Engine 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...
read moreB407 Damaged During Autorotation Training
Bell 407 Damaged During Autorotation Training (PHI, N451PH) On 23 May 2023 PHI Bell 407 N451PH was damaged during new hire autorotation training at Abbeville, Louisiana. According to the NTSB safety investigation report published on 27 July 2023: The check pilot and the pilot receiving instruction were performing initial new hire training for the commercial operator. The pilot previously performed three practice 180° autorotations, terminating with a power recovery. The pilot then performed a practice, straight-in, full down autorotation to touchdown on the sod area parallel to the runway. The NTSB provide weather data but wind speed and direction are blank. UPDATE 29 July 2024: Readers have pointed out that the METARS showed nil wind at the time, which would increase the risk. During the touchdown, the two pilots heard a “loud bang.” The helicopter came to rest upright on the sod area and both pilots were able to egress from the helicopter without further incident. A postflight inspection revealed that the main rotor blades struck the tail boom, severing the tail rotor driveshaft. The main rotor blades, the tail boom, and the tail rotor system sustained substantial damage. The NTSB Probable Cause: The pilot’s failure to maintain proper helicopter control during autorotation that resulted in an abnormal ground contact which caused the subsequent main rotor strike on the tail boom that severed the tail rotor driveshaft. Contributing to the accident was the main rotor blowback condition, due to the aft tilting of the main rotor disk. The reference to blowback is unusual in NTSB reports into what is a relatively common type of accident. NTSB describe main rotor blowback occurs by reference to another manufacturers’ data (MD Helicopters): A review of the accident helicopter rotorcraft flight manual (RFM) found no information listed to provide awareness to pilots about the main rotor blowback condition. However, no safety recommendations are made. Safety Resources The European Safety Promotion Network Rotorcraft (ESPN-R) has a helicopter safety discussion group on LinkedIn. One ESPN-R resource is: EHEST Leaflet HE 5 Risk Management in Training. Also see: Why is autorotation management important for safety? within the EASA community site. Also Airbus Helicopters issued Safety Information Notice (SIN) 2896-S-00 (dated 7 July 2015) on simulated engine-off landing (EOL) training. You may also find these Aerossurance articles of interest: Alaskan AS350B3e Accident: Botched Autorotation Practice? Inappropriate Autorotation Training: Police AS350 NVIS Autorotation Training Hard Landing: Changed Albedo Tree Top Autorotation for B206L1 After Loose Fuel Line B-Nut Leaks Latent Engine Defect Downs R44: NR Dropped to Zero During Autorotation Torched Tennessee Tour Trip UPDATE 8 September 2024: B407 Worn Throttle Detent Power Loss Accident Aerossurance has extensive air safety, flight operations, airworthiness, human factors, helidecks, aviation regulation and safety analysis experience. For practical aviation advice you can trust, contact us at: enquiries@aerossurance.com Follow us on LinkedIn and on Twitter @Aerossurance for our latest...
read moreSAR AW139 LOC-I During Positioning Flight
SAR AW139 Loss of Control – Inflight During Positioning Flight (Babcock MCS España EC-NEH) On 12 June 2019, Leonardo AW139 EC-NEH, a Search and Rescue (SAR) helicopter, operated by Babcock MCS España (since sold to Ancala Partners and now trading as Avincis), was damaged during a Loss of Control – Inflight (LOC-I) and a subsequent forced landing. The Accident Flight According to the Spanish Comisión de Investigación de Accidentes e Incidentes de Aviación Civil (CIAIAC) safety investigation report, released in June 2023, the helicopter was being positioned VFR from the Babcock Spanish HQ at Mutxamel Aerodrome (Alicante) to the Spanish Maritime Rescue and Safety Society (SASEMAR) El Musel SAR base (Gijón). The helicopter had recently been purchased by Babcock, only being registered on 30 May 2019. The only person onboard, for what was expected to be a 3.5 hour flight, was the single pilot. The pilot had 6,408 hours of experience, 1,759 on type. The AW139 hours were all with Babcock, accumulated in the previous 11.5 years. Fifty three minutes into the flight the helicopter was in cruise over Serranía de Cuenca “with the Flight Director’s IAS [Indicated Airspeed], LNAV [lateral navigation] and ALT [altitude hold] modes coupled” and the ATT stabilisation system active. At this point, there was what the pilot reported as a “destabilisation of the helicopter”. He noticed strong turbulence which destabilised the helicopter, placing it into a nose-up position, rolling to the right almost 90°, which he managed to recover. During this manoeuvre, he noticed air coming from his left. Later, when he could turn his head, he found that this was due to a rear window that had come off on that side. In