Narrative:

Working departure radar with numerous deviations for WX. Air carrier X checked on climbing to 9000 ft on a summa 5 departure. Climbed to 15000 ft after radar identify. Later pilot asked to deviation west for WX, assigned 250 degree heading. Pilot later requested 220 degree heading and this was approved. Air carrier Y inbound on olm arrival level 10000 ft. Air carrier X was under inbound leg. Air carrier X advised could take turn and asked to confirm assigned altitude. Observed air carrier X climbing through 9200 ft. Issued 9000 ft a turn to 120 degree of traffic at 12 O'clock, 3 mi, 10000 ft. Separation lost. Air carrier X should have been stopped immediately at 9000 ft when deviation requested due to proximity to inbound leg. A traffic call at earlier time could have cued a reiteration of altitude and corrected (prevented) situation. Supplemental information from acn 273729: first officer flying on departure out of seatac air carrier X cleared to 9000 ft. At about 5 DME from seatac I asked and received deviation west for WX. At some point the first officer thought he heard us cleared to 15000 ft in association with a turn. He then armed 15000 ft. I didn't notice this till about 8000 ft. I asked him about it and then called ATC to verify an assigned altitude. When they didn't respond right away, I pushed altitude hold. ATC then said we were assigned 9000 ft and shortly after told us to turn left for traffic at about the same time our TCASII announced 'traffic.' I also got a visual on the air carrier Y. I then took control of the aircraft and uncoupled the autoplt and increase the bank angle. During these maneuvers the aircraft climbed as high as 9400 ft. I also think that in maneuvering to avoid the aircraft, I had visual I may have climbed a couple of hundred ft. After landing talked to ATC in sea.

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Original NASA ASRS Text

Title: ACR X CLB THROUGH OCCUPIED ALT HAD LTSS FROM ACR Y. SYS ERROR.

Narrative: WORKING DEP RADAR WITH NUMEROUS DEVS FOR WX. ACR X CHKED ON CLBING TO 9000 FT ON A SUMMA 5 DEP. CLBED TO 15000 FT AFTER RADAR IDENT. LATER PLT ASKED TO DEV W FOR WX, ASSIGNED 250 DEG HDG. PLT LATER REQUESTED 220 DEG HDG AND THIS WAS APPROVED. ACR Y INBOUND ON OLM ARR LEVEL 10000 FT. ACR X WAS UNDER INBOUND LEG. ACR X ADVISED COULD TAKE TURN AND ASKED TO CONFIRM ASSIGNED ALT. OBSERVED ACR X CLBING THROUGH 9200 FT. ISSUED 9000 FT A TURN TO 120 DEG OF TFC AT 12 O'CLOCK, 3 MI, 10000 FT. SEPARATION LOST. ACR X SHOULD HAVE BEEN STOPPED IMMEDIATELY AT 9000 FT WHEN DEV REQUESTED DUE TO PROX TO INBOUND LEG. A TFC CALL AT EARLIER TIME COULD HAVE CUED A REITERATION OF ALT AND CORRECTED (PREVENTED) SIT. SUPPLEMENTAL INFO FROM ACN 273729: FO FLYING ON DEP OUT OF SEATAC ACR X CLRED TO 9000 FT. AT ABOUT 5 DME FROM SEATAC I ASKED AND RECEIVED DEV W FOR WX. AT SOME POINT THE FO THOUGHT HE HEARD US CLRED TO 15000 FT IN ASSOCIATION WITH A TURN. HE THEN ARMED 15000 FT. I DIDN'T NOTICE THIS TILL ABOUT 8000 FT. I ASKED HIM ABOUT IT AND THEN CALLED ATC TO VERIFY AN ASSIGNED ALT. WHEN THEY DIDN'T RESPOND RIGHT AWAY, I PUSHED ALT HOLD. ATC THEN SAID WE WERE ASSIGNED 9000 FT AND SHORTLY AFTER TOLD US TO TURN L FOR TFC AT ABOUT THE SAME TIME OUR TCASII ANNOUNCED 'TFC.' I ALSO GOT A VISUAL ON THE ACR Y. I THEN TOOK CTL OF THE ACFT AND UNCOUPLED THE AUTOPLT AND INCREASE THE BANK ANGLE. DURING THESE MANEUVERS THE ACFT CLBED AS HIGH AS 9400 FT. I ALSO THINK THAT IN MANEUVERING TO AVOID THE ACFT, I HAD VISUAL I MAY HAVE CLBED A COUPLE OF HUNDRED FT. AFTER LNDG TALKED TO ATC IN SEA.

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.