Fatal Wisconsin Wire Strike When Robinson R44 Repositions to Refuel
Fatal Wisconsin Wire Strike When Robinson R44 Repositions to Refuel (N529DW) There is a theory that people let down their guard when the more complex part of a task is complete. On 9 June 2018 the pilot of Robinson R44 helicopter N529DW, operated by MF Helicopters, had just finished a low-level aerial photography flight at a charity boating event (the Four Horsemen Poker Run) along a series of lakes and rivers near Oshkosh, Wisconsin. The US National Transportation Safety Board (NTSB) explain in their safety investigation report that after 90 minutes of photography in the Lake Winnebago area: The pilot landed the helicopter, off-loaded the photographer, and departed to a nearby airport [Wittman Field] to refuel. Witnesses and surveillance video indicated that the helicopter was flying northwest over the river when, about 1/2 mile from the takeoff location, it contacted…a static wire and a fiber optic line, which were the top two lines of an unmarked five-line array that crossed over the Fox River. The lines were about 100 ft above the water and spanned about 640 ft across the river. The tail rotor separated from the helicopter, and the helicopter subsequently impacted the river. VIDEO on LinkedIn. Witness testimony indicate the accident site was only about 500m from the location teh photographer was dropped off. The NTSB report that the photographer commented… …that they had flown over numerous bridges and power lines during the earlier flight and that they had discussed the location of the power lines in reference to the bridges. The pilot had 559.6 total hours of flight experience, all in the R44. The NTSB say: The circumstances of the accident are consistent with the pilot flying at an unnecessarily low altitude and then failing to maintain clearance from the wires while flying at low level. The helicopter was not fitted with any kind of wire strike protection system. The NTSB do not discuss if the wires were marked on aeronautical chartes but it is unlikely they were. Safety Resources We have written on previous wirestrikes: Sécurité Civile EC145 SAR Wirestrike Firefighting Helicopter Wire Strike Helicopter Wirestrike During Powerline Inspection Fatal MD600 Collision With Powerline During Construction Fatal Wire Strike on Take Off from Communications Site Beware Last Minute Changes in Plan UPDATE 26 July 2020: Impromptu Landing – Unseen Cable UPDATE 20 September 2020: Hanging on the Telephone… HEMS Wirestrike UPDATE 5 March 2021: Wire Strike on Unfamiliar Approach Direction to a Familiar Site UPDATE 14 August 2022: Second Time Unlucky: Fatal Greek Wirestrike High-Wire Illusion UPDATE 3 September 2022: Garbage Pilot Becomes Electric Hooker See also: Avoiding Wire Strikes The European Safety Promotion Network – Rotorcraft (ESPN-R) has published this video and guidance with EASA: Also see: UPDATE 6 June 2020: Fish Spotting Helicopter Strikes Glassy Sea UPDATE 23 January 2021: US Air Ambulance Near Miss with Zip Wire and High ROD Impact at High Density Altitude UPDATE 5 February 2021: Inexperienced IIMC over Chesapeake Bay (Guimbal Cabri G2 N572MD): Reduced Visual References Require Vigilance UPDATE 21 December 2021: R44 Unanticipated Yaw Accident During Tailwind Take Off Caught on Video Aerossurance has extensive air safety, operations, SAR, airworthiness, human factors, 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 moreTurbine Dromader M18A Downed by Fuel Contamination: Shell Detector Capsules Misused
Turbine Dromader M18A VH-FOS Downed by Fuel Contamination: Shell Detector Capsules Misused in Malaysia On 25 February 2018, Australian registered PZL-Mielec Dromader M18A VH-FOS departed Keratong airstrip in Malaysia to conduct agricultural crop spraying. Systematic Aviation Services (SAS) had wet leased VH-FOS from Dompter Pty Ltd of Victoria, Australia since 2014 for agricultural flying in Malaysia. It had been modified with a Honeywell TPE331-12UHR-702H turboprop in place of the standard radial engine, most likely under an FAA Supplemental Type Certificate (STC). The Air Accident Investigation Bureau of Malaysia (AAIBM) say in their safety investigation report that it refueled three times before departing on its 9th spray run. At the end of that run the pilot noticed the power setting of 55% has dropped to 35%. After attempting to resolve the power loss the pilot decided to make an emergency landing. While descending toward a small patch of shrub the engine totally failed. The pilot dumped the spray agent and flared the aircraft over the shrubby area until it ready to stall then allowed the aircraft to settle on the bushes. The aircraft impacted