Mind the Gap: Hover Taxi Collision
Mind the Gap: Hover Taxi Collision (Bell 206L) On 30 July 2022 a Bell 206L was hover taxiing from the fuel bowser to park at Newman Airport, Western Australia when the main rotor stuck a hangar. The Australian Transport Safety Bureau (ATSB) occurrence brief identifies neither aircraft or operator. They explain that: While lining up with marking aids on the taxiway, the pilot directed their attention towards a nearby parked helicopter to the right to ensure adequate clearance from the Bell 206L’s main rotor blade. As the pilot moved the 206L forward into the parking bay, there was a loud bang. The pilot reported there was no loss of control or abnormal movement after the sound and continued to land and shut down the helicopter without further incident. During the post-flight inspection, it was identified that one main rotor blade had contacted the end of the gantry which supports the sliding doors of the hangar. The helicopter sustained damage to the main rotor blade tip cap over about 10 cm. Safety Actions According to ATSB: The operator suspended helicopter operations around the apron area where the incident occurred, pending the outcomes of an internal investigation into the incident. The operator will also review the risk analysis of the apron parking in the vicinity of the hangar and assess the current helicopter parking configuration. ATSB Safety Message The FAA helicopter flying handbook advises that when taxiing near hangars or obstructions, the distance between the rotor blade tips and obstructions is difficult to judge. To reduce collision risk, operators should consider human limitations in assessing the hazards and ensure crews maintain situational awareness of the aircraft’s established safe distance for separation from all objects during taxi. Risk assessments on apron parking areas should be reviewed periodically to re-evaluate risks and mitigations. 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: Taxiing AW139 Blade Strike on Maintenance Stand S-92A Collision with Obstacle while Taxying Pedestrian Seriously Injured by Air Ambulance Landing at Melbourne Hospital RLC B407 Reverses into Sister Ship at GOM Heliport Pilatus PC-12 Collided with Pick-Up Truck During Dusk Take Off Investigation into Collision of Truck with Police Helicopter SAR Hoist Cable Snag and Facture, Followed By Release of an Unserviceable Aircraft South Korean Fire-Fighting Helicopter Tail Rotor Strike on Fuel Bowser Ditching after Blade Strike During HESLO from a Ship US BSEE Helideck A-NPR / Bell 430 Tail Strike UK AAIB Report on Two Ground Collisions Ground Collision Under Pressure: Challenger vs ATV: 1-0 Fatal ATC Handover: A Business Jet Collides with an Airport Vehicle on Landing SAR AW101 Roll-Over: Entry Into Service Involved “Persistently Elevated and Confusing Operational Risk” Second Time Unlucky: Fatal Greek Wirestrike High-Wire Illusion Runaway Dash 8 Q400 at Aberdeen after Miscommunication Over Chocks Gazelle Caught Out Jumping a Fence Helideck Safety Alerts: Refuelling Hoses and Obstructions Air Ambulance Helicopter Downed by Fencing FOD Snagged Sling Line Pulled into Main Rotor During HESLO Shutdown Ambulance / Air Ambulance Collision Hazardous Hangar Hovertaxy The UK CAA has issued this infographic on distraction: 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 moreSuspected Drone Strike on Helicopter
Suspected Drone Strike on S300C Helicopter N2158T On 23 June 2022 Schweizer 300C N2158T struck an object when 500 ft AGL over Boonville, North Carolina. The US National Transportation Safety Board (NTSB) explain in their safety investigation report, issued 1 November 2022, that the pilot, who had 14,000 hours of flying experience, had looked up after radio frequency change to see… …a “drone hovering” in the path of the helicopter.He reported that it struck the main rotor disk at the 2 o’clock position and it “disintegrated.” The pilot evaluated the helicopter for vibrations or damage and elected to return to the departure airport, which was 3.5 miles away. Substantial damage was found on one main rotor blade. Main Rotor Blade (MRB) Damage to Schweizer 300C N2158T (Credit: NTSB) A sample was taken at the site of the main rotor blade damage and tested negative for bird DNA. However: A search for the unmanned aerial system was performed, however, no device was located.No Low Altitude Authorization and Notification Capability (LAANC) authorizations were requested for the area at the time of the accident. Additionally, no operational waivers had been filed with the Federal Aviation Administration for unmanned aerial system operations in the area at the time of the accident. The NTSB Probable Cause was an inconclusive: The helicopter’s impact with a non-biological object, which resulted in substantial damage to a main rotor blade. 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: Drone / Helicopter Mid Air Collision over LA City Hall ‘Probable’ Say NTSB Helicopter / Drone Mid Air Collision Filming Off-Road Race 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 updates. TRANSLATE with x English Arabic Hebrew Polish Bulgarian Hindi Portuguese Catalan Hmong Daw Romanian Chinese Simplified Hungarian Russian Chinese Traditional Indonesian Slovak Czech Italian Slovenian Danish Japanese Spanish Dutch Klingon Swedish English Korean Thai Estonian Latvian Turkish Finnish Lithuanian Ukrainian French Malay Urdu German Maltese Vietnamese Greek Norwegian Welsh Haitian Creole Persian TRANSLATE with COPY THE URL BELOW Back EMBED THE SNIPPET BELOW IN YOUR SITE “> Enable collaborative features and customize widget: Bing Webmaster Portal...
