PA28 has close encounter with B737 near gary; in.

Attributes
ACN	675122
Time
Date	200510
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : gyy.airport
State Reference	IN
Altitude	msl single value : 5200
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : c90.tracon
Operator	general aviation : personal
Make Model Name	PA-28 Cherokee/Archer II/Dakota/Pillan/Warrior
Operating Under FAR Part	Part 91
Flight Phase	descent : intermediate altitude
Flight Plan	None
Aircraft 2
Controlling Facilities	tracon : c90.tracon
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : commercial
Experience	flight time last 90 days : 20 flight time total : 400 flight time type : 100
ASRS Report	675122
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	conflict : airborne critical
Independent Detector	other flight crewa
Resolutory Action	none taken : detected after the fact
Supplementary
Problem Areas	Airspace Structure ATC Human Performance Flight Crew Human Performance
Primary Problem	Airspace Structure

Narrative:

I decided as we got close to gary; in; to go up the lake front to get out of the headwinds as I flew to 10C. We turned to the northwest about 10 NM southeast of gyy and started our descent from 6500 ft to 3500 ft as we went over gary and then past gary to 2500 ft to avoid the chicago class B airspace. Normally; the big iron comes into ord class B airspace at about 7000-8000 ft MSL; but as we passed through 5200 ft MSL; 2 NM south of gary; something big passed right underneath me only about 500 ft lower. It was a B737. He came from my 5 O'clock position; that is in my blind spot; but I did not see him until he had passed underneath me and was at my 11 O'clock position. He must have seen me on TCAS and dove below me to avoid hitting us. I told my passenger to take a look back in that direction in case ord was lining up approachs that way and there were more planes. Fortunately; there were none. I had just set my altimeter to gary's setting from their ATIS and doublechked my altitude. I rechked it and it was set correctly. I was not inside the class B airspace. I had been on flight following when I was in south bend's airspace; but they had canceled earlier when I left and entered chicago's airspace. Normally; I do not even try to get flight following around ord and it is rare that the TRACON will give it to you. They simply are too busy.

Original NASA ASRS Text

Title: PA28 HAS CLOSE ENCOUNTER WITH B737 NEAR GARY; IN.

Narrative: I DECIDED AS WE GOT CLOSE TO GARY; IN; TO GO UP THE LAKE FRONT TO GET OUT OF THE HEADWINDS AS I FLEW TO 10C. WE TURNED TO THE NW ABOUT 10 NM SE OF GYY AND STARTED OUR DSCNT FROM 6500 FT TO 3500 FT AS WE WENT OVER GARY AND THEN PAST GARY TO 2500 FT TO AVOID THE CHICAGO CLASS B AIRSPACE. NORMALLY; THE BIG IRON COMES INTO ORD CLASS B AIRSPACE AT ABOUT 7000-8000 FT MSL; BUT AS WE PASSED THROUGH 5200 FT MSL; 2 NM S OF GARY; SOMETHING BIG PASSED RIGHT UNDERNEATH ME ONLY ABOUT 500 FT LOWER. IT WAS A B737. HE CAME FROM MY 5 O'CLOCK POS; THAT IS IN MY BLIND SPOT; BUT I DID NOT SEE HIM UNTIL HE HAD PASSED UNDERNEATH ME AND WAS AT MY 11 O'CLOCK POS. HE MUST HAVE SEEN ME ON TCAS AND DOVE BELOW ME TO AVOID HITTING US. I TOLD MY PAX TO TAKE A LOOK BACK IN THAT DIRECTION IN CASE ORD WAS LINING UP APCHS THAT WAY AND THERE WERE MORE PLANES. FORTUNATELY; THERE WERE NONE. I HAD JUST SET MY ALTIMETER TO GARY'S SETTING FROM THEIR ATIS AND DOUBLECHKED MY ALT. I RECHKED IT AND IT WAS SET CORRECTLY. I WAS NOT INSIDE THE CLASS B AIRSPACE. I HAD BEEN ON FLT FOLLOWING WHEN I WAS IN SOUTH BEND'S AIRSPACE; BUT THEY HAD CANCELED EARLIER WHEN I LEFT AND ENTERED CHICAGO'S AIRSPACE. NORMALLY; I DO NOT EVEN TRY TO GET FLT FOLLOWING AROUND ORD AND IT IS RARE THAT THE TRACON WILL GIVE IT TO YOU. THEY SIMPLY ARE TOO BUSY.

Data retrieved from NASA's ASRS site as of January 2009 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.