How 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detached from the aft end of the above-mentioned inboard main track fell off into the track can, and when the slat was retracted, the assembly was pressed by the track against the track can and punctured it.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...
read moreSecond Time Unlucky: Fatal Greek Wirestrike High-Wire Illusion
Second Time Unlucky: Fatal Greek Wirestrike High-Wire Illusion (iFly Leonardo A109C SX-HTO) On 20 August 2019 Leonardo A109C SX-HTO, operated by iFly, crashed into the sea after striking electric powerlines off Poros Island, Greece moments after take off from a helipad at Galatas. The pilot and both passengers were killed. On approach, unbeknownst to the pilot, he had passed under the cables. The Accident Flight The Greek Air Accident Investigation and Aviation Safety Board (AAIASB) issued their safety investigation report in June 2022. They explain that the helicopter was due to make a multi-sector flight, with an an unlicensed landing site at Galatas being the first stop. iFly’s Operations Manual Part C stated that a high and low reconnaissance should normally be conducted for unsurveyed sites: A high reconnaissance is flow at approximately 300 ft above the site, offset to the site, and into the wind (if direction is known). Minimum speed is 50 kts. At the low reconnaissance the Pilot may descend to a minimum of approximately 50 feet above the highest obstacle along the flight path at a minimum speed of 50 kts. Without a high and low reconnaissance, at the Pilot discretion, the low reconnaissance may be performed on final approach if out of ground effect is available. There are occasions when the high and low reconnaissance need not be performed, such as when, among others, when performing known sites approaches. iFly’s AOC is limited to day VFR operations and their Safety Management System (SMS) Manual was approved by the HCAA. The Aircraft Commander was a 57 year old ex-military officer with almost 7,400 hours of flight experience. Almost half was fixed wing experience. Significantly only 62 hours involved flying single pilot helicopters (A109A & Cs) and all of that had been in the previous 8 weeks, since being employed by iFly. In response to the Aircraft Commander’s request for information on Galatas, he was sent Google Earth images (below) by the operator’s Flight Watch Department. AAIASB make no mention of a survey having been conducted at the site. The pilot e-mailed back that he knew the landing site. The Flight Watcher was aware that there were three medium voltage (20 kV) powerlines 314 m to theeast of the landing site crosses the channel between Galata and Poros Island. They were not visible on the images forwarded, but he was confident from the pilot’s response that the pilot knew the site and was aware of them. AAIASB also state that the charts the pilot had did not show them. The helicopter few the first sector to Galatas with just the pilot aboard. The helicopter approached in a left hand turn from the Southeast. It passed under the cables, landed and parked facing north. AAIASB don’t believe a site recce was conducted before the approach commenced. The two passengers, Russians who had disembarked from a yacht and were en route to Athens airport, boarded the helicopter about 40 minutes later. The helicopter came into a low hover and turned right to face East-Southeast for a take off with a slight tailwind. AAIASB consider this departure direction confirms the pilot was unaware of their near miss with the cables on approach although it may have been influenced by a desire to over fly the yacht several miles offshore to the north east. After take-off, the Helicopter moved horizontally for 8 s at low altitude, followed by a climb for 9 s and the next 3 s...