read moreDouble Trouble: An Operator Lost Two Helicopters in the Same Lake in 12 Hours
Double Trouble: An Operator Lost Two Helicopters in the Same Lake in 12 Hours On 26 April 2022 two helicopters of Coastal Air Services, both performing Part-137 aerial application operations, crashed into Lake Apopka, near Oakland, Florida, just 12 hours apart. Accident 1: B206B N206BX At 07:16 Bell 206B N206BX, was being flown by a 55 year old pilot with 10,725 hours of experience, 3,087 on type. It was one of three helicopters conducting spraying (most likely for mosquito control). Spraying is typically done at 7-15 ft. The US National Transportation Safety Board (NTSB) safety investigation report, issued 13 October 2022, explains: He stated that he established course on his spray line but “lost sight of everything looking forward due to the glare off the water and the sun position.” He recalled having no depth perception when he looked down at the water and could not recall the helicopter impacting the water but recalled a momentary shudder followed by the helicopter coming to rest inverted. The pilot egressed via the right hand front door and received minor injuries. In the accident report form the pilot recommended spraying with the sun behind the aircraft to reduce glare, commence operation later (i.e. when the sun is higher) and that boats on the water add peripheral cues. The NTSB Probable Cause was: A collision with water following a loss of visual reference to the water surface due to sun glare. The Transportation Safety Board of Canada (TSB) recently reported glare as a factor in a wire strike to a Robinson R44 C-FVPA. According to the NTSB after the accident to N206BX… …a safety briefing was held with the pilots, and they were instructed to maintain constant communications with the loader truck. During the safety briefing there was no insight available into the first accident. Flying resumed at 12:15. Accident 2: OH-58A+ N281SP At 19:00 ex-military Garlick Bell OH-58A+ N281SP was being flown by a 54 year old pilot with 16,835 hours of experience. This was only his second day flying for the company. He had woken at 04:00 and had started flying at c07:00. The NTSB explain in their safety investigation report that earlier… …that afternoon the pilot noted that it was difficult to judge his height above the water and advised another company pilot via radio of that fact. …the water was “like a mirror,” which hampered his depth perception. By 18:30 the pilot noticed there were no longer any Florida Fish and Wildlife Conservation Commission (FWC) air boats on the lake. He was operating slightly higher than normal at 15-20 ft and at c 55 knots. Later that evening, during a final application pass while he was looking down at the GPS, the helicopterimpacted the water. In this type of operation pilots use their AG-NAV GPS display to help fly the right spray line. The pilot received minor injuries (scraped shins). He was rescued by climbing on to the skids of the remaining helicopter. This was because the pilot had briefed his colleagues …that because of the alligators he had seen in the lake, if his helicopter went down…he would not be swimming out. The pilot explained during an NTSB phone interview that he had had a near miss during his first day of flying (15 April 2022) with the company...
