Near midair collision between a DC10 and an unknown aircraft.

Attributes
ACN	307738
Time
Date	199506
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sea
State Reference	WA
Altitude	msl bound lower : 1000 msl bound upper : 1500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : sea
Operator	common carrier : air carrier
Make Model Name	DC-10 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : approach descent other
Route In Use	approach : visual
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	other
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : atp
Experience	flight time last 90 days : 200 flight time total : 5000 flight time type : 500
ASRS Report	307738
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : nmac other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : took evasive action other
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 0 vertical : 400
Supplementary
Primary Problem	Flight Crew Human Performance

Narrative:

After being cleared for visual approach to runway 16L at seatac approximately over boeing field, we received a TCASII advisory of traffic below us in our 10 O'clock position. No visual was established. Soon after we got a TCASII RA to monitor our descent, then to climb. Passing 400 ft above traffic we continued our approach into seatac. With the advisory 'clear' a steep but safe approach and landing was concluded. Upon landing we conversed with ground control which informed us that there is no communication between boeing and seatac for TA's, that boeing traffic is VFR and uncontrolled, that it has always been this way, and that both tower supervisors were concerned. I recommend that all traffic into and out of boeing field be controled until clear of conflicting traffic airspace. The 800 ft traffic pattern at boeing field is apparently violated causing undue danger to landing traffic at seatac. We got absolutely no TA's from the towers. 400 ft vertical separation is unacceptable. A positive control system needs to be established due to the close proximity of the airports. The skies are not big enough any longer.

Original NASA ASRS Text

Title: NMAC BTWN A DC10 AND AN UNKNOWN ACFT.

Narrative: AFTER BEING CLRED FOR VISUAL APCH TO RWY 16L AT SEATAC APPROX OVER BOEING FIELD, WE RECEIVED A TCASII ADVISORY OF TFC BELOW US IN OUR 10 O'CLOCK POS. NO VISUAL WAS ESTABLISHED. SOON AFTER WE GOT A TCASII RA TO MONITOR OUR DSCNT, THEN TO CLB. PASSING 400 FT ABOVE TFC WE CONTINUED OUR APCH INTO SEATAC. WITH THE ADVISORY 'CLR' A STEEP BUT SAFE APCH AND LNDG WAS CONCLUDED. UPON LNDG WE CONVERSED WITH GND CTL WHICH INFORMED US THAT THERE IS NO COM BTWN BOEING AND SEATAC FOR TA'S, THAT BOEING TFC IS VFR AND UNCTLED, THAT IT HAS ALWAYS BEEN THIS WAY, AND THAT BOTH TWR SUPVRS WERE CONCERNED. I RECOMMEND THAT ALL TFC INTO AND OUT OF BOEING FIELD BE CTLED UNTIL CLR OF CONFLICTING TFC AIRSPACE. THE 800 FT TFC PATTERN AT BOEING FIELD IS APPARENTLY VIOLATED CAUSING UNDUE DANGER TO LNDG TFC AT SEATAC. WE GOT ABSOLUTELY NO TA'S FROM THE TWRS. 400 FT VERT SEPARATION IS UNACCEPTABLE. A POSITIVE CTL SYS NEEDS TO BE ESTABLISHED DUE TO THE CLOSE PROX OF THE ARPTS. THE SKIES ARE NOT BIG ENOUGH ANY LONGER.

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.