Narrative:

We had been cleared to proceed direct to byi, a VOR on the route segment which we had been assigned to fly. Just after we had gone over the byi VOR ZLC assigned us a crossing restr of 20 mi southeast of byi, at FL310. Our operating altitude was then FL370. I entered byi/117/20 into the FMC, and set FL310 on the MCP of the aircraft. At that time, I noticed that we were 14.4 mi from our point to be crossed at FL310. The controller was saturated, never answered us, went right on to other flts. Frequency congestion was high, and I was unable to contact the controller to advise him that we would not be able to comply with this altitude restr. If I might be allowed to give some figures which illustrate our problem, we were about 420 KTS on our ground speed, or 7 mi per min. At the time we started down, we were about 14.0 mi or less from our restr point. This gives 2 min or less to lose 6000 ft of altitude. While this may be done in some aircraft, it is not possible and should not be necessary to have to lose 3000 ft of altitude per min to comply with a clearance with proper anticipation of the controller/crew. My frustration was being given a clearance with which I was unable to comply with and then not being able to convey this to the controller in a timely manner. In over 20 yrs of airline flying, this is the first time this has ever occurred in my career. It is my hope that it will never happen again. A pilot has to be allowed to respond to a controller's clearance, rather than being given the clearance by a controller, then determining that the clearance cannot be met but not being able to convey this to the controller due to frequency congestion.

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Original NASA ASRS Text

Title: B767 FAILS TO MEET ALT XING RESTR SE OF BYI.

Narrative: WE HAD BEEN CLRED TO PROCEED DIRECT TO BYI, A VOR ON THE RTE SEGMENT WHICH WE HAD BEEN ASSIGNED TO FLY. JUST AFTER WE HAD GONE OVER THE BYI VOR ZLC ASSIGNED US A XING RESTR OF 20 MI SE OF BYI, AT FL310. OUR OPERATING ALT WAS THEN FL370. I ENTERED BYI/117/20 INTO THE FMC, AND SET FL310 ON THE MCP OF THE ACFT. AT THAT TIME, I NOTICED THAT WE WERE 14.4 MI FROM OUR POINT TO BE CROSSED AT FL310. THE CTLR WAS SATURATED, NEVER ANSWERED US, WENT RIGHT ON TO OTHER FLTS. FREQ CONGESTION WAS HIGH, AND I WAS UNABLE TO CONTACT THE CTLR TO ADVISE HIM THAT WE WOULD NOT BE ABLE TO COMPLY WITH THIS ALT RESTR. IF I MIGHT BE ALLOWED TO GIVE SOME FIGURES WHICH ILLUSTRATE OUR PROB, WE WERE ABOUT 420 KTS ON OUR GND SPD, OR 7 MI PER MIN. AT THE TIME WE STARTED DOWN, WE WERE ABOUT 14.0 MI OR LESS FROM OUR RESTR POINT. THIS GIVES 2 MIN OR LESS TO LOSE 6000 FT OF ALT. WHILE THIS MAY BE DONE IN SOME ACFT, IT IS NOT POSSIBLE AND SHOULD NOT BE NECESSARY TO HAVE TO LOSE 3000 FT OF ALT PER MIN TO COMPLY WITH A CLRNC WITH PROPER ANTICIPATION OF THE CTLR/CREW. MY FRUSTRATION WAS BEING GIVEN A CLRNC WITH WHICH I WAS UNABLE TO COMPLY WITH AND THEN NOT BEING ABLE TO CONVEY THIS TO THE CTLR IN A TIMELY MANNER. IN OVER 20 YRS OF AIRLINE FLYING, THIS IS THE FIRST TIME THIS HAS EVER OCCURRED IN MY CAREER. IT IS MY HOPE THAT IT WILL NEVER HAPPEN AGAIN. A PLT HAS TO BE ALLOWED TO RESPOND TO A CTLR'S CLRNC, RATHER THAN BEING GIVEN THE CLRNC BY A CTLR, THEN DETERMINING THAT THE CLRNC CANNOT BE MET BUT NOT BEING ABLE TO CONVEY THIS TO THE CTLR DUE TO FREQ CONGESTION.

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.