Pilot door flies off Cessna 350 in flight

This is an excerpt from a report made to the Aviation Safety Reporting System. The narrative is written by the pilot, rather than FAA or NTSB officials. To maintain anonymity, many details, such as aircraft model or airport, are often scrubbed from the reports.

We worked through all appropriate pre-flight checklists and discussed our flight plan for the morning flight. Our plan was to depart Runway XX at ZZZ and shoot instrument approaches at ZZZ1, ZZZ2, and ZZZ. We would then make a full stop and end the flight at ZZZ. An IFR flight plan was filed with ATC and was to be picked up once airborne.

During the preflight checklists, we did a complete exterior preflight check of the Cessna 350 before discussing how to appropriately board the aircraft. [Name] boarded the passenger side, and I boarded into the pilot side. We discussed how to properly secure the seatbelt, and then had a very detailed description of how to close and secure the door properly by turning the door handle to the proper closed position, to where it drops into the proper detent. I demonstrated to [Name] with my door handle where the correct position for the door handle was when closed.

We taxied out to Runway XX, and proceeded to go through the run-up checklist.

At the end of the checklist, I specifically pointed out that the annunciator panel had all lights off.

During the takeoff climb, approximately 1.5 miles to the northeast of ZZZ, we were climbing through 1,500 feet msl for 3,000 feet. Everything sounded and felt completely normal inside the aircraft. The winds were calm, and the barometric pressure was 30.46. Our climb rate was 500 feet/min and our IAS was 120 knots.

All of the sudden, without any warning, the pilot side door blew off of the aircraft and completely detached.

I leveled off the aircraft, slowed to approach flap speed, while making a left turn back toward ZZZ, and began to make a landing on Runway XY at ZZZ. I was able to maintain complete control of the aircraft with the pilot side door completely gone.

I announced our situation, and that we would be entering a right base to final approach to Runway XY.

I deployed approach flaps and landing flaps, entered a right base leg, slowed to 90 knots, and made a right hand turn for a short final approach to Runway XY, and was able to execute a safe landing.

After landing safely, I taxied back to the hangar, and we shut down and departed the aircraft. We did a detailed inspection of the aircraft and took several photographs of the pilot side door hinges.

We notified the airport authority and local police of our situation.

Since we had a clear idea of our position when the door detached, we drove to the approximate area in my truck. We found the door in a parking lot.

When we located the door, we took several photographs of the door before touching it. The door handle was in the closed position in the proper safety detent.

Both locking pins were engaged, with the forward pin being bent. We retrieved the door and took it back to ZZZ.

Primary Problem: Aircraft

ACN: 1769683