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A B737-200 PIC questions his ILS GS reliability when making an approach to runway 24 and noting that his altitude appeared to be low according to the PAPI indicators at bhm, al.
| Attributes | |
| ACN | 611597 |
| Time | |
| Date | 200403 |
| Day | Thu |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| State Reference | AL |
| Altitude | agl bound lower : 400 agl bound upper : 600 |
| Environment | |
| Flight Conditions | Marginal |
| Weather Elements | other |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : bhm.tracon |
| Operator | common carrier : air carrier |
| Make Model Name | B737-200 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | ils localizer & glide slope : 24 |
| Flight Phase | descent : approach |
| Route In Use | approach : instrument precision arrival : on vectors |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : commercial pilot : instrument pilot : multi engine pilot : atp |
| Experience | flight time last 90 days : 215 flight time total : 16500 flight time type : 790 |
| ASRS Report | 611597 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Events | |
| Anomaly | aircraft equipment problem : critical altitude deviation : overshoot altitude deviation : crossing restriction not met inflight encounter : weather non adherence : clearance non adherence : published procedure non adherence : company policies other anomaly other spatial deviation |
| Independent Detector | atc equipment other atc equipment : papi other flight crewa other flight crewb |
| Resolutory Action | flight crew : took precautionary avoidance action flight crew : became reoriented other |
| Supplementary | |
| Problem Areas | Navigational Facility Flight Crew Human Performance Aircraft |
| Primary Problem | Ambiguous |
Narrative:
Using the autoplt in single channel and level at 3000 ft, we captured the localizer and selected approach mode on the autoplt. The autoplt started to pitch up, so I disconnected it. Just prior to roeby, we started to descend on the GS, but I did not get an altitude xchk at roeby. At 3.5 mi, we had 'on course' and 'on glide path' indications, but as the PAPI came in view through the haze we were very low. I leveled the aircraft off and the ILS indications remained the same. At 1.5 mi, the PAPI and ILS seemed to agree. The rest of the approach and landing went normally. We asked tower about the ILS signal and reported the anomaly. We used the autoplt again for another approach with no unusual indications. We do not know if we had an equipment problem or a ground based problem.
Original NASA ASRS Text
Title: A B737-200 PIC QUESTIONS HIS ILS GS RELIABILITY WHEN MAKING AN APCH TO RWY 24 AND NOTING THAT HIS ALT APPEARED TO BE LOW ACCORDING TO THE PAPI INDICATORS AT BHM, AL.
Narrative: USING THE AUTOPLT IN SINGLE CHANNEL AND LEVEL AT 3000 FT, WE CAPTURED THE LOC AND SELECTED APCH MODE ON THE AUTOPLT. THE AUTOPLT STARTED TO PITCH UP, SO I DISCONNECTED IT. JUST PRIOR TO ROEBY, WE STARTED TO DSND ON THE GS, BUT I DID NOT GET AN ALT XCHK AT ROEBY. AT 3.5 MI, WE HAD 'ON COURSE' AND 'ON GLIDE PATH' INDICATIONS, BUT AS THE PAPI CAME IN VIEW THROUGH THE HAZE WE WERE VERY LOW. I LEVELED THE ACFT OFF AND THE ILS INDICATIONS REMAINED THE SAME. AT 1.5 MI, THE PAPI AND ILS SEEMED TO AGREE. THE REST OF THE APCH AND LNDG WENT NORMALLY. WE ASKED TWR ABOUT THE ILS SIGNAL AND RPTED THE ANOMALY. WE USED THE AUTOPLT AGAIN FOR ANOTHER APCH WITH NO UNUSUAL INDICATIONS. WE DO NOT KNOW IF WE HAD AN EQUIP PROB OR A GND BASED PROB.
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.