Mooney M20K N4387W accident near St. Augustine, Florida

Probable cause

The pilot’s failure to maintain adequate airspeed of the airplane while in the traffic pattern, which resulted in an aerodynamic stall/spin. Contributing was the pilot’s distraction due to the in-flight opening of the main cabin door, which resulted from the incorrect closure of the door before takeoff.

NTSB analysis

Shortly after takeoff, the pilot reported to the air traffic controller that he had a door that had “popped open,” and the controller cleared the flight to return for landing. A review of ADS-B data and surveillance video revealed that, while the airplane was on the base leg for the approach back to the departure airport, it entered a steep, nose-down descent while rolling to the right, consistent with an aerodynamic stall/spin. Postaccident examination of the airplane revealed that both of the airplane’s doors (the rear baggage door and the main cabin door) remained attached to the airframe. Examination of the rear baggage door revealed damage consistent with it having been closed and latched at the time of impact; this included damage on the door latch pins (which were found extended) and striker plates indicating that the rear baggage door latch pins had been forced past the striker plates during the impact sequence.

Examination of the main cabin door upper and aft center latch components revealed no damage to the latch pins and striker plates, indicating that the door was likely not closed and latched at the time of impact. Because the examination of the door lock and latching mechanisms did not reveal any mechanical failure or malfunction that would have precluded normal operation, the door was likely not closed properly before takeoff. The examination of the remainder of the airframe and the engine did not reveal any mechanical malfunction or failure that would have precluded normal operation.

According to the airplane’s Pilot’s Operating Handbook (POH), if the main cabin door is not properly closed, it may come unlatched in flight but will not affect the airplane’s flight characteristics. The POH prescribed either returning to the field and landing normally or climbing the airplane to a safe altitude to perform the procedures for shutting and latching the door.

The airplane was equipped with an engine data monitor that recorded various engine data parameters for the entire accident flight. A review of the engine data revealed that, at the time that the monitor stopped recording, all readings were consistent with normal engine operation and a high power setting. Based on these data, it is likely that, during the aerodynamic stall/spin, the pilot added full power to the engine in an attempt to recover from the aerodynamic stall/spin. According to the POH, to recover from a spin, it is necessary to bring the engine back to idle; however, the POH also stated that stalls at low altitude are extremely critical and that up to 2,000 ft of altitude may be lost during a one-turn spin and recovery. Thus, due to the airplane being below traffic pattern altitude when it entered the aerodynamic stall/spin, it is unlikely that the pilot could have recovered even if he had properly conducted the spin recovery items.

Text from the NTSB. Open the NTSB docket for ERA24FA154 for the full record.