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Air carrier landing sfo receives erroneous glideslope signal inside the outer marker. Tower advises that maintenance working on equipment.
| Attributes | |
| ACN | 173399 |
| Time | |
| Date | 199103 |
| Day | Fri |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : sfo |
| State Reference | CA |
| Altitude | msl bound lower : 1600 msl bound upper : 1600 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tower : sfo |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Flight Phase | descent : approach |
| Route In Use | arrival other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : flight engineer pilot : atp |
| Experience | controller non radar : 2 flight time last 90 days : 210 flight time total : 6100 flight time type : 1600 |
| ASRS Report | 173399 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | none taken : detected after the fact |
| Consequence | faa : reviewed incident with flight crew |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | other |
Narrative:
At above position, G/south flags appeared on both captain and first officer ADI and HSI's. After approximately 30 seconds, flags disappeared and reception of G/south signal appeared normal. Aircraft was on G/south before the flags and showed slightly high after flags disappeared. Flight path was corrected and approach continued. At 500' AGL, the aircraft appeared quite low visually, but still showed on G/south on all cockpit INS. Flight path was adjusted higher to produce a normal visibility 'picture.' landing was normal. After landing, the low G/south was reported to the tower. We were informed by sfo tower that maintenance was in progress on the G/south for runway 28R. This was our first report of the signal being OTS. No NOTAM was published, nor was there any NOTAM on the ATIS which was recently updated. Timely notification of so important navaids outage is imperative to prevent aircraft encountering approach light stands, etc. Please pass the word.
Original NASA ASRS Text
Title: ACR LNDG SFO RECEIVES ERRONEOUS GLIDESLOPE SIGNAL INSIDE THE OUTER MARKER. TWR ADVISES THAT MAINTENANCE WORKING ON EQUIPMENT.
Narrative: AT ABOVE POS, G/S FLAGS APPEARED ON BOTH CAPT AND F/O ADI AND HSI'S. AFTER APPROX 30 SECS, FLAGS DISAPPEARED AND RECEPTION OF G/S SIGNAL APPEARED NORMAL. ACFT WAS ON G/S BEFORE THE FLAGS AND SHOWED SLIGHTLY HIGH AFTER FLAGS DISAPPEARED. FLT PATH WAS CORRECTED AND APCH CONTINUED. AT 500' AGL, THE ACFT APPEARED QUITE LOW VISUALLY, BUT STILL SHOWED ON G/S ON ALL COCKPIT INS. FLT PATH WAS ADJUSTED HIGHER TO PRODUCE A NORMAL VIS 'PICTURE.' LNDG WAS NORMAL. AFTER LNDG, THE LOW G/S WAS RPTED TO THE TWR. WE WERE INFORMED BY SFO TWR THAT MAINT WAS IN PROGRESS ON THE G/S FOR RWY 28R. THIS WAS OUR FIRST RPT OF THE SIGNAL BEING OTS. NO NOTAM WAS PUBLISHED, NOR WAS THERE ANY NOTAM ON THE ATIS WHICH WAS RECENTLY UPDATED. TIMELY NOTIFICATION OF SO IMPORTANT NAVAIDS OUTAGE IS IMPERATIVE TO PREVENT ACFT ENCOUNTERING APCH LIGHT STANDS, ETC. PLEASE PASS THE WORD.
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.