read moreFire Extinguisher Cover Fenestron FOD
Fire Extinguisher Cover Fenestron FOD (Air Evac Lifeteam Airbus EC135P2+ N228MT) On 19 July 2022 air ambulance Airbus EC135P2+ N228MT of Air Evac Lifeteam was damaged by FOD when landing at Mount Vernon Airport, Illinois (caught on VIDEO, along with some bizarre groundcrew dance moves). According to the US National Transportation Safety Board (NTSB) safety investigation report (issued 22 September 2022): Shortly before touchdown, a cloth fire extinguisher cover from a nearby mobile fuelling unit was blown airborne from the main rotor system wash. The cloth fire extinguisher cover was ingested into the tail rotor (the fenestron). During the cloth fire extinguisher cover ingestion sequence, the fenestron hub flexed, the metal fenestron hub cover detached, and it was also ingested. The hub cover is held in place by six retaining clips in a lip around the inner circumference of the Fenestron hub. The pilot was able to land the helicopter without further incident. The helicopter sustained substantial damage to the fenestron. The operator explained to the NTSB that this type of cover did not have any form of lanyard but it was common practice to secure the bag under the extinguisher’s metal retaining band. It is not clear how this particular extinguisher was secured on the day. NTSB say that… The operator additionally reported that foreign object debris checks are conducted by crew members anytime they are on the pad and that the mobile fuelling unit is inspected during the daily fuel quality check. The operator also didn’t volunteer the associated procedures or training for these FOD checks and fuel system inspection. One might suspect that relying on employees looking for FOD “anytime they are on the pad” would be a relatively ineffective measure in this case, where the ‘debris’ was intended to be where it was. NTSB Probable Cause NTSB state the self evident probable cause: The inadequate securement of the cloth fire extinguisher cover, which resulted in it being blown off the fire extinguisher and ingested into the helicopter’s fenestron during the landing. No safety recommendations were raised. Footnotes The NTSB do make an incidental comment in their report that the (then) Accident Investigation Board Norway (now NSIA) had previously issued a safety recommendation regarding the securement of the fenestron hub cover. This related to an incident on 13 April 2006 to HEMS EC135P2 LN-OOD. That occurred when “a considerable amount of snow passed through the lower part of the Fenestron” when the tail contacted a snow bank during landing at a remote site That resulted in “permanent deformation of all the rotor blades” and a pulsating load that caused the cover to detach. This was however assessed as legally not an ‘unsafe condition’ as a release only occurs after FOD impact. Another fenestron cover was lost when on 19 November 2015 when EC135P2+ N36RX when the fenestron of that air ambulance ingested a towel that, for reasons that are unclear, was in an unsecured container near the landing site. After the 2015 accident the NTSB issued a safety alert: Helicopter Landing Sites: Free from Debris (SA-57). The operator of N228MT circulated this 2 days after their accident at the request of the “FAA“ (actually the NTSB). Sharp eyed readers will have spotted in the video a plastic water bottle being left unsecured on the fuel bowser too. 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: FOD and an AS350B3 Accident...
read moreCanadian B212 Crash: A Defective Production Process
Canadian B212 Crash: A Defective Production Process (Yellowhead Helicopters C-GYHQ, Alberta) On 28 June 2021, Yellowhead Helicopters Bell 212 C-GYHQ was destroyed when it broke up in-flight while supporting fire fighting operations near Evansburg, Alberta. The pilot, the sole occupant was killed. The Transportation Safety Board of Canada (TSB) explain in their safety investigation report, issued 7 September 2022, that… …as the helicopter was approaching the landing area to pick up the final group of fire fighters, one of the main rotor blades separated from the rotor head assembly. The second rotor blade and rotor head assembly then broke free from the helicopter and the helicopter crashed. Investigators observed that the main rotor hub strap retaining pin of blade A had failed. TSB say that just eight days earlier… …both main rotor hub straps and the associated retaining pins had been replaced with new parts acquired from Bell. This work was completed to comply with the requirement to replace the parts after 1200 flight hours or 24 months. On 22 June 2021, a local post-maintenance test flight was conducted. No defects were noted. Between 22 and 27 June 2021, the occurrence helicopter accrued 18.9 flight hours. The main rotor hub strap retaining pins had accrued approximately 21.4 hours time in service at the time of the occurrence. The investigators go on to explain that significantly: Metallurgical analysis of the 4 pins (part number 204-012-104-005) revealed that the failed pin (serial number FNFS90, bottom of figure below) was manufactured from 316 stainless steel, whereas the other 3 pins (serial numbers