B737 crew had track deviation.

Attributes
ACN	443170
Time
Date	199907
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : sea.vortac
State Reference	WA
Altitude	msl single value : 4000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : s46.tracon
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	other other vortac
Flight Phase	climbout : vacating altitude
Route In Use	departure sid : mountain 4
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	443170
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : multi engine pilot : commercial
ASRS Report	443174
Events
Anomaly	non adherence : clearance non adherence : company policies non adherence : published procedure other spatial deviation
Independent Detector	other flight crewa
Resolutory Action	controller : issued alert controller : issued new clearance
Supplementary
Problem Areas	Flight Crew Human Performance Company Aircraft
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Early turn on SID. During a mountain 4 departure from sea from runway 34L, turned at 6.6 DME above the required 4000 ft instead of the published 8 DME. During preflight study of the departure, the captain misread the DME for the turn and when constructing an FMS waypoint to aid in departure orientation, entered 5 DME instead of the correct 8 DME. ATC advised us that we had turned early and then gave us vector on course. Nothing else was said about the early turn.

Original NASA ASRS Text

Title: B737 CREW HAD TRACK DEV.

Narrative: EARLY TURN ON SID. DURING A MOUNTAIN 4 DEP FROM SEA FROM RWY 34L, TURNED AT 6.6 DME ABOVE THE REQUIRED 4000 FT INSTEAD OF THE PUBLISHED 8 DME. DURING PREFLT STUDY OF THE DEP, THE CAPT MISREAD THE DME FOR THE TURN AND WHEN CONSTRUCTING AN FMS WAYPOINT TO AID IN DEP ORIENTATION, ENTERED 5 DME INSTEAD OF THE CORRECT 8 DME. ATC ADVISED US THAT WE HAD TURNED EARLY AND THEN GAVE US VECTOR ON COURSE. NOTHING ELSE WAS SAID ABOUT THE EARLY TURN.

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.