addition, there was the failure of two engines that led him to initiate an autorotation and an emergency landing. When he landed, he became aware that the window on his side was also missing. The flight recorders confirmed that at 13:30:50, the helicopter was flying straight and level at 135 kt IAS (152 kt ground speed) at an altitude of 6,537 ft (1,142 ft AGL) with a heading of 331° when the destabilisation began. It reached its maximum development three seconds later. Roll was increasing to the left until, at 3 seconds (13:30:53), it reached a maximum value of -140°. Yaw underwent variations in both directions with maximum opposite rates of variation of +70°/s and -31°/s. Pitch ranged from -12° to +22°. After the maximum destabilisation of the helicopter at 13:30:53, with a roll to the left of -140°, the pilot tried to regain control of the helicopter. Rate of decent peaked at 6,500 ft/min at 13:30:55 with a engine overspeed and the main rotor reaching 115% NR. Within six seconds after the start of the event, the failure of the electronic controllers of the two engines (EEC) was recorded, which changed the mode of operation from automatic (AUTO) to manual (MAN). At 13:31:01, 11 seconds after the start of the event, the helicopter recovered its attitude. The speed had dropped to 75 kt IAS, course changed to 239° and 473 ft in altitude had been lost. There was a descent that lasted 46 seconds until a controlled run-on landing in open countryside at 13:31:47 with a 57 m ground roll. The pilot was uninjured. The ground, grassy and wet, had undulations and sinkholes. The...
read moreBK117 Offshore Medevac CFIT & Survivability Issues
BK117 Offshore Medevac CFIT & Survivability Issues (Southern Lakes BK117C1 ZK-IMX, Southern Ocean off Auckland Islands) On 22 April 2019 Southern Lakes Helicopters Airbus / Kawasaki BK117C1 ZK-IMX suffered a Controlled Flight into Terrain / Water (CFIT/W) while positioning for an offshore medical evacuation (medevac) flight. The Accident The New Zealand Transport Accident Investigation Commission (TAIC) issued their safety investigation report on 22 April 2023. TAIC explain the helicopter, based at Te Anau, was tasked for a medevac from a fishing vessel in the Southern Ocean off Auckland Islands. The casualty “required urgent hospital treatment” (though their medical condition is not elaborated upon) and “the first aid stocks on the vessel needed replenishment”. The operator had 8 helicopters (a mix of BK117s, AS350s, EC120s and R44s). They held a New Zealand CAA Part 135 approval. TAIC give very little other information about them, although while they… …had substantial procedure manuals for major operations, such as flying in the Antarctic or when working with the local search and rescue organisation, the guidance procedures for this high-risk type of operation was spread across several sections of the exposition. Ominously: Much of the operator’s experience had yet to be documented. In the early 2000’s Ambulance New Zealand and the NZ Helicopter Association had developed a joint standard called the ‘New Zealand Aeromedical and Air Rescue Standard’ (NZAARS). This standard reportedly did not apply because “this flight was a privately-funded medical evacuation”. There is no clarity on how the flight was tasked or by who. TAIC comment that: The operator had found from experience that standard aviation weather forecast information was not reliable for the Southern Ocean. They obtained their own weather information from several different but well-known sources, including the automatic weather station (AWS) on Enderby Island, then made their own assessment. As they were aware of the cold front approaching they planned to position to Enderby Island (the ‘positioning flight’) before it arrived and stay overnight at a hut where the operator had a fuel store. The next day the helicopter would rendezvous with the fishing vessel, hoist aboard the casualty and after refuelling again at Enderby Island, return to New Zealand on 23 April 2019 in the clearer air behind the cold front. On board for the visual flight rules (VFR) positioning flight were a single pilot, a paramedic in the front left hand seat, and a hoist operator in the cabin. The pilot had 6673 hours in total (all VFR). They had trained on night vision goggles (NVGs) in 2013 and had 73 hours on NVG experience, but had done less than 1 hour in the last 90 days. The pilot did not hold an instrument rating and and had only flown to Auckland Islands once before. The paramedic had a logged time 198 hours on NVGs but worked for another company and was only called in when medevacs occurred. The pilot had completed Helicopter Underwater Escape Training (HUET) in July 2013. The paramedic’s last HUET was in May 2018 and the hoist operator, who was a casual part-time employee, had completed HUET in September 2013. Our observation: two of the crew had therefore not done HUET in over 5½ years and two were casual staff who were only called in when their specialist skills was required. TAIC explain...
