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Air carrier X descent to occupied altitude had less than standard separation from air carrier Y. System error.
| Attributes | |
| ACN | 309090 |
| Time | |
| Date | 199507 |
| Day | Sat |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : rjaa |
| State Reference | FO |
| Altitude | msl bound lower : 35000 msl bound upper : 35000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : rjtg tower : ack |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other |
| Flight Phase | cruise other |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise other |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 200 flight time total : 12500 flight time type : 6000 |
| ASRS Report | 309090 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 120 flight time total : 7000 flight time type : 350 |
| ASRS Report | 310288 |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : published procedure non adherence : required legal separation |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | none taken : detected after the fact |
| Consequence | Other |
| Miss Distance | horizontal : 99999 vertical : 0 |
| Supplementary | |
| Air Traffic Incident | Operational Error |
Narrative:
Air carrier X shortly after passing calma we requested descent to FL350 and received it. Very shortly after reaching FL350 air carrier Y asked us if we could see the aircraft behind him at FL350. We had talked earlier when he passed below us and he assumed we were at FL370 yet. The target on his TCASII was intermittent. He said the target was 30 mi behind him. We were the target. Shortly after that ATC cleared us to FL330 due to traffic. When queried about traffic we were told it was air carrier Y. The only reason we caught the loss of separation was Y's TCASII. Some of these type sits could be avoided by having TCASII with a range greater than we currently have. Supplemental information from acn 310288: after passing 'calma' we requested descent to FL350 and received clearance. After reaching FL350 Y asked us on pacific remote (128.95) if we could see the aircraft at FL350 behind him at 30 NM, displayed on his TCASII. That aircraft was us. Shortly after that tokyo radio cleared us to FL330 'due to traffic.' we queried tokyo about the traffic and were told it was Y. TCASII with greater range capability caught this error. Nopac separation standards say 10 mins or less with mach technique applied.
Original NASA ASRS Text
Title: ACR X DSCNT TO OCCUPIED ALT HAD LTSS FROM ACR Y. SYS ERROR.
Narrative: ACR X SHORTLY AFTER PASSING CALMA WE REQUESTED DSCNT TO FL350 AND RECEIVED IT. VERY SHORTLY AFTER REACHING FL350 ACR Y ASKED US IF WE COULD SEE THE ACFT BEHIND HIM AT FL350. WE HAD TALKED EARLIER WHEN HE PASSED BELOW US AND HE ASSUMED WE WERE AT FL370 YET. THE TARGET ON HIS TCASII WAS INTERMITTENT. HE SAID THE TARGET WAS 30 MI BEHIND HIM. WE WERE THE TARGET. SHORTLY AFTER THAT ATC CLRED US TO FL330 DUE TO TFC. WHEN QUERIED ABOUT TFC WE WERE TOLD IT WAS ACR Y. THE ONLY REASON WE CAUGHT THE LOSS OF SEPARATION WAS Y'S TCASII. SOME OF THESE TYPE SITS COULD BE AVOIDED BY HAVING TCASII WITH A RANGE GREATER THAN WE CURRENTLY HAVE. SUPPLEMENTAL INFO FROM ACN 310288: AFTER PASSING 'CALMA' WE REQUESTED DSCNT TO FL350 AND RECEIVED CLRNC. AFTER REACHING FL350 Y ASKED US ON PACIFIC REMOTE (128.95) IF WE COULD SEE THE ACFT AT FL350 BEHIND HIM AT 30 NM, DISPLAYED ON HIS TCASII. THAT ACFT WAS US. SHORTLY AFTER THAT TOKYO RADIO CLRED US TO FL330 'DUE TO TFC.' WE QUERIED TOKYO ABOUT THE TFC AND WERE TOLD IT WAS Y. TCASII WITH GREATER RANGE CAPABILITY CAUGHT THIS ERROR. NOPAC SEPARATION STANDARDS SAY 10 MINS OR LESS WITH MACH TECHNIQUE APPLIED.
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.