BE20 pilot reported descending below charted altitude on approach to M01; and attributed the deviati...

Attributes
ACN	1517956
Time
Date	201802
Local Time Of Day	1201-1800
Place
Locale Reference	M01.Airport
State Reference	TN
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	Super King Air 200
Operating Under FAR Part	Part 91
Flight Phase	Initial Approach
Route In Use	Other RNAV 17 at M01
Flight Plan	IFR
Component
Aircraft Component	Autopilot
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine Flight Crew Instrument Flight Crew Flight Instructor
Experience	Flight Crew Last 90 Days 200 Flight Crew Total 7600 Flight Crew Type 1500
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Overshoot Deviation - Procedural Published Material / Policy Deviation - Procedural Clearance Inflight Event / Encounter CFTT / CFIT

Narrative:

The altitude selector was mis-set and the descent was started after passing the (IAF) faxip. The aircraft was flown several hundred feet below the MEA of 1900 feet prior to arriving at the FAF vagdy. The error was detected during a scan and observation that glideslope was not captured nor passage of the FAF at vagdy had occurred. A climb was initiated back toward 1900 feet. At vagdy station passage; glideslope was captured for the lpv and the approach was continued to the landing.just as memphis approach gave the clearance for the RNAV (GPS) 17 via faxip; the autopilot failed and the aircraft had to be hand flown. Numerous attempts were made to try and reset the autopilot to no avail while in transit to faxip. ATC was contacted and informed that I would fly the procedure turn and did not want vectors to final. While in the procedure turn; the altitude selector was mis-set as a result of the autopilot distractions.in retrospect; I should have informed ATC that I just experienced an autopilot failure and specifically requested vectors to the final approach course.

Original NASA ASRS Text

Title: BE20 pilot reported descending below charted altitude on approach to M01; and attributed the deviation to an Autopilot failure.

Narrative: The altitude selector was mis-set and the descent was started after passing the (IAF) FAXIP. The aircraft was flown several hundred feet below the MEA of 1900 feet prior to arriving at the FAF VAGDY. The error was detected during a scan and observation that Glideslope was not captured nor passage of the FAF at VAGDY had occurred. A climb was initiated back toward 1900 feet. At VAGDY station passage; Glideslope was captured for the LPV and the approach was continued to the landing.Just as Memphis approach gave the clearance for the RNAV (GPS) 17 via FAXIP; the autopilot failed and the aircraft had to be hand flown. Numerous attempts were made to try and reset the autopilot to no avail while in transit to FAXIP. ATC was contacted and informed that I would fly the Procedure Turn and did not want vectors to final. While in the Procedure Turn; the altitude selector was mis-set as a result of the autopilot distractions.In retrospect; I should have informed ATC that I just experienced an autopilot failure and specifically requested vectors to the final approach course.

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.

BE20 pilot reported descending below charted altitude on approach to M01; and attributed the deviation to an autopilot failure.