Fiery Fatal AW119 Accident in Russia After Loss of Tail Rotor Control
Fiery Fatal AW119 Accident in Russia After Loss of Tail Rotor Control (RA-01908) On 30 December 2018 four people died when privately operated Leonardo AW119 MII Koala RA-01908 crashed near Ulan-Ude in Eastern Siberia. The IAC/MAK safety investigation report (issued 22 November 2021) explains that while attempting to land at the village of Berezovka on a football pitch: An eyewitness saw…the helicopter began to gain altitude over the football field. In the climb, the helicopter began to rotate clockwise, moving towards the forest. The helicopter crashed in the forest and caught fire. The occupants were ejected from the fuselage (the investigators believe they were not wearing their seat belts). The signal from the helicopter’s Emergency Locator Transmitter (ELT) was not received. Safety Investigation At c 01:45UTC (09:45 Local Time) the pilot appears to have decided to return to their departure point. The helicopter had already deviated from the straight line route to their intended destination (in pink below) and the helicopter had “made vigorous maneuvering, including when flying at an extremely low altitude of ≈ 50 m at a speed of less than 50 km / h”. During such manoeuvres, the load on the tail rotor would have been high. The investigators speculate this could have been some form of fault-finding after the pilot detected an abnormality, though we observe that they may have been done for some other reason and this would have accelerated the damage investigators subsequently found. Certainly no distress call was made and no difficulties mentioned in radio communication. At 02:18 the aircraft started to descend to make an landing on a football pitch. This was a more open area than the private landing site at the helicopter’s base. It got to less that 30 ft above the pitch before climbing. The witness saw it rotate around its axis as it rose to 350 ft or more and drift over the adjacent forest before it then crashed. During examination of the wreckage it was identified that the duplex bearing of the Tail Rotor Pitch Change Shaft had failed and the cover that serves as the end cap of the mechanism was missing. According to investigators, further examination showed that, most likely during maintenance by Ural Helicopter Company, one of the two inner race had been installed in reverse, lengthening the assembly. Examination of the work cards for past 100 hour tail rotor related inspections show that those due at 500 and 700 flying hours were not done (the accident occurred at 701.1 hours). The investigators suspect that there was a misunderstanding that if a tail rotor balance (item 12a on the work card) was not done then the inspection (12b) also was not required. The investigators are confident that if the cover was missing it would have been spotted ore-flight and so concluded it must have been released in flight. The misassembly would have resulted in applying a load to unscrew the retaining nut that resulted in “abnormal control input on the tail rotor blades that may have caused the loss of control in yaw of the helicopter”. The nut should however be spilt pinned, suggesting a further maintenance error. Leonardo’s specialists comment that initially the bearings would have been kept in place due to thermal expansion but they could not withstand the axial load indefinitely and the wear rate would accelerate. Investigators comment that: Most likely, in the process...
read moreSnagged Sling Line Pulled into Main Rotor During HESLO Shutdown
Snagged Sling Line Pulled into AS350B3 Main Rotor During HESLO Shutdown (Mount Difficult, VIC) The Australian Transport Safety Bureau (ATSB) report that on 20 June 2021, an Airbus Helicopters AS350B3 was damaged and a ground crewmember injured at the end of Helicopter External Sling Load Operations (HESLO) on Mount Difficult, near Horsham, Victoria. ATSB identify neither the registration nor the operator. The helicopter was being operated single pilot with a 100 ft long line, supported by a second pilot acting as ground crew. The two pilots had worked extensively together, swapping roles, during the unspecified project. We note that a 20 year A$33.2 million project to create a 160 km trail along the spine of Victoria’s Grampian range, past Mount Difficult, was opened in November 2021. The helicopter had completed the 8 lifts required that day and at 1350 Local Time returned to the Helicopter Landing Site (HLS) near the worksite. The ATSB explain that the HLS was… …was a confined area on the edge of a rock ledge with trees and shrubs nearby. The established procedure was to lower the remote hook and line to the ground before releasing the line from the belly of the aircraft at the lowest safe height. The helicopter would then reposition for an approach. This allowed the helicopter to approach the HLS without the 100 ft line attached. The pilot placed the line to the south of the HLS and re-positioned to land. Most of the line was lying on the ground, but a small section of the line was suspended in a sapling 10–12 ft right front of the aircraft nose. The aircraft landed clear of the line, and after receiving confirmation from the ground crew member that the landing position looked safe, the helicopter was shut down. As the engine spooled down