In-Flight Break-up of King Air C90 After Wing Spar Repaired Against Manufacturer’s Advice
In-Flight Break-up of King Air C90 After Wing Spar Repaired Against Manufacturer’s Advice (N3688P, Falcon Executive Aviation) On 10 July 2021 Beech King Air C90 N3688P broke-up in flight and crashed near Wikieup, Arizona. The aircraft was operated Falcon Executive Aviation in support of firefighting for the Federal Bureau of Land Management (BLM), The pilot and the US Forest Service (USFS) Air Tactical Group Supervisor onboard were fatally injured. The US National Transportation Safety Board (NTSB) issued their safety investigation report on 23 August 2023. The Accident Flight The aircraft was on station for about 45 minutes, completing multiple orbits over the Cedar Basin wildfire. One witness saw the aircraft the descend in a steep dive. No distress call was heard and it impacted mountainous desert terrain. Another witness, a firefighter, observed the outboard left wing falling to the ground shortly after the aircraft had impacted the ground. The Safety Investigation Investigators found that: The main wreckage was mostly consumed by a post-crash fire. Debris was scattered over an area of several acres. The outboard left wing was found about 1250 m from the main wreckage. It had separated outboard of the engine nacelle. The C90 was manufactured in 1980. It had been flown as a aerial supervision / reconnaissance aircraft for firefighting since 2007. This involved operating in orbits at c 1000-3500 ft AGL. It was not used in the more demanding lead aircraft role (low level operation to lead in a larger firefighting aircraft for its drop). The aircraft had flown 17,262.6 hours and 15,475 cycles at the time of the accident. Since 2007, it had accumulated 3,507 hours and 1,877 cycles. The NTSB examined the maintenance history of the aircraft. Since 1990, FAA Airworthiness Directive (AD) 89-25-10, Wing Main Spar Inspection had been applicable. This required inspection of “the wing lower forward spar attach fittings, center section, and outboard wing spar caps adjacent to the attach fitting”. It stated: If any crack is found in a main spar lower cap or fitting, prior to further flight repair or replace the defective part using the instructions and limitations specified in the Beech SIRM or other FAA approved instructions provided by Beech Aircraft Corporation. On this aircraft… A total of 16 wing spar inspections were accomplished since the AD became effective and 6 times since the airplane went on contract to the USFS in 2007. Further, the annual spar cap visual inspection for cracks and corrosion [as specified in the Beech Structural Inspection and Repair Manual (SIRM) 57-13-01] was accomplished 16 times since 2007. However, in March 2021… During a scheduled [AD 89-25-10 and SIRM 57-13-01] maintenance inspection…eddy current (EC) non-destructive testing (NDT) of a left wing’s lower forward spar cap detected a crack in a fastener hole. The hole was then oversized/reamed to a larger size, but the EC reinspection still produced a crack indication. The operator then submitted a structural damage report and service request detailing the crack indication to the aircraft manufacturer. The manufacturer responded in April 2021 that this necessitated the replacement of “the center section forward spar cap, center section forward lower fittings and both outboard main spar assemblies.” The email response…to FAS also included the warning below from their published instructions for wing structure inspections in the SIRM 57-13-01, (in part [emphasis in...
