N678SWCessna 421C

On July 13, 2021, about 1042 Pacific daylight time (PDT), a Cessna 421C, N678SW, was destroyed when it was involved in an accident near Monterey, California. The pilot and passenger were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

Review of recorded communications from the Monterey air traffic control tower revealed that before takeoff the pilot canceled their instrument flight rules (IFR) clearance and requested a visual flight rules (VFR) on top clearance. The controller subsequently cleared the airplane to the Salinas VOR via the Monterey Five departure and to proceed VFR-ON-TOP. The controller issued a clearance for takeoff and shortly after, instructed the pilot to contact the Oakland Air Route Traffic Control Center (ARTCC).

Review of recorded communications from the Oakland ARTCC revealed that the pilot established radio communication with the Oakland ARTCC controller as the airplane ascended through 1,700 ft mean sea level (msl). The controller observed on the radar display the airplane was turning in the wrong direction and issued an immediate right turn to a heading of 030° which was acknowledged by the pilot. The controller then immediately issued two low altitude alerts with no response from the pilot. No further radio communication from the pilot was received.

Recorded automatic dependent surveillance-broadcast (ADS-B) data provided by the Federal Aviation Administration (FAA) showed that the airplane departed from runway 10R at 1738:44 and ascended to 1,075 ft msl before a right turn was initiated. The data showed that at 1740:14, the airplane continued to ascend in a right turn and reached an altitude of 2,000 ft msl before a descent began. The airplane continued in a right descending turn until ADS-B contact was lost at 1740:38, at an altitude of 775 ft msl, about 520 ft southwest of the accident site as seen in figure 1.

Figure 1: View of airplane ADS-B track.

A witness located near the accident site reported that he observed the accident airplane descend below the cloud layer in a nose low attitude with the landing gear retracted. The witness stated that the airplane made a right descending turn and impacted the top of a pine tree before it traveled below the tree line out of sight, followed by the sound of an explosion.

A review of the pilot’s logbook indicated that a flight review was accomplished on July 17, 2020. The flight instructor reported that during the flight, an instrument proficiency check was also conducted. However, an instrument proficiency check endorsement dated July 17, 2020 was not observed in the pilot logbook. In the 12 months preceding to the accident flight, the pilot accumulated about 0.3 hours of simulated instrument flight, 0.7 hours of actual instrument flight and no instrument approaches.

The preliminary weather for MRY reported that at 1054 PDT, wind from 280° at 7 knots, visibility of 9 statute miles, ceiling overcast at 800 ft above ground level (agl), temperature of 15°C and dew point temperature of 11°C, altimeter setting of 29.99 inches of mercury, remarks included: station with a precipitation discriminator.

A High-Resolution Rapid Refresh numerical model sounding near the accident site supported cloudy conditions from about 1,100 to 1,700 ft with a freezing level at about 17,000 ft. The wind below 2,000 ft was from the west at magnitudes less than 10 knots. A temperature inversion was noted between 1,600 and 4,600 ft.

A pilot on a decent to landing at MRY, in the hours leading to the accident, reported that cloud tops were near 2,000 ft msl with the bases at about 800 ft msl.

Examination of the accident site revealed that the airplane impacted trees about 1 mile south of the departure end of runway 10R. The first identifiable point of contact (FIPC) was a 50 to 75 ft tall tree that had damaged limbs near the top of the tree. The debris path was oriented on a heading of about 067° and was about 995 ft in length from the FIPC, as seen in figure 3. The main wreckage was located about 405 ft from the FIPC. Various portions of aluminum wing skin, right wing, flap, aileron, engine, propeller blades, and propeller hub were observed throughout the debris path. Additionally, several trees were damaged throughout the debris path. The fuselage came to rest upright against a residential structure at an elevation of 447 ft msl.

Figure 3: View of accident site diagram.

A postaccident examination of the airframe and engines revealed rotational continuity throughout both engines and no evidence of mechanical malfunctions or failures were identified that would have precluded normal operation.

The FAA Civil Aeromedical Institute's publication, "Introduction to Aviation Physiology," defines spatial disorientation as a “loss of proper bearings; state of mental confusion as to position, location, or movement relative to the position of the earth.” Factors contributing to spatial disorientation include changes in acceleration, flight in IFR conditions, frequent transfer between visual flight rules and IFR conditions, and unperceived changes in aircraft attitude.

The FAA’s Airplane Flying Handbook (FAA-H-8083-3B) describes some hazards associated with flying when the ground or horizon are obscured. The handbook states, in part, the following:

The vestibular sense (motion sensing by the inner ear) in particular can and will confuse the pilot. Because of inertia, the sensory areas of the inner ear cannot detect slight changes in airplane attitude, nor can they accurately sense attitude changes that occur at a uniform rate over a period of time. On the other hand, false sensations are often generated, leading the pilot to believe the attitude of the airplane has changed when, in fact, it has not. These false sensations result in the pilot experiencing spatial disorientation.

An autopsy of the pilot was performed by the Monterey County Sheriff’s Office – Coroner Division in Salinas, California. The cause of death was “multiple blunt force injuries.”

Toxicology testing performed at the FAA Forensic Sciences Laboratory found no drugs of abuse.