the ground crew member commenced sorting and coiling the line into the back of the aircraft. This placed tension on the line between the coiled section in the helicopter and the looped section in the tree, thereby bringing the line into the path of the rotor disc. This was caught by a blade and subsequently entangled the rotor head. The line pulled the ground crew member’s arm upwards, snared their lower leg and body, before pulling them sideways along the ground. The crew member sustained minor bruising to their face, right elbow, left leg and foot and was later cleared of concussion or serious injury. The line was later found to have wrapped around the mast, resulting in minor damage to the swashplate, mast, rotor head and main rotor blades. Safety Actions After the incident a safety briefing was conducted with all the operators pilots “which included an incident analysis, review of procedures and safety measures”. The ATSB report that “a new requirement was introduced that now states that objects should not be raised above shoulder height while under the rotor disc”. While that seems of low connection to the incident, as reported by ATSB the operator also updated their Operations Manual, Daily Safety Briefing and Emergency Plan) to clarify that: movement of equipment, including aerial work equipment, into and out of aircraft should be conducted while the rotor is stationary unless strictly necessary; and coiling of lines and the assembly of equipment must be completed outside the rotor disc unless the rotor is completely stationary. Our Observations This is a good example of never letting...
read moreAir Methods AS350B3 Air Ambulance Tucson Tail Strike
Air Methods AS350B3 Air Ambulance Tail Strike at Tucson Medical Center, AZ (N544AM) On 16 October 2021 an Air Methods Corp (AMC) helicopter air ambulance Airbus Helicopters AS350B3, N544AM, suffered a tail rotor strike on landing on an elevated helidpad at Tucson Medical Center, Arizona. The four occupants were uninjured. The US National Transportation Safety Board (NTSB) has released a brief preliminary report and (on 21 December 2021) a short public docket. The helicopter was transporting a patient in daylight from Nogales, Arizona. The pilot had flown 3188 hours, 161 on type. As the helicopter came over the elevated helipad the tail rotor contacted the handle of a large wheeled fire extinguisher. What is noticeable is the extinguisher potion and that the helicopter had landed significantly off centre. The satellite imagery shown in Google Maps suggests this is not uncommon. Furthermore the extinguisher, which the satellite imagery above suggests is normally in this location (albeit with no apparent ready access or safe space for any waiting ground personnel), is only marginally higher than a series of metal handrails around the helideck shown below. There is no perimeter netting to minimise obstructions as is common elsewhere (e.g.: UK CAA CAP1264: Standards for helicopter landing areas at hospitals). One would hope the safety investigation considers the layout of hospital’s heliport and the adequacy of the design standards used. As seen above, not only was the tail rotor damaged but debris impacted the tail boom and punctured the horizontal stabiliser. In 2017 the FAA changed Part 135 so that helicopter air ambulance operators have to comply with a new Flight Data Monitoring (FDM) System requirement, FAR 135.607. FAA AC 135-14B Helicopter Air Ambulance (HAA) Operations explains that the system… …should record digital or analog raw data, images, cockpit voice or ambient audio recordings or any combinations thereof which ideally yield at least the following flight information: • Location; • Altitude; • Heading; • Speeds (airspeed and groundspeed); • Pitch, yaw, and roll attitudes and rate of change; • Engine parameters; • Main rotor RPM; • Ambient acoustic data; • Radio ambient audio; and • Any other parameter the operator deems necessary (e.g., high definition video recording looking forward including instrument panel and forward cockpit windshield view, intercommunications system (intercom) between pilot and medical crew, communications with air traffic control (ATC), OCS, base operations, first responders at scene, hospital, etc.) So a competent and comprehensive safety investigation would have access to extensive data, and other non-volatile memory data (such as GPS data) from the aircraft too, to evaluate the approach and determine the effectiveness of the FDM program in routinely monitoring approaches and providing constructive feedback to crews. NTSB Probable Cause (UPDATE: 29 April 2022) The NTSB issued this laughably un-insightful probable cause: The pilot’s failure to maintain clearance from ground equipment during landing. 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: Air Ambulance B407 Hospital Helipad Deck Edge Tail Strike During Shallow Approach South Korean Fire-Fighting Helicopter Tail Rotor Strike on Fuel Bowser Air Methods AS350B3 Night CFIT in Snow NTSB on LA A109S Rooftop Hospital Helipad Landing Accident Air Ambulance Helicopter Fell From Kathmandu Hospital Helipad (Video) US Air Ambulance Near Miss with Zip Wire and High ROD Impact at High Density Altitude Air Ambulance Helicopter Downed by Fencing FOD Ambulance / Air Ambulance Collision Beware Last Minute...
