Mooney M20K — Sylmar, CA

What happened

The pilot was at the completion of a cross-country flight during daytime instrument meteorological conditions. A review of air traffic control (ATC) audio recordings and automatic dependent surveillance-broadcast (ADS-B) data showed that the pilot advised ATC he was inbound on the instrument landing system instrument approach, the airplane was established on the localizer to runway 16R, and the air traffic controller cleared the pilot to land. About 1 minute later, as the airplane was near the final approach fix, it began a series of climbing and descending turns to the south and west of the approach course over high terrain. The air traffic controller queried the pilot and provided multiple instructions to both climb and turn to the south. The pilot initially flew to the south as directed but soon began maneuvering to the west and north. The pilot’s final response to ATC instructions occurred when the airplane was at an altitude of about 2,744 ft mean sea level (msl). No further radio communication from the pilot acknowledging the controller’s instructions was received.

The ADS-B data showed that the airplane turned left slightly 23 seconds later, followed by a series of mostly right turns. Throughout the final turn, the airplane’s altitude fluctuated over 400 ft. The last recorded radar target was at an altitude of 2,638 ft msl, within the vicinity of the accident site.

The wreckage was located adjacent to a downed powerline within mountainous terrain at 2,315 ft msl. All major structural components of the airplane were located within the debris path. Postaccident examination of the wreckage revealed no evidence of any preexisting mechanical malfunction that would have precluded normal operation with the airframe or engine.

The pilot’s communications with ATC as the flight deviated from the approach course included delayed response, incomplete readback of instructions, and transmissions consistent with increasing stress. These communications occurred while the airplane’s ground track was off course, both laterally and vertically. The airplane maneuvers were inconsistent with the charted approach and ATC instructions.

The airplane’s altitude and heading deviations on the approach indicate the pilot was not reliably and positively controlling the airplane by reference to instruments. Pilot communications early in this period were nominal. However, as off-course maneuvering continued and became more erratic, the pilot’s communications became distressed, suggesting he recognized the difficulty he was having controlling the airplane. As the restricted visibility conditions and maneuvering were conducive to the development of spatial disorientation, it is likely that the pilot experienced spatial disorientation before losing control of the airplane.

An editorial "what led to it / how to avoid it" analysis for this accident is generated separately and will appear here.