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TCASII RA, sensing a potential conflict commands an evasive action descent for air carrier crew. Altitude deviation altitude excursion in non adherence to ATC clearance.
| Attributes | |
| ACN | 245933 |
| Time | |
| Date | 199307 |
| Day | Tue |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : zob |
| State Reference | OH |
| Altitude | msl bound lower : 12500 msl bound upper : 13000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : iah |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Flight Phase | cruise other |
| Route In Use | arrival other arrival star : star enroute : on vectors enroute airway : zob |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | general aviation : personal |
| Make Model Name | Small Aircraft, Low Wing, 2 Eng, Retractable Gear |
| Flight Phase | cruise other |
| Flight Plan | VFR |
| 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 : 12000 flight time type : 200 |
| ASRS Report | 245933 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other controllera |
| Resolutory Action | flight crew : exited adverse environment flight crew : took evasive action |
| Consequence | Other |
| Miss Distance | horizontal : 0 vertical : 1000 |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
Airline medium large transport level 13000 ft MSL on a vector from grr direct to polar intersection, polar 1 arrival to dtw. Advised by center of traffic, a light twin at 13500 ft 11 O'clock becoming 12 O'clock, 5 mi. While visually searching for traffic, TCASII showed blue target ahead -- altitude plus 400 ft. As traffic visually idented and first officer advised ATC, TCASII gave a yellow TA, then quickly issued an RA, 'descend, descend now,' commanding a 2000 FPM descent. I immediately idled thrust, disengaged autoplt, and initiated descent, with descent rate approaching 1000 FPM and a few hundred ft below 13000 ft. TCASII issued 'clear of conflict.' leveled at 12500 ft, first officer advised ATC of RA. ATC cleared us to 12000 ft as traffic passed over us. Rest of flight to dtw uneventful. Only question in my mind is why ATC, knowing proximity of traffic, did not initially give us a change of heading or altitude.
Original NASA ASRS Text
Title: TCASII RA, SENSING A POTENTIAL CONFLICT COMMANDS AN EVASIVE ACTION DSCNT FOR ACR CREW. ALTDEV ALT EXCURSION IN NON ADHERENCE TO ATC CLRNC.
Narrative: AIRLINE MLG LEVEL 13000 FT MSL ON A VECTOR FROM GRR DIRECT TO POLAR INTXN, POLAR 1 ARR TO DTW. ADVISED BY CTR OF TFC, A LIGHT TWIN AT 13500 FT 11 O'CLOCK BECOMING 12 O'CLOCK, 5 MI. WHILE VISUALLY SEARCHING FOR TFC, TCASII SHOWED BLUE TARGET AHEAD -- ALTITUDE PLUS 400 FT. AS TFC VISUALLY IDENTED AND FO ADVISED ATC, TCASII GAVE A YELLOW TA, THEN QUICKLY ISSUED AN RA, 'DSND, DSND NOW,' COMMANDING A 2000 FPM DSCNT. I IMMEDIATELY IDLED THRUST, DISENGAGED AUTOPLT, AND INITIATED DSCNT, WITH DSCNT RATE APCHING 1000 FPM AND A FEW HUNDRED FT BELOW 13000 FT. TCASII ISSUED 'CLR OF CONFLICT.' LEVELED AT 12500 FT, FO ADVISED ATC OF RA. ATC CLRED US TO 12000 FT AS TFC PASSED OVER US. REST OF FLT TO DTW UNEVENTFUL. ONLY QUESTION IN MY MIND IS WHY ATC, KNOWING PROX OF TFC, DID NOT INITIALLY GIVE US A CHANGE OF HDG OR ALT.
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.