FNFS49, FNFS54, and FNFS75) were manufactured from H11 tool steel. Bell sub-contracted the manufacture of main rotor hub strap retaining pins to 3 suppliers. All 4 retaining pins installed on the occurrence helicopter were manufactured by Fore Machine Company (FMC). As FMC held no FAA approval, nor was it required to be. The manufacture of the pins at FMC was subject to a first article inspection process, conducted for Bell by a third-party using personnel trained and approved by Bell, before ultimately being released by bell.. Bell conducts oversight of its suppliers and audited FMC at their Haltom City, Texas facility in Forth Worth in 2016, 2017, and 2019. Bell’s last audit of FMC before the occurrence pins were manufactured (in 2018) was completed on 17 August 2017 and covered Appendix I: Special Requirements for Offload of Bell Planning Operations, and Appendix VI: “Controlled Item Program” Supplier Requirements of Bell’s Supplier Quality Requirements Manual. This audit resulted in 2 findings, one related to FMC’s documentation control procedures, and the other related to measurement section analysis. Additional Bell personnel would generally visit FMC facilities… …on an average of 1 to 3 times a month for various reasons, including completing source inspections, reviewing non-conformances…and verifying, validating, and rectifying defects. During site visits, Bell personnel would regularly walk through the stores area to ensure that the area was orderly and that raw material was correctly identified and tagged. These oversight activities and site visits did not result in any significant observations or recommendations… The FAA audits Bell’s vendor audits and supplier oversight. The last FAA audit of Bell/FMC, was conducted on 1 May 2018. Remarkably (emphasis added) the TSB… …determined that, when the occurrence pins were manufactured in the fall of 2018, FMC stored the raw material in its stores area by material diameter, not by...
read moreSheriff Super Puma Brownout Accident: NTSB Report
Sheriff Super Puma Brownout Accident: NTSB Report (LASD AS332L1 N950SG) On 19 March 2022, Airbus AS332L1 Super Puma N950SG of the Los Angeles County Sheriff Department (LASD) was destroyed in a brownout landing accident near Azusa, California. Four occupants received serious injuries, and the other two escaped with minor injuries. The aircraft came to rest at a cliff edge. News Report VIDEO. In the short US National Transportation Safety Board (NTSB) safety investigation report, issued on 9 September 2022 and the associated public docket it is explained that the police helicopter, callsign Air Rescue 5, had been tasked to conduct a HEMS / air ambulance flight to transfer a patient from a road accident in a canyon in the Angeles National Forest. Oddly in the accident report form the LASD did not declare the applicable regulations a being ‘Public Aircraft’ but incorrectly as a ‘Part 91 Air Ambulance Flight’ The aircraft commander had 5,382 hours experience, 1243 on type. The co-pilot had 2,686 hours experience, 297 on type. There were also a crew chief (hoist operators), two medics and a UCLA doctor onboard. The initial plan had been to land on the main road itself, but the space was filled by vehicles unable to progress due to the road accident. The crew then decided to land in an unmetalled turnout (or a dirt passing area) and conducted at least two low recce passes. The crew chief (CC) called out a ‘stinger’ (tree) obstacle that the aircraft commander (PIC) acknowledged. In their interview with the CC: The CC stated that the PIC said that he was going to stay close to the roadway in case they get into some brownout. The CC stated that he thought the PIC was ready for a brown out situation. The CC stated that they started the approach and were kind of coming in a sideways angle facing the south toward the tree. He said the dirt wasn’t too bad and about 7 to 10 feet above the ground. He still had visibility and was in the process of clearing the rotors and the tail. He said that the called those out (rotors and tail clear). The aircraft commander was maintaining the adjacent asphalt road as a reference through the cockpit bubble window. [The CC] looked out toward the ground and noticed that they were drifting forward. He said, “Scotty you’re drifting forward, hold.” He said that they were continuing to move so he said it again, “Scotty you’re drifting forward, hold, I need you to hold right here.” He said that they continued to drift, and he called out the tree at 12 o’clock. He said that it felt like they climbed a little bit, and that he could clearly see the blades moving toward the trees, then everything happened right after that. The aircraft came to rest on its left side. The crew chief was thrown clear of the fuselage but restrained by his crew harness. Accident site VIDEO. The PIC (Pilot Flying) told the NTSB he had been aware of the brownout risk and: They started the approach, and the PIC called out that he still had visual reference to the road. While about 5 feet above the ground, he heard one of the crew in the back call “hold.” The crew chief didn’t elaborate, he just said “hold.” The PIC placed the helicopter into a...
