A C170B pilot was surprised by less than standard separation from an air carrier.

Attributes
ACN	358708
Time
Date	199701
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : uin
State Reference	IL
Altitude	agl bound lower : 8100 agl bound upper : 8200
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : pia
Operator	general aviation : personal
Make Model Name	Cessna 170
Operating Under FAR Part	Part 91
Flight Phase	descent other
Flight Plan	None
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	other : unknown
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : atp pilot : cfi
Experience	flight time last 90 days : 20 flight time total : 20000 flight time type : 300
ASRS Report	358708
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe conflict : airborne less severe
Independent Detector	other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	Other
Miss Distance	horizontal : 700 vertical : 200
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	other

Narrative:

Descending VFR. Transponder mode C reported inoperative 30 mins before. Had declined flight following from pia approach. Destination remote grass strip. I had not seen other aircraft, probably due to blind spot behind right door post area. Difference in speed. I don't think other aircraft was aware of me. Future action -- more methodical scanning around blind spots and better use of flight following and monitoring center frequency.

Original NASA ASRS Text

Title: A C170B PLT WAS SURPRISED BY LTSS FROM AN ACR.

Narrative: DSNDING VFR. XPONDER MODE C RPTED INOP 30 MINS BEFORE. HAD DECLINED FLT FOLLOWING FROM PIA APCH. DEST REMOTE GRASS STRIP. I HAD NOT SEEN OTHER ACFT, PROBABLY DUE TO BLIND SPOT BEHIND R DOOR POST AREA. DIFFERENCE IN SPD. I DON'T THINK OTHER ACFT WAS AWARE OF ME. FUTURE ACTION -- MORE METHODICAL SCANNING AROUND BLIND SPOTS AND BETTER USE OF FLT FOLLOWING AND MONITORING CTR FREQ.

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.