read moreR44 “Unanticipated Yaw” Accident During Tailwind Take Off Caught on Video Say NTSB
R44 “Unanticipated Yaw” Accident During Tailwind Take Off Caught on Video Say NTSB(N3264U) On 20 December 2020 Robinson R44 N3264U crashed at Morris Municipal Airport/Washburn Field, Illinois The pilot received minor injuries. In their safety investigation report the US National Transportation Safety Board (NTSB) explain that the pilot has 1650 hours of flying experience, 280 on type. There were three weather observations recorded from around the accident time and the wind was from 240° to 250° at 6 to 7 knots, with no reported gusts. The pilot was practicing “pickups and set downs in the same spot on the ramp and the wind was from the west as he completed these maneuvers. During the final maneuver, the wind shifted, and he lost control of the helicopter”. An airport surveillance video showed that during accident sequence, the helicopter was facing east when it briefly touched down and wobbled, then lifted up as the tail boom swung around in a clockwise direction. The tail rotor impacted the ramp then climbed and continued to rotate. The helicopter completed about 1.5 rotations as it descended and impacted the ground and rolled onto its right side. The tail rotor struck the ground early in the sequence. NTSB note that Robinson issued a safety notice on unanticipated yaw in May 2013: A pilot’s failure to apply proper pedal inputs in response to strong or gusty winds during hover or low-speed flight may result in an unanticipated yaw… To avoid unanticipated yaw, pilots should be aware of conditions (a left crosswind, for example) that may require large or rapid pedal inputs. Practising slow, steady state hovering pedal turn will help maintain proficiency ibn controlling yaw. Hover training with a qualified instructor in varying wind conditions may also be helpful. NTSB Probable Cause The pilot’s inadequate pedal application during liftoff with a tailwind, which resulted in a loss of yaw control and a subsequent impact with terrain. Or was this simply mishandling? Watch the video and make your own decision! 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: Unanticipated Yaw: Loss of Control During Landing Site Survey Grand Canyon Air Tour Tragic Tailwind Landing Accident Inexperienced IIMC over Chesapeake Bay: Reduced Visual References Require Vigilance US Air Ambulance Near Miss with Zip Wire and High ROD Impact at High Density Altitude Fatal Wisconsin Wire Strike When Robinson R44 Repositions to Refuel Impromptu Landing – Unseen Cable A Try and See Catastrophe: R44 Accident in Norway in Bad Weather Fatal B206L3 Cell Phone Discount Distracted CFIT Tragic Texan B206B3 CFIT in Dark Night VMC Fatal Wisconsin Wire Strike When Robinson R44 Repositions to Refuel Fatal R44 Loss of Control Accident: Overweight and Out of Balance Latent Engine Defect Downs R44: NR Dropped to Zero During Autorotation Helicopter Destroyed in Hover Taxi Accident Firefighting AW139 Loss of Control and Tree Impact UPDATE 9 July 2022: R44 Ditched After Loss of TGB & TR: Improper Maintenance Airbus have discussed unanticipated yaw phenomena and the ‘myth of LTE’ here: 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 moreDutch Maritime NH90 Caribbean Accident: Focus on the Survivability Issues