read moreGarbage Pilot Becomes Electric Hooker
Garbage HESLO Pilot Becomes Electric Powerline Hooker (Helitrans AS350B3 LN-OGA) On 16 October 2021, Helitrans Airbus AS350B3 LN-OGA was tasked with moving large bags of rubbish as a Helicopter External Sling Load Operation (HESLO) in the Lofoten archipelago in Northern Norway. During a positioning sector the underslung load line cut three low voltage power lines. The Accident Flight The Norwegian Safety Investigation Authority (NSIA) explain in their safety investigation report (issued in Norwegian only on 30 August 2022) that the local waste management company had gathered rubbish at 15 waterfront locations which need transfer to 6 landfill sites. The task was estimated to take two days. It had been delayed by weather and only started on 15 October 2022 when 13 lifts were performed, carrying 3-6 bags on each. The pilot, who had 1,282 hours of flight experience, had spent a couple of hours planning the evening before using iPad application Air Nav Pro, maps and satellite data. It was not possible to do a ground recce at all the sites. At 10:00 on 16 October 2022 the helicopter again left Leknes Airport with the pilot, a load master and an employee of the waste company. The weather was better than the previous day, with good visibility and 10–15 knots south-easterly wind. At the collection point, the loader and the customer’s representative left the helicopter, and the pilot began the flight by transporting the large bags to the predefined landfill at Banhammaren, at the southern tip of Mortsund. The flight route to the landfill was south of Mortsundholmen and the last part of the approach to Banhammaren was made from the south. At the landfill site the pilot could released the load by electrically activating a hook at the lower end of the 15 m long line. Three round trips were required to move 11 bags of rubbish. On the first two return sectors the pilot flew back the route they had flown outbound, south of Mortsundholmen. After the third load was delivered the helicopter needed to pick up the ground party and head to the next collection point. On this return flight the pilot choose to fly down the centre of a narrow strait between Mortsundholmen and Mortsund. Unbeknown to the pilot there were three 5.6 mm 230V powerlines across this strait at amount 55 feet (below the then 100 feet threshold for reporting aviation obstacles). On the way through the strait, the commander spotted a power line pole on the north side of the strait and looked down through the helicopter’s floor window. In the window he saw three power lines…. Soon after, he felt a jerk… The captain quickly realized that the cargo line had caught in the power line and immediately opened the helicopter’s cargo hook with the electric release mechanism. The cargo line was disconnected and fell into the sea without causing any damage to property or people [it was later recovered by divers]. The NSIA note that a October 2020 regulation change in Norway will require obstacles >50 feet to be reported by July 2025. NSIA Analysis NSIA were complementary about the pilot’s planning, but note that the mapping data naturally did not show the cables as they were not, nor needed to be, reported. The decision to make the last departure across the strait between Mortsundholmen and Mortsund therefore becomes incomprehensible. The pilot suggested that contributing factor to that choice of route “may have been that he had a different focus when the...