read moreSouth Korean Night Black Hole Spatial Disorientation Fatal Helicopter Accident
South Korean Night Black Hole Spatial Disorientation Helicopter Fatal Accident (National 119 Rescue Airbus Helicopters H225 HL9619) On 31 October 2019 emergency service Airbus H225 HL9619 of National 119 Rescue crashed into the sea just 14 seconds after take off from the island of Dokdo during a patient transfer medevac flight. All 7 occupants died in the accident. The South Korean Aviation and Railway Accident Investigation Board (ARAIB) issued their safety investigation report (in Korean) on 6 November 2023. This accident summary is based on a translation of this report. Note: ambiguities after translation did made interpretation challenging but we are confident the content here represents the final report accurately. The Accident Flight National 119 Rescue is fire-fighting, air ambulance, mountain & maritime Search and Rescue (SAR) organisation, ultimately a part of the Korean National Fire Agency. The helicopter was tasked to fly east from Daegu on the mainland to Dokdo Heliport on an rocky offshore island, to retrieve a fisherman who was on the island after had suffering a severed finger on a fishing vessel. On board were 5 crew (two pilots, a flight engineer / hoist operator, a winchman and paramedic). The captain had 3,827 flying hours total experience, 444 on type. The first officer had 2,666 flying hours total experience, 307 on type. The flight crew had no prior experience landing at Dokdo and investigators state that during their flight planning the crew were unable to obtain “information about the terrain of the landing area or the heliport to the extent the crew desired”. The helicopter departed Daegu at 22:33 and refuelled successfully at Ulleungdo island en route. The captain complained of being tired during the flight. The captain was working an extended shift due to a business trip involving another pilot. The aircraft was fitted with a Night Vision Imaging System (NVIS). Investigators note that the… National Fire Agency does not have a clear basis for the operation of night vision equipment., Pilots selectively use night vision equipment depending on individual preference. Evidence from an Appareo Vision 1000 recording system confirmed the pilots were using their Night Vision Goggles (NVGs) when the aircraft departed, though the Vision 1000 video recording ceased during the flight. Cockpit Voice Recorder (CVR) evidence was that the NVG continued to be used intermittently as necessary during the flight. CVR data suggested that Automatic Flight Control System (AFCS) selections were not being verbalised and “there were cases where the first officer did not realize the captain’s intentions”. The 25 m square Dokdo heliport, at an elevation of 177 ft, was operated by the Gyeongbuk Provincial Police Agency, but they lacked specific heliport procedures and personnel with relevant competencies. This was the first night landing at the site in 3 years. Two of the four perimeter flood lights were unserviceable, though the green perimeter lights were serviceable. Visibility was good with no clouds or sea fog but little illumination form the waxing crescent moon. There was a crosswind at Dokdo, that was likely to have induced turbulence and no illuminated windsock. The helicopter landed at Dokdo at 23:24 after one missed approach (with a torque exceedance). The missed approach followed a miscommunication between aircraft and ground resulted in all lights at the site being briefly extinguished. During the second landing attempt a person...
read moreHelicopter Water Impact Accident: Safety of Airborne Geophysical Survey Operations
Helicopter Water Impact Accident: Safety of Airborne Geophysical Survey Operations (Synergy Aviation Guimbal Cabri G2 C-GSYN) On 8 October 2021, Guimbal Cabri G2 C-GSYN of Synergy Aviation impacted Wachigabau Lake, Quebec during a geophysical survey flight for survey company Novatem. The pilot sustained serious injuries, but egressed underwater and swam to shore. Context of the Flight The Transportation Board of Canada (TSB) issued their safety investigation report on 31 August 2023. TSB explain the helicopter was operating from Chapais, Quebec and that morning, the pilot (407 hours total, 235 on type and trained at the operator’s own flight school) was tasked with two low-level geophysical survey flights before ferrying the helicopter to Amos/Magny Airport (CYEY), Quebec, for maintenance. Synergy had started operating survey flights for Novatem in mid 2020, developing their Guimbal Aeromagnetic Survey Procedure (GASP). TSB explain that: Under the heading Safety, the GASP stated that “[h]azards to consider are wires, persons or livestock, trees, rising terrain, and water.” However the document did not offer mitigations on how to deal with these hazards. Rather, it referred readers to the Exercise 22 – Low Level Operations of the Helicopter Flight Training Manual on TC’s website. The GASP’s section on flight planning and hazard assessment listed 9 hazards to consider, including lakes, rising terrain, and tall standalone obstacles (e.g., trees), but it did not provide clear guidance on how to assess and mitigate those hazards within the context of aerial work, aeromagnetic survey work, low-level flying, or over-water operations. The helicopter was equipped with a nose boom, or ‘stinger’, containing a magnetometer. The Novatem aeromagnetic survey monitor, mounted to the right of the console directly in front of the pilot, displayed the survey blocks and flight tracks. It displayed height above sea level but did not display height above ground because the helicopter was not equipped with a radar altimeter. A conventional barometric altimeter was the only instrument on board that provided a useable indication of the helicopter’s altitude. Importantly: To obtain quality data, the helicopter must consistently maintain the optimal height (approximately 25 m [82 feet] over land and water) on all survey lines. This means that the helicopter is required to fly the contour of the terrain as much as possible. Novatem has stated that some variations in height due to obstacles and other safety concerns are acceptable, and data collected can be corrected with software calculations and extrapolation algorithms. However: While some pilots, including the occurrence pilot, had been briefed verbally by the chief pilot on the requirement to fly the contour of the terrain, the requirement to fly at and maintain the optimal height of 25 m (82 feet) was not clearly communicated. Neither the requirement to fly and maintain the optimal height of 25 m (82 feet) nor the requirement to fly the contour of the terrain was included in the GASP. As it was not part of the Operations Manual, the GASP was not reviewed by the regulator, Transport Canada. Without the integration of a precise height indication on board, the pilots were left to visually estimate and rely solely on feedback from Novatem to determine whether they had flown a proper flight profile at the correct height. This also left them to determine and maintain their height using visual cues only. In relation to training to prepare for this...
