Date: 202103
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 40
Light: Daylight
Aircraft: PA-23 Apache/Geronimo Apache
Operator: FBO
Operating under: Part 91
Flight plan: None
Mission: Training
Flight phase: Cruise
Airspace: Class E ZZZ
Aircraft component: AC Generation
Component problem: Failed
Reporter organization: Other Flight School
Reporter function: Pilot Not Flying; Instructor
Reporter qualification: Flight Crew Commercial; Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Multiengine
Human factors: Troubleshooting; Communication Breakdown; Time Pressure
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Returned To Departure Airport; Flight Crew Landed in Emergency Condition; Flight Crew Inflight Shutdown; Flight Crew Requested ATC Assistance / Clarification; General Maintenance Action
Contributing factors: Procedure; Aircraft
Primary problem: Aircraft

Narrative: My student and I were conducting a routine multi engine training flight. As part of this flight we had decided we would be doing a full engine shutdown; feather and in air restart. We shutdown and feathered the engine at 4;000 feet. About 1-2 minutes elapsed before we briefed and began to run through the engine restart procedure. When we engaged the start; we only got a half rotation from the propeller. We tried a couple different restart variations; priming; different throttle and mixture positions; but we still had the issue of not getting enough power to turn the engine over enough times to unfeather it. After 3-4 start attempts; all of the electrical components in the cockpit became inoperative. Avionics; intercom; transponder and transponder were all inoperative. After all the avionics and intercom shut off; we began to troubleshoot the issue. We recycled the avionics master; minimized electrical load and squawked 7600 in the event the transponder was still transmitting. I knew we needed to start back towards the airport regardless of whether we got the electrical system back up; because the likelihood of us getting the engine restarted with a clear electrical issue was slim to none; seeing as getting an engine out of feather takes a significant amount electrical power. Our next course of action was to get in touch with ATC. We did not have cell service at 4;000 ft.; (altitude at which the shutdown occurred) so we started a slow descending left turn (into the good engine) in hopes of getting service. I was not going to let us go below 3;000 [ft.]. At around 3;500 ft. I got enough cell service to call ZZZ Approach; using the Bluetooth on my headset and phone to talk with them. I told ZZZ Approach we had experienced an electrical failure and that we were also single engine. At this time I also [received priority]. Approach was able to give us a heading to fly to intercept final and during that time while we proceeded towards the airport; we ran through our engine securing checklist and single engine approach and landing checklist; we briefed the landing and determined I would fly the final approach and landing. With the checklist and briefing done; all that was left was to fly the approach. We got our landing clearance over the phone; got the gear down and established a final approach speed of 125 MPH. The landing on Runway XX was uneventful; with the aircraft touching down in the first 3rd of the runway. ARFF (Airport Rescue and Fire Fighting) units were on alert and followed us down the runway to where we exited at Taxiway XX. As we were coming to a stop on [Taxiway] XX all our avionics turned back on; so we were able to contact Ground to get our taxi clearance back to the [FBO]. An air guard fire personnel did a quick check of the aircraft; asked if we were ok and then we were able to taxi back to our flight school ramp without incident.




Synopsis: PA-23 instructor pilot reported loss of all electrical power after shutting an engine down for air restart training; requiring a return to departure airport.