read moreDC3-TP67 CFIT: Result-Oriented Subculture & SMS Shelfware
DC3-TP67 CFIT: Result-Oriented Subculture & SMS Shelfware (North Star Air Basler DC3-TP67 C-FKAL) On 3 December 2019, North Star Air Douglas DC-3C Basler Turbo Conversions TP67 (DC3-TP67) C-FKAL impacted terrain 200 m short of the runway threshold at Sachigo Lake Airport (CZPB), Ontario while manoeuvring in poor weather during a daytime, supposedly VFR, cargo flight from Red Lake Airport (CYRL), Ontario. Both pilots escaped uninjured. History of the Accident Flight The Transportation Safety Board of Canada (TSB) explain in their safety investigation report, issued on 4 August 2022, that when the aircraft commander checked the weather at 0700 Local Time and instrument meteorological conditions (IMC) were reported. The aircraft commander had joined the company in 2017. He had 14,000 hours of experience (2,900 on the TP67 and c9,000 on the piston engine DC-3). He had been involved in another North Star Air TP67 accident on 20 June 2019. In contrast the co-pilot had only 1,100 hours of experience and North Star Air was his first job as a pilot. There was therefore a large cockpit gradient. The flight departed CYRL under visual flight rules (VFR) at 0800 The reported weather at the time was broken ceiling at 1200 feet AGL and an overcast layer based at 2000 feet AGL. Shortly after takeoff, the aircraft entered, and climbed above, the cloud layers before reaching the planned cruising altitude, which was not in accordance with the applicable regulations for VFR flights. At the Top of Decent the crew obtained the 0800 weather report for CZMD. This “remained generally unchanged” from the 0700 report. The crew… …elected to carry out a visual approach to Runway 10. The captain initiated a descent through the cloud layers by reference to the flight instruments. Once the aircraft broke out of cloud at very low level, the aircraft was not in a position to continue with the planned visual approach. Rather than a go-around: The captain made low-level manoeuvres in an attempt to land, flying a large 360° turn, as low as 100 feet AGL (i.e. about 400 feet below the required minimum altitude), and then flew a manoeuvre similar to a left-hand circuit, which brought the aircraft within close proximity to a significant obstacle (a 150-foot tall tower), in meteorological conditions below the VFR minimum requirements. Furthermore: Given that the captain had not briefed the first officer, the latter was unaware of the captain’s intentions and began calling out airspeed and altitudes. On the last attempt, during the low-level downwind leg, when the aircraft passed abeam the threshold of Runway 10, the captain initiated a left-hand turn and began descending. About 10 seconds later, the aircraft collided with terrain, in a near wings-level attitude, approximately 650 feet southwest of the threshold of Runway 10. The aircraft slid 350 feet southward along the ground before it came to a rest on a southwesterly heading. The ELT activated but as the antenna broke off the signal was not detected. The TSB Safety Investigation The investigators noted that… …during the 2 months before the occurrence, all the flights conducted by the captain had been in accordance with VFR. However, for more than 10% of the flights, the weather at destination was reported to be conducive to IMC. Additionally, approximately 35% of the flights were conducted in weather where the pilots would have lost visual reference to the ground at some...
read moreFuel Tube Installation Trouble
Fuel Tube Installation Trouble (Jet2 B757 G-LSAN) On 7 August 2012 Jet2 Boeing 757-2K2 G-LSAN diverted in flight after a fuel leak was detected. The UK Air Accidents Investigation Branch (AAIB) safety investigation report explains that approximately three hours into a post-maintenance check flight the flight crew identified a 600 kg lateral fuel imbalance. They determined this to be due to fuel leak from the right hand Rolls-Royce RB211-535E4 engine. The crew carried out the ‘Engine Fuel Leak’ QRH checklist, shutdown the right engine being shut down and diverted to Newcastle Airport. Inspection of revealed that the leak was from pump-end flanged joint of the fuel supply tube running between the high pressure (HP) fuel pump and the fuel flow governor. The fuel supply tube had been installed during the prior C-check as part of recommended Service Bulletin RB.211-73-G230. This SB was developed to the replace earlier standards of fuel tube that were the source of previous fuel leaks (e.g. as occurred to B757-28A G-TCBA on 12 June 2010). Investigators found one of the two bolts that attached the flange to the HP fuel pump body were only finger-tight and the O-ring seal had been nipped on installation, resulting in a portion being missing. The AAIB note that: Both attachment bolts were new items that had been fitted during the installation of the fuel tube, however the bi-hex head of the lower bolt exhibited an unexpected degree of galling consistent with a socket slipping off the head of the bolt during tightening of the bolted-flange joint. Examination showed the wire-thread insert had been ” ‘picked up’ during insertion of the bolt, causing a progressive roundingover of the bolt’s threads as the bolt was tightened”. However, trials done for the AAIB at an overhaul shop indicated that it was “unlikely that the damaged wire-thread insert caused the lower bolt to remain only partially inserted”. AAIB also checked the torque wrench used and confirmed it was properly calibrated. AAIB did observe fresh galling and scratch marks both around the lower bolt hole and the periphery of the fuel tube flange interface. This indicated that difficulty was experienced installing the fuel tube. Further investigation revealed that both engine pylons had needed to be removed during the C-check, so the SB had been incorporated with the engine removed from the aircraft and installed in a transport cradle. The lower parts of the engine, including the area where the fuel tubes were to be replaced, were close to the ground and partially obstructed by the cradle’s steel framework. These restrictions made access significantly more difficult than if the engine had been mounted on its pylon, or in an engine overhaul fixture. Additionally: Following the incident the engine manufacturer conducted an investigation into the installation difficulty of both the supply and overspill return fuel tubes as specified in the SB. This activity showed that for both fuel tubes, it was significantly easier for a mechanic to align and torque the HP fuel pump flange bolts before then tightening the fuel flow governor flange bolts, which is the reverse of the bolt tightening sequence specified in the SB. Retention of the O-rings within the grooves in the fuel tube flanges was also identified as a problem, particularly at the HP fuel pump ends where access and visibility are limited. Application of a viscous assembly fluid to specification OMat 1069, which is approved for use on fuel system components, was identified as...
