Accidents: September 2021

 - September 9, 2021, 2:20 PM

Preliminary Reports

Alberta Firefighting Accident Triggers Emergency AD

Bell 212, June 28, 2021, Evansburg, Alberta, Canada - Investigators probing the crash of a firefighting helicopter near Evansburg, Alberta, found that a main rotor hub strap pin had sheared off in flight, causing a main rotor blade to separate from the aircraft. The solo pilot was killed when the helicopter crashed into the woods en route to pick up a group of forest firefighters, igniting an additional fire. The failed pin was reported to have been installed only 20 flight hours earlier.

Inspection of another Canadian Bell 212 helicopter found that a main rotor hub strap pin from the same manufacturer had deformed after approximately 29 hours in service. Transport Canada issued an emergency airworthiness directive on July 5 requiring immediate replacement of all pins with the same part number and serial number prefix of “FNFS,” applicable to specific serial numbers of Bell 212, 204B, 205A-1, and 205B helicopters. The FAA issued its own emergency AD the following day, extending it to the model 205A. About 400 helicopters worldwide are believed to be affected.

Nine Deaths in Swedish Skydiving Accident

deHavilland DHC-2 Turbo Beaver, July 8, 2021, Orebro, Sweden - Eight parachutists and the pilot were killed in the crash of their jump plane. Initial reports, including a statement by the head of the civil aviation division of the Swedish Accident Aviation Authority (SHK), suggested that it went down in an open field to the left of the runway immediately after takeoff.

This was Sweden’s second skydiving accident involving nine fatalities in just over two years. On July 14, 2019, a GippsAero GA8 Airvan crashed onto an island in the Ume River shortly after takeoff from the Umea Airport. There were no survivors.

On July 13, the SHK reported that the on-site phase of the investigation had been concluded and the wreckage recovered to the SHK’s facilities in Strängnäs. They cautioned, however, that “The investigation is expected to continue for a long period.”

Two Perish in Apparent King Air Breakup

Beech C90, July 10, 2021, Wikieup, Arizona - The pilot and Air Tactical Group supervisor were killed when the twin-engine turboprop crashed onto the side of a ridgeline while conducting aerial reconnaissance and supervision in the vicinity of the Cedar Basin fire. The airplane had been on station for approximately 45 minutes, making multiple orbits of the scene, before disappearing from radar contact while descending through 2,300 feet agl at 151 knots. A witness saw it “in a steep dive towards the ground.” No distress calls were received.

The main wreckage was consumed by a post-crash fire, but debris was scattered over several acres. The left wing was found 0.79 miles northeast of the main wreckage and showed no thermal damage, suggesting it separated prior to impact.

Final Reports

Forced Landing Exposes Maintenance Discrepancies

Hughes 369D, Aug. 1, 2019, Follebu, Gausdal Municipality, Innlandet County, Norway - The two crewmembers escaped without injury but the helicopter was severely damaged after losing engine power at an altitude of three meters (10 feet) while setting up for a precautionary landing. About 52 minutes into the powerline inspection flight, the pilot noticed unusual vibrations, which were not initially apparent to the imaging systems operator but gradually increased in intensity. “A metallic sound” began about 30 seconds later and likewise intensified. All engine instruments remained in their normal ranges, but the pilot decided to land in order to inspect the helicopter.

After reconnoitering the area, he set up a slow approach to a grassy field, then began repositioning closer to the adjoining road. The noise and vibration abruptly increased and the torque meter readings became unstable, so the pilot decided to land immediately. As he brought the helicopter to a hover, there was a loud bang from somewhere behind the cockpit. The helicopter rotated 60-70 degrees left while falling to the ground, collapsing the right skid and striking the tail stinger and main rotor blades. The pilot shut down the engine before the crew evacuated.

Teardown inspection at the manufacturer’s headquarters in Arizona found that the main transmission input pinion had fractured. While the fracture itself was traced to fatigue, other anomalies were found within the gearbox, which had previously been opened to comply with AD 87-18-12. Among the irregularities were loose main bearings attributed to excessively thick adjustment shims; a bushing around the pinion’s bearings that had been installed rotated 90 degrees from its correct position, obstructing oil flow; and blockage of the pinion’s internal bore by two cylinders of “cork-like material” that investigators compared to “wine corks,” adding that they were “not installed as part of any approved maintenance procedure” but were “a very creative, but highly irregular way of stopping a leak” from the main gearbox into the pinion’s inner bore that might have propagated through the incipient fatigue fracture.

