History of Flight
On November 23, 2021, at about 1033 Pacific standard time, an experimental, amateur-built Zenith Zodiac 601XL, registration N601KS, was destroyed in an accident near Temecula, California. The pilot, operating under 14 Code of Federal Regulations Part 91 for personal flight, was fatally injured.
Data from an onboard Appareo Stratus GPS/ADS-B receiver revealed that the airplane departed runway 18 at French Valley Airport (F70) at 1020. It initiated a climbing left turn to the southeast, reaching approximately 3,600 ft mean sea level (msl) about seven minutes later. After reaching the shores of Vail Lake, about 10 miles southeast, the airplane began a 180° descending right turn to a heading of roughly 320°, back toward F70.
Over the next three minutes, the airplane gradually descended from 2,800 to 2,400 ft msl while maintaining an airspeed of about 100 knots. It then pitched approximately 60° nose-down while rolling about 90° right, descending at a rate that reached 9,600 ft per minute before data ended.
Around that time, a witness in a front yard about 3 miles southeast of F70 reported hearing a loud bang, then looking overhead to see an airplane flying northwest. The airplane rolled inverted while diving diagonally into the ground. After impact, debris fell from the sky almost directly above the witness. Multiple other witnesses in the housing development reported similar observations: a loud booming sound followed by an airplane diving toward the ground with debris falling.
The FAA does not record common traffic advisory frequency (CTAF) transmissions at F70; however, CTAF audio was recorded by a public streaming service. The recording, captured shortly before 1033, contained a sound consistent with buffeting wind noise and a person in distress, possibly shouting “help.” Family members later confirmed that the recording sounded like the pilot.
Personnel Information
The pilot’s last logbook entry was for a flight review six days before the accident, conducted in a Piper PA23-250. At that time, his total flight experience was 855.1 hours. Most recent flight experience was in a multi-engine Beech D95A; he obtained his helicopter rating on September 9, 2021. His total experience in the accident airplane was 10.3 hours, accumulated during 12 flights between December 12, 2020, and January 10, 2021. The pilot had an arrangement with the owner to fly the airplane at any time. The owner was unaware of the flight on the accident day, and the reason for the flight could not be determined.
Aircraft Information
The airplane was completed by the owner in 2007, receiving a special airworthiness certificate in November of that year. It was subsequently involved in a hard landing event requiring replacement of both wings, fuselage repairs, and canopy replacement. The airplane was taken out of service in 2014 for an engine rebuild after 45 total flight hours; the rebuild and a condition inspection were completed on September 1, 2020. Logbooks indicated that the owner performed Phase I flight testing, and on December 20, 2020, the airplane had accrued 54 total flight hours and was authorized for Phase II. The accident pilot then flew the airplane six more times through January 10, 2021.
The Zodiac CH 601 series was the subject of an FAA Special Airworthiness Information Bulletin (SAIB) CE-10-08 (November 7, 2009), which identified concerns with the wing structure following in-flight structural failures. The kit manufacturer provided a wing upgrade modification package. The airplane’s maintenance logbooks indicated these modifications were completed in June 2012, along with the addition of aileron balance weights. The airplane was equipped with an autopilot, but it had been disabled by the owner and never used.
Wreckage and Impact Information
The airplane came to rest inverted and nose-down in a field. The airframe was compressed aft, with the engine and firewall aligned with the trailing edge of the wings. Both wings sustained crush damage through to the aft spar; both fuel tanks were breached, and fuel odor was present in the soil. A 70-ft-long debris field consisting of aluminum fragments, flight instruments, and clear canopy acrylic shards extended west from the main wreckage. The pilot’s flight bag, iPad, seat cushion, sun visor, and a fuel sump jar were located about 400 ft east of the main wreckage, dispersed below the descending segment of the flight track.
Flight controls and corresponding control surfaces sustained impact damage and were severely deformed and separated; examination revealed no preimpact failures. The fuel system had multiple breaches, but all fittings were tight, and the fuel selector valve appeared in the right tank position. A significant quantity of canopy fragments were dispersed west of the initial impact point; remnants of the canopy frame were comingled with the main wreckage. The canopy sides remained attached to the rear bow, and the forward bow had broken away from the left side structure.
The engine sustained extensive impact damage, with sections of the intake manifold and most accessories detached. The firewall had formed around the rear of the engine. There was no evidence of catastrophic internal engine failure or oil leak. The propeller hub remained attached to the crankshaft; both composite blades had detached at their roots. One blade exhibited leading edge nicks, dents, and chordwise scratches consistent with rotation at impact; the other blade was bent about 6 inches from the root but otherwise intact. Ground and drone searches of the area below the flight track leading up to the initial upset did not reveal any other cabin contents, airplane parts, or canopy material.
