Cpr jet given an expedited clearance for descent through 11000 ft. It was at 16000 ft and had not received any descent clearance. ARTCC radar controller had crossing traffic separation based upon that original clearance. Loss of separation occurred. Reporter states that frequency congestion blocked reception.

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Attributes
ACN	371522
Time
Date	199706
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : oak
State Reference	CA
Altitude	msl bound lower : 16000 msl bound upper : 16000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : oak
Operator	general aviation : corporate
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Navigation In Use	Other Other
Flight Phase	cruise other descent other
Route In Use	arrival other enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 4900 flight time type : 280
ASRS Report	371522
Person 2
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : undershoot conflict : airborne less severe non adherence : clearance non adherence : required legal separation other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other other
Consequence	Other
Miss Distance	horizontal : 4000 vertical : 500
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error other

Narrative:

While descending into sfo, we were cleared to 16000 ft. We continued on the course assigned, and next received instructions from the controller to expedite the descent through 11000 ft. We asked him what altitude he wanted us at, that we were assigned 16000 ft, and his reply was to point out B737 traffic crossing right to left. He put us in a 360 degree turn and shortly thereafter, another controller took over. No one ever said whether there was a conflict and I believe someone else may have blocked an altitude change, due to the volume of aircraft on the frequency and number of previous occurrences of blocked xmissions.

Original NASA ASRS Text

Title: CPR JET GIVEN AN EXPEDITED CLRNC FOR DSCNT THROUGH 11000 FT. IT WAS AT 16000 FT AND HAD NOT RECEIVED ANY DSCNT CLRNC. ARTCC RADAR CTLR HAD XING TFC SEPARATION BASED UPON THAT ORIGINAL CLRNC. LOSS OF SEPARATION OCCURRED. RPTR STATES THAT FREQ CONGESTION BLOCKED RECEPTION.

Narrative: WHILE DSNDING INTO SFO, WE WERE CLRED TO 16000 FT. WE CONTINUED ON THE COURSE ASSIGNED, AND NEXT RECEIVED INSTRUCTIONS FROM THE CTLR TO EXPEDITE THE DSCNT THROUGH 11000 FT. WE ASKED HIM WHAT ALT HE WANTED US AT, THAT WE WERE ASSIGNED 16000 FT, AND HIS REPLY WAS TO POINT OUT B737 TFC XING R TO L. HE PUT US IN A 360 DEG TURN AND SHORTLY THEREAFTER, ANOTHER CTLR TOOK OVER. NO ONE EVER SAID WHETHER THERE WAS A CONFLICT AND I BELIEVE SOMEONE ELSE MAY HAVE BLOCKED AN ALT CHANGE, DUE TO THE VOLUME OF ACFT ON THE FREQ AND NUMBER OF PREVIOUS OCCURRENCES OF BLOCKED XMISSIONS.

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.