ZID controller experienced operational error at FL320 involving three aircraft that resulted from an...

Attributes
ACN	821847
Time
Date	200902
Local Time Of Day	1801-2400
Place
Locale Reference	ZID.ARTCC
State Reference	IN
Environment
Flight Conditions	Mixed
Light	Dusk
Aircraft 1
Make Model Name	B717 (Formerly MD-95)
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Aircraft 2
Make Model Name	EMB ERJ 170/175 ER&LR
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Person 1
Function	Enroute
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Non Radar 2 Air Traffic Control Radar 18 Air Traffic Control Time Certified In Pos 1 (yrs) 15
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict
Miss Distance	Horizontal 13500 Vertical 700

Narrative:

Aircraft #1; aircraft X; northbound level flight at FL330 on the WEEDA1 arrival. Aircraft #2; aircraft Y; westbound level at FL320 direct mie. Aircraft #3; aircraft Z; northbound level flight at FL330 on the GEMNI2 arrival. Aircraft Z and aircraft Y were traffic. Aircraft Z was issued clearance when clear of aircraft Y to descend from FL330 to FL300 at 1;500 FPM rate of descent. Aircraft X mistakenly took the clearance for aircraft Z. Aircraft X read back clearance stating the altitude to maintain; then the rate of descent assignment; then the aircraft call sign. I missed the incorrect call sign readback. Aircraft X initiated descent with traffic aircraft Y at FL320. I noticed aircraft X descending and issued clearance to climb to FL330 and fly heading 270 degrees and issued clearance for aircraft Y to fly heading 360 degrees. Aircraft X took the clearance for aircraft Z; and when aircraft X read back the clearance using a 'nonstandard' radio format instead of responding with the call sign first; then the control instructions; I failed to realize the mistake.

Original NASA ASRS Text

Title: ZID Controller experienced operational error at FL320 involving three aircraft that resulted from an incorrect altitude clearance readback that was missed.

Narrative: Aircraft #1; Aircraft X; northbound level flight at FL330 on the WEEDA1 Arrival. Aircraft #2; Aircraft Y; westbound level at FL320 direct MIE. Aircraft #3; Aircraft Z; northbound level flight at FL330 on the GEMNI2 Arrival. Aircraft Z and Aircraft Y were traffic. Aircraft Z was issued clearance when clear of Aircraft Y to descend from FL330 to FL300 at 1;500 FPM rate of descent. Aircraft X mistakenly took the clearance for Aircraft Z. Aircraft X read back clearance stating the altitude to maintain; then the rate of descent assignment; then the aircraft call sign. I missed the incorrect call sign readback. Aircraft X initiated descent with traffic Aircraft Y at FL320. I noticed Aircraft X descending and issued clearance to climb to FL330 and fly heading 270 degrees and issued clearance for Aircraft Y to fly heading 360 degrees. Aircraft X took the clearance for Aircraft Z; and when Aircraft X read back the clearance using a 'nonstandard' radio format instead of responding with the call sign first; then the control instructions; I failed to realize the mistake.

Data retrieved from NASA's ASRS site as of April 2012 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.

ZID controller experienced operational error at FL320 involving three aircraft that resulted from an incorrect altitude clearance readback that was missed.