Preliminary Reports

Freighter Destroyed Attempting Takeoff

Beech C99, Oct. 7, 2024, Norfolk, Nebraska

The solo pilot was killed and the majority of the aircraft consumed by the post-crash fire when the Part 135 cargo flight went down immediately after takeoff. Airport surveillance footage showed the airplane taking off from Runway 20 of the Norfolk Regional Airport, banking left, and descending into the ground. It struck about 640 yards southeast of the runway’s departure end and came to rest 24 yards further east in a flat, near wings-level attitude.

The flaps were found retracted and the landing gear extended. Flight control continuity appeared to have been continuous prior to impact. Fire damage prevented reading the cockpit instruments, and no non-volatile memory devices were found in the wreckage. Prevailing weather included clear skies with 10 miles visibility and six-knot winds from 160 degrees.

Seven Survive Departure Crash

Daher TBM 700, Oct. 29, 2024, Pinedale, Wyoming

One passenger was seriously injured when the single-engine turboprop crashed departing after a fuel stop. The pilot and the other five passengers escaped with minor injuries. A witness on the field reported that heavy snow was falling while 40 gallons of fuel were added to each tank and the six passengers boarded. The pilot “cleared the snow off the airplane with a brush,” and the snowfall was described as “light” during its taxi and takeoff roll.

Shortly after it lifted off from Runway 29, the airplane’s left wing dropped and struck the ground. It came to rest in a snow drift adjacent to the runway with “substantial” damage to the left wing and fuselage. Weather conditions recorded 10 minutes before the accident included four miles visibility under 600-foot scattered and 3,200-foot broken cloud layers with a temperature of -1 and dew point of -2 Celsius. Prevailing winds were not reported.

Final Reports

K-MAX Rotor Breakup Traced to Control Flap Failure

Kaman Aerospace K-1200, Oct. 4, 2021, Killam Bay, British Columbia, Canada

Debris recovered from the accident site, including pieces of all four blades, indicated that the helicopter’s main rotor system broke up in flight. The solo pilot conducting external load operations from a logging site to an offshore pen was killed when the helicopter fell nose-first into the pen eight seconds after releasing its load. Search-and-rescue efforts were initiated as soon as the operator lost radio contact with the pilot, but it took eight days to locate the underwater wreckage using sonar.

The Kaman K-1200 is an unusual design that uses two counterrotating main rotors with two blades each, thus eliminating torque reaction and the need for a tail rotor. The planes of their rotation intersect; a 12.5-degree outward tilt in each rotor pylon and a 90-degree offset in blade positions allows them to intermesh. Flight-control inputs are transmitted via control rods to 35-inch servo flaps located along each blade’s trailing edge. Deflection of the servo flap imposes torsional loads that twist the blade’s 50-inch elastic working section, changing its angle of attack.

Extensive analysis led the Transportation Safety Board to conclude that a fracture of an internal bond joint in one of the left rotor’s servo flaps caused fatigue cracking of the flap’s skin, resulting in the departure of the aft (trailing edge) two-thirds of the flap’s structure. This in turn “created an out-of-track condition that caused a cyclic imbalance and a sudden vibration of the left main rotor system, the flutter of the three other rotor blades, and the failure of the left pylon structure. This led to the collision between a blade on the left rotor and a blade on the right rotor that resulted in the in-flight breakup of the rotor system.”

Two fatal U.S. accidents also involved collisions between the K-1200’s main rotor blades; the second, in August 2020, was specifically attributed to a servo flap failure. The manufacturer has also received three field service reports of servo flap failures in which the pilots landed safely. On June 1, 2023, Kaman revised the K-1200 maintenance manual with instructions for repairing chordwise paint cracks in the servo flaps that require removing the flap from service if the crack extends beyond the paint layer.

Maintenance, Airmanship Errors Contribute to Runway Excursion

Eclipse Aerospace EA500, Nov. 3, 2022, Mesa, Arizona

An excessively fast approach, a misaligned wheel speed transducer (WST), and a missed step in the emergency procedures combined to render the right brake inoperative and send the very light jet off the left side of a 5,100-foot runway. The pilot and copilot were not injured, but the airplane sustained damage to the nose, both flaps, and all three legs of the landing gear after coming to rest in a six-foot-deep drainage culvert.

The accident occurred on the jet’s first flight after maintenance, including its 24-month/300-hour airframe inspection, had been performed at the Henderson (Nevada) Executive Airport. Both pilots recalled normal braking before takeoff, though while taxiing slowly due to rain. The flight was uneventful.

Running the before-landing checklist, the pilot confirmed that the anti-lock braking system (ABS) was armed and pressed the ALL INTERRUPT switch to verify that the yaw damper was disengaged. He reported landing just beyond the 1,000-foot markings on Falcon Field’s Runway 22L, but when he applied the brakes the airplane drifted left without slowing. The copilot called for him to activate the ALL INTERRUPT switch; the pilot replied that he already had.

Full right rudder failed to correct the turn. The jet exited the left side of the runway, crossed two taxiways and dropped into the culvert.

ADS-B and onboard recorded data showed that the approach and landing were flown about 20 knots faster than the appropriate reference speed. The runway slopes down 0.6 degrees, and the four-knot tailwind reported earlier had increased to 10 knots. The lift provided by the additional speed limited braking effectiveness; the weight-on-wheels sensors did not activate until 2,490 feet down the runway.

Investigators subsequently found that the right WST had not been correctly aligned with the hubcap after maintenance, leading the ABS to erroneously detect a locked right wheel and release pressure to that brake. Holding down the ALL INTERRUPT switch would have disabled the ABS and restored braking function, but the recorded onboard data showed that it had only been depressed briefly once, during approach.

Interrupted Maintenance Led to Nose Gear Failure

Cessna Citation 525A CJ2, Oct. 28, 2023, Paris-Le Bourget Airport, France

After the crew made a successful emergency landing, investigators found that the reason the nose gear had neither retracted nor extended was that maintenance personnel failed to reconnect the actuators to the gear doors during a routine inspection of the gear well. The connecting hardware was found in a plastic bag taped to the left door actuating rod.

The jet departed Le Bourget for Farnborough Airport in the U.K. at 21:23 local time with one passenger on board. It was its first flight after several days of scheduled maintenance.

Extended discussions with air traffic control followed the crew’s unsuccessful attempt to use the standby gear extension system. Because the Citation is not equipped to dump fuel, they burned off excess fuel in nearly three hours of low--altitude flight following vectors from ATC. After much additional discussion the airport decided not to foam the runway, and the jet landed safely on Le Bourget’s Runway 25.

Maintenance staff interviewed by investigators described a confusing organizational structure, with no clear lines of responsibility for specific tasks. The initial landing gear inspection was conducted by the least experienced member of the six-person team, a 19-year-old who’d joined the company two months earlier.

After inspecting the nose gear well, he asked whether he should reinstall the door actuator hardware and was told not to do so before a more senior technician inspected the work. The doors were subsequently held closed with aluminum tape while the airplane was towed out of the hangar for an engine run-up; fragments of the tape were found on the bottoms of the doors after the accident. A red flag attached to the gear doors was removed by the same senior technician on the mistaken assumption that he had already performed that inspection.