Dutch Maritime NH90 Caribbean Accident: Focus on the Survivability Issues On 19 July 2020, a Royal Netherlands Navy NHIndustries NH90 NATO Frigate Helicopter (NFH) N-324 was destroyed in a water impact in the Caribbean off Aruba. The accident occurred alongside the Holland-class offshore patrol vessel HMNLS Groningen during a series of deck landings to keep the ship’s flight deck officer current. Two of the four crew died. The aircraft, which capsized and initially floated inverted, sank the next day after the forward flotation bags deflated. The Dutch Safety Board (DSB or Onderzoeksraad) issued a safety investigation report (in Dutch only) on 9 December 2020. They concluded a water impact occurred after airspeed reduced during the downwind leg with insufficient power input at a height that prevented recovery (a Loss of Control-Inflight [LOC-I]). They also highlighted survival issues associated with the two fatalities. Just 3 days later we published our analysis of the DSB to highlight some of the important lessons: NH90 Caribbean Loss of Control – Inflight, Water Impact and Survivability Issues. The Defence Safety Inspectorate (IVD) have now published their deeper investigation report (issued, again in Dutch only, on 2 December 2021). The IVD confirmed the DSB conclusions and make 5 safety recommendations. In this article we are going to concentrate on the survivability aspects. The Water Impact and Capsize On the eighth flight the helicopter did a lower circuit than before, less than 100 ft, as the plan was to take photos of the ship. The ship was steaming at just 3 knots in a direction of 108º and the wind was from 100º and 20-25 knots. The waves were 3 m high, the air temperature 31ºC and the sea temperature 29ºC. The helicopter passed down the right-hand side of the ship downwind: Because the ground speed was kept almost constant at 38 knots during the turn and the helicopter turned to downwind (with a tailwind), the airspeed decreased. With decreasing speed below 80 knots, more power was needed to keep flying horizontally at the same height. The helicopter started to descend with the descent speed initially increasing to about 370 feet per minute (fpm) at a height of 67 feet (about 20 meters) above the water’s surface. It is unclear whether the crew was aware that speed and altitude were decreasing. One second before the helicopter had descended to 67 feet, the pilot gave a forward input to the cyclic stick and then reduced power by 24 percent by moving the collective down. This further increased the rate of descent to 1,360 fpm and it became inevitable that the helicopter would hit the water. Upon impact the tail broke away. The IVD say that the simultaneous shift in CG and the loss of tail rotor torque meant the aircraft overturned “almost immediately”. The emergency flotation system was armed and automatically deployed, so the aircraft remained floating inverted. Crew Positions, Aircrew Equipment Assembly (AEA) and Cabin Safety Equipment There were four occupants on board at the time of the accident; in the front sat a pilot as captain (Pilot in Command, PIC) and a Tactical Coordinator (TACCO), in the back sat a Helicopter Sensor Operator (HSO) and a Rescue Operator Airborne Marksman (ROAM). The helicopter was configured as standard for an operation in the Caribbean at the time of the accident. In the cabin, near the right cabin door, there was a gun mount with an automatic weapon on...
