 |
37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
|
Air carrier mg altitude deviation excursion from clearance altitude in response to TCAS ii RA for unreported VFR traffic.
| Attributes | |
| ACN | 172758 |
| Time | |
| Date | 199103 |
| Day | Tue |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : sbj |
| State Reference | NJ |
| Altitude | msl bound lower : 18000 msl bound upper : 18500 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tower : iah |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Navigation In Use | Other |
| Flight Phase | cruise other descent other |
| Route In Use | enroute airway : zny |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp pilot : instrument pilot : cfi |
| Experience | flight time last 90 days : 250 flight time total : 11000 flight time type : 240 |
| ASRS Report | 172758 |
| 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 |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified |
| Resolutory Action | flight crew : returned to intended course or assigned course flight crew : took evasive action |
| Consequence | Other |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | other |
Narrative:
As we began our descent from 18000', our TCAS gave a 'traffic, traffic' warning, followed almost immediately by a 'climb, climb' warning, with a minimum 1500 FPM climb rate. We executed an immediate climb to 18500' when the TCAS announced, 'clear of traffic.' we questioned the controller who stated there was VFR traffic at 17500'. We then resumed our descent. The previous controller gave us direct to solberg VOR to cross 40 mi west at 13000' (we were at 18000'). Before our descent we were turned over to the next controller who stated allentown was back up and we should proceed direct. We explained to him that we were getting a flag on allentown, so he then cleared us direct to solberg with the original crossing restriction of 40 mi west at 13000'. By the time all this transpired, we would have had to expedite our descent to make that restriction, and in fact started our descent when the TCAS gave the warning. It is possible that the controller was distracted from the 17500' VFR traffic and never called it to use because of the allentown VOR's erratic signal. I believe our TCAS system and immediate pilot input avoided a potential conflict.
Original NASA ASRS Text
Title: ACR MG ALT DEVIATION EXCURSION FROM CLRNC ALT IN RESPONSE TO TCAS II RA FOR UNREPORTED VFR TRAFFIC.
Narrative: AS WE BEGAN OUR DSNT FROM 18000', OUR TCAS GAVE A 'TFC, TFC' WARNING, FOLLOWED ALMOST IMMEDIATELY BY A 'CLB, CLB' WARNING, WITH A MINIMUM 1500 FPM CLB RATE. WE EXECUTED AN IMMEDIATE CLB TO 18500' WHEN THE TCAS ANNOUNCED, 'CLR OF TFC.' WE QUESTIONED THE CTLR WHO STATED THERE WAS VFR TFC AT 17500'. WE THEN RESUMED OUR DSNT. THE PREVIOUS CTLR GAVE US DIRECT TO SOLBERG VOR TO CROSS 40 MI W AT 13000' (WE WERE AT 18000'). BEFORE OUR DSNT WE WERE TURNED OVER TO THE NEXT CTLR WHO STATED ALLENTOWN WAS BACK UP AND WE SHOULD PROCEED DIRECT. WE EXPLAINED TO HIM THAT WE WERE GETTING A FLAG ON ALLENTOWN, SO HE THEN CLRED US DIRECT TO SOLBERG WITH THE ORIGINAL XING RESTRICTION OF 40 MI W AT 13000'. BY THE TIME ALL THIS TRANSPIRED, WE WOULD HAVE HAD TO EXPEDITE OUR DSNT TO MAKE THAT RESTRICTION, AND IN FACT STARTED OUR DSNT WHEN THE TCAS GAVE THE WARNING. IT IS POSSIBLE THAT THE CTLR WAS DISTRACTED FROM THE 17500' VFR TFC AND NEVER CALLED IT TO USE BECAUSE OF THE ALLENTOWN VOR'S ERRATIC SIGNAL. I BELIEVE OUR TCAS SYS AND IMMEDIATE PLT INPUT AVOIDED A POTENTIAL CONFLICT.
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.