Potential conflict between 2 departure air carrier lgts on simultaneous departure.

Attributes
ACN	218027
Time
Date	199208
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : sea
State Reference	WA
Altitude	msl bound lower : 2500 msl bound upper : 2500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sea tower : sea
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	climbout : intermediate altitude
Route In Use	departure other departure sid : sid
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	climbout : intermediate altitude
Route In Use	departure other departure sid : sid
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 12000 flight time type : 8000
ASRS Report	218027
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : clearance non adherence : far other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	controller : issued new clearance flight crew : took evasive action other
Consequence	Other
Miss Distance	horizontal : 750 vertical : 750
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation
Situations
ATC Facility	procedure or policy : unspecified

Narrative:

We were cleared after takeoff for a mountain 2 departure which requires a restriction of 4000 at 8 DME north of sea on the 338 degree radial. After gear retraction at 2500 MSL at 3 DME on the sea 338 degree radial, we received a TA message on the TCASII followed by an RA of 'descend, descend.' as I began the maneuver to follow the TCASII advisory, the copilot saw another air carrier large transport twin at our 3 O'clock position very close and above us. The twin was in a climb, but evidently, did not see us. The copilot estimated the large transport Y to be 500 to 1000 ft laterally and 500 to 1000 ft above us. As soon as I reached 0 climb on the vsi, the TCASII 'red line' disappeared and the 'clear of conflict' message was heard. Departure control was informed of our TCASII message and they immediately leveled us at 3000 ft. No further conflict resulted. I believe this incident was caused by the large transport Y's losing sight of us and not informing departure. Also by not being staggered far enough behind us on takeoff. We took off on 34L and the large transport took off a short time later on 34R.

Original NASA ASRS Text

Title: POTENTIAL CONFLICT BTWN 2 DEP ACR LGTS ON SIMULTANEOUS DEP.

Narrative: WE WERE CLRED AFTER TKOF FOR A MOUNTAIN 2 DEP WHICH REQUIRES A RESTRICTION OF 4000 AT 8 DME N OF SEA ON THE 338 DEG RADIAL. AFTER GEAR RETRACTION AT 2500 MSL AT 3 DME ON THE SEA 338 DEG RADIAL, WE RECEIVED A TA MESSAGE ON THE TCASII FOLLOWED BY AN RA OF 'DSND, DSND.' AS I BEGAN THE MANEUVER TO FOLLOW THE TCASII ADVISORY, THE COPLT SAW ANOTHER ACR LGT TWIN AT OUR 3 O'CLOCK POS VERY CLOSE AND ABOVE US. THE TWIN WAS IN A CLB, BUT EVIDENTLY, DID NOT SEE US. THE COPLT ESTIMATED THE LGT Y TO BE 500 TO 1000 FT LATERALLY AND 500 TO 1000 FT ABOVE US. AS SOON AS I REACHED 0 CLB ON THE VSI, THE TCASII 'RED LINE' DISAPPEARED AND THE 'CLR OF CONFLICT' MESSAGE WAS HEARD. DEP CTL WAS INFORMED OF OUR TCASII MESSAGE AND THEY IMMEDIATELY LEVELED US AT 3000 FT. NO FURTHER CONFLICT RESULTED. I BELIEVE THIS INCIDENT WAS CAUSED BY THE LGT Y'S LOSING SIGHT OF US AND NOT INFORMING DEP. ALSO BY NOT BEING STAGGERED FAR ENOUGH BEHIND US ON TKOF. WE TOOK OFF ON 34L AND THE LGT TOOK OFF A SHORT TIME LATER ON 34R.

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.