Close proximity air carrier-small transport GA-small aircraft 20 NM south of bna.

Attributes
ACN	169794
Time
Date	199102
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : bna
State Reference	TN
Altitude	msl bound lower : 4500 msl bound upper : 4500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : bna
Operator	common carrier : air carrier
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	descent other
Route In Use	enroute : on vectors enroute : direct
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Aircraft, High Wing, 1 Eng, Fixed Gear
Flight Phase	cruise other
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : commercial pilot : atp
Experience	flight time last 90 days : 180 flight time total : 3000 flight time type : 1300
ASRS Report	169794
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Experience	flight time last 90 days : 200 flight time total : 2700 flight time type : 430
ASRS Report	169633
Events
Anomaly	conflict : airborne less severe non adherence : far
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted
Consequence	Other
Miss Distance	horizontal : 200 vertical : 0
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	other

Narrative:

At approximately 4500' MSL in a normal rate descent I saw a high wing small aircraft at our 10 O'clock, same altitude. Judging by the closure rate, I kept descending normally while watching the other aircraft. The small aircraft closed to approximately 200' horizontal and moved from our 10 O'clock to 7 O'clock position, at which time it appeared to pull up to avoid us. ATC was notified immediately at my first sighting of the small aircraft, when I saw it at 10 O'clock position. We were informed that 'it just popped up,' after which we were given vectors for bna. We were on an IFR flight plan which requires horizontal and vertical sep from all traffic, regardless of WX conditions. I personally find it hard to believe that the small aircraft 'just popped up,' considering it's altitude of 4500' MSL. In my view, there must have been a primary target on ATC radar, even if the small aircraft did not use a transponder--especially when both aircraft were so near a terminal airport area.

Original NASA ASRS Text

Title: CLOSE PROX ACR-SMT GA-SMA 20 NM SOUTH OF BNA.

Narrative: AT APPROX 4500' MSL IN A NORMAL RATE DSNT I SAW A HIGH WING SMA AT OUR 10 O'CLOCK, SAME ALT. JUDGING BY THE CLOSURE RATE, I KEPT DSNDING NORMALLY WHILE WATCHING THE OTHER ACFT. THE SMA CLOSED TO APPROX 200' HORIZ AND MOVED FROM OUR 10 O'CLOCK TO 7 O'CLOCK POS, AT WHICH TIME IT APPEARED TO PULL UP TO AVOID US. ATC WAS NOTIFIED IMMEDIATELY AT MY FIRST SIGHTING OF THE SMA, WHEN I SAW IT AT 10 O'CLOCK POS. WE WERE INFORMED THAT 'IT JUST POPPED UP,' AFTER WHICH WE WERE GIVEN VECTORS FOR BNA. WE WERE ON AN IFR FLT PLAN WHICH REQUIRES HORIZ AND VERT SEP FROM ALL TFC, REGARDLESS OF WX CONDITIONS. I PERSONALLY FIND IT HARD TO BELIEVE THAT THE SMA 'JUST POPPED UP,' CONSIDERING IT'S ALT OF 4500' MSL. IN MY VIEW, THERE MUST HAVE BEEN A PRIMARY TARGET ON ATC RADAR, EVEN IF THE SMA DID NOT USE A XPONDER--ESPECIALLY WHEN BOTH ACFT WERE SO NEAR A TERMINAL ARPT AREA.

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.