Narrative:

En route at FL350 we received a clearance to descend FL310 for traffic, cross psp at FL240. We started a descent for FL310 at a rate of 1200 FPM thinking that this was sufficient in that ATC did not request to expedite or be at FL310 by a certain time. Out of approximately FL330, ATC informed us that our descent was not in accordance with the aim, and not to slow our descent. We expedited the descent out of FL310 and continued a normal descent to FL240. We had assumed that a descent over 1000 FPM was all that was required. Now looking back at the aim it requires optimum rate consistent with operating characteristics of the aircraft. Optimum rate would have been about twice as fast. We could have presented a situation for less than minimum sep.

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Original NASA ASRS Text

Title: DESCENT RATE NOT IN ACCORDANCE WITH THE AIM AND THE CTLRS EXPECTATIONS.

Narrative: ENRTE AT FL350 WE RECEIVED A CLRNC TO DSND FL310 FOR TFC, CROSS PSP AT FL240. WE STARTED A DSCNT FOR FL310 AT A RATE OF 1200 FPM THINKING THAT THIS WAS SUFFICIENT IN THAT ATC DID NOT REQUEST TO EXPEDITE OR BE AT FL310 BY A CERTAIN TIME. OUT OF APPROX FL330, ATC INFORMED US THAT OUR DSCNT WAS NOT IN ACCORDANCE WITH THE AIM, AND NOT TO SLOW OUR DSCNT. WE EXPEDITED THE DSCNT OUT OF FL310 AND CONTINUED A NORMAL DSCNT TO FL240. WE HAD ASSUMED THAT A DSCNT OVER 1000 FPM WAS ALL THAT WAS REQUIRED. NOW LOOKING BACK AT THE AIM IT REQUIRES OPTIMUM RATE CONSISTENT WITH OPERATING CHARACTERISTICS OF THE ACFT. OPTIMUM RATE WOULD HAVE BEEN ABOUT TWICE AS FAST. WE COULD HAVE PRESENTED A SITUATION FOR LESS THAN MINIMUM SEP.

Data retrieved from NASA's ASRS site as of August 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.