read moreInvestigation into B212 Accident off UAE 7 September 2023
Investigation into B212 Offshore Helicopter Accident off UAE 7 September 2023 (Aerogulf A6-ALD) On 7 September 2023 Aerogulf Services Bell 212 A6-ALD crashed into the Arabian Gulf of the UAE at c 20:06 Local Time during a night offshore training flight. Both pilots were fatally injured. The Accident Flight The Air Accident Investigation Sector (AAIS) of the United Arab Emirates GCAA, in a preliminary report, issued 6 October 2023, stated that the helicopter departed Al Maktoum International Airport (OMDW), Dubai, for the Aras Driller jack-up drilling rig located off the emirate of Umm Al Quwain at c 19:18 Local Time. The Aircraft Commander (9011 hours total time), the trainer, was in the left seat as pilot monitoring (PM), and the Co-pilot (7031 hours total time) was the pilot flying (PF) in the right seat. The intent was to make 5 offshore landings to maintain night recency. The Aerogulf Ops Manual Part D states… ..flight crew will keep their night recency using a FFS [Full Flight Simulator] or the real aircraft completing 3 night take off, each followed by a traffic pattern and a subsequent landings every 90 days. The training objective were: The helicopter climbed to 1100 ft and proceeded along the coast to the jack-up with an ETA of 19:40 Local Time. At 19:38 Local Time the radio operator on Aras Driller passed the latest weather data: “rvariable windspeed ranging from 7 to 9 knots coming from the 60°, visibility between 7 to 8 knots [sic – presumably nautical miles or km] and 1002 millibar air pressure”. At 19:46 Local Time the PM contacted the radio operator to inform him that they were 2 minutes away from landing. The radio operator confirmed they had a ‘green deck’ (i.e. the helideck was available). At 19:50 Local Time, the Bell 212 landed on helideck, heading southeast. It took off ay 19:52 Local Time and headed north east. Within 3minutes, it turned and descended for a second landing, again heading south east. After the second landing, it took off again at 19:59 Local Time and performed a second circuit landing for the third time at 20:03 Local Time. At 20:05 Local Time, the helicopter took off again. One minute later the Helideck Landing Officer (HLO) called the radio operator, reporting that the helicopter had crashed c 600 m away to the north west. The Search and Rescue (SAR) Activity At 20:08 Local Time, the radio operator notified the rig management and initiated a distress call for SAR. The rig launched a fast rescue craft. They were not able to locate any survivors but found an inflated liferaft with some debris attached The investigators say: The SAR rescue team reached the site in about 45 minutes after they were notified. The team swiftly initiated operation within the designated area. Its not clear what SAR asset this was, but it appears to have been a boat, as they go on to say: About 1 hour 20 minutes after the initial notification, a SAR helicopter arrived at the site. Equipped with powerful high beam focus lights fitted on it, the SAR helicopter conducted an intensive survey of the anticipated site. At the same time, the SAR rescue boat gathered all floating debris, which encompassed a small part of the helicopter. The following day after…the...