with the ground cushioned by the shrub. The pilot escaped uninjured but the aircraft was destroyed. The Safety Investigation It had rained heavily the day before. The aircraft was parked under the shade of palm tree as were the fuel drums it was to be refueled from. Sourcing fuel from drum stock increases the risk of fuel contamination. The motorised fuel pump and hose were left covered but on the ground. Fuel sampling were done by the ground handler before each refuelling as to check if there is any contamination of the fuel. Checking of fuel contamination visually from 4 drains were done after each refuelling. Both pilot and ground handler [stated] that there was no trace of water found on each fuel check/drain after the last refuelling. Investigators took a fuel sample from the airframe filter at the crash site. Contamination could be seen. When the sample was tested with water detector capsule, it is confirmed the fuel was contaminated with water. A similar result occurred when the engine fuel control unit filter was checked. The portable fuel pump filter was however found not to have been contaminated. However, this was only tested after 11 days and the investigators suspect any water had since evaporated. The ground handler was using Shell Water Detector Capsules, distributed by ASC (a recognised industry best practice – although disappointingly neither Shell or ASC refer to use on aircraft fuel samples on their websites, as usage shown is based entirely on JIG fuel supply procedures [i.e. to the wing]). However, the method employed was not as recommended. The ground handler was dropping a capsule into the fuel sample and swirling. The correct method is to attach a capsule to a syringe (without a needle), dip in the fuel sample and extract fuel into the syringe through the capsule. If there is water contamination, the colour of the capsule will immediately change. It is not clear if a syringe was available. AAIB Malaysia say: The storage life for unused Shell Water Detector capsule is 9 months from the time of manufacture. The capsules used by the ground handler were manufactured in [September] 2014. As shown in the video this is actually an expiry date and so the capsules were 40 months out of date. While the ground handler had been employed by SAS for many years he had never...
read moreMisted Masks: AAIB A319 Report Reveals Oxygen Mask Lessons
Misted Masks: AAIB A319 Report Reveals Oxygen Mask Lessons (EasyJet G-EZNM) EasyJet Airbus A319-111 G-EZNM was in the cruise at FL290 en route from Newcastle to Bristol on 11 May 2019. The co-pilot was Pilot Flying (PF) and the commander was Pilot Monitoring (PM). The UK Air Accidents Investigation Branch (AAIB) explain in their safety investigation report that: …the co-pilot noticed an acrid burning smell. Upon looking to the rear of the flight deck both crew members observed smoke in front of the flight deck door and rising to shoulder height behind their seats. They donned their oxygen masks, and the commander took control of the aircraft and continued to communicate with ATC; the co-pilot actioned the ‘SMOKE/FUMES/AVNCS [avionics] SMOKE’ checklist in the quick reference handbook (QRH). The commander transmitted MAYDAY to ATC, selected the emergency transponder code, and the crew started an emergency descent… AAIB determined that: The source of the smoke was probably an accumulation of dust in the transformer rectifier unit (TRU). However: About 90 seconds after the pilots donned them, their oxygen masks misted up, obscuring their vision. The co-pilot was able to read the checklist by holding it close to the mask, but could not read his flight instruments. The commander removed his oxygen mask so he could see the flight instruments, having first informed the co-pilot that he would do so and agreeing this was the least risk option [however] it exposed the commander to potentially hazardous fumes. Upon removing his mask the commander noticed the smoke had dissipated. The flight crew prudently decided to divert to Birmingham when they realised that airport was closer. During the descent the crew made an announcement to passengers… After this the smoke became perceptible in the cockpit again. The commander then informed the co-pilot that he felt “a little bit wobbly” but well enough to continue. As his oxygen mask had cleared he refitted it, and it did not mist up again. The aircraft landed safely at Birmingham. Investigating the Oxygen Mask Performance The mask type fitted to G-EZNM was a ‘MF10’ full-face mask-regulator that provides protection during depressurisation and smoke events, while allowing the pilots to communicate with each other. The window has two lenses with an air