Small aircraft overtaken by jet flying below the TCA floor. Near midair collision.

Attributes
ACN	190595
Time
Date	199110
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sea
State Reference	WA
Altitude	msl bound lower : 2800 msl bound upper : 2800
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sea tower : pit
Operator	general aviation : personal
Make Model Name	Small Aircraft
Flight Phase	cruise other
Flight Plan	VFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	descent : approach descent other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : private
Experience	flight time last 90 days : 12 flight time total : 168 flight time type : 140
ASRS Report	190595
Person 2
Affiliation	Other
Function	observation : passenger
Qualification	other other : other
Events
Anomaly	conflict : nmac other anomaly other
Independent Detector	other other : unspecified cockpit
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 300 vertical : 100
Supplementary
Primary Problem	Flight Crew Human Performance

Narrative:

I was in level flight below the seattle TCA. My passenger, upon turning around to place personal items in the back seta of my small aircraft, warned me of a large aircraft overtaking me from the rear. When I looked and saw what might occur, I took evasive action by climbing and turning away from the large jet. I estimate it passed approximately 100 ft below and 300 ft behind my previous location. In my opinion this situation would have been prevented if the large jet had been required to remain within the seattle TCA while on approach to seatac.

Original NASA ASRS Text

Title: SMA OVERTAKEN BY JET FLYING BELOW THE TCA FLOOR. NMAC.

Narrative: I WAS IN LEVEL FLT BELOW THE SEATTLE TCA. MY PAX, UPON TURNING AROUND TO PLACE PERSONAL ITEMS IN THE BACK SETA OF MY SMA, WARNED ME OF A LARGE ACFT OVERTAKING ME FROM THE REAR. WHEN I LOOKED AND SAW WHAT MIGHT OCCUR, I TOOK EVASIVE ACTION BY CLBING AND TURNING AWAY FROM THE LARGE JET. I ESTIMATE IT PASSED APPROX 100 FT BELOW AND 300 FT BEHIND MY PREVIOUS LOCATION. IN MY OPINION THIS SITUATION WOULD HAVE BEEN PREVENTED IF THE LARGE JET HAD BEEN REQUIRED TO REMAIN WITHIN THE SEATTLE TCA WHILE ON APCH TO SEATAC.

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.