Air carrier X descent through occupied altitude had less than standard separation from Y. System err...

Attributes
ACN	213769
Time
Date	199206
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : pop
State Reference	FO
Altitude	msl bound lower : 24000 msl bound upper : 24000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : mdcs
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent other
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 8000 flight time type : 85
ASRS Report	213769
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 6000 flight time type : 200
ASRS Report	214568
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	Other
Miss Distance	horizontal : 30000 vertical : 500
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X cruising from sju to pop. Just as we changed to sdq center at 25000, we were getting some light icing and light turbulence. I requested a lower altitude to stay out of the clouds, sdq cleared us to 20000 if we could descend below 24000 by 107 mi as we were going through 24000 and 109 mi we heard another aircraft Y state that they were at 24000 and 109 mi from pop, we never saw the other aircraft Y. We were IMC at that time. Since we were using omega and the other was probably using VOR, I estimate we missed by about 5 mi. Contributing to this incident was my willingness to change altitude in non radar environment knowing that sdq most of the time will approve the changes.

Original NASA ASRS Text

Title: ACR X DSCNT THROUGH OCCUPIED ALT HAD LTSS FROM Y. SYS ERROR.

Narrative: ACR X CRUISING FROM SJU TO POP. JUST AS WE CHANGED TO SDQ CTR AT 25000, WE WERE GETTING SOME LIGHT ICING AND LIGHT TURB. I REQUESTED A LOWER ALT TO STAY OUT OF THE CLOUDS, SDQ CLRED US TO 20000 IF WE COULD DSND BELOW 24000 BY 107 MI AS WE WERE GOING THROUGH 24000 AND 109 MI WE HEARD ANOTHER ACFT Y STATE THAT THEY WERE AT 24000 AND 109 MI FROM POP, WE NEVER SAW THE OTHER ACFT Y. WE WERE IMC AT THAT TIME. SINCE WE WERE USING OMEGA AND THE OTHER WAS PROBABLY USING VOR, I ESTIMATE WE MISSED BY ABOUT 5 MI. CONTRIBUTING TO THIS INCIDENT WAS MY WILLINGNESS TO CHANGE ALT IN NON RADAR ENVIRONMENT KNOWING THAT SDQ MOST OF THE TIME WILL APPROVE THE CHANGES.

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.

Air carrier X descent through occupied altitude had less than standard separation from Y. System error.