read moreCanadian Flat Light CFIT
Canadian Flat Light CFIT (Quebec Service Aérien Gouvernemental Bell 206LT TwinRanger C-GSQA) On 22 January 2020 Bell 206LT TwinRanger 206L4 conversion C-GSQA of the Quebec Government Air Service (Service Aérien Gouvernemental or SAG) struck the frozen, snow-covered surface of Lac Saint-Jean in a Controlled Flight Into Terrain (CFIT) accident. The helicopter was destroyed and despite serious injuries, the pilot was able to egress and call SAG operations to report the accident. The SAG had purchased this aircraft in 1994 and it was modified in accordance with Supplemental Type Certificate (STC) SH01-30 to be powered by two Rolls-Royce 250-C20R turboshaft engines. The Accident Flight The Transportation Safety Board of Canada (TSB) explain in their safety investigation report (issued on 1 December 2021) that two SAG helicopters were tasked that morning to provide air support to a search for snowmobilers reported missing the day before. This involved flying for c 50 minutes at just 100 ft over a frozen lake. Early in the afternoon, one of the helicopters, C-GSQA was released from this assignment… …given that only one aircraft was required to continue the search, and given that the rear sliding door of the occurrence helicopter was difficult to close… The pilot (7291 hours total experience, 1050 on the B206, 158 on the B206 Twin) was alone on board, took off from Saint-Henri-de-Taillon at 1402, bound for the La Tuque Aerodrome. There was no precipitation and visibility was approximately 25 miles. The pilot flew deliberately slowly… …to stay under the maximum speed allowed for an open sliding door (90 knots) in case the door accidentally opened in flight. Approximately 7 minutes after takeoff, the helicopter struck the frozen, snow-covered surface of the lake and came to rest on its left side. The TSB Safety Investigation The helicopter was equipped with a satellite flight tracking system which transmitted GPS position, altitude, and ground speed every two minutes. This data was examined. On the inbound flight the two helicopters had hugged the shoreline. For the return flight in the afternoon, the occurrence pilot had planned to fly at a low altitude (approximately 500 feet AGL) because there was a headwind. The aircraft took off …at 1402 and flew a track that was almost parallel to the eastern shore of the lake. At 1406, at an altitude of 305 feet AGL and 1 NM laterally from the shore, the aircraft was approaching a group of islands 1.3 NM ahead. The pilot veered right, flying west of the islands. At 1408, the aircraft was 2.4 NM laterally from the shore at an altitude of 330 feet AGL. The aircraft struck the surface of the lake about 1 minute later, approximately 1.34 NM further. The angle between the height of the last recorded position at 1408 and the point of impact was approximately 2.3°. The main debris at the accident site was scattered over a distance of approximately 260 feet, along a straight line… The extent of the debris indicates that the horizontal speed at the time of impact was likely high, and that the angle at which the aircraft hit the frozen surface of the lake must have been shallow, which is characteristic of a CFIT accident… The rear sliding door was still solidly attached to its track and the integrity of the rear cabin was not compromised. The helicopter was equipped with a single radio altimeter (RADALT) in addition to a conventional pressure altimeter. The RADALT decision height selector bug allows the pilot to choose a minimum...
read moreGrey Charter in French Guiana: IIMC and LOC-I
Grey Charter in French Guiana: IIMC and LOC-I (AB206 F-HGJL) On 2 May 2018 Agusta Bell AB206B3 F-HGJL crashed in the jungle of French Guiana during a flight for a gold mining company after inadvertent entry to instrument meteorological conditions (IIMC) and a Loss of Control-Inflight (LOC-I). The wreckage was located 5 hours later. The pilot and one passenger were dead but a second passenger was found alive, seriously injured. History of the Accident Flight According to the safety investigation report, issued on 18 November 2021 by the French Bureau d’Enquêtes et d’Analyses pour la Sécurité de l’Aviation Civile (the BEA) in French only, the pilot had departed at c 13:28 Local Time on a Visual Flight Rules (VFR) flight from the Funair operating base at Macouria to the gold mine at Grand Usine 93 nm away. F-HGJL was neither equipped for instrument flight mor equipped with windscreen wipers. The passengers were going to carry out a repair on an excavator at the mine. The surviving passenger said “the weather was fine when they took off”. Shortly before 13:50 the aircraft climbed from around 900ft to 1644ft before a rapid decent (up to 5600ft/min) and ground impact at c 15:51. The BEA were able to reconstruct the flight using data from the Garmin GPSMAP296 and a Helisafe data recorder aboard. During the final climb oscillations in engine gas generator speed indicated to the investigators that potentially the pilot was attempting to slow the helicopter to either avoid entering cloud or because they had indeed entered cloud. Additionally, vertical