gap between them. The internal lens has an anti-fogging coating. Pushing the N/100% (N – normal flow) selector into the 100% position, on the regulator control, supplies 100% oxygen (item 3 below). After pushing the N/100% rocker into 100% position, rotating the emergency pressure selector in the direction of the arrow to the emergency position provides 100% oxygen with an overpressure (item 2 below). The overpressure eliminates condensation or fogging of the mask, and prevents smoke, smell or ashes from entering the mask Upon investigation: Both emergency pressure selectors were found not to have been rotated to the EMERGENCY position. The commander was unable to recall if he had selected EMERGENCY. However, if they both had, even for a short period, it is likely the condensation would have been removed, enabling the commander to keep his mask on and breath 100% oxygen during the remainder of the flight. This would probably have improved the physiological condition he reported, which may have been caused by inhaling fumes. Removing the condensation in this way would also have allowed the co-pilot to properly monitor the aircraft’s...
read moreSurvival Flight Fatal Accident: Air Ambulance Operator’s Poor Safety Culture
Survival Flight Fatal Accident: Air Ambulance Operator’s Poor Safety Culture (B407 N191SF, Ohio) On 29 January 2019, at 0650 local time Bell 407 air ambulance helicopter N191SF, collided with forested rising terrain about 4 miles NE of Zaleski, Ohio. The pilot, flight nurse, and flight paramedic were all fatally injured and the helicopter destroyed. The helicopter was operated by Viking Aviation doing business as Survival Flight (not to be confused with Survival Flight University of Michigan Metro Aviation). The flight departed Mt. Carmel Hospital, Grove City, Ohio at 0628, destined for Holzer Meigs Hospital, Pomeroy, Ohio, about 69 miles SE. The Accident Flight The US National Transportation Safety Board (NTSB) say in their safety investigation report, abstract and 2,600 page public docket that Holzer Meigs Hospital had first contacted MedFlight, another helicopter air ambulance operator, for the patient transport flight at 0601. MedFlight refused the flight due forecast icing and snow. The hospital next contacted HealthNet Aeromedical Services. HealthNet said they would perform a “weather check” and get back to the hospital. After the call with HealthNet, the hospital contacted Survival Flight, a relatively new operator in the area since June 2018, who accepted the flight within 3 minutes (HealthNet subsequently called back to turn down the flight after 6 minutes studying the weather). This is a practice called ‘Helicopter Shopping‘ (see below). According to the Survival Flight Operations Control Specialist (OCS) on duty at the time of the accident at the Survival Flight Operations Control Centre (OCC) in Batesville, Arkansas, the hospital did not mention MedFlight had turned down the flight and there were no entries in a website called weatherturndown.com (see below). They also explained that it was the night shift pilot who had accepted the flight (in just 28 seconds)… …while he was on the phone with that pilot reviewing flight details about 0612, he was told that, due to the upcoming shift change, the day pilot would be taking the flight [they were en route by car and 5 minutes away]. The night shift pilot, who had been awoken by the OCS… …asked the accident pilot while she was driving to the helicopter if she needed anything. He had already briefed the accident pilot concerning the flight request and the accident pilot had told him she already had her helmet and knee-board with her. Twilight would start at 0710 with sunrise at 0739. He asked if she needed the night vision goggles (NVGs) and she told him that she did not. He then notified the medical crew that there was a flight request and proceeded to the helipad to prepare the helicopter. By the time the accident pilot arrived he had the helicopter started and was preparing to program the waypoint information into the navigation system. He handed the accident pilot the pilot phone and she boarded the helicopter. He then returned to the base. It appears no pre-flight risk analysis form was completed (see below). The pilot did have an iPad but the NTSB could not determine if she checked the weather herself. OCC recordings indicated at 0625, the accident pilot contacted the OCS via onboard satellite radio to confirm the destination for the flight. At 0627, the accident pilot again called the OCS, but this time to request the coordinates of Holzer Meigs Hospital. At 0629, the OCS called the accident pilot requesting her flight release information. She...
