Air carrier X had less than standard separation from air carrier Y. System error.

Attributes
ACN	145012
Time
Date	199005
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : gij
State Reference	IL
Altitude	msl bound lower : 23000 msl bound upper : 33000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zau tracon : lax
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Heavy Transport, Low Wing, 4 Turbojet Eng
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 4
ASRS Report	145012
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
Resolutory Action	none taken : detected after the fact
Consequence	faa : investigated
Miss Distance	horizontal : 24600 vertical : 100
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier medium large transport X was on the high altitude frequency with air carrier heavy Y on the low altitude frequency in a step climb under. The mode C of air carrier X was observed to be leaving FL230 and was issued FL230. Consequently air carrier X had in fact leveled at FL230 and air carrier Y leveled with less than required sep. Supplemental information from acn 145088: air carrier X called on frequency climbing to FL230. Air carrier X was climbed to FL330, but pilot read back FL230. Controller missed readback. After leveling at FL230, air carrier X lost sep with air carrier Y climbing to FL230 being worked by low altitude controller.

Original NASA ASRS Text

Title: ACR X HAD LESS THAN STANDARD SEPARATION FROM ACR Y. SYSTEM ERROR.

Narrative: ACR MLG X WAS ON THE HIGH ALT FREQ WITH ACR HVY Y ON THE LOW ALT FREQ IN A STEP CLB UNDER. THE MODE C OF ACR X WAS OBSERVED TO BE LEAVING FL230 AND WAS ISSUED FL230. CONSEQUENTLY ACR X HAD IN FACT LEVELED AT FL230 AND ACR Y LEVELED WITH LESS THAN REQUIRED SEP. SUPPLEMENTAL INFO FROM ACN 145088: ACR X CALLED ON FREQ CLBING TO FL230. ACR X WAS CLBED TO FL330, BUT PLT READ BACK FL230. CTLR MISSED READBACK. AFTER LEVELING AT FL230, ACR X LOST SEP WITH ACR Y CLBING TO FL230 BEING WORKED BY LOW ALT CTLR.

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.