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A320 first officer complains that the msp ILS runway 12R GS is unprotected from aircraft taxiing in front of the signal when the WX is 800 ft 2 mi or better causing fluctuations in the GS signal when making the full ILS approach. Tower issued minimum safe altitude warnings during approach.
| Attributes | |
| ACN | 533464 |
| Time | |
| Date | 200112 |
| Day | Sat |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : msp.airport |
| State Reference | MN |
| Altitude | msl bound lower : 2400 msl single value : 2200 |
| Environment | |
| Flight Conditions | IMC |
| Weather Elements | Fog Ice Rain |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tower : msp.tower tracon : i90.tracon |
| Operator | common carrier : air carrier |
| Make Model Name | A320 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent : approach |
| Route In Use | approach : instrument precision |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : flight engineer pilot : commercial pilot : atp |
| Experience | flight time last 90 days : 200 flight time total : 8000 flight time type : 1500 |
| ASRS Report | 533464 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Events | |
| Anomaly | altitude deviation : overshoot inflight encounter : weather non adherence : published procedure other anomaly other other spatial deviation |
| Independent Detector | atc equipment : msaw aircraft equipment other aircraft equipment : ils glide indication other flight crewa |
| Resolutory Action | flight crew : became reoriented flight crew : overrode automation flight crew : exited adverse environment |
| Consequence | faa : investigated |
| Supplementary | |
| Problem Areas | Weather Aircraft FAA Navigational Facility |
| Primary Problem | Navigational Facility |
| Situations | |
| Navigational Aid | MSP.ILS |
Narrative:
While on the ILS approach to runway 12R at msp, and IMC, we experienced several large fluctuations of the GS signal, causing abrupt changes in pitch and power. I disconnected the autoplt and continued the approach. Inside the OM, just after breaking out of the clouds, the GS made a full-scale up deflection and stayed there. ATIS WX was 1800 ft 4 mi. Actual WX 1200 ft (ragged) and 2 mi. Continued using localizer minimums causing low altitude alert in tower. Other aircraft ahead of and behind us reported similar problems. This has been a recurring problem at msp. They only protect the GS when WX is below 800 ft/2 mi. I feel the current policy at msp creates an unacceptable hazard. The GS should be protected whenever ILS approachs are in use. Otherwise, they should advertise localizer only approachs, or visuals, with the notation 'GS unreliable' until such a time as the GS anomalies are fixed.
Original NASA ASRS Text
Title: A320 FO COMPLAINS THAT THE MSP ILS RWY 12R GS IS UNPROTECTED FROM ACFT TAXIING IN FRONT OF THE SIGNAL WHEN THE WX IS 800 FT 2 MI OR BETTER CAUSING FLUCTUATIONS IN THE GS SIGNAL WHEN MAKING THE FULL ILS APCH. TWR ISSUED MINIMUM SAFE ALT WARNINGS DURING APCH.
Narrative: WHILE ON THE ILS APCH TO RWY 12R AT MSP, AND IMC, WE EXPERIENCED SEVERAL LARGE FLUCTUATIONS OF THE GS SIGNAL, CAUSING ABRUPT CHANGES IN PITCH AND PWR. I DISCONNECTED THE AUTOPLT AND CONTINUED THE APCH. INSIDE THE OM, JUST AFTER BREAKING OUT OF THE CLOUDS, THE GS MADE A FULL-SCALE UP DEFLECTION AND STAYED THERE. ATIS WX WAS 1800 FT 4 MI. ACTUAL WX 1200 FT (RAGGED) AND 2 MI. CONTINUED USING LOC MINIMUMS CAUSING LOW ALT ALERT IN TWR. OTHER ACFT AHEAD OF AND BEHIND US RPTED SIMILAR PROBS. THIS HAS BEEN A RECURRING PROB AT MSP. THEY ONLY PROTECT THE GS WHEN WX IS BELOW 800 FT/2 MI. I FEEL THE CURRENT POLICY AT MSP CREATES AN UNACCEPTABLE HAZARD. THE GS SHOULD BE PROTECTED WHENEVER ILS APCHS ARE IN USE. OTHERWISE, THEY SHOULD ADVERTISE LOC ONLY APCHS, OR VISUALS, WITH THE NOTATION 'GS UNRELIABLE' UNTIL SUCH A TIME AS THE GS ANOMALIES ARE FIXED.
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.