ZID controller overlooks traffic situation, descending an E145 through the altitude of an MD80.

Attributes
ACN	453633
Time
Date	199911
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : rod.vortac
State Reference	OH
Altitude	msl bound lower : 25500 msl bound upper : 26000
Environment
Flight Conditions	IMC
Weather Elements	Turbulence
Light	Night
Aircraft 1
Controlling Facilities	artcc : zid.artcc
Operator	common carrier : air carrier
Make Model Name	EMB ERJ 145 ER&LR
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	cruise : enroute altitude change
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zid.artcc
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	pilot : private
Experience	controller limited radar : 16 controller non radar : 17 controller radar : 15 controller time certified in position1 : 16 flight time total : 150
ASRS Report	453633
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne critical inflight encounter : weather inflight encounter : turbulence non adherence : required legal separation non adherence : published procedure
Independent Detector	atc equipment : conflict alert aircraft equipment : tcas other flight crewa other flight crewb
Resolutory Action	flight crew : returned to original clearance flight crew : took evasive action
Consequence	faa : investigated
Miss Distance	horizontal : 1000 vertical : 200
Supplementary
Problem Areas	Flight Crew Human Performance Airspace Structure ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X was swbound at FL260. Aircraft Y was nebound at FL250. Numerous reports throughout the day about continuous light chop, occasional moderate with turbulence. Aircraft X requested descent to FL240 to try to find a smoother ride. Aircraft X was cleared to FL240, overlooking aircraft Y. When the situation was realized, aircraft X was cleared immediately to FL260, aircraft Y was turned 40 degrees left and descended to FL240. Aircraft passed and advised ATC that they were returning to previous altitudes after responding to TCASII. Both aircraft advised they were filing near midair collision.

Original NASA ASRS Text

Title: ZID CTLR OVERLOOKS TFC SIT, DSNDING AN E145 THROUGH THE ALT OF AN MD80.

Narrative: ACR X WAS SWBOUND AT FL260. ACFT Y WAS NEBOUND AT FL250. NUMEROUS RPTS THROUGHOUT THE DAY ABOUT CONTINUOUS LIGHT CHOP, OCCASIONAL MODERATE WITH TURB. ACFT X REQUESTED DSCNT TO FL240 TO TRY TO FIND A SMOOTHER RIDE. ACFT X WAS CLRED TO FL240, OVERLOOKING ACFT Y. WHEN THE SIT WAS REALIZED, ACFT X WAS CLRED IMMEDIATELY TO FL260, ACFT Y WAS TURNED 40 DEGS L AND DSNDED TO FL240. ACFT PASSED AND ADVISED ATC THAT THEY WERE RETURNING TO PREVIOUS ALTS AFTER RESPONDING TO TCASII. BOTH ACFT ADVISED THEY WERE FILING NMAC.

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.