acceleration reached a maximum of 1.8 g “which could indicate that the helicopter had entered an area of turbulence”. Investigators were not able to conclude if the subsequent descent was deliberately initiated but did conclude that ultimately there was a loss of control – inflight. A video captured by a passenger on their phone at 14:48 showed that “the helicopter was operating in a very cloudy, rainy environment with poor visibility” according to the BEA. The pilot of the first helicopter on scene to search for survivors stated that the weather was typical for French Guyana in the rainy season with a low ceiling, variable visibility (dropping from 5 km during successive squalls). Météo-France estimated the cloud base in the area was between 1,000 and 1,200 ft and that there was heavy precipitation between 12:30 and 16:00. The wreckage was found in a narrow clearing. Two trees were damaged. One likely by the main rotor (a potion of blade was found 30m away) and the other by the left-hand skid, that most likely resulted in the helicopter rolling onto its right-hand side. Investigators determined that “the helicopter struck the ground with very low horizontal speed”. In the two seconds preceding impact, the decrease in vertical speed could be consistent with an attempt to flare by the pilot. No pre-impact defects with the aircraft were found. The Pilot The pilot was 27, held a CPL(H) and had just 234 hours of total time and only 14 hours on type. He did not hold an Instrument Rating but was said to be familiar with operating in a jungle environment and the local weather conditions. He also had 768 hours as a HEMS Technical Crew Member (TCM). The pilot had formed his own company in October 2017 to offer his services as an independent pilot, seemingly with...
read moreTCM’s Fall from SAR AW139 Doorway While Commencing Night Hoist Training
TCM’s Fall from SAR AW139 Doorway While Commencing Night Hoist Training (Babcock MCS Spain EC-KLM) On 16 July 2018 Babcock Mission Critical Services Spain SAR Leonardo AW139 EC-KLM was conducting night rescue training offshore Valencia, Spain. Wind speed was low, 5 knots, and the sea was Sea State 2 (0.1 to 0.5 m waves). The aircraft was hovering, about 50 ft above a vessel when the rescuer exited the cabin to be hoisted down. They however fell from the aircraft into the sea. The rescuer was recovered by the aircraft and transferred to hospital. They suffered a serious injury, an upper crush fracture of the T12 vertebra. The Accident Flight On 30 June 2021 the Spanish Comisión de Investigación de Accidentes e Incidentes de Aviación Civil (CIAIAC) released their safety investigation report into this accident. This is only available in Spanish so we have translated it to compile for this summary. The helicopter, callsign Helimer 201, was based at Valencia as part of a contracted SAR service for the Spanish Maritime Rescue and Safety Society (SASEMAR). A routine flight was planned that night to maintain crew currency. The needs of each crew member were evaluated during the pre-flight briefing. They were prioritised based on which expiry date was closer and a suitable sequence agreed. After starting the engines at 23:00 Local Time, the aircraft headed offshore to rendezvous with a vessel for training. On board were two pilots and two Technical Crew Members (TCMs); a hoist operator and a rescuer (aka winchman). The hoist operator was 37 and dual qualified with 228 flying hours as a hoist operator and 746 as a rescuer. The rescuer was 34 and had 730 flying hours in that role. They are among 120 employed by the operator (70 of which are dual qualified). In the 15 days prior, the rescuer had been scheduled for two day shifts followed by two night shifts, five days off, five day shifts, followed by the night shift during which the fall occurred. On that morning they did however perform a routine mandatory medical examination (described as a ‘stress test’) at a hospital in Valencia. The TCMs were in the cabin of the AW139. The cabin can be separated from the cockpit by a roller blind and has independent lighting controls. The aircraft was equipped with an advanced digital intercom system (or ICS). The rescuer also carried POLYCOM and VHF radios. Inside the cabin there where four folding seats attached to the structure. Below is the seat used by the rescuer, showing the hardpoint where their harness lifeline is attached when they are moving in the cabin. This is one of four available to the TCMs. A dual hoist assembly is fitted to the right-hand side of the aircraft. There is the standard cabin step below the doorway (modified to avoid hoist cable snagging). As hand holds there are flexible handles on the sides of the doorway (shown above) and a rope that runs along the upper edge of the doorway. The training began with two approaches to hover alongside the vessel using the helicopter’s Automatic Flight Control Systems (AFCS). These were successfully completed before the next of two planned exercises; one to lower the rescuer to the vessel and then the recovery of a manakin from the water. During the second approach the rescuer prepared their...
