Less than standard separation between 2 corp aircraft. Operational error.

Attributes
ACN	94967
Time
Date	198809
Day	Tue
Local Time Of Day	0001 To 0600
Place
Locale Reference	atc facility : cmh
State Reference	OH
Altitude	msl bound lower : 16000 msl bound upper : 16200
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zid
Operator	general aviation : corporate
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other
Route In Use	enroute airway : zid
Flight Plan	IFR
Aircraft 2
Operator	general aviation : corporate
Make Model Name	Light 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 : 4 controller radar : 1
ASRS Report	94967
Person 2
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : overshoot non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : unspecified
Resolutory Action	none taken : insufficient time
Consequence	faa : investigated
Miss Distance	horizontal : 6000 vertical : 200
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Aircraft was issued descent clearance to 17000' pilot read back 11000'. I did not catch the incorrect readback due to fatigue, frequency congestion and heavy traffic. The 2 aircraft passed with less than standard separation. Aedp activated. Callback conversation with reporter revealed the following: confirmed time of day. Reporter says not unusual to have up to 30 aircraft in sector during that period. Very heavy workload and frequency congestion with aircraft stepping all over each other because they were using 3 or 4 different frequencys. Since incident they now get all aircraft on same frequency. Also have more help on midwatch. Got information from reporter reference both aircraft and miss distances. C/a activated at same time as aedp. Noticed aircraft Y descending through 16700', but rate of descent so great that aircraft was down through altitude of aircraft X (16000') before controller could take any action. Both aircraft saw the other aircraft. At time of incident there were 22 data blocks, 10 aircraft on reporter frequency with 3 climbing, 1 descending and 3 on vectors.

Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION BETWEEN 2 CORP ACFT. OPERATIONAL ERROR.

Narrative: ACFT WAS ISSUED DSCNT CLRNC TO 17000' PLT READ BACK 11000'. I DID NOT CATCH THE INCORRECT READBACK DUE TO FATIGUE, FREQ CONGESTION AND HVY TFC. THE 2 ACFT PASSED WITH LTSS. AEDP ACTIVATED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: CONFIRMED TIME OF DAY. RPTR SAYS NOT UNUSUAL TO HAVE UP TO 30 ACFT IN SECTOR DURING THAT PERIOD. VERY HVY WORKLOAD AND FREQ CONGESTION WITH ACFT STEPPING ALL OVER EACH OTHER BECAUSE THEY WERE USING 3 OR 4 DIFFERENT FREQS. SINCE INCIDENT THEY NOW GET ALL ACFT ON SAME FREQ. ALSO HAVE MORE HELP ON MIDWATCH. GOT INFORMATION FROM REPORTER REF BOTH ACFT AND MISS DISTANCES. C/A ACTIVATED AT SAME TIME AS AEDP. NOTICED ACFT Y DSNDING THROUGH 16700', BUT RATE OF DSCNT SO GREAT THAT ACFT WAS DOWN THROUGH ALT OF ACFT X (16000') BEFORE CTLR COULD TAKE ANY ACTION. BOTH ACFT SAW THE OTHER ACFT. AT TIME OF INCIDENT THERE WERE 22 DATA BLOCKS, 10 ACFT ON RPTR FREQ WITH 3 CLBING, 1 DSNDING AND 3 ON VECTORS.

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.