Narrative:

We were flying into sfo on the modesto 2 arrival. The FMC was programmed for the descent to arrive at cedes at 11000 ft and 250 KTS. Our initial descent clearance was to descend to FL240 at 290 KTS. The first officer was flying and started a capture descent, the profile was captured normally. As we approached the leveloff at FL240 we got a frequency change. I took the change and checked in with the next controller. He responded by giving us a clearance to cross groan at or above 14000 ft to cross cedes at 11000 ft and 230 KTS as well as the altimeter setting. I read back the clearance as the first officer programmed the FMC. The first officer was confused about the clearance and took some time setting up the descent. During the time that it took to level off, change frequencys and set up the new descent, we were high on the profile and had slowed to 250 KTS. The first officer was not correcting the slow speed or high profile fast enough and I suggested going to vertical speed to get back on profile. In the few moments it took to work this out the controller asked our speed. I told him 250 KTS. He asked us to speed up to 300 KTS and asked us why we had slowed. I told him that the airplane had slowed because we had gotten the descent clearance late and the airplane was attempting to make the cedes restr. He asked the air carrier X airplane behind us if they had any problems with the descent and they said they had no problems. He then requested we descend at 320 KTS. We complied with all his requests. He told us we should not slow because he had airplanes behind us. I told him that I was about to tell him our speed when he asked. He was not impressed and again asked why it had happened. He wondered if it was an FMC function. I told him that it was energy management. We got no indication from the controller of any separation infractions, he just seemed annoyed. We were then handed off to sfo approach. Looking back, I realize that I should have done a better job monitoring the PF. We should not have let the FMC slow the aircraft during the leveloff. When I noticed the speed though, I should have told ATC right away. The first officer and I debriefed the problem after the flight and agreed to send in a report. Our debrief revealed that the first officer was concerned about the descent speed because of a restr on the use of speed brakes above 300 KTS on our aircraft. He was hesitant to speed up to make the restr because of his concern for the restr. I was concerned about being high on the profile and the need to speed up and get down. I did not accurately convey this point to him. He did not tell me of his concern for the speed brake restr. We were both initially confused about the change to the profile, and we were too slow in responding to the change the new descent clearance contained 2 altitude restrs, one speed restr and an altimeter setting. They all came after a frequency that occurred as we were leveling off during a profile descent. I saw the need to keep going down and to keep the speed up. The first officer did not sense the urgency and I neglected to point this out to him. We did not match the level of automation to the situation. All these helped to contribute to the speed deviation.

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Original NASA ASRS Text

Title: A B738 CREW, DSNDING INTO SFO, SLOWED TO 250 KTS WITHOUT ADVISING ATC.

Narrative: WE WERE FLYING INTO SFO ON THE MODESTO 2 ARR. THE FMC WAS PROGRAMMED FOR THE DSCNT TO ARRIVE AT CEDES AT 11000 FT AND 250 KTS. OUR INITIAL DSCNT CLRNC WAS TO DSND TO FL240 AT 290 KTS. THE FO WAS FLYING AND STARTED A CAPTURE DSCNT, THE PROFILE WAS CAPTURED NORMALLY. AS WE APCHED THE LEVELOFF AT FL240 WE GOT A FREQ CHANGE. I TOOK THE CHANGE AND CHKED IN WITH THE NEXT CTLR. HE RESPONDED BY GIVING US A CLRNC TO CROSS GROAN AT OR ABOVE 14000 FT TO CROSS CEDES AT 11000 FT AND 230 KTS AS WELL AS THE ALTIMETER SETTING. I READ BACK THE CLRNC AS THE FO PROGRAMMED THE FMC. THE FO WAS CONFUSED ABOUT THE CLRNC AND TOOK SOME TIME SETTING UP THE DSCNT. DURING THE TIME THAT IT TOOK TO LEVEL OFF, CHANGE FREQS AND SET UP THE NEW DSCNT, WE WERE HIGH ON THE PROFILE AND HAD SLOWED TO 250 KTS. THE FO WAS NOT CORRECTING THE SLOW SPD OR HIGH PROFILE FAST ENOUGH AND I SUGGESTED GOING TO VERT SPD TO GET BACK ON PROFILE. IN THE FEW MOMENTS IT TOOK TO WORK THIS OUT THE CTLR ASKED OUR SPD. I TOLD HIM 250 KTS. HE ASKED US TO SPD UP TO 300 KTS AND ASKED US WHY WE HAD SLOWED. I TOLD HIM THAT THE AIRPLANE HAD SLOWED BECAUSE WE HAD GOTTEN THE DSCNT CLRNC LATE AND THE AIRPLANE WAS ATTEMPTING TO MAKE THE CEDES RESTR. HE ASKED THE ACR X AIRPLANE BEHIND US IF THEY HAD ANY PROBS WITH THE DSCNT AND THEY SAID THEY HAD NO PROBS. HE THEN REQUESTED WE DSND AT 320 KTS. WE COMPLIED WITH ALL HIS REQUESTS. HE TOLD US WE SHOULD NOT SLOW BECAUSE HE HAD AIRPLANES BEHIND US. I TOLD HIM THAT I WAS ABOUT TO TELL HIM OUR SPD WHEN HE ASKED. HE WAS NOT IMPRESSED AND AGAIN ASKED WHY IT HAD HAPPENED. HE WONDERED IF IT WAS AN FMC FUNCTION. I TOLD HIM THAT IT WAS ENERGY MGMNT. WE GOT NO INDICATION FROM THE CTLR OF ANY SEPARATION INFRACTIONS, HE JUST SEEMED ANNOYED. WE WERE THEN HANDED OFF TO SFO APCH. LOOKING BACK, I REALIZE THAT I SHOULD HAVE DONE A BETTER JOB MONITORING THE PF. WE SHOULD NOT HAVE LET THE FMC SLOW THE ACFT DURING THE LEVELOFF. WHEN I NOTICED THE SPD THOUGH, I SHOULD HAVE TOLD ATC RIGHT AWAY. THE FO AND I DEBRIEFED THE PROB AFTER THE FLT AND AGREED TO SEND IN A RPT. OUR DEBRIEF REVEALED THAT THE FO WAS CONCERNED ABOUT THE DSCNT SPD BECAUSE OF A RESTR ON THE USE OF SPD BRAKES ABOVE 300 KTS ON OUR ACFT. HE WAS HESITANT TO SPD UP TO MAKE THE RESTR BECAUSE OF HIS CONCERN FOR THE RESTR. I WAS CONCERNED ABOUT BEING HIGH ON THE PROFILE AND THE NEED TO SPD UP AND GET DOWN. I DID NOT ACCURATELY CONVEY THIS POINT TO HIM. HE DID NOT TELL ME OF HIS CONCERN FOR THE SPD BRAKE RESTR. WE WERE BOTH INITIALLY CONFUSED ABOUT THE CHANGE TO THE PROFILE, AND WE WERE TOO SLOW IN RESPONDING TO THE CHANGE THE NEW DSCNT CLRNC CONTAINED 2 ALT RESTRS, ONE SPD RESTR AND AN ALTIMETER SETTING. THEY ALL CAME AFTER A FREQ THAT OCCURRED AS WE WERE LEVELING OFF DURING A PROFILE DSCNT. I SAW THE NEED TO KEEP GOING DOWN AND TO KEEP THE SPD UP. THE FO DID NOT SENSE THE URGENCY AND I NEGLECTED TO POINT THIS OUT TO HIM. WE DID NOT MATCH THE LEVEL OF AUTOMATION TO THE SIT. ALL THESE HELPED TO CONTRIBUTE TO THE SPD DEV.

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.