Flight crew flying the san lyndi 4 STAR was cleared to cross imp at FL240 then cleared to 10;000 ft;...

Narrative:

We were level FL300 outside of imp. We received the lyndi 4 star from la center. Captain was flying he gave me the aircraft to program the FMC. We received a clearance to cross imp at FL240. The captain programmed the FMC I set the MCP. We received descent instruction to 10000 ft and programmed the MCP to 10000 ft on the STAR jackk is 12000B 10000A based on this information and absent of a descend now clearance we believed we were on the correct path for the approach. Then ATC called and ask why we haven't descended having been cleared to 10000 we told him we understood we were cleared the arrival he said no we were not cleared the arrival descend now I hit flch; pulled the power back and pulled full speed brakes. In the descent we received a TA from an aircraft 8000 ft below us. We received a clearance to cross jackk at 10000 ft. We were level 26-25 miles before jackk. Corrective action have the company file for the arrival before the dep. We as pilots could ask the controller and not assume we believe to be true and what he believes to be true. It would of only taken one more radio call on are part and both of us would of been on the same page. Next time I will double check with center so this won't happen again.

Original NASA ASRS Text

Title: Flight crew flying the SAN LYNDI 4 STAR was cleared to cross IMP at FL240 then cleared to 10;000 ft; but assumed ATC meant JACKK at between 12;000 ft and 10;000 ft. ATC informed them they were not cleared to descend via; just descend. During the high rate descent; the TCAS TA alerted.

Narrative: We were level FL300 outside of IMP. We received the LYNDI 4 star from LA center. Captain was flying he gave me the aircraft to program the FMC. We received a clearance to cross IMP at FL240. The Captain programmed the FMC I set the MCP. We received descent instruction to 10000 ft and programmed the MCP to 10000 ft on the STAR JACKK is 12000B 10000A based on this information and absent of a descend now clearance we believed we were on the correct path for the approach. Then ATC called and ask why we haven't descended having been cleared to 10000 we told him we understood we were cleared the arrival he said no we were not cleared the arrival descend now I hit FLCH; pulled the power back and pulled full speed brakes. In the descent we received a TA from an aircraft 8000 ft below us. We received a clearance to cross JACKK at 10000 ft. We were level 26-25 miles before JACKK. Corrective action have the company file for the arrival before the dep. We as pilots could ask the controller and not assume we believe to be true and what he believes to be true. It would of only taken one more radio call on are part and both of us would of been on the same page. Next time I will double check with center so this won't happen again.

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	1311237
Time
Date	201511
Place
Locale Reference	SAN.Airport
State Reference	CA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Widebody Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	STAR LYNDI 4
Flight Plan	IFR
Person 1
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Flight Engineer Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 40 Flight Crew Total 15000 Flight Crew Type 600
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Procedural Clearance Deviation - Procedural FAR

Flight crew flying the san lyndi 4 STAR was cleared to cross imp at FL240 then cleared to 10;000 ft; but assumed ATC meant jackk at between 12;000 ft and 10;000 ft. ATC informed them they were not cleared to descend via; just descend. During the high rate descent; the TCAS TA alerted.