read moreMaintenance Distraction in Bell 407 Accident
Maintenance Distraction in Bell 407 Accident (N98ZA, Zip Aviation) On 4 June 2022 Bell 407 N98ZA of New York air tour operator Zip Aviation crashed shortly after commencing a positioning flight to JFK International Airport, New York following maintenance at Caldwell Essex County Airport, New Jersey. The Accident Flight According to the NTSB safety investigation report published on 20 September 2023, about 5 minutes after departure, at an altitude of about 500 ft amsl, the Appareo Vision 1000 onboard recording system captured the pilot (872 hours total time, 29 on type) saying, “what is going on here?”. The pilot [when about 2 miles south of Teterboro Airport] subsequently contacted air traffic control and requested to return to the departure airport, but he did not declare an emergency or state that he needed assistance. Upon initial contact with the tower controller at the destination airport, the pilot stated that he “might need the runway”. As the helicopter approached the airport and its indicated airspeed began to decay below about 30 knots, the helicopter entered a right yaw and completed several 360° rotations around the main rotor mast before impacting terrain next to the runway, resulting in substantial damage. The Safety Investigation The Bell 407’s tail rotor was installed the day before after the replacement of four feathering bearings. Examination by investigators revealed that the tail rotor crosshead drive plate, which was positioned behind the pitch change rod attachment nut, was not bolted to the tail rotor crosshead, as prescribed in the maintenance manual. The two attachment bolts were not present, and no remnants of any bolts were found in their threaded receptacles in the crosshead drive plate The threads were undamaged and showed no signs of corrosion, deformation, smearing, or cross-threading. During interview… The director of maintenance (DOM), who performed the task, stated that he conducted the tail rotor assembly installation by laying out the parts on a maintenance cart; performing the installation procedure, including the mast nut torque application; and having a mechanic verify the mast nut torque. He then finished the installation and had another mechanic verify the work. The mechanic who did the verification did hold a Inspection Authority and Zip Aviation did not “have an active RII [Required Inspection Item] program”. Despite promoting maintenance human factors (HF) for many years, there is still no FAA requirement to do independent inspections on this size of aircraft. A company pilot performed a preflight inspection of the helicopter, ground functional checks, and three consecutive maintenance runs to balance the tail rotor. The accident flight was the first flight after completion of this work. Significantly: According to the DOM, between the mast nut torque application and completion of the tail rotor assembly installation, he was “called out” to consult on two different aircraft repairs. The DOM did not recall the amount of time that elapsed before he resumed the installation work. After the accident Zip Aviation developed an RII program. NTSB Probable Cause The failure of maintenance personnel to properly secure the tail rotor crosshead drive plate and the failure of maintenance personnel, the maintenance pilot, and the accident pilot to detect the error, which led to the helicopter’s loss of tail rotor antitorque. Also causal was the pilot’s failure to maintain the helicopter’s airspeed at or above effective translational lift and...
read moreLighthouse HESLO Accident
Lighthouse HESLO Accident (AS350B2 F-GJRP, La Vieille, Brittany) On 6 July 2022 Airbus AS350B2 F-GJRP operated by Mont Blanc Hélicoptères, part of HBG France, was involved in an dramatic loss of control accident during a Helicopter External Sling Load Operation (HESLO) in support of maintenance at La Vieille lighthouse, off Pointe du Raz, Brittany for the Brest Lighthouses and Beacons Service (SPBB). One member of the ground party was crushed between a load and the stone balconey of the lighthouse. The accident was caught on video: The Accident Flight The BEA issued their safety investigation report in French on 21 September 2023. At c09:00 the helicopter landed at a staging area on the mainland, a short distance from the lighthouse. The SPBB site manager was present at the landing site but the SPBB ground party was already at the lighthouse. The helicopter operator’s Task Specialist was briefed that they would be unable to travel to the lighthouse to inspect the loads due to tidal conditions. Furthermore the SPBB team at the lighthouse, who were to hook up the returning loads, contrary to normal practice, had no radio. At 10:45 the first operations commenced with a 30 m sling. On board were the pilot (4,130 flight hours, 2,310 on type) and the Task Specialist, who was in the cabin, in the left rear seat, to provide the pilot with guidance. The wind was from the north at around 6 kt, gusting 8 kt. Initially loads were moved from the base of the lighthouse. The pilot explained that during lighthouse missions, he uses the rearview mirror, rather than the vertical reference window, to prevent his gaze from being focused on the waves, which, according to him, can lead to spatial disorientation. With the 30 m sling to collect packages at the bottom of the lighthouse, its visual reference was the weather vane at the top of the dome of the Vieille lighthouse. A sea mist around noon led the pilot to pause flying. The wind strengthened and was from north-northwest, at 15 kt, gusting 20 kt. Operations commenced again at 14:00. One more load was moved from the base of the lighthouse, then a 10 m sling was fitted to move load from the balcony of the lighthouse that surrounds the lantern. The first was a 326 kg load. The pilot explains that piloting with a 10 m sling to recover the loads at the top of the lighthouse was simpler due to the position of the helicopter in relation to the dome of the lighthouse. However there was concern about the strengthening wind. The BEA explain that: From 14:26:55., the pilot turned to follow a westerly course before turning towards the lighthouse five seconds later. It then turns left to translate vertically to the lighthouse balcony facing west, at an altitude of approximately 40 m. From 14:27:26 ( point❶), the pilot turns to the left and translates eastwards slightly south of the lighthouse balcony. During this period, vertical or close to the vertical of the lighthouse terrace, the pilot sees in the rearview mirror that an SPBB agent on the terrace is trying to catch the hook. After taking his eyes off the rearview mirror to maintain control of the helicopter and the trajectory, the pilot no longer sees the...
