N9MBNorthrop/Air Museum N9M · 1945

On April 22, 2019, about 1209 Pacific daylight time, a Northrop N9M airplane, N9MB, was destroyed when it was involved in an accident near Norco, California. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

Representatives from the Planes of Fame Air Museum, Chino, California, reported that the accident flight was a post-maintenance check flight in preparation for their annual air show.

Multiple witnesses adjacent to the accident site saw the airplane flying on an east-northeasterly heading at a low altitude. One witness, who was a pilot, was located about 0.5 mile southeast of the accident site and reported seeing the accident airplane in level flight with what sounded like a cruise power setting; both engines appeared to be functioning. The witness said that the airplane then pitched upward no more than 15°, and during the climb, the airplane banked left about 10 to 20°, before it abruptly banked to the right until the airplane was inverted. The witness added that once the airplane was inverted, the engines began to sputter; however, as the roll continued, the engines' rpm increased quickly, and the airplane entered a "diving right corkscrew turn." The airplane continued to descend below a tree line out of the witness's view; however, he could hear "a very loud noise from the engines" followed by the sound of impact; he subsequently saw a rising plume of black smoke.

Another witness stated that the airplane appeared to initiate a "barrel roll" at a low altitude and begin to wobble back and forth before the canopy separated from the airplane. The witness added that the airplane wobbled a second time before it rolled to the right and descended into the ground.

Review of radar data obtained from the Federal Aviation Administration (FAA) showed a primary radar target on an easterly heading about 3 miles south of Chino Airport, Chino, California, as seen in figure 1; no altitude information was available. The last return was about 0.3 mile west of the accident site.

Two videos were submitted by witnesses who were located along the flight path and near the accident site. In the first video, the airplane was seen flying in a level attitude with both engines operating. The airplane was not visible in the second video; however, the sound of both engines could be heard from the start of the recording until a plume of smoke could be seen in the upper left corner of the video frame. Variances in the tone of the engine noise could be heard during the last 14 seconds of the recording.

Figure 1. View of radar track information, with witness video locations depicted.

The pilot held type ratings in A-320, ATR-42, ATR-72, Cl-65, CV-LB30, DC-9, B-25, and SF-340 aircraft. Personnel from Planes of Flame Air Museum estimated that the pilot had accumulated about 25 hours of flight time in the accident airplane over the span of about 4 years. The pilot was wearing a parachute during the accident flight.

The single-seat, tricycle retractable gear flying wing airplane, serial number 04, was powered by two 300-horsepower Franklin XO-540-7 engines, serial numbers 88 and 89, driving two Hamilton Standard 2B20-225 constant speed propellers. The airplane's flight control system primarily comprised control cables that extended to all primary flight controls, with hydraulic-boosted actuators.

The single-seat, tricycle retractable gear flying wing airplane, serial number 04, was powered by two 300-horsepower Franklin XO-540-7 engines, serial numbers 88 and 89, driving two Hamilton Standard 2B20-225 constant speed propellers. The airplane's flight control system primarily comprised control cables that extended to all primary flight controls, with hydraulic-boosted actuators.

The airplane impacted the outpatient housing yard of the California Rehabilitation Center. The debris path was oriented on a heading of about 124° magnetic and measured about 474 ft long and 200 ft wide. The first identified point of contact (FIPC) was green lens fragments, consistent with the right wing navigational light lens, as shown in figure 2. From the FIPC, a blue-and-yellow colored mark extended about 32 ft to a large ground impression/crater that measured about 2 ft deep and 3 ft wide. Within the ground scar were remains of the right engine. The ground scar extended about 16 ft and contained portions of the cockpit, nose landing gear, and airframe structure. Wood debris, various fragments of both engines, and airframe structure were located throughout the debris path. The left and right propeller assemblies were located about 100 ft from the FIPC. The farthest portion of debris was a propeller blade tip, located about 474 ft from the FIPC.

Figure 2. Initial impact marks and start of debris path.

Canopy structure and window debris was located about 60 ft northwest of the FIPC and about 330 ft west of the FIPC. Both areas where window and canopy structure were located were in the opposite direction of the debris path, as shown in figure 3.

Figure 3: Accident site overview.

The heavily fragmented wreckage was recovered for further examination. Remains of all major structural components were located throughout the wreckage, including both engines, flight controls, wing structure, engine mounts, propellers, cockpit structure, canopy, and landing gear. The seatbelt clasp ends were located within the recovered wreckage and found in the unlatched position.

Remains of flight control cables were located throughout the recovered debris, in addition to portions of flight control structure. All the separations in the located cables exhibited splayed signatures, consistent with overload separation. Additionally, all of the recovered control cable turnbuckles were intact and had either safety clips or safety wire in place. The flight control trim drums were located within the wreckage with the trim cables still attached. All trim drums exhibited varying degrees of impact damage.

The left and right elevon box actuator housings were located within the recovered wreckage. Both boxes exhibited varying degrees of impact damage. The hydraulic actuators within the boxes were impact damaged. The hydraulic selector valve and follower linkages were impact damaged.

The left and right engines were both displaced from the engine mounts and were fragmented into multiple pieces. Both crankcases were severely fragmented. Remains of all sixteen cylinders, pistons, and connecting rods were observed within the recovered wreckage. Both crankshafts were severely deformed. The torque convertors and driveshafts were impact damaged.

The outboard portion of one propeller was separated about 15 inches from the tip, with a large portion of the leading edge missing, consistent with impact with a circular object. The opposing blade exhibited some aft bending with varying degrees of leading-edge damage. The other propeller exhibited "S" bending on both blades with varying degrees of leading-edge impact marks.

The Riverside County Coroner's Office, Perris, California, performed an autopsy of the pilot. The pilot's cause of death was multiple traumatic injuries.

The FAA's Forensic Sciences Laboratory performed toxicology testing on the pilot's tissue samples, which revealed 22 (mg/dL, mh/hg) of ethanol in the muscle.

A secondary laboratory performed toxicological testing of muscle samples. Unspecified amounts of ethanol and pseudoephedrine/ephedrine were detected. The testing did not measure its quantity and did not distinguish pseudoephedrine from ephedrine.