Narrative:

We were at cruise (27000 ft) just below redline airspeed. Center asked our airspeed. We replied 275 KIAS. Center asked if we could increase airspeed. We replied negative. They did not ask us to maintain any particular airspeed nor indicate a relative airspeed such as 'maintain best forward speed.' they then asked an airline to maintain 250 KTS for spacing. They did not indicate to either of us who the spacing was from. Although we assumed it was us. Some time later, we were given a descent to FL240. As we had been just on top at FL270, the descent put us into the clouds and subsequent moderate turbulence. The passenger were unable to avoid spilling their drinks. I slowed the aircraft to 220 KTS and stabilized the descent. We then checked on the passenger. I would estimate 1 min passed during this time. We then advised ATC we had slowed to 220 KTS. We did not hear any discussion on the frequency, which would have indicated a reduction in spacing was occurring. After a min or 2 further we were given a phone number to call upon landing. During the phone call we were told there had been no violation of separation standards, but that we should have advised ATC of our speed reduction sooner, as the airliner was gaining on us at 100-110 KTS. We asked how that could be if he was assigned 250 KTS (only 30 KTS faster than we were going). ATC replied that they were descending him on top of us and he probably couldn't slow down that much in the descent. At no time on the radio did we hear the airline claim he couldn't comply with the speed restr. I guess in the future I will advise ATC on speed changes sooner. But I would also expect ATC to advise me if they need a certain speed for separation. I would also expect the pilot of the other aircraft to advise ATC if he is unable to comply with an assigned airspeed.

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Original NASA ASRS Text

Title: CPR JET REDUCED SPD WITHOUT INFORMING ATC. SPD DEV.

Narrative: WE WERE AT CRUISE (27000 FT) JUST BELOW REDLINE AIRSPD. CTR ASKED OUR AIRSPD. WE REPLIED 275 KIAS. CTR ASKED IF WE COULD INCREASE AIRSPD. WE REPLIED NEGATIVE. THEY DID NOT ASK US TO MAINTAIN ANY PARTICULAR AIRSPD NOR INDICATE A RELATIVE AIRSPD SUCH AS 'MAINTAIN BEST FORWARD SPD.' THEY THEN ASKED AN AIRLINE TO MAINTAIN 250 KTS FOR SPACING. THEY DID NOT INDICATE TO EITHER OF US WHO THE SPACING WAS FROM. ALTHOUGH WE ASSUMED IT WAS US. SOME TIME LATER, WE WERE GIVEN A DSCNT TO FL240. AS WE HAD BEEN JUST ON TOP AT FL270, THE DSCNT PUT US INTO THE CLOUDS AND SUBSEQUENT MODERATE TURB. THE PAX WERE UNABLE TO AVOID SPILLING THEIR DRINKS. I SLOWED THE ACFT TO 220 KTS AND STABILIZED THE DSCNT. WE THEN CHKED ON THE PAX. I WOULD ESTIMATE 1 MIN PASSED DURING THIS TIME. WE THEN ADVISED ATC WE HAD SLOWED TO 220 KTS. WE DID NOT HEAR ANY DISCUSSION ON THE FREQ, WHICH WOULD HAVE INDICATED A REDUCTION IN SPACING WAS OCCURRING. AFTER A MIN OR 2 FURTHER WE WERE GIVEN A PHONE NUMBER TO CALL UPON LNDG. DURING THE PHONE CALL WE WERE TOLD THERE HAD BEEN NO VIOLATION OF SEPARATION STANDARDS, BUT THAT WE SHOULD HAVE ADVISED ATC OF OUR SPD REDUCTION SOONER, AS THE AIRLINER WAS GAINING ON US AT 100-110 KTS. WE ASKED HOW THAT COULD BE IF HE WAS ASSIGNED 250 KTS (ONLY 30 KTS FASTER THAN WE WERE GOING). ATC REPLIED THAT THEY WERE DSNDING HIM ON TOP OF US AND HE PROBABLY COULDN'T SLOW DOWN THAT MUCH IN THE DSCNT. AT NO TIME ON THE RADIO DID WE HEAR THE AIRLINE CLAIM HE COULDN'T COMPLY WITH THE SPD RESTR. I GUESS IN THE FUTURE I WILL ADVISE ATC ON SPD CHANGES SOONER. BUT I WOULD ALSO EXPECT ATC TO ADVISE ME IF THEY NEED A CERTAIN SPD FOR SEPARATION. I WOULD ALSO EXPECT THE PLT OF THE OTHER ACFT TO ADVISE ATC IF HE IS UNABLE TO COMPLY WITH AN ASSIGNED AIRSPD.

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.