Air carrier captain reported receiving a GPWS alert during departure after turning too early.

Attributes
ACN	1500896
Time
Date	201712
Local Time Of Day	1201-1800
Place
Locale Reference	IAD.Tower
State Reference	DC
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Large Transport
Operating Under FAR Part	Part 121
Flight Phase	Initial Climb
Route In Use	SID JCOBY THREE
Flight Plan	IFR
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Total 5020
Events
Anomaly	Deviation - Procedural FAR Deviation - Procedural Published Material / Policy Deviation - Procedural Clearance Deviation - Track / Heading All Types Inflight Event / Encounter CFTT / CFIT

Narrative:

We were initially assigned the jcoby 3 departure out of iad. When cleared for takeoff from runway 30 we were assigned heading 320. At 400 ft I turned to heading 320. In the turn we had GPWS 'too low terrain'. I went toga and we climbed out with no other terrain indications. Being distracted by this I went off course of the departure and ATC asked if we were on the departure. We replied we were correcting to it. At altitude I reviewed the departure and saw that instructions are to climb to 820 ft before turning. Once ATC gave me the heading on takeoff I mentally did away with the departure and this was my error.

Original NASA ASRS Text

Title: Air Carrier Captain reported receiving a GPWS alert during departure after turning too early.

Narrative: We were initially assigned the JCOBY 3 departure out of IAD. When cleared for takeoff from runway 30 we were assigned heading 320. At 400 ft I turned to heading 320. In the turn we had GPWS 'too low terrain'. I went TOGA and we climbed out with no other terrain indications. Being distracted by this I went off course of the departure and ATC asked if we were on the departure. We replied we were correcting to it. At altitude I reviewed the departure and saw that instructions are to climb to 820 ft before turning. Once ATC gave me the heading on takeoff I mentally did away with the departure and this was my error.

Data retrieved from NASA's ASRS site 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.