TCASII logic descended air carrier X through Y after X was above Y.

Attributes
ACN	272478
Time
Date	199405
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : cle
State Reference	OH
Altitude	msl bound lower : 8200 msl bound upper : 8200
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : cle
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	general aviation : personal
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	VFR
Person 1
Affiliation	government : faa
Function	controller : departure
Qualification	controller : radar
Experience	controller radar : 15
ASRS Report	272478
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 : clearance
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 12000 vertical : 0
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I was working departure control at cle. Air carrier X was placed on a radar vector for a climb from 6000 ft to 11000 ft. The vector was issued to 'go behind' a lear Y at 7000 ft. When climb was issued, traffic was also issued to X on the lear and a VFR/1200 at 12 O'clock and 10 mi mode C 8100 ft. When X was above the lear, a vector around the VFR target was offered and accepted by X. X appeared 2 mi lateral (parallel in course) and 100 ft above the VFR intruder when mode C on X began to indicate a descent. The descent created a concern about the lear -- now 5 mi ahead -- 1000 ft below -- and slowing speed for sequence into cle. There was no mention by flight crew of responding to an RA. It appears that TCASII issued a descent RA to a TCASII aircraft established above and assigned lower altitude than the intruder aircraft.

Original NASA ASRS Text

Title: TCASII LOGIC DSNDED ACR X THROUGH Y AFTER X WAS ABOVE Y.

Narrative: I WAS WORKING DEP CTL AT CLE. ACR X WAS PLACED ON A RADAR VECTOR FOR A CLB FROM 6000 FT TO 11000 FT. THE VECTOR WAS ISSUED TO 'GO BEHIND' A LEAR Y AT 7000 FT. WHEN CLB WAS ISSUED, TFC WAS ALSO ISSUED TO X ON THE LEAR AND A VFR/1200 AT 12 O'CLOCK AND 10 MI MODE C 8100 FT. WHEN X WAS ABOVE THE LEAR, A VECTOR AROUND THE VFR TARGET WAS OFFERED AND ACCEPTED BY X. X APPEARED 2 MI LATERAL (PARALLEL IN COURSE) AND 100 FT ABOVE THE VFR INTRUDER WHEN MODE C ON X BEGAN TO INDICATE A DSCNT. THE DSCNT CREATED A CONCERN ABOUT THE LEAR -- NOW 5 MI AHEAD -- 1000 FT BELOW -- AND SLOWING SPD FOR SEQUENCE INTO CLE. THERE WAS NO MENTION BY FLC OF RESPONDING TO AN RA. IT APPEARS THAT TCASII ISSUED A DSCNT RA TO A TCASII ACFT ESTABLISHED ABOVE AND ASSIGNED LOWER ALT THAN THE INTRUDER ACFT.

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.