read moreCulture and CFIT in Côte d’Ivoire
Culture and CFIT in Côte d’Ivoire (ALAT SA342M Gazelle) On 10 July 2018, Airbus Helicopters (formerly Aérospatiale) SA342M Gazelle 3866 of the French Army 3rd Combat Helicopter Regiment (3e RHC) was completing an exercise with troops of the Armed Forces of Côte d’Ivoire (FACI) 20 km SE of Abidjan, Ivory Coast, when the crew made a loss pass over the troops. The French liaison officer on the ground requested the helicopter conduct a second mock strafing pass. History of the Flight The helicopter had first came from the east and passed the group on the ground at only c65-100 ft before climbing to make a tight turn and decent before a return pass. The aircraft however descended steeply and struck a power line and a pole before impacting the ground. One crew member died and the other was seriously injured in this controlled flight into terrain event (although this would strictly be coded as a Low Altitude [‘LALT’] event in the CAST/ICAO Common Taxonomy). BEA-E Safety Investigation and Analysis Investigators of the BEA-Etat (BEA-E) note in their safety investigation report (only available in French) that it is likely the manoeuvre to reverse direction was commenced at too low a speed and started at too low a height (100 kts and 165 ft is recommended). Furthermore it is likely that the right turn was tighter than recommended, which required more power to be diverted to the fenestron. There was also a 6 kt tailwind during the decent that may not have been considered by the crew. The crew may also have been surprised by reaching the servo reversibility threshold. The investigators also comment that in 2012 the strafing role was removed from the Gazelle fleet so there had been no recent training in the manoeuvre. The impromptu manoeuvre was labelled as both a ‘thrill-seeking’ and a ‘routine violation’ by the BEA-E investigators, who note that the exercise had been relatively unstimulating (the local troops had been practicing vectoring the helicopter to a target). Less sophisticated organisations might stop their analysis here or just focus on the culpability of the personnel directly involved. The BEA-E thankfully took a more sophisticated approach. First they consider the perception of risk. Both pilots were qualified in tactical flight (leading to a belief in their chances of success) and regularly carry out this type of flight training or operation. The pass below the minimum overflight height did not occur early but late in the session, or after over an hour of evolution of the work area with possibility to recognize and become familiar with the area (belief its ability to control the situation). Finally, it seems that this first pass at a height of less than 165 ft had resulted no comment by the present ground staff, including from the patrol leader on the ground (belief on the look of others). They comment that group decision-making, compared to individual decision-making tend to focus more on the potential positive benefits and that “young adults, particularly young men are known to be a population with an excess risk of accidents compared to other demographic groups as violation behaviours are more frequent”. Consequently, and entirely predictably: The group and its demographic and sociological characteristics favored the adoption of risky behaviour. Less obvious is that the detachment had only recently returned to full strength (3 Gazelles) after a “long period” with just one. This resulted in a increase in flying to clear the backlog of taskings. Working hours were consequently extended and...
