|37000 Feet||Browse and search NASA's
Aviation Safety Reporting System
|Local Time Of Day||0601 To 1200|
|Locale Reference||airport : sea|
|Altitude||msl bound lower : 1500|
msl bound upper : 1800
|Controlling Facilities||tower : sea|
|Operator||common carrier : air carrier|
|Make Model Name||Large Transport, Low Wing, 3 Turbojet Eng|
|Flight Phase||descent : approach|
|Route In Use||approach : visual|
|Make Model Name||Small Aircraft, Low Wing, 2 Eng, Retractable Gear|
|Affiliation||company : air carrier|
|Function||flight crew : first officer|
|Qualification||pilot : atp|
pilot : flight engineer
|Experience||flight time last 90 days : 210|
flight time total : 4900
flight time type : 210
|Function||flight crew : single pilot|
|Qualification||pilot : private|
|Anomaly||conflict : nmac|
non adherence : published procedure
|Independent Detector||other flight crewa|
|Resolutory Action||none taken : insufficient time|
|Consequence||faa : reviewed incident with flight crew|
|Miss Distance||vertical : 300|
|Primary Problem||Flight Crew Human Performance|
We were cleared the bay visual at sea (16R). On glide slope . Abeam the north end of the runways at boeing field (just inside the 'park' outer marker), we passed directly over a twin small aircraft I immediately asked tower if they had seen the twin on radar. They did not reply, and I asked again. Tower said they did not see the traffic. I was surprised. So I called tower, on the ground and asked why they did not see our traffic. The tower supervisor said that ATC's radar had difficulty picking-up traffic if they were low-level and in our relative position on final. I think that sea has all the ingredients for a midair collision: inadequate radar coverage (insofar as low level VFR traffic is concerned). VFR corridor underlying the floor (1600' MSL) of the TCA. In fact, it underlies the glide slope by only approximately 200 VFR traffic departing nearby boeing field.the field is adjacent to the 16L and 16R approach south to sea. No apparent coordination between towers of either airport where boeing field departures conflict with aircraft making approach to seam. Recommend: lower TCA to surface (vice 1600') all along the 16R ILS final sequence. Get better radar coordination between tower to prevent potential conflicts.
Original NASA ASRS Text
Title: NMAC BETWEEN ACR LGT ON APCH AND GA SMA.
Narrative: WE WERE CLRED THE BAY VISUAL AT SEA (16R). ON GLIDE SLOPE . ABEAM THE NORTH END OF THE RWYS AT BOEING FIELD (JUST INSIDE THE 'PARK' OUTER MARKER), WE PASSED DIRECTLY OVER A TWIN SMA I IMMEDIATELY ASKED TWR IF THEY HAD SEEN THE TWIN ON RADAR. THEY DID NOT REPLY, AND I ASKED AGAIN. TWR SAID THEY DID NOT SEE THE TFC. I WAS SURPRISED. SO I CALLED TWR, ON THE GND AND ASKED WHY THEY DID NOT SEE OUR TFC. THE TWR SUPERVISOR SAID THAT ATC'S RADAR HAD DIFFICULTY PICKING-UP TFC IF THEY WERE LOW-LEVEL AND IN OUR RELATIVE POSITION ON FINAL. I THINK THAT SEA HAS ALL THE INGREDIENTS FOR A MIDAIR COLLISION: INADEQUATE RADAR COVERAGE (INSOFAR AS LOW LEVEL VFR TFC IS CONCERNED). VFR CORRIDOR UNDERLYING THE FLOOR (1600' MSL) OF THE TCA. IN FACT, IT UNDERLIES THE GLIDE SLOPE BY ONLY APPROX 200 VFR TFC DEPARTING NEARBY BOEING FIELD.THE FIELD IS ADJACENT TO THE 16L AND 16R APCH S TO SEA. NO APPARENT COORDINATION BETWEEN TWRS OF EITHER ARPT WHERE BOEING FIELD DEPS CONFLICT WITH ACFT MAKING APCH TO SEAM. RECOMMEND: LOWER TCA TO SURFACE (VICE 1600') ALL ALONG THE 16R ILS FINAL SEQUENCE. GET BETTER RADAR COORDINATION BETWEEN TWR TO PREVENT POTENTIAL CONFLICTS.
Data retrieved from NASA's ASRS site as of August 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.