Late descent caused loss of separation between aircraft.

Attributes
ACN	105785
Time
Date	198903
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : hut
State Reference	KS
Altitude	msl bound lower : 31000 msl bound upper : 31000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zkc
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	cruise other
Route In Use	enroute : on vectors
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
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
ASRS Report	105785
Person 2
Affiliation	company : air carrier
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 other controllera
Resolutory Action	controller : issued new clearance other
Consequence	faa : investigated
Miss Distance	horizontal : 28000 vertical : 100
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Medium large transport X on course wbound J18 level FL310. Medium large transport Y departed den then from hlc direct and landing hut-ict. Medium large transport Y issued descent clearance to FL250 from FL330 approximately 4 mins prior to confliction (possibly longer) and on a direct heading of approximately 120 degrees. Medium large transport Y was at FL310 when C/a activated. A turn was previously issued to medium large transport X of 20 degrees right to attempt to ensure sep prior to conflict activation. Also track history on medium large transport Y showed a turn of at least 10 degrees to the left. Oedp activated within seconds after C/a, resulting in 100' vertical, 4.8 latitude. Factors: 1) 14-15 aircraft in sector, 4-5 sep problems occurring. 2) medium large transport Y turned away or drifted from hut into jet stream, which slowed ground speed. 3) medium large transport Y's rate of descent (my best guess) was 400 FPM, slower than I expected. 4) I recognized deteriorating situation prior (about 30 seconds or less) to C/a and turned medium large transport X. 5) C/a did not recognize potential situation nor activate until aircraft approximately 6-7 mi apart. I believe it should be made mandatory for pilots to advise if they cannot comply with aim suggested descent rates. We are held responsible for pilot actions which contribute to these types of situations.

Original NASA ASRS Text

Title: LATE DESCENT CAUSED LOSS OF SEPARATION BETWEEN ACFT.

Narrative: MLG X ON COURSE WBOUND J18 LEVEL FL310. MLG Y DEPARTED DEN THEN FROM HLC DIRECT AND LNDG HUT-ICT. MLG Y ISSUED DSCNT CLRNC TO FL250 FROM FL330 APPROX 4 MINS PRIOR TO CONFLICTION (POSSIBLY LONGER) AND ON A DIRECT HDG OF APPROX 120 DEGS. MLG Y WAS AT FL310 WHEN C/A ACTIVATED. A TURN WAS PREVIOUSLY ISSUED TO MLG X OF 20 DEGS RIGHT TO ATTEMPT TO ENSURE SEP PRIOR TO CONFLICT ACTIVATION. ALSO TRACK HISTORY ON MLG Y SHOWED A TURN OF AT LEAST 10 DEGS TO THE LEFT. OEDP ACTIVATED WITHIN SECS AFTER C/A, RESULTING IN 100' VERT, 4.8 LAT. FACTORS: 1) 14-15 ACFT IN SECTOR, 4-5 SEP PROBS OCCURRING. 2) MLG Y TURNED AWAY OR DRIFTED FROM HUT INTO JET STREAM, WHICH SLOWED GND SPD. 3) MLG Y'S RATE OF DSCNT (MY BEST GUESS) WAS 400 FPM, SLOWER THAN I EXPECTED. 4) I RECOGNIZED DETERIORATING SITUATION PRIOR (ABOUT 30 SECS OR LESS) TO C/A AND TURNED MLG X. 5) C/A DID NOT RECOGNIZE POTENTIAL SITUATION NOR ACTIVATE UNTIL ACFT APPROX 6-7 MI APART. I BELIEVE IT SHOULD BE MADE MANDATORY FOR PLTS TO ADVISE IF THEY CANNOT COMPLY WITH AIM SUGGESTED DSCNT RATES. WE ARE HELD RESPONSIBLE FOR PLT ACTIONS WHICH CONTRIBUTE TO THESE TYPES OF SITUATIONS.

Data retrieved from NASA's ASRS site as of August 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.