read moreAS350B3 Rolls Over: Pilot Caught Out By Engine Control Differences
AS350B3 Rolls Over: Pilot Caught Out By Engine Control Differences (Helibravo AS350B3 D-HAUE) On 4 September 2019, Airbus Helicopters AS350B3 D-HAUE operated in Portugal by Helibravo – Aviação for fire-fighting rolled over on take off at Pampilhosa da Serra. One of the 6 persons on board received a minor injury. The Portuguese accident investigation agency, GPIAAF, say in their safety investigation report that: According to the pilot’s statements, the engine start-up and flight preparation procedures were normal with no relevant issues to record until the time the Flight Mode was selected, and a sudden increase in engine power was noticed. Immediately soon after, the aircraft begins a vertical movement with some oscillations. The aircraft rotated 90º clockwise, rose from the ground to a height of about one meter and the pilot could not counteract the low tail attitude and the descent aircraft movement. The aircraft touched hard on the back right of the skid and a tail rotor strike on the ground occurred. The aircraft returned to the air and rotated around its longitudinal axis until the main rotor also touched the ground. The aircraft fell on its right side, about 3 meters ahead of the initial contact point. From the readings taken from the engine data (VEMD [(Vehicle and Engine Monitoring Display]), it was possible to confirm two main rotor rotational speed peaks above the 448 rpm that is the maximum value recorded by the unit. (note: certification limit for AS350B3 ([Arriel] 2B) main rotor rpm is 390 +4/-5 rpm) The pilot had flown 1833.5 hours in total, including 1655.5 hours in the AS350B2 and B3 series. Of note is that he had very little experience with the Safran Arriel 2B powered AS350B3 (but more with the Arriel 2B1). The operator uses, mainly during the firefighting season, a mixed fleet of AS350 B3 helicopters equipped either with Arriel 2B and Arriel 2B1 engines (MOD 073254), that have different procedures for initiating the flight mode. The crashed aircraft was equipped with an Arriel 2B engine (pre-mod 073254) in which engine control is performed via a Digital Engine Control Unit (DECU) with single channel governor and mechanical redundant system. Differences in the operation of the various aircraft models are addressed by the operator in pre-season training… One of the main differences between aircraft versions (2B and 2B1), and relevant to the event, are the pre-engine start-up procedures and takeoff power selection for the FLIGHT mode. The AS350B3 helicopter equipped with an Arriel 2B engine has a single-channel engine governor and DECU back-up MANUALLY controlled using the mechanical system of the twist grip. As stated on the flight manual section 4.1, the twist grip must be in the “FLIGHT” detent before carrying out the starting procedure. The flight mode selection is done using the three-position selector (OFF-IDLE-FLT/AR-RAL-VOL). In contrast: …the AS350B3 helicopter equipped with an Arriel 2B1 engine has a dual-channel engine governor and an automatic backup control (EBCAU [Engine Back-Up Control Ancillary Unit]); the simplified twist grip must be in the “IDLE” detent before carrying out the starting procedure (section 4.3 of flight manual). The flight mode selection is done using the two-position selector (OFF-ON) And then rotate the twist grip to the FLIGHT/VOL position. On the accident aircraft with the older model (2B) the pilot needs to select the three position start-selector in the ceiling ([marked on the illustration below] 1) to Off/Idle/Flight,...