read moreR66 Loss of Control Investigation Hampered by Lack of Cockpit Video
Robinson R66 LOC-I Investigation Hampered by Lack of Cockpit Video (N450MC) On 9 January 2020 at c20:29 Local Time privately owned Robinson R66 N450MC was destroyed in an accident near Mechanicsburg, Pennsylvania. The pilot and passenger both died. The US National Transportation Safety Board (NTSB) safety investigation report, issued 28 June 2022, explains that: The helicopter pilot was conducting a night cross-country flight in visual meteorological conditions. The pilot was 58 and had just over 2000 hours experience, 167 on type. The pilot attended a [Roninson] safety course in February 2019 for the R66. At that time, the pilot had not accumulated any hours in the R66. …the instructor indicated that the pilot had “very good control” of the helicopter when performing normal and emergency procedures and that he was “very comfortable practicing the [autorotations].” The instructor suggested that the pilot obtain more training on emergency procedures. The pilot was rated “average” on all demonstrated maneuvers. Investigators report that: Recorded data showed that while the helicopter was flying at an altitude of about 2,300 ft mean sea level and at an indicated airspeed of about 107 knots, slight pitch and roll oscillations occurred for about 20 seconds followed by a left roll that continued until the helicopter was inverted. A main rotor blade contacted the tailboom, leading to an in-flight breakup over a residential area. NTSB Safety Investigation Pitch and roll hardly changed before the in-flight upset, so the investigators concluded that the autopilot was mostly likely engaged when the pitch and roll oscillations started. The oscillations could have been the result of: the autopilot reacting to an external disturbance (moderate-to-severe turbulence was reported in the area) pilot control inputs in-flight malfunction of the autopilot’s roll servo actuator The investigators say: While any of these scenarios might have precipitated the initial oscillations, none would have precluded the pilot from overriding the autopilot and manually flying the helicopter. The helicopter was equipped with devices that recorded flight and engine data at a rate of at least one parameter every second. However, the lack of an on-board crash-resistant cockpit imaging system hampered the investigators ability to reach a conclusion. NTSB has issued a safety recommendation install crash-resistant flight recorders with cockpit imaging systems for existing helicopters. Robinson responded that… …it incorporated a cockpit camera system as standard equipment on all similar model helicopters manufactured beginning the year after the accident and offered as a kit for existing helicopters the same year. However, those camera systems were not crash-resistant. During 2001 and 2009, the pilot was diagnosed with obstructive sleep apnea and coronary artery disease, respectively. The pilot was using a continuous positive airway pressure (CPAP) device for the sleep apnea “with good adherence and symptom control”. The heart problem was assessed as a “mild-to-moderate” and “did not require stenting or surgery”. The pilot did not show the typical symptoms of heart failure. Small quantities of clonazepam and ethanol were found during toxicology testing but NTSB were not able to determine if these were relevant. Overall the NTSB concluded that: [No] operational evidence indicated that the pilot’s performance was deficient during the flight time preceding the oscillations. Investigators make no comment on the possibility of disorientation during a night VMC flight. NTSB Probable Cause A severe left roll excursion after the onset of pitch and roll oscillations, which were not arrested...
read moreFenestron Failure EC130B4 Hawaii
Fenestron Failure EC130B4 Hawaii (N11QK, Blue Hawaiian Helicopters) On 5 March 2020 Airbus EC130B4 N11QK, of Blue Hawaiian Helicopters, was damaged in an accident near Kalapana, Hawaii, during a Part 135 air tour flight. Two passengers suffered minor injuries, the pilot and three other passengers were unharmed. The Accident Flight The US National Transportation Safety Board (NTSB) explain in their safety investigation report, released 16 August 2022, that the second of a pair of helicopters that had departed Hilo International Airport heading for an area known as the ‘Old Ocean Entry‘, a lava flow. As the helicopter passed over the shoreline, the pilot [7878 hours total, 1969 on type] noticed a significant, high frequency airframe vibration. He said that as soon as the vibration started, the tail rotor chip annunciator light briefly illuminated, and as the vibration continued, the tail rotor chip light “flickered.” The vibration and noise stopped after a few seconds and the chip light extinguished. The pilot selected a large open area as a precautionary landing site and slowed the helicopter on the approach. As the helicopter slowed, he raised the collective, and applied right tail rotor pedal, but the nose of the helicopter veered to the left. The pilot noted that he eventually applied full right tail rotor pedal, but the nose of the helicopter continued to the left. About 200 feet above ground level, with the right tail rotor pedal fully depressed, the helicopter began to spin to the left. To stop the spin, he attempted to gain forward airspeed but eventually closed the engine throttle and preformed a hovering [sic] autorotation. He stated that the helicopter descended, touched down hard, and subsequently rolled onto its right side, sustaining substantial damage to the fuselage, tail boom, and the main rotor drive system. The NTSB Safety Investigation One of the 10 fenestron blades had been released at the blade root, where the blade’s drain port is situated. The released part of the blade was found in the fenestron outer fairing. The fracture surface was flat starting at the aft end of the blade, up until about two-thirds of the distance to the leading edge, while the forward section exhibited shear lips. Examination of the fracture surface infected that… …the failure initiated from two separate origin areas, one on either side of the drain hole at or near its intersection with the aft rib face and grew progressively along the blade chord through about 60% of the blade before fracturing in overstress. The origin areas had been damaged with no identifiable features. Further from the origin, variable-spaced fatigue striations were observed, consistent with high cycle fatigue crack growth. The blade exhibited some geometric anomalies, its rib thickness was measured at 1.27-1.70 mm and the drain hole offset measured 0.23 mm. The acceptable engineering limit specified on the technical drawing was 2.3±0.3mm and ±0.2 mm respectively. Three other blades from N11QK were found to have fatigue cracks aligned with the blade drain hole on the suction side of the blade. Airbus Helicopters performed a root cause analysis that identified various potential factors that could contribute to the crack development. The two that were judged to be the main contributors were water drain hole geometry and rib thickness. Additionally predictions during design underestimated blade loads and it has since been shown that more sideslip manoeuvres occur in service that anticipated. Airbus Helicopters issued Alert Service Bulletin No. EC130-05A033 on 10 August 2020 to provide instructions to inspect blades at the drain hole section and establish replacement criteria. ...
