History of Flight
On April 6, 2018, about 1710 Pacific daylight time, a Mooney M20J airplane, registration N9133Z, was destroyed in an accident near Petaluma Municipal Airport (O69) in Petaluma, California. The private pilot, operating under Title 14 Code of Federal Regulations Part 91 for a personal flight, sustained fatal injuries.
At about 1657, the pilot contacted Flight Service to request an instrument flight rules (IFR) clearance from Petaluma Municipal Airport to Fallbrook Community Airpark (L18), Fallbrook, California. The pilot reported he would depart runway 29 and was ready for immediate departure. He received his IFR clearance at 1700 with a void time of 1710.
A witness, a pilot familiar with O69 operations, was on the airport office deck monitoring the common traffic frequency when he heard the accident pilot broadcast taxiing to runway 29. He then observed the airplane taxi to runway 11 and remain in the runup area for about 15 minutes. Around 1700, the pilot announced, "Petaluma traffic, Mooney departing Runway 29"; the witness transmitted "Runway 11," to which the pilot replied, "Thank you. I appreciate the help." The witness saw the airplane depart runway 11 and climb to about 300 ft above ground level before initiating a shallow left turn and disappearing into fog. He reported no unusual engine sounds; the engine sounded strong, smooth, and normal.
Another witness reported that the accident airplane landed at O69 around 1645 the previous day and taxied to the fuel island. He helped the pilot obtain fuel, observed him sump the fuel tanks after refueling, and instructed him where to park. The accident pilot queried a FedEx pilot on the appropriate instrument departure procedure for runway 29. On the day of the accident, the pilot returned to the airport about 1645 and walked to his airplane for preflight. About 1700, as the witness was leaving, he saw the airplane in the runway 11 runup area. He returned about 1800 to aid in the search.
The pilot never established radio contact with Oakland Air Route Traffic Control Center (ZOA) after takeoff. At 1723, ZOA received an emergency locator transmitter signal near O69; an alert notice was issued by the FAA at 1803. Aerial search was hindered by weather; ground search by local law enforcement and first responders located the wreckage about 2200, about 1 mile north of O69.
Meteorological Information
The National Weather Service surface analysis chart for 1700 depicted station models near the accident site with air temperatures in the low- to mid-60s°F, dew point near 60°F, temperature-dew point spreads of 2°F or less, south wind 5–10 knots, moderate rain, and overcast skies. Constant pressure charts from the NWS Storm Prediction Center showed a low-level trough northeast of the site, typically associated with enhanced lift, gusty winds, fronts, clouds, precipitation, and potential low-level wind shear (LLWS) and turbulence.
AIRMETs Sierra and Tango, valid at accident time, warned of IFR conditions due to precipitation and mist, mountain obscuration, and moderate turbulence below 10,000 ft msl. A High-Resolution Rapid Refresh model sounding for 1700 indicated surface wind from 163° at 5 knots, becoming westerly through 5,000 ft and increasing to 25 knots, with possible light LLWS between surface and 100 ft agl and light to moderate clear air turbulence in several layers between 2,000 and 14,000 ft.
Pilot reports from about 2 hours before to 2 hours after the accident indicated cloud ceilings around 400–700 ft agl with moderate turbulence. An urgent PIREP at 1438 near San Francisco International Airport (SFO), about 43 miles south, reported LLWS +/-15 knots at 1,900 ft on final approach.
Wreckage and Impact Information
The accident site was in a muddy mustard field with rolling hills at about 307 ft msl. The airplane impacted in a near-vertical attitude on a heading of about 200°, and a postcrash fire ensued. All major components were located at the site. Both wing fuel tanks ruptured. The cockpit and cabin were largely consumed by fire, and the aft fuselage exhibited extensive accordion-style crushing.
The right wing separated from the fuselage and came to rest forward on the right side. The right fuel cap was secure but its seal thermally damaged. The right aileron remained attached but impact damaged; the right flap separated and bent up at both ends near midspan. The left wing sustained accordion-style leading edge crushing near the tip, lessening toward the root. The left fuel cap was secure but its seal showed cracks around the circumference. Left aileron and flap remained attached, relatively undamaged; the left flap was in the up position. Left main landing gear retracted; right main landing gear separated but remained attached to its linkage.
Vertical and left horizontal stabilizer, left elevator, and rudder remained attached and relatively free of impact damage. Right horizontal stabilizer and elevator sustained impact damage. Flight control continuity was verified from cabin to rudder; elevator control continuity established from elevator via push/pull tube to aft fuselage to cabin, where melted due to fire. Left aileron continuity established to wing root; right aileron continuity established to wing root where push/pull tube fractured with overload features.
Examination of the airframe revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The engine and propeller separated and were buried in about 3 ft of soft mud. The engine sustained extensive impact damage. Propeller remained attached; both blades exhibited leading edge polishing. Manual rotation produced compression in all four cylinders, with valve train and gear train continuity. The single-drive dual magneto separated and was impact damaged; blue spark observed on only one lead per rotation at the magneto but on all leads at the left distributor in order. The vacuum pump had a fractured carbon rotor (three pieces) but all vanes whole and in position; drive coupling intact. A liquid consistent with water was present in the fuel flow divider under the diaphragm, estimated at half of the remaining liquid (consistent with 100LL aviation fuel).
Medical and Pathological Information
An autopsy under the authority of the Sonoma County Coroner attributed the pilot's cause of death to multiple blunt force and thermal injuries. The FAA Forensic Sciences Laboratory performed toxicology testing; carbon monoxide and cyanide testing was not performed, no ethanol detected in urine, and testing identified 2.184 µg/ml doxylamine in urine and 1.877 µg/ml in liver. Doxylamine is a sedating antihistamine used for cold/allergy symptoms and available over-the-counter as a sleep aid.