Large transport in climb had near midair collision with small transport twin.

Attributes
ACN	191553
Time
Date	199110
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : sac
State Reference	CA
Altitude	msl bound lower : 9400 msl bound upper : 9600
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	climbout : intermediate altitude
Route In Use	enroute airway : zoa
Flight Plan	IFR
Aircraft 2
Operator	general aviation : personal
Make Model Name	Small Transport
Flight Phase	cruise other
Flight Plan	None
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : atp
Experience	flight time last 90 days : 250 flight time total : 6800 flight time type : 800
ASRS Report	191553
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : instrument pilot : atp
Experience	flight time last 90 days : 50 flight time total : 7000 flight time type : 50
ASRS Report	191183
Events
Anomaly	conflict : nmac non adherence : far other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 100 vertical : 200
Supplementary
Primary Problem	Flight Crew Human Performance

Narrative:

I was working as the first officer on flight from sfo to ord on oct/sun/91. On the climb out we were on a 038 heading to sac VOR on the 218 radial, 18 DME, climbed to 9600 ft. TCASII advised traffic, traffic. I then positioned TCASII on the 10 mi range from 20 mi and saw target at 12:30/-02 ft. Immediately we got the TCASII climb, climb. The captain (flying) pulled back to approximately 2000-2500 FPM till we received the monitor vertical speed. The so saw a low wing twin pass by our 1:30-2 O'clock position. We then asked ATC about that traffic and their response was they saw what they called a pop-up traffic at 9400 ft (then disappeared). I believe the light twin was flying in the TCA without calling anyone at 9400 ft. When he saw us he then pitched down and turned his transponder (off or stand by). I believe had we not had TCASII there would have been a possibility of contact. TCASII should be enforced on all aircraft.

Original NASA ASRS Text

Title: LGT IN CLB HAD NMAC WITH SMT TWIN.

Narrative: I WAS WORKING AS THE FO ON FLT FROM SFO TO ORD ON OCT/SUN/91. ON THE CLBOUT WE WERE ON A 038 HDG TO SAC VOR ON THE 218 RADIAL, 18 DME, CLBED TO 9600 FT. TCASII ADVISED TFC, TFC. I THEN POSITIONED TCASII ON THE 10 MI RANGE FROM 20 MI AND SAW TARGET AT 12:30/-02 FT. IMMEDIATELY WE GOT THE TCASII CLB, CLB. THE CAPT (FLYING) PULLED BACK TO APPROX 2000-2500 FPM TILL WE RECEIVED THE MONITOR VERT SPD. THE SO SAW A LOW WING TWIN PASS BY OUR 1:30-2 O'CLOCK POS. WE THEN ASKED ATC ABOUT THAT TFC AND THEIR RESPONSE WAS THEY SAW WHAT THEY CALLED A POP-UP TFC AT 9400 FT (THEN DISAPPEARED). I BELIEVE THE LIGHT TWIN WAS FLYING IN THE TCA WITHOUT CALLING ANYONE AT 9400 FT. WHEN HE SAW US HE THEN PITCHED DOWN AND TURNED HIS TRANSPONDER (OFF OR STAND BY). I BELIEVE HAD WE NOT HAD TCASII THERE WOULD HAVE BEEN A POSSIBILITY OF CONTACT. TCASII SHOULD BE ENFORCED ON ALL 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.