Date: 202009
Local time of day: 0001-0600
Location: ZZZ.ARTCC, US
Flight conditions: IMC
Weather elements / visibility: Rain; Thunderstorm
Aircraft: Aero Commander 500 Series
Operator: Air Carrier
Operating under: Part 135
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Cruise
Aircraft component: Reciprocating Engine Assembly
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: Single Pilot; Captain
Reporter qualification: Flight Crew Flight Instructor; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Diverted; Flight Crew Inflight Shutdown
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: I completed the weight and balance paperwork; the preflight inspection; and prepared for departure from ZZZ1 to ZZZ2. I taxied to Runway XX from the FBO (Fixed Base Operator); announced my intentions on the CTAF frequency; taxied into position on Runway XX and held for a brief moment allowing for the engines to come up to 2000 RPM; and to look at the engine indications to ensure all indices were within operational limitations which they were; I released the brakes and the aircraft accelerated at the normal rate.Upon rotation and climbing above 500 ft.; I reduced power to 2500 RPM; turned to 090 degrees and contacted Departure. Departure gave me the standard departure for our CASW flights from ZZZ1 allowing me climb to 2;000 ft. MSL (Mean Sea Level) before turning to approximately 320 degrees North West towards ZZZZZ with a climb to 6;000 ft. MSL. I reached cruising altitude; reduced the throttle; set the mixtures; and adjusted pitch. The weather at the time was IMC (Instrument Meteorological Conditions) with moderate rain. Shortly after passing over the highway corridor and just south of ZZZZZ; Departure handed me off to Center. Center acknowledged the handoff; and issued me direct ZZZ2 when able. As I was inputting direct ZZZ2 in the Garmin 650 GNS; I noticed that there was increasing rudder pressure on my right foot. I immediately looked at the RPM gauge and noticed that I was losing power in the left engine. I looked at the oil pressure gauge and I still had pressure; the oil temp was within limits; and cylinder temp was good. Fuel flow was however low. There was no warning as to an impending power loss; no loss of oil pressure; no backfiring or popping noises coming from the engine; just silence. I immediately turned on the boost pump; and put the throttles; prop levers and mixture handles to full. The right engine responded; but the left continued to windmill. I notified ATC that I was having an issue with my left engine; and that I would get back with them. I then went to 'Memory Items' and began to shut down and feather the left engine. I pulled the throttle lever first; then the prop lever; and the mixture. The left engine continued to 'windmill' and cause significant drag. If I recall; ATC then asked if I was requesting priority handling. I do not recall if I did or not; but I believe I had requested priority handling. With a wind-milling prop; I was unable to maintain altitude and began a slow descent. At about 4000 ft. MSL; I broke out of the clouds and ATC notified me that ZZZ airport was available. I was continuing to descend; and despite trying to hold altitude I was unable to even with the #2 engine practically at full throttle. I then noticed my airspeed was dropping below 140; I then elected at that point to proceed directly to the ZZZ airport and land; and I notified ATC. On my way down I went through the emergency checklist for engine out; I however did not get to the abnormal procedure as I needed to concentrate on getting the airport lights on; and get lined up for the runway as I figured I only and one shot at it. Upon landing at the ZZZ airport; I was able to taxi into the ramp area on one engine. The Sheriff Department responded; and I spoke with the deputy. He gave me the contact number for Center and I called and notified them that I had made it to the ground safely without any damage to myself or the aircraft.After parking and securing the aircraft on the general aviation ramp at ZZZ; I inspected the aircraft. There was no sign of a catastrophic failure; no abnormal signs of oil on the outside of the engine cowling and no abnormal signs of oil on the inside of the cowling. The prop appeared to be in full feather; and I used the prop paddle to reset the prop to low pitch. I then attempted to start the engine; and to my surprise it started. I then brought the power up; and at about 1200 -1400 rpm the engine began to sputter and quit. I advanced the throttle and the engine backfired; coughed; sputtered a bit more; but then it regained full power and operated 'normally' at about 2000 RPM. Oil pressure was good; fuel flow was still low. I then shut down the engine and made no further attempt to restart.




Synopsis: AC50 Pilot reported an engine failure in cruise flight.