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The mtpp runway 10 ILS glideslope rose slowly then quickly dropped; causing a B737-800 autopilot to chase it at an unacceptable rate down. The autopilot was disconnected and a visual approach completed.
| Attributes | |
| ACN | 1033301 |
| Time | |
| Date | 201208 |
| Local Time Of Day | 0601-1200 |
| Place | |
| Locale Reference | MTPP.Airport |
| State Reference | FO |
| Environment | |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | B737-800 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Final Approach |
| Flight Plan | IFR |
| Person 1 | |
| Function | Pilot Flying Captain |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Events | |
| Anomaly | ATC Issue All Types Inflight Event / Encounter Unstabilized Approach |
Narrative:
During ILS/DME runway 10 approach; aircraft [was] on autopilot tracking slightly below glidepath until approximately 1;800 AGL when nose pitched up slightly and power came up to correct to glidepath then glideslope dropped below horizon and autopilot chased it down resulting in an unacceptable sink rate. Disconnected autopilot and corrected to visual approach. I believe the ILS at mtpp should be tested for accuracy and proper functioning. I fly this [approach] a lot and observe the glide slope and localizer to be erratic constantly. The problem is; it is insidious and if you don't fly this [approach] a lot it can take someone by surprise. It acts like it is working normal then the glideslope slowly drifts up or down slowly. Suggest using only RNAV approaches.
Original NASA ASRS Text
Title: The MTPP Runway 10 ILS glideslope rose slowly then quickly dropped; causing a B737-800 autopilot to chase it at an unacceptable rate down. The autopilot was disconnected and a visual approach completed.
Narrative: During ILS/DME Runway 10 approach; aircraft [was] on autopilot tracking slightly below glidepath until approximately 1;800 AGL when nose pitched up slightly and power came up to correct to glidepath then glideslope dropped below horizon and autopilot chased it down resulting in an unacceptable sink rate. Disconnected autopilot and corrected to visual approach. I believe the ILS at MTPP should be tested for accuracy and proper functioning. I fly this [approach] a lot and observe the glide slope and localizer to be erratic constantly. The problem is; it is insidious and if you don't fly this [approach] a lot it can take someone by surprise. It acts like it is working normal then the glideslope slowly drifts up or down slowly. Suggest using only RNAV approaches.
Data retrieved from NASA's ASRS site as of July 2013 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.