read moreAS350B3 Dynamic Rollover When Headset Cord Snags Unguarded Collective
AS350B3 LN-OTR Dynamic Rollover When Headset Cord Snags Unguarded Collective On 12 September 2017 Airbus Helicopters AS350B3 LN-OTR, operated by Helitrans, rolled over onto its side shortly after landing on slightly sloping ground at Laksefjordvidda in the northern district of Finnmark, Norway. All four occupants escaped uninjured. The helicopter sustained extensive damage but the seats and cabin floor structure were intact. The Accident Flight The Accident Investigation Board Norway (AIBN) investigation report (issued 12 May 2020 in Norwegian only), explains that the helicopter was chartered to support hunting inspections by three government agencies. This involved first searching to find hunters and then landing to check their weapons and licenses. The aircraft deployed from its base at Alta at 0800 and made the 1 hour 50 minute flight to the village of Skiippagurra with the pilot and a ‘task specialist’ / ‘loader’ on board. On arrival detail planning commenced with the customer’s inspectors. Due to the nature of the task, the pilot was only told in advance the general area to be searched. The search area could be adjusted if necessary so the flight could be conducted under Visual Flight Rules (VFR). Initially, the client had announced that two inspectors should be on the flight. This was changed to allow three people to participate and the pilot therefore carried out a new weight and balance calculation. Before departure, the helicopter’s fuel tanks were filled completely. The commander’s calculation showed that the total weight was well within the maximum allowable weight of the helicopter. It was decided the loader would not join the flight, though the logic for this decision is not discussed in the report. The controls on the left side of the cockpit were therefore dismantled. One passenger was seated in the front left seat and the other two passengers were seated in the back of the cabin. The pilot flew the helicopter from the front right seat. Before departure, the pilot briefed the passengers on how the helicopter’s doors could be opened and closed, as well as how the seat belts worked. After the passengers were taken on board and the pilot carried out an external inspection of the helicopter, the helicopter’s engine was started and at. In 1125, they took off to begin the task. All four wore headsets. Helmets were not usual for this type of tasking say AIBN. While south west of the village some All Terrain Vehicle (ATV) tracks were spotted, which the inspectors took some photographs of. The pilot tried to fly to a particular hunting cabin that the inspectors wanted to fly over, but that was curtailed due to fog so they headed to the west of the village. Shortly thereafter, they spotted some people, tents and three ATVs [34 km west of the village]. It was decided that the helicopter should land so that the inspectors could carry out a check. The pilot found a suitable landing site on gently sloping terrain covered with heather. As the hunters had lit a fire its smoke gave a clear indication of the wind direction. The helicopter landed into wind and sat softly against a slightly sloping surface, from right to left in the direction of travel of the helicopter. The right skid consequently touched the ground first and after the collective lever was further reduced, the left skid also came into contact with the ground. The pilot explained that the helicopter was steady after landing and that everything felt normal at this time. To be “absolutely sure” that the helicopter was stable, the pilot would habitually...
read moreEuropean Search and Rescue (SAR) Competition Bonanza: Northern Norway SAR, Netherlands SARHC, Ireland SAR Aviation and UK’s UKSAR2G
European Search and Rescue (SAR) Competition Bonanza (Northern Norway SAR, Netherlands SARHC, Ireland SAR Aviation and UK’s UKSAR2G) With the offshore oil and gas market depressed, offshore helicopter operators and other aviation service providers will be pleased by a surge in business opportunities for outsourced government SAR helicopter and aviation contracts. Norway, Netherlands, Ireland and the UK with UKSAR2G (listed in order of expected contract award) are commencing competitions for contract commencement from 2022-2024. In this article we collate what has been publicly announced so far for each competition and the current arrangements these will replace. Northern Norway SAR Helicopter Tender: Ministry of Justice and Public Security This tender, for ‘Procurement of Rescue Helicopter Services for Tromsø, Svalbard and for the Police’, was released in April 2020. It is for a new SAR helicopter in the northern city of Tromsø and the replacement of the current aircraft for the Arctic Ocean archipelago of Svalbard. Both helicopters are required in 2022, but they could be awarded in separate lots or together. The contract(s) will be for 6 years plus 2 x 2 year extensions. The Ministry of Justice and Public Security will manage the contract on behalf of the Governor of Svalbard (Sysselmannen) and the Norwegian Police. It will supplement the main SAR service provided by the Royal Norwegian Air Force (RNoAF), which is transitioning from Westland Sea Kings to 16 Leonardo AW101s. The SAR service in Svalbard is currently provided under contract let by the Governor by Lufttransport (a subsidiary of NHV) with two Airbus Helicopters AS332L1 Super Puma. Operations there include operating from the Governor’s support vessel, Polarsyssel. The procurement will involve a dialogue with bidders on their