TCASII gave faulty information in a see and be seen situation.

Attributes
ACN	264956
Time
Date	199402
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : atl
State Reference	GA
Altitude	msl bound lower : 13000 msl bound upper : 13400
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
Navigation In Use	Other
Flight Phase	climbout : intermediate altitude cruise other
Route In Use	enroute airway : atl
Flight Plan	IFR
Aircraft 2
Make Model Name	Beechcraft Twin Piston Undifferentiated or Other Model
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Person 1
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : commercial pilot : flight engineer pilot : instrument pilot : atp
Experience	flight time last 90 days : 200 flight time total : 4600 flight time type : 1600
ASRS Report	264956
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance other anomaly other other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 900 vertical : 700
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Departure control called VFR traffic 12 O'clock, 8 mi, indicating 14400 ft 'do you have him in sight.' TCASII warned 'traffic, traffic' and all 5 pairs of eyes (3 pilots, 1 FAA ATC jumpseater, 1 deadhead pilot jumpseater) went outside. Approximately 30 seconds later (at 13400 ft MSL), TCASII gave a monitor vertical speed' and first officer and so spotted traffic at 12 - 12: 30 position, twin (beech?) left wing high (right turn) very slightly above us (800 ft). Captain initiated descent and left turn and TCASII told us to 'climb, climb.' we passed about 700 ft below and 800þ1000 ft horizontal to traffic, descending to 13000 ft and turning 25-30 degrees off direct course. TCASII gave bad resolution, but maybe departure could have given us some avoidance turn a bit sooner. All of us were operating legally, and had we leveled off at 14000 ft we would have missed by 400 ft or so (providing the other aircraft wasn't descending, but why risk it?) see and be seen in a busy departure corridor doesn't always work! I suggest further emphasis to VFR pilots to request flight following, particularly when transiting certain busy departure rtes and especially when VFR around major hub airports. While both aircraft were operating legally, the likelihood of an in-flight collision was very high in this case -- and really the captain used outstanding cockpit resource management skills by descending and turning based on input from first officer and so, as the center windshield post blocked his view of the other aircraft initially.

Original NASA ASRS Text

Title: TCASII GAVE FAULTY INFO IN A SEE AND BE SEEN SIT.

Narrative: DEP CTL CALLED VFR TFC 12 O'CLOCK, 8 MI, INDICATING 14400 FT 'DO YOU HAVE HIM IN SIGHT.' TCASII WARNED 'TFC, TFC' AND ALL 5 PAIRS OF EYES (3 PLTS, 1 FAA ATC JUMPSEATER, 1 DEADHEAD PLT JUMPSEATER) WENT OUTSIDE. APPROX 30 SECONDS LATER (AT 13400 FT MSL), TCASII GAVE A MONITOR VERT SPD' AND FO AND SO SPOTTED TFC AT 12 - 12: 30 POS, TWIN (BEECH?) L WING HIGH (R TURN) VERY SLIGHTLY ABOVE US (800 FT). CAPT INITIATED DSCNT AND L TURN AND TCASII TOLD US TO 'CLB, CLB.' WE PASSED ABOUT 700 FT BELOW AND 800þ1000 FT HORIZ TO TFC, DSNDING TO 13000 FT AND TURNING 25-30 DEGS OFF DIRECT COURSE. TCASII GAVE BAD RESOLUTION, BUT MAYBE DEP COULD HAVE GIVEN US SOME AVOIDANCE TURN A BIT SOONER. ALL OF US WERE OPERATING LEGALLY, AND HAD WE LEVELED OFF AT 14000 FT WE WOULD HAVE MISSED BY 400 FT OR SO (PROVIDING THE OTHER ACFT WASN'T DSNDING, BUT WHY RISK IT?) SEE AND BE SEEN IN A BUSY DEP CORRIDOR DOESN'T ALWAYS WORK! I SUGGEST FURTHER EMPHASIS TO VFR PLTS TO REQUEST FLT FOLLOWING, PARTICULARLY WHEN TRANSITING CERTAIN BUSY DEP RTES AND ESPECIALLY WHEN VFR AROUND MAJOR HUB ARPTS. WHILE BOTH ACFT WERE OPERATING LEGALLY, THE LIKELIHOOD OF AN INFLT COLLISION WAS VERY HIGH IN THIS CASE -- AND REALLY THE CAPT USED OUTSTANDING COCKPIT RESOURCE MGMNT SKILLS BY DSNDING AND TURNING BASED ON INPUT FROM FO AND SO, AS THE CTR WINDSHIELD POST BLOCKED HIS VIEW OF THE OTHER ACFT INITIALLY.

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.