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ARTCC controller had less than standard separation while descending an medium large transport through altitude of large transport.
| Attributes | |
| ACN | 85251 |
| Time | |
| Date | 198804 |
| Day | Mon |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : bos |
| State Reference | MA |
| Altitude | msl bound lower : 16000 msl bound upper : 16000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zbw tower : dtw |
| Operator | common carrier : air carrier |
| Make Model Name | Large Transport, Low Wing, 3 Turbojet Eng |
| Flight Phase | climbout : intermediate altitude cruise other |
| Route In Use | enroute : on vectors enroute airway : zbw |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | general aviation : corporate |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Flight Phase | descent other |
| Route In Use | enroute : on vectors |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : radar |
| ASRS Report | 85251 |
| Person 2 | |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : required legal separation |
| Independent Detector | atc equipment other atc equipment : unspecified other controllera |
| Resolutory Action | controller : issued new clearance other |
| Consequence | Other |
| Miss Distance | horizontal : 28080 vertical : 0 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
Medium large transport Y was handed off to me descending from FL240 to 150. Large transport X was handed off to me from approach control climbing to 14000'. Using the computer ground speeds and the J circle (5 mi circle used at center for sep). I observed medium large transport Y at 350 KTS and large transport X at 330 KTS. Large transport X was intrail and to the left of medium large transport Y be a measured 7 mi. I climbed large transport X to his requested altitude of 16000' and he leveled off. Speeds still remained constant for both. About 1 min later I descended medium large transport Y to 11000' as he was landing at bdl airport, which was about another 50 mi. As medium large transport Y went below FL180 descending to 11000' his ground speed dropped to 330 KTS. At about this time large transport X increased his ground speed to 390 KTS. I turned both aircraft 260 degrees heading to medium large transport Y and 240 degree heading to large transport X. Minimum sep went to 4.68 mi as altitudes passed and then increased because of the headings. No evasive action was needed. Had I known of the speed changes I would have assigned indicated speeds to both aircraft. The controllers' handbook and the airmen's information manual both state that the pilot is required to tell ATC of speed changes of more than 10 KTS. Also large transport X company has its own order out for their aircraft to fly a 300 IAS for fuel savings. Large transport X had to be doing around 350 IAS.
Original NASA ASRS Text
Title: ARTCC CTLR HAD LESS THAN STANDARD SEPARATION WHILE DESCENDING AN MLG THROUGH ALT OF LGT.
Narrative: MLG Y WAS HANDED OFF TO ME DSNDING FROM FL240 TO 150. LGT X WAS HANDED OFF TO ME FROM APCH CTL CLBING TO 14000'. USING THE COMPUTER GND SPDS AND THE J CIRCLE (5 MI CIRCLE USED AT CENTER FOR SEP). I OBSERVED MLG Y AT 350 KTS AND LGT X AT 330 KTS. LGT X WAS INTRAIL AND TO THE LEFT OF MLG Y BE A MEASURED 7 MI. I CLBED LGT X TO HIS REQUESTED ALT OF 16000' AND HE LEVELED OFF. SPDS STILL REMAINED CONSTANT FOR BOTH. ABOUT 1 MIN LATER I DSNDED MLG Y TO 11000' AS HE WAS LNDG AT BDL ARPT, WHICH WAS ABOUT ANOTHER 50 MI. AS MLG Y WENT BELOW FL180 DSNDING TO 11000' HIS GND SPD DROPPED TO 330 KTS. AT ABOUT THIS TIME LGT X INCREASED HIS GND SPD TO 390 KTS. I TURNED BOTH ACFT 260 DEGS HDG TO MLG Y AND 240 DEG HDG TO LGT X. MINIMUM SEP WENT TO 4.68 MI AS ALTS PASSED AND THEN INCREASED BECAUSE OF THE HDGS. NO EVASIVE ACTION WAS NEEDED. HAD I KNOWN OF THE SPD CHANGES I WOULD HAVE ASSIGNED INDICATED SPDS TO BOTH ACFT. THE CTLRS' HANDBOOK AND THE AIRMEN'S INFO MANUAL BOTH STATE THAT THE PLT IS REQUIRED TO TELL ATC OF SPD CHANGES OF MORE THAN 10 KTS. ALSO LGT X COMPANY HAS ITS OWN ORDER OUT FOR THEIR ACFT TO FLY A 300 IAS FOR FUEL SAVINGS. LGT X HAD TO BE DOING AROUND 350 IAS.
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.