read moreEC135 Air Ambulance CFIT when Pilot Distracted Correcting Tech Log Errors
Airbus EC135P2+ Air Ambulance CFIT when Pilot Distracted Correcting Tech Log Errors (Med-Trans / LifeForce 6 N558MT, North Carolina) On 9 March 2023 LifeForce Airbus EC135P2+ air ambulance N558MT, operated by Med-Trans Corporation (part of Global Medical Response), suffered a Controlled Fight into Terrain (CFIT) during a night time patient transfer near Franklin, North Carolina. The helicopter stuck trees atop high ground an force landed on to a road. Three of the occupants received minor injuries and the fourth escaped uninjured. The US National Transportation Safety Board (NTSB) safety investigation report was published 6 June 2023. The Accident Flight The helicopter was based as Western Carolina Airport, Andrews, North Carolina. The pilot was working a 06:30 to 18:30 shift. The 51 year old pilot had 4723 flying hours of experience, 1867 on type according to the accident report form. We suspect this may be just civil time as the pilot is a former USMC squadron commander. At c17:50 a request was received for a patient transfer between two hospitals. This would have been the pilots fourth tasking of the day, but the pilot stated to the NTSB “we felt confident we could complete the flight within the 14-hr window” (presumably the applicable duty time limit). At 18:13 they arrived at Erlanger Western Carolina Hospital, Murphy, North Carolina to collect the patient. The pilot stated that while the patient was prepared for flight there was one distraction for the pilot, a call with the Regional Area Manager (RAM): I was instructed to double check maintenance due times to ensure we would not overfly any inspections due to a temporary glitch between RAMCO (company maintenance program) and FlightLog that was being rectified. Subsequently: I computed and recorded the weight & balance information in the flight log for the upcoming leg and attached the NVG [Night Vision Goggles] battery pack and mount to my helmet in anticipation of donning the goggles during the next leg… There is no indication that the NVGs were tested. The flight was forecast as 38 minutes and twilight was at c19:19. Weather was workable: reporting and forecasting VFR along the route. The majority of the reports…indicated 10SM, -RA, BKN 060 30.14. The pilot commented to NTSB that the highest obstacle en route was 6,100 ft with several 5,000 to 5,500 ft peaks too. The helicopter departed shortly after 18:45. Upon reaching Vy (65kts) I selected IAS (indicated airspeed) mode on the autopilot and HDG (heading) mode to take us just north of the Tusquitte Spine (an east west running ridge..). At c18:50: I dialled in 5500’ and shifted to V/S (vertical speed) mode with AltA (Altitude Acquire). Upon reaching that altitude airspeed increased to ~110 KIAS (~132 Kts ground speed.) Although, the pilot was intending to don NVGs they were not mounted on the pilot’s helmet ready to flip down. They were in fact “resting on the logbook” (i.e. Technical Log) on the empty front seat. I was just about to remove the caps and don them when I chose instead to relocate the logbook to the pilot door compartment where we typically stow it during flight. With logbook in hand, I decided to double check the printed-out RAMCO due values against the logbook values since we had already flown over four hours that day with an...
