Potential conflict. 1 aircraft with TCASII, the other not.

Attributes
ACN	285029
Time
Date	199410
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ard
State Reference	PA
Altitude	msl bound lower : 12500 msl bound upper : 12500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : n90
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 135
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	VFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 4700 flight time type : 4300
ASRS Report	285029
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	conflict : airborne less severe other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 3000 vertical : 500
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

In level cruise flight at 12500 ft, visually contacted traffic at our 10 O'clock position, approximately 2 mi on collision course. Immediately initiated descending right turn. Other aircraft maintained its heading but also initiated descent. At the time of occurrence, we were receiving traffic advisories from ATC. Through post occurrence discussion on the frequency it became apparent that the other aircraft was responding to commands from its TCASII. We were not TCASII equipped. (Several seconds after initiating our evasive maneuver ATC alerted us to the traffic including that the other aircraft was climbing.) one noteworthy observation is that in the unique situation where a conflict exists between a TCASII equipped and a non- TCASII equipped aircraft where the non-TCASII equipped pilot first makes visual contact and initiates evasion the TCASII system can actually work against collision avoidance. Here I assume, the TCASII command was based on our aircraft maintaining level flight and was slow in recognizing our descent, also, the controller claimed the other aircraft was in a climb, presumably just before it started its descent. Much greater separation would have resulted if the other aircraft had not responded to TCASII and stayed its course and climb.

Original NASA ASRS Text

Title: POTENTIAL CONFLICT. 1 ACFT WITH TCASII, THE OTHER NOT.

Narrative: IN LEVEL CRUISE FLT AT 12500 FT, VISUALLY CONTACTED TFC AT OUR 10 O'CLOCK POS, APPROX 2 MI ON COLLISION COURSE. IMMEDIATELY INITIATED DSNDING R TURN. OTHER ACFT MAINTAINED ITS HDG BUT ALSO INITIATED DSCNT. AT THE TIME OF OCCURRENCE, WE WERE RECEIVING TFC ADVISORIES FROM ATC. THROUGH POST OCCURRENCE DISCUSSION ON THE FREQ IT BECAME APPARENT THAT THE OTHER ACFT WAS RESPONDING TO COMMANDS FROM ITS TCASII. WE WERE NOT TCASII EQUIPPED. (SEVERAL SECONDS AFTER INITIATING OUR EVASIVE MANEUVER ATC ALERTED US TO THE TFC INCLUDING THAT THE OTHER ACFT WAS CLBING.) ONE NOTEWORTHY OBSERVATION IS THAT IN THE UNIQUE SIT WHERE A CONFLICT EXISTS BTWN A TCASII EQUIPPED AND A NON- TCASII EQUIPPED ACFT WHERE THE NON-TCASII EQUIPPED PLT FIRST MAKES VISUAL CONTACT AND INITIATES EVASION THE TCASII SYS CAN ACTUALLY WORK AGAINST COLLISION AVOIDANCE. HERE I ASSUME, THE TCASII COMMAND WAS BASED ON OUR ACFT MAINTAINING LEVEL FLT AND WAS SLOW IN RECOGNIZING OUR DSCNT, ALSO, THE CTLR CLAIMED THE OTHER ACFT WAS IN A CLB, PRESUMABLY JUST BEFORE IT STARTED ITS DSCNT. MUCH GREATER SEPARATION WOULD HAVE RESULTED IF THE OTHER ACFT HAD NOT RESPONDED TO TCASII AND STAYED ITS COURSE AND CLB.

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.