outline solutions this summer before best and final offers (BAFO) in August 2020 and contract award in September 2020, leaving plenty of time to mobilise during 2022. Video: https://youtu.be/JGb23RLbnbI Norwegian SAR Cooperation Plan Briefing video UPDATE 17 Febuary 2021: The agressive timeline was not achieved. The standtill period was only entered on 17 February 2021 with the annouvement that CHC were the presfrred bidder. The contract was valued at NOK 1860 million (EUR 188 million) for the initial 6 years. Netherlands SAR Helicopter Tender: Ministry of Defense / Netherlands Coastguard (NLCG / Kustwacht) The tender pre-selection for the ‘Search-and-Rescue Helicopter Capacity (SARHC) for the Netherlands Coastguard‘ was released in April 2020 by the Defence Materiel Organisation (DMO) of the Ministry of Defense of the Netherlands (MOD NL). This is for a 10 year contract that will replace the current service provided by NHV with two Airbus Helicopters AS365 helicopters in Den Helder and Pistoolhaven, Rotterdam. The service supports 6 different government ministries. The Dutch schedule leading to “starting preferably from 1 July 2022” consists of determining a shortlist of candidates in Q3 2020 before two rounds of bidding in late 2020 and contract award in Q2 2021: Video: https://youtu.be/YDzVu5Dzs84 NLCG have two Dornier (now RUAG) Do228 fixed wing aircraft too, which they looked to replace under a separate competition launched in 2019. Video: https://youtu.be/Mhoi0xbJkvU UPDATE 6 August 2010: PAL Aerospace is reported to have received notice of the preliminary contract award decision on the Do228 replacement: PAL Aerospace and its consortium member JetSupport, [will] modify and deliver two fully missionized Dash 8 aircraft, provide crew training on all systems and support the operation of the aircraft for an initial 10-year period with an option to extend for two additional one-year term Ireland SAR Aviation Tender: Irish Coast Guard (IRCG) The IRCG issued a Prior Information Notice (PIN) early in May 2020:...
read moreUngreased Japanese AS332L Tail Rotor Fatally Failed
Ungreased Japanese AS332L Tail Rotor Fatally Failed (Toho Air Sevices JA9672) On 8 November 2017, Airbus Helicopters AS332L Super Puma JA9672 of Toho Air Service crashed in Gunma prefecture after the tail rotor separated from the aircraft as the crew prepared to make an emergency landing. There were four people on board, who all died. There was a post crash fire. The Japan Transport Safety Board (JTSB) concluded in their safety investigation report (published in Japanese on 23 April 2020) that: It is highly probable that the crash occurred because the tail rotor separated from the aircraft when it tried to make an emergency landing due to abnormal vibration that occurred during the flight… The tail rotor separated from the fuselage because the spindle bolt of the white tail rotor blade flapping hinge broke and the tail rotor became unbalanced… It is presumed that the spindle bolt broke because the bearing of the flapping hinge was damaged [which] was not detected by inspection. The following JTSB presentation slides that we have translated show the accident sequence: These graphics illustrate how lucky the 17 occupants of Bond AS332L G-PUMH were in 1995 when a tail rotor flapping hinge retainer had failed due to a fatigue crack emanating from a grease nipple hole while returning from a North Sea offshore installation. G-PUMH was able to make a safe landing at Longside, near Peterhead. Background Toho use their AS332Ls for construction projects. Early in the history of the of the AS332L, the manufacturer had noticed that using Shell Aeroshell 14 grease in tail rotor pitch change hinge bearings had increased the tendency for false brinelling to occur. In 1991 Exxon Mobil MOBILPLEX 47 grease was introduced as an alternative. This was a great success but in February 2008 production of MOBILPLEX 47 was abandoned. Subsequently the manufacturer noticed that on the return to the inferior Shell grease a… …reduction in the reliability of the tail rotor hub bearing [occured], especially within the helicopter operating range under hot and humid conditions. Coincidentally, before this accident occurred on 6 December 2016, Aerossurance spoke at a breakout session organised by EASA at their 10th Rotorcraft Symposium in Cologne on rotor and rotor drive system safety. One of the points made in that session was that a crucial contribution that the oil industry can make to helicopter safety is the production of optimised lubricants, even though they may have a small market. The continued airworthiness of the five AS332L tail rotor flapping hinges were reliant on greasing every 10 flying hours (or daily if parked in hot and humid conditions), as well as 50 and 250 hour inspection. The newer four bladed AS332L2 and EC225 tail rotors feature an improved design. JTSB could not find evidence of a seal replacement on that blade since June 2014 and postulate the seal had been deteriorating by 2017. As the aircraft was parked outside in high humidity during summer 2017 that would have allowed moisture ingress into the grease. Unfortunately it appears the maintenance personnel were not aware that they should have re-greased the tail rotor due to the humid environment each day either. Inspections from July 2017 started to show the grease in the white blade’s hub starting to turn increasingly black and by September 2017 “movement of the white blade was not smooth”. JTSB believe these were indications of bearing deterioration. However, no corrective maintenance action was taken...
