Air carrier X had less than standard separation from air carrier Y. System error. Air carrier X TCASII RA evasive action taken. Non adherence to ATC clearance. Pilot deviation.

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Attributes
ACN	184731
Time
Date	199107
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : bdl
State Reference	CT
Altitude	msl bound lower : 6000 msl bound upper : 6000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : bdl
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	climbout : intermediate altitude descent : approach descent other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
ASRS Report	184731
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : undershoot conflict : airborne less severe non adherence : required legal separation non adherence : clearance non adherence : published procedure
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera
Resolutory Action	none taken : unable
Consequence	faa : investigated
Miss Distance	horizontal : 12000 vertical : 0
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation Operational Error

Narrative:

Air carrier X was issued a descent from 7000 to 5000 sebound on vectors to bdl ILS runway 24. Air carrier Y on a parallel course descending out of 7600 was instructed to stop descent at 6000 and placed on vectors to follow air carrier X. At approximately 4 1/2 mi from each other, air carrier X responded to a TCASII RA when leaving 5900 and initiated a climb and then a descent. This operational error would not have occurred if air carrier X didn't change from descent to a climb. Eliminate TCASII within 20 mi from landing airport. TCASII issue RA's to unknown traffic on 1200 beacon codes.

Original NASA ASRS Text

Title: ACR X HAD LTSS FROM ACR Y. SYS ERROR. ACR X TCASII RA EVASIVE ACTION TAKEN. NON ADHERENCE TO ATC CLRNC. PLTDEV.

Narrative: ACR X WAS ISSUED A DSCNT FROM 7000 TO 5000 SEBOUND ON VECTORS TO BDL ILS RWY 24. ACR Y ON A PARALLEL COURSE DSNDING OUT OF 7600 WAS INSTRUCTED TO STOP DSCNT AT 6000 AND PLACED ON VECTORS TO FOLLOW ACR X. AT APPROX 4 1/2 MI FROM EACH OTHER, ACR X RESPONDED TO A TCASII RA WHEN LEAVING 5900 AND INITIATED A CLB AND THEN A DSCNT. THIS OPERROR WOULD NOT HAVE OCCURRED IF ACR X DIDN'T CHANGE FROM DSCNT TO A CLB. ELIMINATE TCASII WITHIN 20 MI FROM LNDG ARPT. TCASII ISSUE RA'S TO UNKNOWN TFC ON 1200 BEACON CODES.

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.