N414RSCessna 414A · 1981

On February 3, 2019, at 1345 Pacific standard time, a Cessna 414 airplane, N414RS, was destroyed when it was involved in an accident near Yorba Linda, California. The pilot and four people on the ground sustained fatal injuries, and two people on the ground sustained serious injuries. The airplane was operated as a 14 Code of Federal Regulations Part 91 personal flight.

Review of Federal Aviation Administration (FAA) radar and audio communications data revealed that, after departing Fullerton Municipal Airport (FUL), Fullerton, California, about 1339, the pilot initiated a climbing left turn to the east. Visual meteorological conditions (VMC) existed at the departure airport; however, the weather transitioned to instrument meteorological conditions (IMC) with precipitation, microburst, and rain showers over the accident area. During the takeoff clearance, the FUL tower controller cautioned the pilot about deteriorating weather conditions about 4 miles east of FUL. Radar data showed that, about 5 1/2 minutes after takeoff, the airplane was about 7,800 ft above ground level (agl) before it entered a rapid, descending right turn and subsequently impacted the ground. Review of recorded data downloaded from the airplane’s Appareo Stratus 2S unit revealed that, at 1344:55, the airplane’s altitude was 5,500 ft agl with a right bank angle of about 110° and a pitch angle of about -35° nose down. Between 1345:03 and 1345:10, the pitch angle fluctuated between 45° nose down and 75° nose up, the bank angle fluctuated between 170° left and 150° right, and the airplane had descended to 1,000 ft agl. The last recorded data showed the airplane about 40° nose up with a 30° right bank and about 500 ft agl.

Several witnesses near the accident site reported seeing the airplane exit the clouds at a high descent rate, followed by airplane parts breaking off. One witness reported that he saw the airplane exit the overcast cloud layer with a nose down pitch of about 60°and remain in that attitude for about 4 to 5 seconds “before initiating a high-speed dive recovery,” at the bottom of which, the airplane began to roll right as the left horizontal stabilizer separated from the airplane, immediately followed by the remaining empennage. He added that the left wing then appeared to shear off near the left engine, followed by the wing igniting. An outdoor home security camera, located about 0.5 mile north-northwest of the accident location, captured the airplane exiting the clouds trailing black smoke and then igniting.

The airplane was approved for day and night instrument flight rules operations and equipped with deice boots, but it was not certified for flight into known icing conditions. The airplane was equipped with S-Tec System 55x autopilot, which was tested on May 1, 2020, and it was deemed operational.

The 1400 High Resolution Rapid Refresh model data depicted a lifted condensation level at 627 ft agl, a free convection level at 632 ft agl and a convective condensation level at 1,608 ft agl. The sounding showed a greater than 90% relative humidity from the surface through 8,000 ft mean sea level. The sounding indicated an unstable to conditionally unstable environment from the surface through 6,500 ft agl with a stable layer above 6,500 through 14,000 ft agl. The sounding also showed the possibility of clouds from 1,100 to about 8,600 ft agl.

The 1330 and 1345 Geostationary Operational Environmental Satellite-17 visible imagery showed broken-to-overcast cloud cover above the accident site at the accident time with the cloud cover moving from southwest to northeast. The visible satellite imagery showed several bands of cumuliform clouds moving across the region and over the accident site during the 15-minute period.

At 1245, an AIRMET advisories Tango and Sierra, which were valid for the area including the accident site, warned of moderate turbulence below 12,000 ft and mountain obscuration conditions due to clouds, precipitation, and mist.

The airplane was approved for day and night instrument flight rules operations and equipped with deice boots, but it was not certified for flight into known icing conditions. The airplane was equipped with S-Tec System 55x autopilot, which was tested on May 1, 2020, and it was deemed operational.

Examination of the accident site revealed that the wreckage debris was scattered throughout a neighborhood and that the wreckage area was about 1,000 ft long and 800 ft wide on a south-to-north orientation. Sections of the tail were found at the far south end of the debris field. The far north area contained the left engine, left propeller, and the fuselage. About 700 ft northeast from the first recovered piece of debris, the right engine and the right propeller impacted an asphalt road and came to rest in a nearby front yard. The left wing was found about 716 ft north of the first recovered piece of debris, about 140 ft southwest of a burned house. Fragments of the outboard right wing (which also contained a fuel tank) were found in the house. The fuselage with the attached right inboard wing, and the left propeller and left engine were found about 310 ft downhill from the house on a heading of 310°.

The left and right outboard wings had separated near the outboard edge of the nacelles. The right outboard wing was almost entirely consumed by fire, and the left outboard wing exhibited moderate fire damage. The left wing forward spar upper cap was deformed down and aft, and the lower cap was deformed downward at the fracture location. The left inboard wing rear spar upper and lower caps were deformed downward at the fracture location. The right wing inboard forward spar upper cap was deformed down and aft, and the forward spar lower cap was deformed downward at the fracture location. The right inboard wing rear spar upper and lower caps were deformed downward at the fracture location. The left- and right-wing spar fractures all had a dull, grainy appearance consistent with overstress separation.

