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An acd DC10-30 flight crew has an near midair collision with VFR traffic that appears to be climbing. Flight crew follows their RA and clears the traffic and continues to sea.
| Attributes | |
| ACN | 343078 |
| Time | |
| Date | 199608 |
| Day | Sat |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : sea |
| State Reference | WA |
| Altitude | msl bound lower : 12500 msl bound upper : 13000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zse |
| Operator | common carrier : air carrier |
| Make Model Name | DC-10 30 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other |
| Flight Phase | descent other |
| Route In Use | arrival other arrival star : star |
| Flight Plan | IFR |
| Aircraft 2 | |
| Make Model Name | Any Unknown or Unlisted Aircraft Manufacturer |
| Operating Under FAR Part | Part 91 |
| Flight Phase | climbout : intermediate altitude cruise other |
| Flight Plan | VFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : flight engineer pilot : atp pilot : private |
| Experience | flight time last 90 days : 200 flight time total : 19500 flight time type : 1700 |
| ASRS Report | 343078 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : commercial pilot : instrument |
| Events | |
| Anomaly | conflict : nmac other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa |
| Resolutory Action | flight crew : took evasive action |
| Consequence | Other |
| Miss Distance | horizontal : 0 vertical : 400 |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
Narrative:
Cleared to cross 'jaksn' intersection on glasr arrival at sea-tac. While descending through 13500 ft, we were issued a possible VFR target at 11 O'clock, 12500 ft and 2 mi out. I began to level off at 13000 ft as a precaution, while we looked for the aircraft. TCASII suddenly gave us an RA to 'climb now,' which we complied with. Saw target aircraft at same instant right below and just ahead of us. Vertical separation according to TCASII was 400 ft. During climb, at 14000 ft, TCASII issued 'clear of conflict.' no further problems. The entire occurrence, start to finish was probably less than 2 mins. The original 'heads-up' call of possible traffic by the controller allowed me to start slowing my descent rate and level at 13000 ft, while looking outside for traffic. RA from TCASII was just as advertised, and in this case probably prevented a midair. Sea-tac airport had earlier been landing to south, runway 16R, which requires a 'jaksn' crossing of 12000 ft, but had switched runways to landing north, runway 34R, which requires a 16000 ft crossing. Controller wasn't aware of the runway change, and was still issuing the 12000 ft altitude to arrs.
Original NASA ASRS Text
Title: AN ACD DC10-30 FLC HAS AN NMAC WITH VFR TFC THAT APPEARS TO BE CLBING. FLC FOLLOWS THEIR RA AND CLRS THE TFC AND CONTINUES TO SEA.
Narrative: CLRED TO CROSS 'JAKSN' INTXN ON GLASR ARR AT SEA-TAC. WHILE DSNDING THROUGH 13500 FT, WE WERE ISSUED A POSSIBLE VFR TARGET AT 11 O'CLOCK, 12500 FT AND 2 MI OUT. I BEGAN TO LEVEL OFF AT 13000 FT AS A PRECAUTION, WHILE WE LOOKED FOR THE ACFT. TCASII SUDDENLY GAVE US AN RA TO 'CLB NOW,' WHICH WE COMPLIED WITH. SAW TARGET ACFT AT SAME INSTANT RIGHT BELOW AND JUST AHEAD OF US. VERT SEPARATION ACCORDING TO TCASII WAS 400 FT. DURING CLB, AT 14000 FT, TCASII ISSUED 'CLR OF CONFLICT.' NO FURTHER PROBS. THE ENTIRE OCCURRENCE, START TO FINISH WAS PROBABLY LESS THAN 2 MINS. THE ORIGINAL 'HEADS-UP' CALL OF POSSIBLE TFC BY THE CTLR ALLOWED ME TO START SLOWING MY DSCNT RATE AND LEVEL AT 13000 FT, WHILE LOOKING OUTSIDE FOR TFC. RA FROM TCASII WAS JUST AS ADVERTISED, AND IN THIS CASE PROBABLY PREVENTED A MIDAIR. SEA-TAC ARPT HAD EARLIER BEEN LNDG TO S, RWY 16R, WHICH REQUIRES A 'JAKSN' XING OF 12000 FT, BUT HAD SWITCHED RWYS TO LNDG N, RWY 34R, WHICH REQUIRES A 16000 FT XING. CTLR WASN'T AWARE OF THE RWY CHANGE, AND WAS STILL ISSUING THE 12000 FT ALT TO ARRS.
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.