B777 captain reported unclear instructions from ATC.

Attributes
ACN	1651362
Time
Date	201906
Place
Locale Reference	SFO.Airport
State Reference	CA
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B777 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	STAR PIRAT2
Flight Plan	IFR
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument
Experience	Flight Crew Last 90 Days 179 Flight Crew Total 13106 Flight Crew Type 1635
Events
Anomaly	ATC Issue All Types Deviation - Procedural Published Material / Policy

Narrative:

Have a procedural complaint about new arrival into sfo. The PIRAT2 RNAV arrival is new and for a while was not being used by ATC. Old arrival procedure was direct pirat - cross pirat at 10;000 [feet]. New procedure has numerous step down fixes; altitudes; and speeds. Today we were filed PIRAT2 and when we got in radar contact with oakland; were given direct pirat; cross at 10;000 [feet]. RNAV procedure says pirat 15;000 [feet] or below. Fix prior to pirat has speed at 260 kts.; so we asked 'do you need a speed at pirat?'; ATC says no. So now I'm wondering are we on the arrival or not. ATC never said descend via; or cancel PIRAT2. From pirat on; there are two more fixes/speeds. Do we need to follow the path or not? Now a frequency change and a very busy controller; who say expect vectors for ILS. I was confused as what we should doing. All worked out; but this has happened to me before; and ATC needs to get verbiage correct; i.e. 'Cleared to descend via PIRAT2; except cross pirat at 10;000 [feet]' or something else. I know the fix is to just ask; but sometimes you don't have time to go into a whole dissertation as to what ATC expects.

Original NASA ASRS Text

Title: B777 Captain reported unclear instructions from ATC.

Narrative: Have a procedural complaint about new arrival into SFO. The PIRAT2 RNAV arrival is new and for a while was not being used by ATC. Old arrival procedure was direct PIRAT - cross PIRAT at 10;000 [feet]. New procedure has numerous step down fixes; altitudes; and speeds. Today we were filed PIRAT2 and when we got in radar contact with Oakland; were given direct PIRAT; cross at 10;000 [feet]. RNAV procedure says PIRAT 15;000 [feet] or below. Fix prior to PIRAT has speed at 260 kts.; so we asked 'Do you need a speed at PIRAT?'; ATC says no. So now I'm wondering are we on the arrival or not. ATC never said descend via; or cancel PIRAT2. From PIRAT on; there are two more fixes/speeds. Do we need to follow the path or not? Now a frequency change and a very busy controller; who say expect vectors for ILS. I was confused as what we should doing. All worked out; but this has happened to me before; and ATC needs to get verbiage correct; i.e. 'cleared to descend via PIRAT2; except cross PIRAT at 10;000 [feet]' or something else. I know the fix is to just ask; but sometimes you don't have time to go into a whole dissertation as to what ATC expects.

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.