read moreHeliski Flat Light Flight into Terrain
Heliski Flat Light Flight into Terrain (Alpine Air Alaska, AS350D, N99676) On 15 March 2022, Airbus AS350D N99676 of Alpine Air Alaska was damaged near Valdez. Alaska when landing on a glacier during a heliski operation. The pilot, the sole occupant, suffered minor injuries. The US National Transport Safety Board (NTSB) explain in their safety investigation report, issued on 5 July 2022, that the pilot had 9779 hours of flight experience and stated… …that while on approach….to pick up a group of skiers, flat light conditions made it difficult to discern topographical features on the snow-covered, featureless, glacial terrain. The pilot said that during the approach, he inadvertently allowed the helicopter to descend below his intended approach path… The helicopter touched down c 200m short of his intended landing site. The helicopter subsequently rolled to the left and the main rotor blades struck the snow-covered terrain. The helicopter sustained substantial damage to the main rotor blades, tail rotor blades, tail boom, and fuselage. NTSB Probable Cause The pilot’s failure to maintain a proper approach path in flat light conditions, which resulted in landing short of the intended landing spot and impact with terrain. 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: Canadian Flat Light CFIT – sadly this accident was fatal Antarctic Helicopter Accidents Alaskan AS350 CFIT With Unrestrained Cargo in Cabin Low Viz Helicopter CFIT Accident, Alaska Austrian Police EC135P2+ Impacted Glassy Lake Fish Spotting Helicopter Strikes Glassy Sea EC135P2 Spatial Disorientation Accident HEMS EC135T1 CFIT During Mountain Take Off in Poor Visibility A Short Flight to Disaster: A109 Mountain CFIT in Marginal Weather HEMS Black Hole Accident: “Organisational, Regulatory and Oversight Deficiencies” Taiwan NASC UH-60M Night Medevac Helicopter Take Off Accident RCMP AS350B3 Left Uncovered During Snowfall Fatally Loses Power on Take Off EC130B4 Destroyed After Ice Ingestion – Engine Intake Left Uncovered UPDATE 7 January 2023: Blinded by Light, Spanish Customs AS365 Crashed During Night-time Hot Pursuit UPDATE 30 August 2025: Flat Light B206L4 Alaskan CFIT & 11 Hour Emergency Response Delay UPDATE 15 February 2024: Transportation Safety Board of Canada (TSB) has published their safety investigation report into the crash of Airbus AS350B2 C-FYDA of Great Slave Helicopters on Griffith Island, Nunavut on 21 April 2021. Flat light was a factor. EHEST Leaflet HE 13 Weather Threat For VMC Flights: 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 moreSchiebel Camcopter S-100 Engine Failure Results in Baltic Crash
Schiebel Camcopter S-100 Engine Failure Results in Baltic Crash On the 4 May 2022 a Norwegian registered Schiebel Camcopter S-100 rotorcraft Unmanned Air Vehicle (UAV) crashed into the Baltic near Staberhuk in Germany after an engine failures. The German Federal Bureau of Aircraft Accident Investigation (BFU) explain in their interim safety investigation report that the 200 kg Unmanned Air System (UAS) has been conducted ship environmental emissions sampling for the European Maritime Safety Agency (EMSA) and the Bundesamt für Seeschifffahrt und Hydrografie (BSH). At 1300:56 hrs , the UAV took off in manual flight mode (MANU VTOL Mode)… At 1302 hrs, the pilot activated the automatic flight mode (AUTO FLIGHT). During the flight, the UAV was up to 30 NM away from the take-off site. The pilot activated the manual flight mode (MANU FLIGHT) a total of seven times in order to approach a vessel manually in low altitude and measure emissions. Flight altitudes were between 71 ft and 267 ft AMSL. Between 1508:51 hrs and 1512:15 hrs, while the UAV was in manual flight mode, loss of link occurred… The recorded engine parameters (cooling water temperature, rotor cooling and exhaust gas temperature) prior to the loss of link and afterwards were within the normal range. At 1514:55 hrs, the pilot activated the automatic flight mode and the UAV commenced a return to base cruising at c 85 kt . At 1531 hrs, the UAV began to reduce speed. …after waypoint 11 was reached at an altitude of about 220 ft, the last programmed waypoint 12 was approached at 1534:20 hrs with a ground speed of about 15 kt and a rate of descent of about 315 ft/min. At 1534:56 hrs, the recorded rotation speed of the engine of previously 7,100 rpm and that of the main rotor of 1,187 rpm plunged within one second. …the UAV was about 50 m east of the Fehmarn beach in horizontal flight at about 90 ft above the water with a ground speed of 1 kt. At 1535 hrs, the UAV crashed into the Baltic Sea. The flotation system fitted to the left side of the fuselage deployed automatically and kept the UAV close to the surface. This was shortly before the Pilot Control Operator (PCO) would have taken over from the Pilot in Command for a manual landing. Safety Investigation The engine was disassembled by investigators. It was determined that parts of the coating inside the Wankel rotary engine had separated and the rotor had been blocked by coating debris. We will update this article as more details emerge. 