B737 captain reported being confused with either to follow the local control instruction or the depa...

Narrative:

Initially cleared to 'climb via' an RNAV SID on the pre departure clearance. Iad tower issued a heading in the takeoff clearance without restating the altitude. If vectored off a SID with previous clearance to 'climb via' a new altitude clearance must accompany the vector.upon check-in with departure control; they immediately cleared us direct to the first point on the SID.two issues:1) tower needs to give an altitude along with the heading if they're going to vector us off a 'climb via' SID.2) why is tower giving us a heading if departure control puts us right back on the SID 30 seconds later?this is the third report filed for the same issue at iad.

Original NASA ASRS Text

Title: B737 Captain reported being confused with either to follow the Local Control instruction or the Departure Control instruction of being on a vector or climbing via a SID. This is the third time the reporter has had this problem at IAD.

Narrative: Initially cleared to 'climb via' an RNAV SID on the PDC. IAD tower issued a heading in the takeoff clearance without restating the altitude. If vectored off a SID with previous clearance to 'climb via' a new altitude clearance must accompany the vector.Upon check-in with departure control; they immediately cleared us direct to the first point on the SID.Two issues:1) Tower needs to give an altitude along with the heading if they're going to vector us off a 'climb via' SID.2) Why is tower giving us a heading if departure control puts us right back on the SID 30 seconds later?This is the third report filed for the same issue at IAD.

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.

Attributes
ACN	1374633
Time
Date	201607
Place
Locale Reference	IAD.Airport
State Reference	DC
Aircraft 1
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Initial Climb Takeoff
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	ATC Issue All Types Deviation - Procedural Published Material / Policy Deviation - Track / Heading All Types

B737 captain reported being confused with either to follow the local control instruction or the departure control instruction of being on a vector or climbing via a SID. This is the third time the reporter has had this problem at iad.