read moreThe Loss of RAF F-35B ZM152: An Organisational Accident
The Loss of RAF F-35B ZM152 from HMS Queen Elizabeth: An Organisational Accident On 17 November 2021, Lockheed Martin F-35B Lightning II ZM152 (BK-18) of Royal Air Force (RAF) 617 Squadron, crashed into the eastern Mediterranean, during take off from HMS Queen Elizabeth. As the ship sailed past the wreckage before it sank, an intake blank was seen to float free. Was the loss of this £81.1 million fighter simply because ‘someone’ was negligent or incompetent? No. In this deep dive case study we will demonstrate that real life is more complex. We look at how the 148 page Service Inquiry Report, published by the Defence Safety Authority on 10 August 2023, identified systemic organisational factors. This requires understanding the organisational context of the accident, not just the actions of individuals in the minutes and hours beforehand. Organisational Accidents James Reason, Professor Emeritus, University of Manchester popularised the expression ‘organisational accident’ with his seminal 1997 book Managing the Risks of Organizational Accidents. He used the term to differentiate simple ‘individual accidents’ involving just one person from complex accidents involving more people, organisations, technology and systems. Reason explained that: Organizational accidents have multiple causes involving many people operating at different levels of their respective companies. Such accidents result from ‘latent organisational failures’ that are like pathogens that have infected the organisation. In the earlier, 1995 book, Managing the Risks of Organizational Accidents, Maurino, Reason, et al give examples: Lack of top-level management safety commitment or focus Conflicts between production and safety goals Poor planning, communications, monitoring, control or supervision Organizational deficiencies leading to blurred safety and administrative responsibilities Deficiencies in training Poor maintenance management or control Monitoring failures by regulatory or safety agencies Reason famously illustrated how pathogens build up through the concept of the swiss cheese model, where each layer of cheese represents a defensive barrier. Latent holes in the cheese, the pathogens, are introduced by both local workplace and organisational factors that remain dormant until holes in every layer align. Often the last line of defence is breached by a human action but focusing on that in safety investigations, means the inherent pathogens are ignored and barriers and control remain unfixed. The Aerossurance visualisation of this model is that as time progresses many of these holes will dynamically change size and position as circumstances change, either increasing or decreasing the risk. In practice human actions also routinely plug the holes too, knowingly or unknowingly. Another reason that focusing on the actions or inactions of one individual can mean missing the big picture. Pathogens as Precursors to this Accident: Critical Context on How the ‘Holes in the Cheese’ were Created 617 Squadron and HMS Queen Elizabeth In 2017 the National Audit Office (NAO) summarised the wider UK’s Carrier Enabled Power Projection (CEPPP) programme as follows: After personnel underwent training at MCAS Beaufort, South Carolina, 617 Squadron reformed at RAF Marham, home of the UK Lightning Force, in April 2018 with the F-35B, the Short Take Off and Vertical Landing (STOVL) variant of the F-35. The aircraft is powered by a Pratt and Whitney F135 engine. For STOVL operations there is a Rolls-Royce three-bearing swivel nozzle at the rear, a shaft driven vertical lift fan forward and two wing mounted roll posts. HMS Queen Elizabeth is the first of a pair of 65,000 t Royal...
