|37000 Feet||Browse and search NASA's
Aviation Safety Reporting System
|Local Time Of Day||1201 To 1800|
|Locale Reference||navaid : zzz.vor|
|Altitude||msl bound lower : 35000|
msl bound upper : 35300
|Controlling Facilities||artcc : zzz.artcc|
|Operator||common carrier : air carrier|
|Make Model Name||MD-83|
|Operating Under FAR Part||Part 121|
|Navigation In Use||other vortac|
|Flight Phase||cruise : enroute altitude change|
|Controlling Facilities||artcc : zzz.artcc|
|Make Model Name||Any Unknown or Unlisted Aircraft Manufacturer|
|Flight Phase||cruise : level|
|Affiliation||company : air carrier|
|Function||flight crew : captain|
oversight : pic
|Anomaly||conflict : nmac|
non adherence : required legal separation
|Independent Detector||other flight crewa|
|Resolutory Action||flight crew : took evasive action|
|Miss Distance||horizontal : 0|
vertical : 400
|Problem Areas||ATC Human Performance|
|Primary Problem||ATC Human Performance|
|Air Traffic Incident||Operational Error|
ATC gave us instructions to descend from FL360 to FL350. As we started descent; we noticed opposite direction TCAS traffic heading directly towards us at FL350. I think the traffic distance was then about 10-14 mi on the TCAS scale. My initial thinking was that this traffic should also be descending. As we passed about FL354; we noticed that the traffic was now highlighted on the TCAS display; and we were on a perfect head-on collision course. During this time we were unable to question the controller due to constant radio chatter. The TCAS traffic warning alert then sounded; then after about 2-3 seconds; TCAS traffic climb RA warning sounded. At the time of the RA; we were in an approximately 600-800 FPM descent. I think the range to traffic was now about 5 mi and closing fast and TCAS showed threat aircraft about 300 ft below us. I immediately disconnected the autoplt; and started the required climb. As we re-leveled at FL360; the controller then realized the conflict and with urgency in his voice; he instructed us to maintain FL360. I believe he also initially asked us to turn about 80 degrees left; towards the west. As the traffic zoomed underneath and past us; I explained to the controller that his earlier instruction to have us descend to FL350 placed us directly into conflict with head-on traffic. The controller responded 'the other aircraft was deviating and that he was not talking with him.' the controller then apologized and said it was his mistake. I told controller that 'the TCAS saved us today.' as I reflect more on the incident; I firmly believe that TCAS did likely prevent possible tragedy since the WX was IMC and the controller did not amend our instructions until the threat aircraft was virtually passing under us -- with no time to react. Side note: during the rapid transition from descent to climb; we did encounter a brief 3-4 second G load induced (moderate) airframe buffet; which felt much like the high altitude stall buffet training we get in the simulator. I do not believe any limitations were exceeded; however; a logbook entry was made as precaution.
Original NASA ASRS Text
Title: MD80 EXPERIENCES CLOSE ENCOUNTER WITH TRAFFIC DEVIATING WX WHO WAS AT THE SAME FLIGHT LEVEL TO WHICH THEY WERE DESCENDING. ATC ADVISED HE WAS NOT TALKING TO THE TRAFFIC.
Narrative: ATC GAVE US INSTRUCTIONS TO DSND FROM FL360 TO FL350. AS WE STARTED DSCNT; WE NOTICED OPPOSITE DIRECTION TCAS TFC HDG DIRECTLY TOWARDS US AT FL350. I THINK THE TFC DISTANCE WAS THEN ABOUT 10-14 MI ON THE TCAS SCALE. MY INITIAL THINKING WAS THAT THIS TFC SHOULD ALSO BE DSNDING. AS WE PASSED ABOUT FL354; WE NOTICED THAT THE TFC WAS NOW HIGHLIGHTED ON THE TCAS DISPLAY; AND WE WERE ON A PERFECT HEAD-ON COLLISION COURSE. DURING THIS TIME WE WERE UNABLE TO QUESTION THE CTLR DUE TO CONSTANT RADIO CHATTER. THE TCAS TFC WARNING ALERT THEN SOUNDED; THEN AFTER ABOUT 2-3 SECONDS; TCAS TFC CLB RA WARNING SOUNDED. AT THE TIME OF THE RA; WE WERE IN AN APPROX 600-800 FPM DSCNT. I THINK THE RANGE TO TFC WAS NOW ABOUT 5 MI AND CLOSING FAST AND TCAS SHOWED THREAT ACFT ABOUT 300 FT BELOW US. I IMMEDIATELY DISCONNECTED THE AUTOPLT; AND STARTED THE REQUIRED CLB. AS WE RE-LEVELED AT FL360; THE CTLR THEN REALIZED THE CONFLICT AND WITH URGENCY IN HIS VOICE; HE INSTRUCTED US TO MAINTAIN FL360. I BELIEVE HE ALSO INITIALLY ASKED US TO TURN ABOUT 80 DEGS L; TOWARDS THE W. AS THE TFC ZOOMED UNDERNEATH AND PAST US; I EXPLAINED TO THE CTLR THAT HIS EARLIER INSTRUCTION TO HAVE US DSND TO FL350 PLACED US DIRECTLY INTO CONFLICT WITH HEAD-ON TFC. THE CTLR RESPONDED 'THE OTHER ACFT WAS DEVIATING AND THAT HE WAS NOT TALKING WITH HIM.' THE CTLR THEN APOLOGIZED AND SAID IT WAS HIS MISTAKE. I TOLD CTLR THAT 'THE TCAS SAVED US TODAY.' AS I REFLECT MORE ON THE INCIDENT; I FIRMLY BELIEVE THAT TCAS DID LIKELY PREVENT POSSIBLE TRAGEDY SINCE THE WX WAS IMC AND THE CTLR DID NOT AMEND OUR INSTRUCTIONS UNTIL THE THREAT ACFT WAS VIRTUALLY PASSING UNDER US -- WITH NO TIME TO REACT. SIDE NOTE: DURING THE RAPID TRANSITION FROM DSCNT TO CLB; WE DID ENCOUNTER A BRIEF 3-4 SECOND G LOAD INDUCED (MODERATE) AIRFRAME BUFFET; WHICH FELT MUCH LIKE THE HIGH ALT STALL BUFFET TRAINING WE GET IN THE SIMULATOR. I DO NOT BELIEVE ANY LIMITATIONS WERE EXCEEDED; HOWEVER; A LOGBOOK ENTRY WAS MADE AS PRECAUTION.
Data retrieved from NASA's ASRS site as of May 2009 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.