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 Goes Walkabout: Hemispherical Human Factors Hiccup Software Bug and High Winds Down Drone Facebook Aquila Drone Accident: Gust Induced Structural Failure Drone Operation Injury USAF MQ-9A Reaper Lever Confusion: Human Factors Drone Pilot Injured in US Prison Geo-fence Incident Inspection UAS Collides with PNG LNG Export Jetty UPDATE 7 August 2022: Fuel Tube Installation Trouble Aerossurance has extensive air safety, operations, SAR, UAS/RPAS/Drone, engine design & certification, 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...
read moreB212 LOC-I: Windshear Encounter in the Lee of Mountain Ridge
Bell 212 Loss of Control – Inflight: After Windshear Encounter in the Lee of Mountain Ridge (Airspan Helicopters C-GNYI) On 5 March 2021, Bell 212 C-GNYI of Airspan Helicopters, on contract to electrical power utility BC Hydro, crashed on Bowen Island, British Columbia. The two pilots both received serious injuries. History of the Accident Flight The Transportation Safety Board of Canada (TSB) explain in their safety investigation report, issued 28 July 2022, that according to weather forecasts consulted during flight planning… …moderate, with localized severe, mechanical turbulence and low-level wind shear were expected in the area… Though the strong winds were a concern, the flight was dispatched with the knowledge that it would be a turbulent flight. The PIC [the operator’s President and Operations Manager, who had 9126 hours of experience, 1247 on type] made the decision to depart based on an improving forecast later in the day, the desire to complete the operational flight, and the observation that other aircraft were operating in and out of Sechelt Aerodrome. The second pilot [who had 5757 hours of experience, 480 on type] then began to prepare the helicopter for the flight. …while in the cruise… the helicopter entered wind shear and experienced a sudden, dramatic right roll with nose-down pitch. Unrestrained items in the cabin struck the pilots, and an impact on the second pilot’s helmet made their visor cover to move temporarily blocking their vision as a critical moment. After regaining control, the number 2 engine experienced an uncommanded in-flight shutdown and the flight controls became very hard to manipulate. A location on nearby Bowen Island, BC, was selected for an emergency landing; however, the helicopter was still difficult to control and the pilots were unable to manoeuvre it to the desired location. During the descent, the helicopter began a rapid rotation to the right, which the pilots were unable to arrest. After several rotations, the helicopter collided with trees and came to rest on a rocky ridge approximately 270 feet above sea level on the northwest corner of Bowen Island. Fortunately there was no post-crash fire as… …fuel lines under the cabin floor panel were compromised during the impact and began leaking fuel onto the pilots, who were still seated in the inverted fuselage, restrained by their safety harnesses. The PIC assisted the second pilot, whose foot was pinned in the footwell, and they both egressed successfully. The TSB Safety Investigation & Analysis The TSB explain that: On the morning of the occurrence, strong south easterly winds were blowing in the vicinity of the accident site. The west side of Bowen Island is dominated by a long ridge which is anchored at the south end by Mount Gardner with an elevation of 2388 feet ASL. The flight’s intended destination, Cypress Provincial Park, is approximately 6 NM east of Bowen Island. Within the park are Mount Strachan with an elevation of 4714 feet ASL and Black Mountain with an elevation of 4016 feet ASL. The final minutes…would have been flown on the downwind, or lee side, of this terrain. Lee effects are described in The Weather of British Columbia as follows: When the winds blow against a steep cliff or over rugged terrain, gusty turbulent winds result. Eddies often form downwind of the hills, which create stationary zones of stronger and lighter winds. These zones of strong winds are fairly...
