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

Attributes
ACN	181162
Time
Date	199106
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : abe
State Reference	PA
Altitude	msl bound lower : 27500 msl bound upper : 28000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zny
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	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	climbout : intermediate altitude cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 6
ASRS Report	181162
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : overshoot conflict : airborne less severe inflight encounter : weather non adherence : required legal separation non adherence : published procedure non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	faa : investigated
Miss Distance	horizontal : 27000 vertical : 500
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X was landing at iad and was given to me at FL280. Due to a thunderstorm the aircraft asked to deviate and a west of course deviation was approved. The aircraft was issued a clearance to descend to FL200 north of lancaster, PA. Air carrier Y was climbed to FL280 wbound and due to the deviation the planes were going to be less than standard separation apart. Alternate instructions were issued to air carrier Y to stop his climb at FL270 and the air carrier X to maintain FL280. Air carrier Y flight went through the altitude to FL275 and then back down to FL270.

Original NASA ASRS Text

Title: ACR X HAD LTSS FROM ACR Y. SYSTEM ERROR.

Narrative: ACR X WAS LNDG AT IAD AND WAS GIVEN TO ME AT FL280. DUE TO A TSTM THE ACFT ASKED TO DEVIATE AND A W OF COURSE DEV WAS APPROVED. THE ACFT WAS ISSUED A CLRNC TO DSND TO FL200 N OF LANCASTER, PA. ACR Y WAS CLBED TO FL280 WBOUND AND DUE TO THE DEV THE PLANES WERE GOING TO BE LTSS APART. ALTERNATE INSTRUCTIONS WERE ISSUED TO ACR Y TO STOP HIS CLB AT FL270 AND THE ACR X TO MAINTAIN FL280. ACR Y FLT WENT THROUGH THE ALT TO FL275 AND THEN BACK DOWN TO FL270.

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.