FOR APPROX 35 SECONDS. HE THEN STARTED BACK DOWN AND THAT IS WHEN I ASKED HIM TO BE OUT OF FL290 IN 10 SECONDS OR LESS. THAT IS WHERE SEPARATION WAS LOST AT FL294 AND 4 MI.

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.