Heading track deviation on departure procedure.

Attributes
ACN	192779
Time
Date	199110
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sea
State Reference	WA
Altitude	msl bound lower : 4000 msl bound upper : 6000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sea
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	climbout : intermediate altitude cruise other
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 : instrument pilot : atp pilot : cfi pilot : flight engineer
Experience	flight time last 90 days : 150 flight time total : 10000 flight time type : 1000
ASRS Report	192779
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	non adherence : clearance non adherence : published procedure other spatial deviation
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

I programmed FMS to fly summa SID out of sea runway 34L. SID called for tracking out sea R-338 degree to 8 DME, then right turn to 070 degree heading. FMS began turn at about 6 1/2-7 DME to lead turn, taking into account turn radius, instead of flying to 8 DME and then starting turn. I'll have to watch out for this trick next time.

Original NASA ASRS Text

Title: HDG TRACK DEV ON DEP PROC.

Narrative: I PROGRAMMED FMS TO FLY SUMMA SID OUT OF SEA RWY 34L. SID CALLED FOR TRACKING OUT SEA R-338 DEG TO 8 DME, THEN R TURN TO 070 DEG HDG. FMS BEGAN TURN AT ABOUT 6 1/2-7 DME TO LEAD TURN, TAKING INTO ACCOUNT TURN RADIUS, INSTEAD OF FLYING TO 8 DME AND THEN STARTING TURN. I'LL HAVE TO WATCH OUT FOR THIS TRICK NEXT TIME.

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.