ZID controller realizes speed overtake situation too late to maintain legal separation.

Attributes
ACN	517300
Time
Date	200107
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : zid.artcc
State Reference	IN
Altitude	msl single value : 23000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid.artcc
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zid.artcc
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : vacating altitude
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar pilot : instrument
Experience	controller time certified in position1 : 14 flight time total : 300
ASRS Report	517300
Person 2
Affiliation	government : faa
Function	controller : radar controller : supervisor oversight : supervisor
Experience	controller non radar : 6 controller radar : 10 controller time certified in position1 : 3 controller time certified in position2 : 6
ASRS Report	518054
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	atc equipment : conflict alert other controllera
Resolutory Action	controller : issued new clearance
Consequence	faa : investigated
Miss Distance	horizontal : 25800 vertical : 400
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

First aircraft slowed to 250 KTS. Second aircraft was overtaking. Second aircraft was turned to avoid conflict with first aircraft in descent. Headings should have been assigned earlier. First aircraft's speed should have been deleted. Supplemental information from acn 518054: I was acting controller in charge, monitoring a busy sector with a handoff position being utilized. I then noticed another sector getting busy and assigned a radar associate position to assist a radar only sector. 2 mins after the associate plugged in the error occurred. The radar associate was on a coordination line when the radar controller descended the second aircraft through the altitude of the first aircraft. In my opinion there are 3 causal factors in this error. First and foremost, the inexperience and inadequate ability of the radar controller. He was certified (and some would question why) approximately 3 months ago. Secondly, he was unaware of a speed difference (faster aircraft in back) even though the slower speed on the lead aircraft had been coordinated. And lastly, he turned the trailing aircraft south when he probably should have turned him north.

Original NASA ASRS Text

Title: ZID CTLR REALIZES SPD OVERTAKE SIT TOO LATE TO MAINTAIN LEGAL SEPARATION.

Narrative: FIRST ACFT SLOWED TO 250 KTS. SECOND ACFT WAS OVERTAKING. SECOND ACFT WAS TURNED TO AVOID CONFLICT WITH FIRST ACFT IN DSCNT. HDGS SHOULD HAVE BEEN ASSIGNED EARLIER. FIRST ACFT'S SPD SHOULD HAVE BEEN DELETED. SUPPLEMENTAL INFO FROM ACN 518054: I WAS ACTING CIC, MONITORING A BUSY SECTOR WITH A HDOF POS BEING UTILIZED. I THEN NOTICED ANOTHER SECTOR GETTING BUSY AND ASSIGNED A RADAR ASSOCIATE POS TO ASSIST A RADAR ONLY SECTOR. 2 MINS AFTER THE ASSOCIATE PLUGGED IN THE ERROR OCCURRED. THE RADAR ASSOCIATE WAS ON A COORD LINE WHEN THE RADAR CTLR DSNDED THE SECOND ACFT THROUGH THE ALT OF THE FIRST ACFT. IN MY OPINION THERE ARE 3 CAUSAL FACTORS IN THIS ERROR. FIRST AND FOREMOST, THE INEXPERIENCE AND INADEQUATE ABILITY OF THE RADAR CTLR. HE WAS CERTIFIED (AND SOME WOULD QUESTION WHY) APPROX 3 MONTHS AGO. SECONDLY, HE WAS UNAWARE OF A SPD DIFFERENCE (FASTER ACFT IN BACK) EVEN THOUGH THE SLOWER SPD ON THE LEAD ACFT HAD BEEN COORDINATED. AND LASTLY, HE TURNED THE TRAILING ACFT S WHEN HE PROBABLY SHOULD HAVE TURNED HIM N.

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.