read moreOil & Gas Aerial Survey Aircraft Collided with Communications Tower
Oil & Gas Aerial Survey Aircraft Collided with Communications Tower (Airborne Energy Solutions Cessna 172N C‑GZLU) On 18 September 2022 Airborne Energy Solutions aerial survey Cessna 172N C‑GZLU, surveying oil and gas pipeline infrastructure, collided with a communications tower near Shaunavon, Saskatchewan (a Controlled Flight Into Terrain [CFIT]). Both pilots onboard died. The Accident Flight The Transportation Safety Board of Canada (TSB) issued their safety investigation report on 16 May 2023. The TSB explain that the aircraft had departed Swift Current Airport (CYYN), Saskatchewan at 08:27 Local Time and was conducting a visual flight rules (VFR) flight to gather electronic data for a unnamed client along a route that extended southeast of Shaunavon, then eastward to Estevan. The contract… …required that there be two pilots on board: one to fly the aircraft, the other to monitor the captured electronic data and assist with navigation duties. The pilots switched seats and duties on alternating flight legs. The customer’s “job form” for the survey specified a height of 550 feet AGL (±50 feet). The aircraft was equipped with an altimeter, which indicated altitude in feet ASL; however, it was not equipped with, for example, a radio altimeter, to indicate height in feet AGL. The Pilot Flying, sat in the left seat, held a Commercial Pilot Licence and had 355 hours total flight time, 77 of which were on the C172 for Airborne Energy Solution. The other pilot also held CPL and had 536 hours of total flight time, 529 on type. However: At approximately 1003, the aircraft struck a communications tower approximately 6 an SSW of Shaunavon. The height of the communications tower was 3840 feet ASL, or 440 feet AGL. It was marked and lit in accordance with the Canadian Aviation Regulations. The tower was also depicted on the Regina VFR Navigation Chart. The aircraft’s last recorded position on its flight tracker (at 1001:30) was 1.2 nm WNW of the communications tower at an altitude of 3741 feet above sea level (ASL), which was 572 feet above ground level (AGL). The occurrence aircraft was travelling on a track of 88° true (T) when it struck the communications tower approximately 25 feet below the tower’s highest point. A 4-foot section of the aircraft’s right wing was shorn off and was discovered at the base of the tower. The fuselage then travelled approximately 240 m on a track of 174°T, before impacting the ground. A post-impact fire ensued, which consumed most of the remaining fuselage. TSB note that the… …area forecast for the occurrence area, valid from 0600, indicated clear sky conditions with visibilities greater than 6 statute miles. Weather was not considered to be a factor in this occurrence. However: The sun’s position at the time of the occurrence would have been rising in the east. Solar position calculations indicate that the solar azimuth was 125°T (37° right of the aircraft’s track of 88°T) and the solar elevation was 28° at the time of the collision. It is possible that glare from the sun obscured the pilot’s view of the communications tower. TSB Safety Message Interestingly the treat of glare was not the subject of TSB’s safety message, instead they give the self-evident reminder of… …the importance of consulting available navigational charts when flight planning and in flight so as to avoid colliding with obstacles identified on those charts. Our Observations...
read moreHH-60L Hoist Cable Damage Highlights Need for Cable Guards
Sikorsky HH-60L Hoist Cable Damage Highlights Need for Cable Guards (N964SB, Santa Barbara County Fire Department) On 3 December 2022 Sikorsky HH-60L N964SB of the Santa Barbara County Fire Department suffered hoist cable damage while conducting hoist training from Santa Ynez Airport/Kunkle Field, California. The Incident The helicopter was also equipped with a belly-mounted Kawak Aerial Liquid Delivery System (ALDS) firefighting tank system and elongated landing gear. The Department of the Interior (DOI) & US Forest Service (USFS) SAFECOM aviation safety reporting system report states: …the helicopter slowly approached the deployment location with the Crew Chief seated at the rear door [i.e. the right hand cabin door]. As the rescuer neared the ground, a cable swing developed in which the crew chief determined to be excessive. The Crew Chief decided to bring the rescuer back up to the helicopter… As the cable length reduced the swing amplitude consequently increased and… …the cable swung forward of the aircraft sidestep and wrapped around the backside of the cable guard where two bolt heads were protruding. These screws are reported to have had “sharp edges” and “about 1/4″ of threads showing”. This contact resulted in extensive damage to the hoist cable with 7 of the outer cable strands becoming sheared. The rescuer made it into the aircraft safely, but the cable was not able to be reeled all the way into the drum. The cable hook was secured to the aircraft’s upper strut tiedown and the aircraft was flown back to base, where the cable was changed, and the aircraft was placed back into service. Safety Action Kawak is developing a user-installed kit “that will prevent the deployed cable from coming in contact with any structure on the tank or step.” It will add a “simple but robust bar guard, and will have rub strips along the whole length” and kits and a Service Letter will be distributed to operators free of charge. Our Safety Observations This occurrence highlights the importance of cable guards and considering the credible cable swing arc. The Flight Safety Foundation (FSF) BARSOHO offshore helicopter operations Safety Performance Requirements contains Control 12.4: Hoist Cable Protection: Hoist cables must be protected from damaging contact with aircraft structure. UPDATE 30 May 2024: IOGP has issued version 1 of their Recommended Practice 699 Emergency Response Services. 699/5-1 does require hoist cable protection in a table of equipment, which is good. It is however accompanied by footnote 8. Readers will notice there are only 7 footnotes listed below the table and that footnote 5 (not assigned to an item in the table) actually says: If hoist cable protection is not available due to the aircraft type in use this is to be discussed, agreed and documented with the Company Aviation Advisor. This was the only equipment listed in the table that IOGP recommend can be waived by Company Aviation Advisor (something that was unsuccessfully challenged in two rounds of industry comment). We contend that if an aircraft is proposed to be used for hoisting and it lacks such protection it is both unsuitable and unsafe. Waiving hoist cable protection would be demonstrating gross negligence. Safety Resources The European Safety Promotion Network Rotorcraft (ESPN-R) has a helicopter safety discussion group on LinkedIn. There is this article that considers hoist cables: Helicopter Hoisting and the Human in...
