<< >> NASA ASRS Report 413105, August 1998

With a commuter SF34 aircraft deviating around WX, the approach controller mistakenly descended an opposite direction DH8 through the altitude of the SF34. When the controller realized the potential conflict, it was too late to prevent a loss of separation.

Attributes
ACN	413105
Time
Date	199808
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : buf
State Reference	NY
Altitude	msl bound lower : 5000 msl bound upper : 5000
Environment
Flight Conditions	Mixed
Light	Dusk
Aircraft 1
Controlling Facilities	tracon : buf
Operator	common carrier : air carrier
Make Model Name	Medium Transport, High Wing, 2 Turboprop Eng
Operating Under FAR Part	Part 121
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Operating Under FAR Part	Part 121
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller radar : 13
ASRS Report	413105
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation non adherence : published procedure
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 6000 vertical : 500
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I was working approach radar with level 3-5 precipitation in the area. There was also a report of moderate turbulence in the clouds. I descended a DH8 from 9000 ft to 4000 ft to get under the clouds. I did not advise the aircraft of the opposite direction traffic at 5000 ft deviating around WX. I noticed that the DH8 was out of 6000 ft and the aircraft were 10 NM apart. I attempted turns and dscnts to maintain separation but to no avail. In the future, I will leave more room for aircraft to maneuver in inclement WX.

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Original NASA ASRS Text

Title: WITH A COMMUTER SF34 ACFT DEVIATING AROUND WX, THE APCH CTLR MISTAKENLY DSNDED AN OPPOSITE DIRECTION DH8 THROUGH THE ALT OF THE SF34. WHEN THE CTLR REALIZED THE POTENTIAL CONFLICT, IT WAS TOO LATE TO PREVENT A LOSS OF SEPARATION.

Narrative: I WAS WORKING APCH RADAR WITH LEVEL 3-5 PRECIP IN THE AREA. THERE WAS ALSO A RPT OF MODERATE TURB IN THE CLOUDS. I DSNDED A DH8 FROM 9000 FT TO 4000 FT TO GET UNDER THE CLOUDS. I DID NOT ADVISE THE ACFT OF THE OPPOSITE DIRECTION TFC AT 5000 FT DEVIATING AROUND WX. I NOTICED THAT THE DH8 WAS OUT OF 6000 FT AND THE ACFT WERE 10 NM APART. I ATTEMPTED TURNS AND DSCNTS TO MAINTAIN SEPARATION BUT TO NO AVAIL. IN THE FUTURE, I WILL LEAVE MORE ROOM FOR ACFT TO MANEUVER IN INCLEMENT WX.

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.