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Aircraft equipment operating procedure gets air carrier medium large transport in approach procedure a TCASII RA at 400 ft AGL above runway. Only other aircraft is an large transport awaiting takeoff on taxiway.
| Attributes | |
| ACN | 201617 |
| Time | |
| Date | 199202 |
| Day | Wed |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : gtf |
| State Reference | MT |
| Altitude | agl bound lower : 400 agl bound upper : 600 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tower : gtf |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Flight Phase | descent : approach |
| Route In Use | approach : straight in |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | common carrier : air carrier |
| Make Model Name | Large Transport, Low Wing, 3 Turbojet Eng |
| Flight Phase | ground : holding |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 120 flight time total : 8000 flight time type : 4000 |
| ASRS Report | 201617 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | non adherence : published procedure other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified |
| Resolutory Action | none taken : anomaly accepted |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation other |
Narrative:
We were high on visual approach to runway 21 in gtf, and correcting at approximately 400 ft above TDZ, maybe lower. We received a 'TA' followed by a climb 'RA'. The only airplane in front of us was an air carrier large transport on the taxiway waiting for takeoff. He obviously had his transponder in RA/TA mode. The gtf airport sits on a plateau and the terrain drops off rapidly on the approach end of runway 21. The combination of terrain drop off and being slightly high on the VASI probably gave us a radio altitude above 500 ft AGL, so the TCASII was not inhibited. I am not sure how much the terrain drops off on the approach end of 21, but I would be curious to find out if it is enough to get you above 500 ft AGL on short final before the terrain rises. Billings also has a similar situation off of the approach end of their west landing runway.
Original NASA ASRS Text
Title: ACFT EQUIP OPERATING PROC GETS ACR MLG IN APCH PROC A TCASII RA AT 400 FT AGL ABOVE RWY. ONLY OTHER ACFT IS AN LGT AWAITING TKOF ON TAXIWAY.
Narrative: WE WERE HIGH ON VISUAL APCH TO RWY 21 IN GTF, AND CORRECTING AT APPROX 400 FT ABOVE TDZ, MAYBE LOWER. WE RECEIVED A 'TA' FOLLOWED BY A CLB 'RA'. THE ONLY AIRPLANE IN FRONT OF US WAS AN ACR LGT ON THE TAXIWAY WAITING FOR TKOF. HE OBVIOUSLY HAD HIS TRANSPONDER IN RA/TA MODE. THE GTF ARPT SITS ON A PLATEAU AND THE TERRAIN DROPS OFF RAPIDLY ON THE APCH END OF RWY 21. THE COMBINATION OF TERRAIN DROP OFF AND BEING SLIGHTLY HIGH ON THE VASI PROBABLY GAVE US A RADIO ALT ABOVE 500 FT AGL, SO THE TCASII WAS NOT INHIBITED. I AM NOT SURE HOW MUCH THE TERRAIN DROPS OFF ON THE APCH END OF 21, BUT I WOULD BE CURIOUS TO FIND OUT IF IT IS ENOUGH TO GET YOU ABOVE 500 FT AGL ON SHORT FINAL BEFORE THE TERRAIN RISES. BILLINGS ALSO HAS A SIMILAR SITUATION OFF OF THE APCH END OF THEIR W LNDG RWY.
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.