Tests and Research
No evidence of bird strike was found on any airframe structure. Samples from windshield fragments, both propeller blades, and the vertical and horizontal stabilizer were examined by the Smithsonian Institution’s Feather Identification Lab using DNA and microscopic analysis; none contained bird material.
The airplane was equipped with a forward-hinging, tip-up canopy comprising an aluminum and steel frame and an acrylic bubble (thickness 1/16 to 1/8 inch). Gas struts supported the canopy when open. The original design used an automotive-style latch within the frame that locked into striker pins on either side of the cabin sidewall canopy sill. The Pilot Operating Handbook (POH, revision 2, March 2010) stated in the pre-flight inspection section: “Check that your canopy closes and latches properly on both sides. If in doubt, add a secondary latching system as recommended by the Australian CAA.”
Zenair Ltd published a “MANDATORY ACTION – SAFETY ALERT” on December 6, 2021, about two weeks after the accident. The alert documented events where canopies had opened in flight and recommended installation of a secondary canopy latch. It referenced “Recreational Aircraft Airworthiness Notice AN 070109-Issue 1” (January 2009) from Recreational Aviation Australia, which mandated a secondary canopy locking device on Zodiac/Zenair/Zenith models with forward-hinging canopies. The notice stated that the canopy was of light construction, prone to distortion during flight, which could cause latches to release, and that the locking mechanism could be latched without adequately locking the canopy. It cited reports where the canopy opened in flight; while those airplanes remained capable of flight, a speed or power reduction resulted in increased turbulent airflow over the elevators and a sudden nose-down attitude. FAA regulations do not mandate compliance with safety alerts, nor are there provisions for issuing airworthiness directives to experimental airplanes.
The NTSB has investigated seven accidents involving Zenith 600 series airplanes whose canopies opened in flight. International accident reports and various Zenith internet forums indicated that multiple pilots encountered similar events. The openings resulted in control difficulties, often leading to high negative G-forces, aggressive nose-down pitch movements, and cabin contents being sucked out.
The airplane’s owner stated that the canopy had once opened during takeoff, accompanied by a loud bang and wind noise. The canopy opened about 6 inches; he was able to maintain control and return to land. Following that event, he disabled the standard lock by removing the striker pins and installed two 2½-inch-long over-center latches mounted to the rear of the canopy frame. He did not install a secondary latch. These over-center latches were held in place with two 1/8-inch aluminum blind rivets per side. Both latches had separated from the airframe and were found with the main wreckage. The canopy latch hooks remained attached to the rear canopy structure. For one latch, the blind rivet head (7/32 inch) was still in place and appeared sheared from the shank (shank not located); the other rivet was missing. The inboard side of the over-centering arm and corresponding threaded portion of the hook exhibited scratches and paint transfer; the mating side of the mounting plate had scratches and grooves in the vertical plane (canopy tilt direction), not present on the second latch. Both rivets were missing from the second latch; its over-centering arm was deformed inward, and its mounting plate was twisted.
The owner stated that due to his height, he moved the seat 4 inches forward and raised it 2 inches to improve forward visibility, and during turbulence his headset often touched the canopy. He surmised that the pilot, who was 8 inches taller, would have needed to lean inboard to avoid touching the canopy. He further noted that turbulence was not uncommon in the accident area.
The POH contained a section titled “Canopy Opening in Flight,” which advised: “Concentrate on flying the airplane. REDUCE SPEED TO 60 KNOTS. RAISE FLAPS. Ignore the canopy and wind noise. Fly a normal approach and landing without flaps, including completing the landing checklist. The canopy will remain raised in an open position about 1 foot. If the canopy opens after lift-off, do not rush to land. Climb to normal traffic pattern altitude, fly a normal traffic pattern, and make a normal landing. Do not release the seat belt and shoulder harness in an attempt to reach the canopy. Leave the canopy alone. Land as soon as practicable and close the canopy once safely on the ground. Do not panic. Try to ignore the unfamiliar wind. Also, do not rush. Attempting to get the airplane on the ground as quickly as possible may result in steep turns at low airspeeds and altitude. Complete all items on the landing checklist. Remember that accidents are almost never caused by an open canopy. Rather, an open canopy accident is caused by the pilot's distraction or failure to maintain control of the airplane.”