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Pc-12 pilot reported an unexpected turn and descent from the autopilot while intercepting the ILS approach.
| Attributes | |
| ACN | 1512150 |
| Time | |
| Date | 201801 |
| Local Time Of Day | 1201-1800 |
| Place | |
| Locale Reference | MRY.Airport |
| State Reference | CA |
| Environment | |
| Flight Conditions | IMC |
| Light | Night |
| Aircraft 1 | |
| Make Model Name | PC-12 |
| Operating Under FAR Part | Part 91 |
| Flight Phase | Final Approach |
| Route In Use | Vectors |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Autopilot |
| Person 1 | |
| Function | Single Pilot |
| Qualification | Flight Crew Air Transport Pilot (ATP) Flight Crew Flight Instructor Flight Crew Instrument Flight Crew Multiengine |
| Experience | Flight Crew Last 90 Days 50 Flight Crew Total 6800 Flight Crew Type 2000 |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Deviation - Track / Heading All Types |
Narrative:
On a part 91 IFR flight to mry; I was over wiggl intersection and cleared for the RNAV GPS Y runway 28L. Airport was VFR until my arrival at wiggl and then went to scattered layer. I loaded the approach and was proceeding; when the controller advised me that tower just told him the field went IFR. He was going to vector me around for the 10R ILS. He then gave me a heading to fly for the ILS 10R approach. I loaded that approach in the GPS and flew his headings until he gave me a 200 heading to intercept the ILS 10R at or above 2600 at zebed. Upon reaching zebed; the airplane started a 30-degree bank turn away from the inbound course of 098 and started a 1200 FPM descent. I quickly looked at my chart just to confirm what the airplane was doing was wrong and at same time; the autopilot disconnected. In a hurry to confirm that the autopilot was off I also hit the yaw damper disconnect. This put the airplane in an uncoordinated turn while I was trying to turn back to the correct course. I did not like what I was seeing on the pfd so I reverted to my back up instruments to get the airplane back on course and altitude. I glanced back at the mfd and noticed that zebed was now missing but the glideslope intercept minck was still showing up so I turned the aircraft to that fix and at the same time set up for a hand flown raw data ILS. During this time frame; I lost the altitude required on the approach and was advised by the controller to climb to 3000 immediately. I climbed back up and flew to intercept the ILS and hand flew the rest of the procedure with no issues. Corrective actions to not have this happen again: I should have asked the controller for a little wider turn to intercept final. I think that short of approach and almost a 100-degree turn and the short distance to zebed was not enough time to get lined up and be down to 1700 feet after zebed for the intercept at minck. Of course; in the future I am not even going to mess around with trying to save the short approach and just go missed and come back around and try again.
Original NASA ASRS Text
Title: PC-12 pilot reported an unexpected turn and descent from the autopilot while intercepting the ILS approach.
Narrative: On a part 91 IFR flight to MRY; I was over WIGGL intersection and cleared for the RNAV GPS Y Runway 28L. Airport was VFR until my arrival at WIGGL and then went to scattered layer. I loaded the approach and was proceeding; when the controller advised me that tower just told him the field went IFR. He was going to vector me around for the 10R ILS. He then gave me a heading to fly for the ILS 10R approach. I loaded that approach in the GPS and flew his headings until he gave me a 200 heading to intercept the ILS 10R at or above 2600 at ZEBED. Upon reaching ZEBED; the airplane started a 30-degree bank turn away from the inbound course of 098 and started a 1200 FPM descent. I quickly looked at my chart just to confirm what the airplane was doing was wrong and at same time; the autopilot disconnected. In a hurry to confirm that the autopilot was off I also hit the Yaw Damper disconnect. This put the airplane in an uncoordinated turn while I was trying to turn back to the correct course. I did not like what I was seeing on the PFD so I reverted to my back up instruments to get the airplane back on course and altitude. I glanced back at the MFD and noticed that ZEBED was now missing but the Glideslope intercept MINCK was still showing up so I turned the aircraft to that fix and at the same time set up for a hand flown raw data ILS. During this time frame; I lost the altitude required on the approach and was advised by the controller to climb to 3000 Immediately. I climbed back up and flew to intercept the ILS and hand flew the rest of the procedure with no issues. Corrective actions to not have this happen again: I should have asked the controller for a little wider turn to intercept final. I think that short of approach and almost a 100-degree turn and the short distance to ZEBED was not enough time to get lined up and be down to 1700 feet after ZEBED for the intercept at MINCK. Of course; in the future I am not even going to mess around with trying to save the short approach and just go missed and come back around and try again.
Data retrieved from NASA's ASRS site 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.