read moreSwinging Snorkel Sikorsky Smash: Structural Stress Slip-up
Swinging Snorkel Sikorsky Smash: Structural Stress Slip-up (Brainerd Helicopters Sikorsky UH-60A Black Hawk N9FH Firefighting STC MCF) On 25 May 2021 Sikorsky UH-60A Black Hawk N9FH of Brainerd Helicopters Inc (parent company to Firehawk Helicopters) crashed near Leesburg International Airport (LEE), Florida. This was during the post-maintenance check flight after installation of a snorkel equipped aerial firefighting system. The restricted category helicopter was destroyed and all 4 occupants died. The US National Transportation Safety Board (NTSB) issued their safety investigation report on 19 April 2023. The Modification Eight days earlier the snorkel/tank system had been installed on this ex-military restricted category helicopter in accordance with a Blackhawk Mission Equipment LLC (BME), Federal Aviation Administration (FAA) Supplemental Type Certificate (STC), number SR00933DE, approved by the by the FAA Denver ACO. BME is a subsidiary of Brainerd Helicopters. Several days of ground testing and calibration were performed before the accident flight, which was the first flight after the 925 gallon carbon composite cabin tank and the external snorkel were installed. The snorkel has non-retractable 15 foot long, 6 inch diameter, flexible hose which hangs from the left side of the tank to allow water uplift in a low hover. The snorkel is outboard of a water chute, that extends out of the left cabin door, as the means to empty the tank. The snorkel is attached to the tank at metal nozzle port which is secured to the tank via a by 8 AN4 bolts fastened to a backing nut plate at carbon fibre flange. The snorkel connects is attached to the nozzle port by a two lever cam-lock (the ‘coupler’). A 7.5 hp pump is mounted at the lower end of the hose. A power cable for the pump and a lightning protection cable run down the length of the snorkel and are secured using nylon zip ties. The snorkel hose and pump assembly [mounted at the bottom] weighs 137.5 pounds. The Fatal Accident Flight The purpose of the local flight was to check the operation of the newly installed fire-fighting system. The helicopter made six uneventful passes in front of the operator’s hangar at LEE and dropped water that was picked up from a lake adjacent to the airport. On the seventh pass, an employee of the operator noticed that the snorkel was swinging. He called the LEE air traffic control [ATC] tower and told the controller to ask the pilot to slow down and land immediately. Before the controller could contact the pilot, the helicopter transitioned to forward flight, gaining altitude and airspeed. During the helicopter’s last pass another witness saw the snorkel swinging in a large circle that came “very close” to the main rotor blades. The employee who contacted ATC said the snorkel was “violently” swinging, then heard a loud bang and… …saw pieces of the helicopter, including the tail section, separate from the helicopter. Afterward, the helicopter started to spin and descended below the tree line. The employee then heard an explosion and saw smoke rise above the tree line. The wreckage was contained in a 31-foot diameter vertical impact crater…in a localized swamp approximately 1,000 feet southeast from the approach end of Runway 3…and had been consumed by fire. The vertical tail, tail rotor, stabilator, and aft portion of the empennage was located about...
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