An air carrier medium large transport turned to avoid a possible TCASII alert activation.

Attributes
ACN	250981
Time
Date	199308
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : etx airport : abe
State Reference	PA
Altitude	msl bound lower : 11000 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	cruise other cruise other
Route In Use	enroute airway : abe
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : cfi pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 250 flight time total : 6000 flight time type : 1000
ASRS Report	250981
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : clearance non adherence : far other anomaly other other spatial deviation
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : took evasive action other
Consequence	Other
Miss Distance	horizontal : 500 vertical : 500
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Approach control advised us that there would be traffic climbing to 500 ft below our altitude. We picked up traffic on TCASII display verifying approach control advisory. At that time the aircraft was about 10 mi in front of us, no visual yet. We are cruising at 320 KTS. TCASII issued traffic warning. Still no visual. At 5 mi with TCASII showing a climb on target, the captain called approach control, advised them we are turning to avoid the target. Approach control said that there is no need for that, due to the fact that the target aircraft was assigned 500 ft below our altitude. At this point, I saw the target aircraft pass off our right side 3 O'clock position by 500 ft maximum and below us. If the aircraft hadn't turned, I'm sure the target would have turned into an RA and issued a climb command. The captain tried to explain that at 320 KTS we wouldn't have had any time to react if the target was off his assigned altitude. There was no other traffic on the TCASII. Approach control should have given us a short turn to avoid the climbing traffic. We never went more than a mi on our deviation.

Original NASA ASRS Text

Title: AN ACR MLG TURNED TO AVOID A POSSIBLE TCASII ALERT ACTIVATION.

Narrative: APCH CTL ADVISED US THAT THERE WOULD BE TFC CLBING TO 500 FT BELOW OUR ALT. WE PICKED UP TFC ON TCASII DISPLAY VERIFYING APCH CTL ADVISORY. AT THAT TIME THE ACFT WAS ABOUT 10 MI IN FRONT OF US, NO VISUAL YET. WE ARE CRUISING AT 320 KTS. TCASII ISSUED TFC WARNING. STILL NO VISUAL. AT 5 MI WITH TCASII SHOWING A CLB ON TARGET, THE CAPT CALLED APCH CTL, ADVISED THEM WE ARE TURNING TO AVOID THE TARGET. APCH CTL SAID THAT THERE IS NO NEED FOR THAT, DUE TO THE FACT THAT THE TARGET ACFT WAS ASSIGNED 500 FT BELOW OUR ALT. AT THIS POINT, I SAW THE TARGET ACFT PASS OFF OUR R SIDE 3 O'CLOCK POS BY 500 FT MAX AND BELOW US. IF THE ACFT HADN'T TURNED, I'M SURE THE TARGET WOULD HAVE TURNED INTO AN RA AND ISSUED A CLB COMMAND. THE CAPT TRIED TO EXPLAIN THAT AT 320 KTS WE WOULDN'T HAVE HAD ANY TIME TO REACT IF THE TARGET WAS OFF HIS ASSIGNED ALT. THERE WAS NO OTHER TFC ON THE TCASII. APCH CTL SHOULD HAVE GIVEN US A SHORT TURN TO AVOID THE CLBING TFC. WE NEVER WENT MORE THAN A MI ON OUR DEV.

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.