read moreEngine Maintenance Introduced FOD that Caused an EC120 Power Loss
Engine Maintenance Introduced FOD that Caused an EC120 Power Loss (N421PB) On 9 April 2021, a private Airbus EC120B, N421PB, was substantially damaged in heavy landing after a loss of engine power near LeRoy, Kansas. The pilot and passenger were were uninjured. The Accident Flight The US National Transportation Safety Board (NTSB) reported in their safety investigation report, issued 16 August 2023 that the pilot (a CPT with 561 hours total and 164 in type) stated that: …while in cruise flight at 2,000 ft, he heard the low rotor speed warning horn but no cockpit caution/warning lights illuminated. The…engine’s free turbine speed and the main rotor speed were “drooped”, and he reduced collective and moved the cyclic control aft to stabilize the main rotor speed. He was able to maintain main rotor speed with about “70%” collective input as indicated on the first limit indicator (FLI). The helicopter decelerated from 100 knots to 85 knots while the pilot maintained the helicopter’s altitude. The pilot and the passenger [also a qualified pilot] began looking for suitable fields to land in, but about 2-3 minutes after the initial main rotor low speed warning horn, the horn resumed a sustained tone for the remainder of the flight. The pilot stated that the main rotor speed continued to decrease as he flew toward an open field for a landing, but he eventually entered an autorotation before reaching the intended field because of the decreasing main rotor speed. [T]he pilot entered a right turn and made an immediate landing in a residential backyard. The helicopter had a high descent rate when it touched down. The landing gear skids were deformed outward and the tail boom and fenestron exhibited buckling/crushing consistent with the tailboom impacting the ground. Safety Investigation Testing confirmed the pilot’s report of the engine being unable to maintain free turbine speed at 100% while under increased loads. Further examination and testing revealed a contaminated fuel injection manifold fuel filter, which restricted the amount of fuel that could be delivered to the engine’s gas generator. A laboratory examination determined the contamination was consistent with a cellulose material. Cellulose is found in natural plant fibers. The spectra of known samples of white paper and white cotton were…compared to the unknown sample and exhibited strong matches. Similar contamination was found in engine’s main fuel filter and fuel control unit (FCU) during disassembly. NTSB concluded that: Based on the known information, the cellulose contamination found in the fuel injector manifold filter was likely introduced during associated fuel system maintenance at an undetermined date. Our Observation While the contamination source was not determined by NTSB it distinct possibility the cellulose was from some form of cleaning cloth or paper towel. This material is often not controlled with the same rigour as tools. for example, yet can also cause damage an in-flight emergencies. A similar previous Aerossurance FOD case study was: FOD Damages 737 Flying Controls Safety Resources The European Safety Promotion Network Rotorcraft (ESPN-R) has a helicopter safety discussion group on LinkedIn. You may also find these Aerossurance articles of interest: Maintenance Human Factors: The Next Generation Aircraft Maintenance: Going for Gold? Rotor Blade Tool Control FOD Incident Maintenance Issues in Fire-Fighting S-61A Accident FOD and an AS350B3 Accident Landing on a Yacht in Bergen Air Ambulance Helicopter Downed by Fencing FOD Tool...
read moreA Concrete Case of Commercial Pressure: Fatal Swiss HESLO Accident
A Concrete Case of Commercial Pressure: Fatal Swiss HESLO Accident (Lions Air Skymedia AS350B3 HB-ZOJ) On 11 June 2018 Airbus AS350B3 HB-ZOJ of Lions Air Skymedia crashed while conducting a Helicopter External Sling Load Operation (HESLO) in the Swiss Alps. The helicopter was destroyed and the pilot died. The Swiss Safety Investigation Board (SUST) issued their safety investigation report on 20 September 2022. A Complex Commercial Context The local cooperative for rural building was upgrading the Surenen alpine cheese dairy on Alp Ebnet. In mid-May 2018, the client placed an order with Fuchs Helikopter AG to transport concrete to the construction site… However, deliveries were requested when Fuch’s only suitable helicopter was committed elsewhere. Hence, these “these orders were passed on to BEO Helicopter AG“. BEO however were not a helicopter owner or operator. They sub-contracted work to Lions Air Skymedia AG (trading as Lions Air Group AG), who owned 50% of BEO. The morning flights on 11 June 2018 were flown by BEO’s co-owner under Lions Air’s approval. However, they were travelling to the UK later that day so a Lions Air pilot was to take over in the afternoon. The afternoon pilot was experience in HESLO and had c11 years of experience in the local area but had a gap holding an AS350 type rating between October 2015 and April 2018. The ground party for the tasking consisted of two personnel from Fuchs (referred to by SUST as Marshal 1 & 2) and a Lions Air trainee they had not worked with before (Marshal 3). The afternoon pilot had also never worked