Narrative:

Air carrier X was inbound to sfo on the runway 28 profile descent. After crossing the 34 DME fix on the oak 151 degree right, at 250 KTS (charted), a descent was begun to 6000'. Shortly after beginning the descent, approach control requested a reduction in airspeed to 210 KTS. The rate of descent was reduced to effect the airspeed reduction and at approximately 28 DME the airspeed was stabilized at 210 KIAS and descent was resulted at a normal rate through 9500'. At this time the approach controller, in an excited voice, ordered 'expedite your descent to 6000' immediately.' the PF pushed the nose down and extended the speed brakes. The controller then issued traffic at 11 O'clock and 3 mi, head-on, passing through 9500'. We acquired the traffic visually and no evasive action was required. At this time we were descending through 8000'. This potential near miss could have been avoided if the controller had issued a more specific descent clearance than that specified on the profile descent procedure to ensure sep from the opp direction traffic. Also, controllers should anticipate that a change in airspeed from the charted speed during an arrival procedure can considerably alter the vertical profile of the procedure.

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Original NASA ASRS Text

Title: ACR X FAILED TO COMPLY WITH ATC CLRNC AND DESCEND TO ASSIGNED ALT IN A TIMELY MANNER.

Narrative: ACR X WAS INBND TO SFO ON THE RWY 28 PROFILE DSNT. AFTER XING THE 34 DME FIX ON THE OAK 151 DEG R, AT 250 KTS (CHARTED), A DSNT WAS BEGUN TO 6000'. SHORTLY AFTER BEGINNING THE DSNT, APCH CTL REQUESTED A REDUCTION IN AIRSPD TO 210 KTS. THE RATE OF DSNT WAS REDUCED TO EFFECT THE AIRSPD REDUCTION AND AT APPROX 28 DME THE AIRSPD WAS STABILIZED AT 210 KIAS AND DSNT WAS RESULTED AT A NORMAL RATE THROUGH 9500'. AT THIS TIME THE APCH CTLR, IN AN EXCITED VOICE, ORDERED 'EXPEDITE YOUR DSNT TO 6000' IMMEDIATELY.' THE PF PUSHED THE NOSE DOWN AND EXTENDED THE SPD BRAKES. THE CTLR THEN ISSUED TFC AT 11 O'CLOCK AND 3 MI, HEAD-ON, PASSING THROUGH 9500'. WE ACQUIRED THE TFC VISUALLY AND NO EVASIVE ACTION WAS REQUIRED. AT THIS TIME WE WERE DSNDING THROUGH 8000'. THIS POTENTIAL NEAR MISS COULD HAVE BEEN AVOIDED IF THE CTLR HAD ISSUED A MORE SPECIFIC DSNT CLRNC THAN THAT SPECIFIED ON THE PROFILE DSNT PROC TO ENSURE SEP FROM THE OPP DIRECTION TFC. ALSO, CTLRS SHOULD ANTICIPATE THAT A CHANGE IN AIRSPD FROM THE CHARTED SPD DURING AN ARR PROC CAN CONSIDERABLY ALTER THE VERT PROFILE OF THE PROC.

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.