read moreHow One Missing Washer Burnt Out a Boeing 737
How One Missing Washer Burnt Out a B737-800 (China Airlines B-18616) On 20 August 2007, shortly after parking on stand at Okinawa-Naha Airport, China Airlines Boeing 737-809 B-18616 suffered a massive fuel leak which ignited. After all 165 persons on board had evacuated, a large explosion occurred in the centre of the aircraft, which burned out completely. Investigators determined this occurred because one washer had fallen off before a nut was attached. The Japan Transport Safety Board (JTSB) safety investigation report explains that it is “highly probable” that: When the Aircraft retracted the slats after landing at Naha Airport, the track can that housed the inboard main track of the No. 5 slat on the right wing was punctured, creating a hole. Fuel leaked out through the hole, reaching the outside of the wing. A fire started when the leaked fuel came into contact with high-temperature areas on the right engine after the Aircraft stopped in its assigned spot, and the Aircraft burned out after several explosions. The reason the slat track was punctured was… …that the downstop assembly having detached from the aft end of the above-mentioned inboard main track fell off into the track can, and when the slat was retracted, the assembly was pressed by the track against the track can and punctured it. The downstop assembly detached because it was… …highly probable that during the maintenance…on the downstop assembly about 1.5 months prior…the washer on the nut side of the assembly fell off, following which the downstop on the nut side of the assembly fell off and then the downstop assembly eventually fell off the track. It is considered highly probable that a factor contributing to the detachment…was the design of the downstop assembly, which was unable to prevent the assembly from falling off if the washer is not installed. Unusually the nut was smaller diameter than the hole the bolt passed through. Despite the fact that the nut was in a location difficult to access during the maintenance works, neither Boeing nor China Airlines had paid sufficient attention to this when preparing the Service Letter and Engineering Order job card, respectively. Also, neither the maintenance operator nor the job supervisor reported the difficulty of the job… There is an excellent short video that illustrates this accident: Flight Safety Australia: It was almost all over: the destruction of China Airlines flight 120 Safety Resources You may also find these Aerossurance articles of interest: B1900D Emergency Landing: Maintenance Standards & Practices Fuel Tube Installation Trouble Fire After O-Ring Nipped on Installation Uncontained CFM56-7 Failures: Southwest B737-700s Uncontained PW1524G Failure During CS100 Certification Testing Machining Defect Cause of V2500 Failure B787 GEnx Fan Shaft Failure USAF Engine Shop in “Disarray” with a “Method of the Madness”: F-16CM Engine Fire Bell 407 Rolls-Royce 250-C47B Uncontained Engine Failure after Bearing Failure NTSB Confirms United Airlines Maintenance Error After 12 Years Machining Defect Cause of V2500 Failure ‘Aggressive’ Grit Blasting Maintenance Leads to Engine Fire & IFSD Micro FOD: Cessna 208B Grand Caravan Engine Failure & Forced Landing Cessna 208 Forced Landing: Engine Failure Due To Re-Assembly Error NDI Process Failures Preceded B777 PW4077 Engine FBO King Air 100 Uncontained TPE331-6 Failure – Inappropriate Repair Scheme B767 Fire and Uncommanded Evacuation After Lockwire Omitted Engine Life Limit Exceedance Caused Logging Helicopter Fatal Accident Engine Failure after Inadvertently Being Put Back into Service Incomplete Coking...
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