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Air carrier Y descent through occupied altitude had less than standard separation from air carrier X. Same company similar a/north. System error.
| Attributes | |
| ACN | 218728 |
| Time | |
| Date | 199208 |
| Day | Wed |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : gdm |
| State Reference | MA |
| Altitude | msl bound lower : 19000 msl bound upper : 21000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | artcc : zbw |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Flight Phase | other |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | common carrier : air carrier |
| Make Model Name | Widebody, Low Wing, 3 Turbojet Eng |
| Flight Phase | descent other other |
| Route In Use | enroute : on vectors |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : radar |
| ASRS Report | 218728 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 180 flight time total : 20000 flight time type : 3000 |
| ASRS Report | 219073 |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : published procedure non adherence : required legal separation |
| Independent Detector | other flight crewa |
| Resolutory Action | controller : issued new clearance other |
| Consequence | faa : investigated |
| Miss Distance | horizontal : 18000 vertical : 0 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
Same company air carrier X FL200, air carrier Y FL210 both in a holding pattern. I issued a descent to air carrier Y to 190 thinking I had cleared air carrier X to 190. Later, air carrier X questioned position. As I was issuing traffic (11 O'clock and 3 mi) air carrier Y mode C went to 207. I cleared air carrier Y to maintain 210 and verify level. He said he had been descending but would climb to 210. I descended air carrier X. Supplemental information from acn 219073: air carrier Y holding VMC over gardner VOR. Descending in the holding pattern a couple thousand ft at a time. Flying outbound at FL230 ZBW said maintain present heading for turn back toward bos and descend to FL190. Both pilots heard 190 and copilot repeated 190 back to the controller. Same company air carrier X was holding at FL190. He could see us visually and sensed something was wrong so he questioned the controller. Controller then told us to maintain 210. We climbed back from approximately 19.6 to 210 and told controller we had read back 190 to her. No further response from controller on the matter.
Original NASA ASRS Text
Title: ACR Y DSCNT THROUGH OCCUPIED ALT HAD LTSS FROM ACR X. SAME COMPANY SIMILAR A/N. SYS ERROR.
Narrative: SAME COMPANY ACR X FL200, ACR Y FL210 BOTH IN A HOLDING PATTERN. I ISSUED A DSCNT TO ACR Y TO 190 THINKING I HAD CLRED ACR X TO 190. LATER, ACR X QUESTIONED POS. AS I WAS ISSUING TFC (11 O'CLOCK AND 3 MI) ACR Y MODE C WENT TO 207. I CLRED ACR Y TO MAINTAIN 210 AND VERIFY LEVEL. HE SAID HE HAD BEEN DSNDING BUT WOULD CLB TO 210. I DSNDED ACR X. SUPPLEMENTAL INFO FROM ACN 219073: ACR Y HOLDING VMC OVER GARDNER VOR. DSNDING IN THE HOLDING PATTERN A COUPLE THOUSAND FT AT A TIME. FLYING OUTBOUND AT FL230 ZBW SAID MAINTAIN PRESENT HDG FOR TURN BACK TOWARD BOS AND DSND TO FL190. BOTH PLTS HEARD 190 AND COPLT REPEATED 190 BACK TO THE CTLR. SAME COMPANY ACR X WAS HOLDING AT FL190. HE COULD SEE US VISUALLY AND SENSED SOMETHING WAS WRONG SO HE QUESTIONED THE CTLR. CTLR THEN TOLD US TO MAINTAIN 210. WE CLBED BACK FROM APPROX 19.6 TO 210 AND TOLD CTLR WE HAD READ BACK 190 TO HER. NO FURTHER RESPONSE FROM CTLR ON THE MATTER.
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.