read moreWhat Lies Beneath: The Scope of Safety Investigations
What Lies Beneath: The Scope of Safety Investigations Oilfield service company Baker-Hughes released a pair of safety videos in 2016 that tell the story of a safety incident. Together they illustrate an important point about safety investigations and how safety investigations ae interpreted (or sometimes misinterpreted). These short videos are meant to be watched in turn with reflection after each in order to get the full learning benefit. The docudrama narrative approach allows viewers to be a fly-on the wall of an incident to see and hear what happened. That gives an insight that safety investigators almost never have. However, in this exercise the downside is that you can’t ask questions and follow-up leads as you might in a normal investigation. That however, is immaterial to the learning the videos provide. Those not familiar with the working on a drilling floor might feel intimidated by the jargon and unfamiliar environment, but don’t let that put you off. Safety investigators not only need to be prepared to use their investigation expertise in unfamiliar circumstances but they need to avoid the hubris of thinking they are more expert at doing work than the workers involved. What Lies Beneath: Video 1 (5:24 mins) Watch the story unfold and think about what happened in the run-up to the incident and what the various people involved did or didn’t do. Feel free to replay again to crystallise your thoughts. You probably have many questions your burning to ask some or all of the players in this story. Note down which of the characters you most want to talk to and why. Only when you have done that, should you play the second video. What Lies Beneath: Video 2 (10:07 mins) A public inquiry chaired by Anthony Hidden QC investigated 1988 Clapham Junction rail accident. In the report of the investigation, known as the Hidden Report, he commented: There is almost no human action or decision that cannot be made to look flawed and less sensible in the misleading light of hindsight. It is essential that the critic should keep himself constantly aware of that fact. The Baker-Hughes videos show that narrowly focusing on the proximal means missing the full context. Aerossurance’s Andy Evans was recently interviewed about safety investigations, the perils of WYLFIWYF (What-You-Look-For-Is-What-You-Find) and some other ‘stuff’ by with Sam Lee of Integra Aerospace: Safety Resources You may also find these Aerossurance articles of interest: How To Develop Your Organisation’s Safety Culture James Reason’s 12 Principles of Error Management Psychology of Blame Airworthiness Matters: Next Generation Maintenance Human Factors Aircraft Maintenance: Going for Gold? B1900D Emergency Landing: Maintenance Standards & Practices Meeting Your Waterloo: Competence Assessment and Remembering the Lessons of Past Accidents Also: Safety Performance Listening and Learning – AEROSPACE March 2017 Learning from Adverse Events: Includes nine principles for incorporating human factors into learning investigations. UPDATE 24 October 2022: The Royal Aeronautical Society (RAeS) has launched the Development of a Strategy to Enhance Human-Centred Design for Maintenance. Aerossurance‘s Andy Evans is pleased to have had the chance to participate in this initiative. Aerossurance has extensive safety management, culture & leadership, flight operations, SAR, airworthiness / maintenance, 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. tt Detected language :...