The one-piece horizontal stabilizer and elevators was separated from the empennage; its left half was deformed downward about 80° forward of the rear spar, and its right half was separated and found mostly intact, including the leading edge, upper and lower skins, and portions of the rear spar. The forward spar was fractured, its center section was separated, and the forward attachment bolts had pulled through the spar web. The forward spar attachment bolts remained installed in the empennage bulkhead. The forward spar upper and lower caps in the center section were separated from the web. The center section lower spar cap exhibited a distinct downward curvature from end to end. The forward spar’s separated center section left and right sections of the forward spar, and the mating forward spar fractures were deformed, consistent with the downward failure of the right and left horizontal stabilizer. The left and right elevator counterweights had separated and were not found in the wreckage. A portion of the left elevator remained attached to the horizontal stabilizer and was deformed aft consistent with the damage to the left horizontal stabilizer. A portion of the right elevator and the trim tab remained attached to the horizontal stabilizer. The elevator torque tube bell crank arm rivets were fractured from the actuator rod.

The right side of the fuselage below the horizontal stabilizer shelf was crushed downward. Paint and rubber transfer marks were found on the fuselage skin below the right side of the stabilizer shelf that matched the transfer marks on the lower surface of the left horizontal stabilizer inboard skin. The left side of the fuselage below the horizontal stabilizer shelf was deformed slightly downward. There was no evidence of repeated contact on the elevator stops in the empennage.

The vertical stabilizer and rudder were separated from the empennage in multiple pieces, and the lower end remained attached to the aft fuselage. The lower portions of the vertical stabilizer forward and rear spars were deformed aft.

The primary flight control cables were traced from the cockpit to their respective flight control surfaces. All cables were broken at different locations consistent with the breaks in the structure. All the cable ends had a splayed, broom-strawed appearance consistent with overload.

The right engine was separated from the wing, and all associated systems except for the fuel manifold valve housing were separated from the engine. The crankcase and crankshaft were fractured in the same area (at the oil transfer collar). All fracture surfaces were consistent with overload. The right magneto was manually rotated, and the impulse coupling made an audible snap. A spark was obtained from the distributor towers during manual rotation of the shaft. The left magneto was fragmented with only the drive shaft and magnet observed. All five of the six remaining sparkplugs exhibited normal combustion deposits and wear. The No. 6 cylinder head was fractured in numerous locations, and its sparkplugs were missing. The engine-driven fuel pump was separated from the engine, and the drive coupling was missing. The pump drive shaft was manually rotated with no binding noted. The throttle body unit and oil pump were disassembled, and no evidence of any anomalies before the in-flight breakup were noted.

The left engine was separated from the wing, and the propeller, left magneto, alternator, vacuum pump, starter motor, and throttle body were separated from the engine. A hole was found in the crankcase over the No. 5 connecting rod area, and it appeared that the case was punctured through from the outside to the inside. Wood debris was observed near the puncture. The crankshaft was fractured at the nose seal, and the fracture surface was consistent with overload. The right magneto was manually rotated, and it produced sparks on all leads. The left magneto was not found at the accident site. All sparkplugs exhibited normal combustion deposits and wear. The engine-driven fuel pump drive coupling was manually rotated, and the pump shaft rotated freely with no binding noted. The throttle body unit and the oil pump were disassembled, and no preaccident anomalies were noted. The oil filter was clean, and no metallic debris was noted. Both the right and left turbochargers were examined, and they exhibited characteristics of normal operation with no evidence of distress before the in-flight breakup.

Examination of the engines and the airframe revealed no evidence of any mechanical malfunctions or failures that would have precluded normal operation.

Spatial Disorientation

The FAA’s 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 instrument meteorological conditions (IMC), frequent transfer between VMC and IMC, and unperceived changes in aircraft attitude.

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

The vestibular sense (motion sensing by the inner ear) in particular tends to confuse the pilot. Because of inertia, the sensory areas of the inner ear cannot detect slight changes in the attitude of the airplane, 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.

The FAA's Forensic Sciences Laboratory conducted toxicology tests on specimens from the pilot, which detected sildenafil, sotalol, telmisartan, and amlodipine in heart blood and urine. Acetaminophen was found in urine. Sildenafil, sotalol, telmisartan, amlodipine and acetaminophen are generally not considered impairing.

In addition, 0.88 ng/mL of delta-9-tetrahydrocanninol (THC), the primary psychoactive component of marijuana, and 2.9 ng/mL of its inactive metabolite, carboxy-delta-9-THC (THC-COOH), were detected in heart blood, and 135.7 ng/mL of THC-COOH, and 13.1 ng/mL of the active metabolite of THC, 11-hydroxy-delta-9-THC (THC-OH), were found in urine. Sixty-seven ng/mL of the diphenhydramine, which is a sedating antihistamine used to treat allergy symptoms and as a sleep aid, was identified in heart blood and urine.

THC has mood-altering effects including euphoria, relaxed inhibitions, disorientation, image distortion, and psychosis. Significant performance impairments are usually observed for at least 1 to 2 hours following marijuana use, and residual effects have been reported up to 24 hours. However, THC and its metabolites are fat soluble and undergo postmortem redistribution, which may significantly increase both central and peripheral levels compared with antemortem findings.

Diphenhydramine carries the following Federal Drug Administration warning:

May impair mental and/or physical ability required for the performance of potentially hazardous tasks (e.g., driving, operating heavy machinery). Compared to other antihistamines, diphenhydramine causes marked sedation; it is also classed as a [central nervous system] depressant and this is the rationale for its use as a sleep aid. Altered mood and impaired cognitive and psychomotor performance may also be observed.

However, diphenhydramine undergoes postmortem redistribution. and it can move back into pooled blood from storage sites. Postmortem central blood levels may increase by about three times.