with any member of the ground party. A second pilot, Pilot 2, was also on site. They had positioned the helicopter and were due to conduct a subsequent tasking that had been cancelled. The Pre-Flight Briefing The afternoon pilot and ground crew met at around 13:00. Marshal 1 specified that the weather had been discussed and the weather radar consulted and it was agreed that only as much as possible should be done based on the weather. Otherwise the order should be interrupted. There was no time pressure. However, in contrast: According to [Marshal] 2, the weather conditions were not mentioned because there was no reason for them. The investigators comment: These different views of Marshal 1 and 2 on the relevance of the weather on this mission indicate that there was no common understanding of safety-related aspects, at least relating to the weather. The Accident Flight At c 13:30 the HESLO operations commenced using a 20 m line and two cement buckets to be moved one at a time. When laying concrete it is essential to complete the ‘pour‘ in one go. Because of the changing visibility and fog conditions, [Pilot 1] chose different flight paths for the individual rotations. After a few rotations, the wind increased from the west. As a result, more and more wafts of fog appeared between the pick-up and drop-off locations. By the 7th rotation Marshal 1 warned Pilot 1 by radio that a band of fog was gathering near the lower cable car mast. Pilot 1 acknowledged that the construction site was still clear at that time for landing if necessary. On each rotation the pilot touched the concrete bucket on the ground to discharge static before positioning to...
read moreMissing Cotter Pin Causes Fatal S-61N Accident
Missing Cotter Pin Causes Fatal S-61N Accident (Croman Sikorsky S-61N N615CK, Barking Sands, Hawaii) On 22 February 2022 Sikorsky S-61N N615CK operated by Croman Corporation was destroyed in an accident at the US Navy Pacific Missile Range Facility (PMRF), Barking Sands, Kauai, Hawaii. The two pilots and two rear crew members (who were Croman mechanics) were fatally injured. The Accident Flight According to the NTSB safety investigation report published on 26 July 2023 the helicopter was conducting a Part 133 Helicopter External Sling Load Operation (HESLO) to do an inert Mk 48 training torpedo recovery with a conical basket/cage system, under contract to the US Navy. Croman had two S-61Ns at Barking Sands, maintained by three maintenance personnel at the PMRF to support the US Navy’s ongoing Pacific submarine training operations. According to automatic dependent surveillance-broadcast (ADS-B) data, after the helicopter departed, it proceeded north-northwest to an area about 44 miles away. After maneuvering in the area, the helicopter proceeded south-southeast to return to PMRF. As the helicopter approached the facility, it crossed the shoreline and began a shallow left turn as it maneuvered to the north, into the prevailing wind. As the helicopter neared the predetermined drop-off site, the left turn stopped, and the helicopter proceeded in a northeasterly direction. Multiple witnesses located near the accident site reported that as the helicopter continued the left turn towards the drop-off site, the turn stopped, and it began to travel in a northeast direction. The witnesses noted that as the helicopter flew about 200 ft above the ground, it gradually pitched nose down and impacted nose first, in a near-vertical attitude. The CVR transcript was as follows: The helicopter came to rest on its left side on a heading of about 230° magnetic. Three ground scars consistent with main rotor blade impact marks were present near the initial airframe ground impact location. The nose bay door for avionics was found near the start of the debris trail, followed by pieces of debris from the cockpit structure and cockpit instruments, and then the remainder of the helicopter. The initial ground impact mark and debris trail leading up to the main wreckage was oriented about 65° magnetic. A postcrash fire consumed most of the cockpit and the cabin, though remnant frame sections were present near the main (forward) landing gear as well as the transmission deck. Safety Investigation An examination of the wreckage revealed the flight control fore/aft servo input link remained connected at its clevis end to the flight control fore/aft bellcrank, located adjacent to the main gearbox. However, the rod end was partially connected to the fore/aft servo input clevises and its bolt had mostly backed out of its normally installed position. The bolt exhibited no evidence of fractures or visible deformation and its threads exhibited no unusual wear. Therefore, the bolt likely backed out of its normally installed position during the accident flight due to the absence of its nut and cotter pin. This would have caused an uncommanded input to the fore/aft servo, resulting in the helicopter’s nose-down attitude, and the inability of the crew to control the pitch attitude of the helicopter. The investigators found that… …according to maintenance records, from 17-29 December 2021, multiple maintenance actions were performed. The director of maintenance and another mechanic travelled...
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