read moreDistracted Dynamic Rollover
Distracted Dynamic Rollover (R22 N19VH) On 6 April 2022 Robinson R22 Beta II N19VH of Quantum Helicopters was damaged at Phoenix-Mesa Gateway Airport, AZ during a night solo training flight. According to the US National Transportation Safety Board (NTSB) safety investigation report (released on 13 July 2022), the helicopter had landed and was rotors running reportedly with “full collective friction applied”. The pilot (who had 177 hours total time, all on the R22) used a torch to view the Hobbs meter. This was due to it being their last solo flight and they wanted to confirm if the flight was going to accumulate sufficient time. Unfortunately “the collective crept up, the helicopter rolled to the right and dynamically rolled over”. The canopy, horizontal stabilizer and main rotor were damaged, although the pilot was uninjured. NTSB Probable Cause The pilot’s failure to maintain helicopter control while on the ground when his attention was diverted, which resulted in a dynamic rollover. Safety Observations and Distraction & Dynamic Rollover Safety Resources The pilot stated in the accident report form that in relation to preventing the accident: I could have prevented the accident by trusting the timer that I had set in the aircraft instead of needed a visual confirmation of the hobbs meter. I could have also rolled down the throttle to lower the RPM’s of the rotor head prior to checking the timer. EHEST Leaflet HE 1 Safety Considerations discuses static and dynamic rollovers. The UK CAA has issued this infographic on distraction: Other 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: Be Careful If You Step Outside!: Unoccupied Rotors Running AS350 Takes Off AS350B3 Rolls Over: Pilot Caught Out By Engine Control Differences AS350B3 Dynamic Rollover When Headset Cord Snags Unguarded Collective Fatal B206L3 Cell Phone Discount Distracted CFIT Cessna 208B Collides with C172 after Distraction HEMS Pilot Seizure While Rotor-Running Taxiing AW139 Blade Strike on Maintenance Stand R44 Force Lands After Improper Repair UPDATE 25 March 2023: Managing Interruptions: HEMS Call-Out During Engine Rinse UPDATE 10 June 2023: EC135 Air Ambulance CFIT when Pilot Distracted Correcting Tech Log Error UPDATE 4 February 2024: HEMS Air Ambulance Landing Site Slide Also on human factors: Professor James Reason’s 12 Principles of Error Management Back to the Future: Error Management …and our review of The Field Guide to Understanding Human Error by Sidney Dekker presented to the Royal Aeronautical Society (RAeS): The Field Guide to Understanding Human Error – A Review 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. OO Detected language :...
read moreR44 Ditched After Loss of TGB & TR: Improper Maintenance
R44 Ditched After Loss of TGB & TR: Improper Maintenance (N1241W, Air Adventures Helicopters, Key West) On 17 June 2019 Robinson R44 N1241W of Air Adventures Helicopters was ditched off Key West, Florida following the in-flight loss of its Tail Gear Box (TGB) and tail rotor during a Part 91 revenue sightseeing flight. The three occupants were all uninjured. History of the Flight The US National Transportation Safety Board (NTSB) safety investigation report explains that: As the helicopter climbed through 300 ft AGL, the pilot [aged 29, 1430 flying hours total, 1274 on type] detected “rapid tail vibrations.” The pilot radioed tower and requested a return to the airport. He proceeded back to the airport when he heard a loud pop and felt a “hard” right yaw. Attempts to regain control of the helicopter with the anti-torque pedals were ineffective. He initiated an autorotation, and the helicopter began to yaw to the left. Again, attempts to regain control of the helicopter were ineffective. As the helicopter descended toward the water, the pilot deployed the floats, and landed the helicopter upright on the water without further incident. Safety Investigation Examination of the helicopter revealed that the tail rotor assembly had separated from the tail boom… As well as losing the means of yaw control this will have also resulted in a significant forward shift in centre of gravity, adding to the challenges the pilot faced. [E]xamination of the mounting hardware between the TGB input cartridge and the tail boom mating flange found that two of the four bolts were missing; both missing bolts came from the right side of the connection. The left side bolts remained secured in place. The missing bolts’ holes in the input cartridge were deformed and were out of round. All of the 4 bolt holes on the input cartridge displayed imprints from the bolt threads, with the deepest imprints on the right sides of the holes, consistent with movement between the lug holes and the bolt shanks. All tail boom flange bolt holes were examined and found that the threading was present, not stripped, and locking inserts present. The NTSB reveal that c60 flying hours and 5 weeks earlier the tail boom assembly had been removed and replaced. As part of this maintenance, the tail rotor input cartridge and gearbox would have been removed from the old tailboom and placed on the new tailboom. It is likely that, during this procedure, the right-side mounting bolts were not completely secured to the tail boom casting locking inserts and properly torqued [the the required 240 in-lbs], which resulted in the failure of the right side mounting bolts. The NTSB report unfortunately contains no further detail on the conduct of this maintenance. Following the replacement of the tail boom, the pilot reported rapid tail rotor vibrations which required multiple attempts to successfully balance the tail rotor as part of the post maintenance checks. NTSB Probable Cause The failure of maintenance personnel to properly secure the right-side tail boom mounting bolts which resulted in the failure of the bolts and an inflight separation of the tail rotor. 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: Compressive Creep and the Loss of a UH-1H’s Tail Rotor Prompt Emergency Landing Saves Powerline Survey Crew After MGB Pinion Failure Fatal $16 Million Maintenance Errors Dramatic Malaysian S-76C 2013 Ditching Video NTSB Report on...
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