read moreCFM56 HPC Titanium Fire Due to VSV Maintenance Assembly Error
CFM56-7 HPC Titanium Fire Due to VSV Maintenance Assembly Error (United Boeing 737-924 N30401) On 21 February 2019 United Airlines Boeing 737-924 N30401, powered by two CFM International CFM56-7B26 turbofan engines, experienced a No. 2 engine failure after a titanium fire during initial climb from Orlando International Airport (MCO), Florida. The US National Transportation Safety Board (NTSB) reported on 27 April 2020 that: At about 7,000 feet altitude, the flight crew reported an “abrupt loud grinding noise and instantaneous boom,” followed by a loss of No. 2 engine power and subsequent uncommanded engine shutdown. The crew initiated quick reference handbook procedures, closed the No. 2 engine fuel shutoff valve, declared an emergency, and returned to MCO, where they made an uneventful overweight single engine landing. A preliminary visual inspection of the No. 2 engine…reported high pressure compressor (HPC) case burn through. The engine was shipped to an overhaul facility for strip: HPC case burn through was observed…to have affected approximately 60% of the circumference. The case surfaces and accessories/lines in proximity to the burn through holes were discolored, sooted and coated in metal spray. The forward sump magnetic chip detector (MCD) plug had metal debris (“fuzz”) accumulation on the magnet and in the filter screen. See VIDEO. A visual examination of the HPC stator cases was performed after removal of the external engine components, and in addition to the case burn through, one HPC stage 1 variable stator vane (VSV) trunnion stem was missing a washer and retaining nut at the 1:30 position. The VSV alignment mark, located on the top of the trunnion stem was positioned (clocked) at a different angle relative to the rest of the vanes in the stage. The HPC rotor was badly damaged During engine disassembly, eight HPC stage 2 rotor blades, including the blade dovetails, were found separated and missing. The HPC stage 2 disk blade slots for each of the eight missing blades had one or more separated disk post corners. There was secondary impact damage observed throughout the gas path aft of HPC inlet guide vanes. The HPT stage 1 blades and the LPT stage 1 nozzle vanes exhibited thermal damage. Metal flakes and debris were collected in the aft sump, adjacent to the No. 4 bearing. …examination of the HPC stage 1 VSV (identified as VSV #33) trunnion stem confirmed that the missing washer and retaining nut identified during the engine teardown resulted in disengagement of the lever arm…allowing the vane to go off-schedule approximately 31 degrees relative to the other HPC stage 1 VSVs. The HPC VSV #33 trunnion stem had a uniform coating of dirt/debris along the full length of the stem consistent with engine operation over an extended period of time without the washer and retaining nut. The laboratory analysis also identified witness marks on HPC VSV #33 indicating that a washer and retaining nut were present at some point, but it could not be determined when the parts were removed or separated. NTSB examined the engine’s maintenance history: The last…shop visit was an engine overhaul at the GE Aviation-Celma maintenance, repair, and overhaul (MRO) facility in Petrópolis, Brazil in July 2014. According to the shop records, 22 of the 82 HPC S1 VSVs were replaced and the remaining VSVs were overhauled. Installation position of the replaced and overhauled S1 VSVs were not...
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