Investigators also determined that the gearbox had been in service 1,000 hours longer than the operator’s records indicated, putting it 749 hours beyond the manufacturer’s recommended overhaul interval. While the precise cause of the fatigue fracture could not be determined, it had most likely begun more than 749 hours before the accident and could have been detected had the overhaul been performed on schedule.

Weather, Regulatory Ambiguity Contribute To Runway Excursion

Beech A100, April 28, 2020, Kugaaruk Airport, Nunavut, Canada - Stiff crosswinds, optical illusions created by blowing snow in low visibility, plowing delays, and potential confusion between the minimum visibilities required for approach versus landing at airports above 60 degrees north latitude all contributed to the runway excursion that damaged a Buffalo Airways freighter on a charter flight from Cambridge Bay to Kugaaruk, Nunavut (CYBB). The airplane veered off the right side of the runway into a snowbank after the right main landing gear hit accumulated snow during the landing roll, causing damage to “the aircraft’s fuselage, nose, engines, propellers, nacelles, flaps, wing centre section, and right wing spar… The right wing was bent up and aft.” The nose gear collapsed and the rim of the right main wheel fractured in overload during the excursion. The pilot and first officer evacuated the airplane without injury.

The crew flew the RNAV approach to Runway 23, which follows a true course of 244 degrees, offset 15 degrees from runway heading. Prevailing weather included visibility of one-quarter mile in blowing snow, 400 feet vertical visibility, and 24- to 33-knot winds from 200 degrees creating a 12- to 16-knot crosswind component. The TSB’s report notes that “To a pilot conducting an approach and landing into drifting snow, the aircraft may appear to be drifting sideways in a direction opposite to the blowing snow. To correct this apparent drift, the pilot might make control inputs that result in undue drift correction…In crosswind conditions, the illusion can be described as a ‘moving runway.’” The crew was able to see the runway but not its centerline, the runway lights, or the precision approach path indicator (PAPI) lights, and the captain landed the airplane at or beyond the right edge of the runway.

For much of the preceding two months, runway maintenance at CYBB had been impeded by the combination of equipment outages and blizzard conditions that made local travel to and from the field unduly hazardous. This was the case the day of the accident, when no snow removal was undertaken. Despite rentals of heavy equipment from the neighboring village, snowbanks eight feet high remained within five feet of the runway lights. A photograph taken during clearing operations the morning after the accident shows the 27-inch-high runway edge lights almost buried in accumulated snow.

The TSB also noted that while airports north of 60 degrees latitude are exempt from minimum visibility requirements for instrument approaches, landing visibility minimums still apply. With no specific listing in the Canada Flight Supplement, the minimum landing visibility at CYBB is the default of ½ statute mile, so while the approach was authorized, the landing was not. The TSB commented that “The application of these two independent requirements can lead to confusion and give some pilots the impression that, if the approach ban is not in effect, landings are authorized without the need to take into account the aerodrome operating visibility requirements.”

Vortex Ring State Claims N.C. Police Helicopter

Bell 206A, Nov. 8, 2020, Raleigh, North Carolina - While attempting to land at the North Carolina Highway Patrol’s training facility, the pilot successfully recovered from two encounters with vortex ring state, also known as “settling with power.” Vortex ring state is a condition in which the combination of high power demand and low airspeed leaves the main rotor operating in its own downwash, significantly reducing its ability to produce lift. Increasing power only aggravates the problem, so recovery depends on regaining forward or sideways motion into undisturbed air.

After the second attempt, the pilot landed at the Highway Patrol’s driver training facility. To reduce power demands, the copilot disembarked before the pilot returned to the ready hangar. During the third landing attempt the helicopter again entered vortex ring state, this time 100 feet lower than in the previous approaches, and the pilot was unable to escape before it descended into treetops, causing a main rotor blade to strike the tail boom. The pilot, who also holds commercial, instructor, and instrument instructor certification in airplanes, made a successful autorotation onto Tryon Road and escaped without injury. He reported 1,878 hours of career flight time, including 101 in type.

This was the second helicopter accident at the training facility in three years. On June 19, 2018, a Bell OH-58A was destroyed by dynamic rollover after the pilot forgot to unhook its left skid from the electric transporter used to move it out of the hangar.     ν