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MD83 flight crew climbed and descended off assigned altitude in response to TCASII RA originating from an aircraft with a malfunctioning mode C.
| Attributes | |
| ACN | 521586 |
| Time | |
| Date | 200108 |
| Day | Sat |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| State Reference | NV |
| Altitude | msl single value : 28000 |
| Environment | |
| Flight Conditions | Mixed |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zla.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | MD-83 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | climbout : intermediate altitude |
| Route In Use | departure sid : ns |
| Flight Plan | IFR |
| Aircraft 2 | |
| Controlling Facilities | artcc : zla.artcc |
| Operator | general aviation : corporate |
| Make Model Name | Any Unknown or Unlisted Aircraft Manufacturer |
| Operating Under FAR Part | Part 91 |
| Flight Phase | climbout : intermediate altitude |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : flight engineer pilot : atp |
| Experience | flight time last 90 days : 240 flight time total : 7800 flight time type : 1980 |
| ASRS Report | 521586 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : required legal separation |
| Independent Detector | atc equipment other atc equipment : radar aircraft equipment : tcas other controllera other flight crewa other flight crewb |
| Resolutory Action | controller : issued advisory controller : separated traffic |
| Consequence | faa : reviewed incident with flight crew |
| Miss Distance | horizontal : 0 vertical : 1000 |
| Supplementary | |
| Problem Areas | ATC Human Performance Flight Crew Human Performance |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | other |
Narrative:
Departing las en route to stl direct cleared by previous ZLA controller to climb to our cruise altitude in the mid thirties. When changed over to next lax controller was told to level off at 28000 ft (this controller's tone led us to believe something was not normal). We promptly leveled at 28000 ft. Lax controller then was pointing traffic to us, which we were unable to visually acquire. The controller then asked the conflicting traffic to confirm his altitude, which he stated 29000 ft. We never had a visual confirmation on this traffic. The TCASII at this time picked him up at 28000 ft. We were not able to confirm altitudes with lax due to radio traffic. Our TCASII then gave us an RA to take evasive climbs then a descent to avoid traffic. Soon to follow was an air carrier aircraft Z responding to a TCASII RA from this same aircraft. We never deviated more than 300 ft from assigned altitude. When we finally contacted ZLA and told them of our RA, he stated that the other aircraft was on a maintenance flight. We were never told of this until after we had to take evasive maneuvers since we could never pick up the aircraft visually. I couldn't believe they would be doing a maintenance test flight in positive control airspace for an inoperative mode C. This aircraft was going to cause havoc to all TCASII equipped aircraft in that very busy section of united stated airspace. I was left no option but to respond to my TCASII since I did not know this aircraft was on a maintenance flight and not knowing his altitude. I figure the air carrier Z crew behind us was also faced with the same predicament. This could have been a very serious event due to the violent maneuvers that were required from the TCASII. We were lucky to still have the seat belt sign illuminated at the time of this event. If this sign was off we would have hurt many people.
Original NASA ASRS Text
Title: MD83 FLC CLBED AND DSNDED OFF ASSIGNED ALT IN RESPONSE TO TCASII RA ORIGINATING FROM AN ACFT WITH A MALFUNCTIONING MODE C.
Narrative: DEPARTING LAS ENRTE TO STL DIRECT CLRED BY PREVIOUS ZLA CTLR TO CLB TO OUR CRUISE ALT IN THE MID THIRTIES. WHEN CHANGED OVER TO NEXT LAX CTLR WAS TOLD TO LEVEL OFF AT 28000 FT (THIS CTLR'S TONE LED US TO BELIEVE SOMETHING WAS NOT NORMAL). WE PROMPTLY LEVELED AT 28000 FT. LAX CTLR THEN WAS POINTING TFC TO US, WHICH WE WERE UNABLE TO VISUALLY ACQUIRE. THE CTLR THEN ASKED THE CONFLICTING TFC TO CONFIRM HIS ALT, WHICH HE STATED 29000 FT. WE NEVER HAD A VISUAL CONFIRMATION ON THIS TFC. THE TCASII AT THIS TIME PICKED HIM UP AT 28000 FT. WE WERE NOT ABLE TO CONFIRM ALTS WITH LAX DUE TO RADIO TFC. OUR TCASII THEN GAVE US AN RA TO TAKE EVASIVE CLBS THEN A DSCNT TO AVOID TFC. SOON TO FOLLOW WAS AN ACR ACFT Z RESPONDING TO A TCASII RA FROM THIS SAME ACFT. WE NEVER DEVIATED MORE THAN 300 FT FROM ASSIGNED ALT. WHEN WE FINALLY CONTACTED ZLA AND TOLD THEM OF OUR RA, HE STATED THAT THE OTHER ACFT WAS ON A MAINT FLT. WE WERE NEVER TOLD OF THIS UNTIL AFTER WE HAD TO TAKE EVASIVE MANEUVERS SINCE WE COULD NEVER PICK UP THE ACFT VISUALLY. I COULDN'T BELIEVE THEY WOULD BE DOING A MAINT TEST FLT IN POSITIVE CTL AIRSPACE FOR AN INOP MODE C. THIS ACFT WAS GOING TO CAUSE HAVOC TO ALL TCASII EQUIPPED ACFT IN THAT VERY BUSY SECTION OF UNITED STATED AIRSPACE. I WAS LEFT NO OPTION BUT TO RESPOND TO MY TCASII SINCE I DID NOT KNOW THIS ACFT WAS ON A MAINT FLT AND NOT KNOWING HIS ALT. I FIGURE THE ACR Z CREW BEHIND US WAS ALSO FACED WITH THE SAME PREDICAMENT. THIS COULD HAVE BEEN A VERY SERIOUS EVENT DUE TO THE VIOLENT MANEUVERS THAT WERE REQUIRED FROM THE TCASII. WE WERE LUCKY TO STILL HAVE THE SEAT BELT SIGN ILLUMINATED AT THE TIME OF THIS EVENT. IF THIS SIGN WAS OFF WE WOULD HAVE HURT MANY PEOPLE.
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.