read moreNVIS Autorotation Training Hard Landing: Changed Albedo
NVIS Autorotation Training Hard Landing: Changed Albedo (Tampa Police Bell 407 N512TP) On 21 June 2021 at 21:45 local time, Bell 407 N512TP of the Tampa Police Department (TPD) was damaged in a hard landing at the Tampa Executive Airport, Florida during autorotation landing training using a Night Vision Imaging System (NVIS). The pilot and instructor were uninjured. The Accident Flight The US National Transportation Safety Board (NTSB) safety investigation report, published on 19 October 2021, explains that the police pilot had 2721 hours of experience, 1472 on type and the contracted instructor had 2047 hours, 112 on type. Their experience operating with Night Vision Googles (NVGs) is not recorded by the NTSB however. A number of exercises had already been successfully conducted that evening in the Garmin 500H equipped helicopter. For this exercise: The pilot determined where on the runway he was going to land and entered the autorotation at an approximate airspeed of 60 knots. When the helicopter was about 90 to 100 ft above the ground, and the engine rpm was at 99-100%, he entered the flare. At the bottom of the flare, the pilot “bumped” up the collective to arrest the rate of descent and levelled out at what he thought was about 7-10 ft above the runway. At that point, the pilot said it felt like the bottom of the helicopter started to fall out from underneath him. Pulling collective had no effect on arresting the sink rate. The low rotor rpm horn sounded right before the helicopter landed hard on the runway. The impact was sufficient to flex the main rotor blades and sever the tail boom. The Safety Investigation The training provider reported that the police pilot had “conducted hundreds of NVG power-off landings to this exact location”. However, since the last one the runway had been repaved. Meanwhile the instructor had not done training at that site but knew it had been used successfully by colleagues for many years when training the TPD. The training provider noted that: The newly paved runway is a deep, dark black color. Due to this fact, its Albedo is near zero. The previous runway color was light gray with mid to high Albedo. They explain: Albedo is a non-dimensional, unitless quantity that indicates how well a surface reflects solar energy. Albedo commonly refers to the “whiteness” of a surface, with zero meaning black and 1 meaning white. A value of zero means the surface is a “perfect absorber” that absorbs all incoming energy. They comment that the new surface would therefore be “like a black hole”. EASA explain in GM1 SPA.NVIS.140: Contrast is one of the more important influences on the ability to correctly interpret the NVG image, particularly in areas where there are few cultural features. Any terrain that contains varying albedos (e.g., forests, cultivated fields, etc.) will likely increase the level of contrast in a NVG image, thus enhancing detail. The more detail in the image, the more visual information aircrews have for manoeuvring and navigating. Low contrast terrain (e.g., flat featureless desert, snow-covered fields, water, etc.) contains few albedo variations, thus the NVG image will contain fewer levels of contrast and less detail. The training provider concluded: Although the profile was correctly flown by the flight crew, the crew encountered a near zero Albedo of the runway surface in the final, most critical aspect of the maneuver which is during the power-off landing phase. This caused an optical illusion of false height and speed relative...
read moreBell 407 Rolls-Royce 250-C47B Uncontained Engine Failure after Bearing Failure
Bell 407 Rolls-Royce 250-C47B Uncontained Engine Failure after Bearing Failure (N120HH) On 24 June 2020 privately owned Bell 407 N120HH was destroyed after an uncontained Rolls-Royce 250-C47B engine failure near Long Marston in Warwickshire, UK. The Accident Flight The UK Air Accidents Investigation Branch (UK AAIB) explain in their safety investigation report (published 30 September 2021) that: The pilot collected the helicopter the day before the accident from Thruxton Aerodrome, Hampshire, where it had been undergoing an annual maintenance check. The maintenance work package included…the 300-hour maintenance inspection on the engine. Unscheduled work arising from this maintenance included replacement of the main transmission freewheel unit and pitch horns. The latter resulted in a requirement for a torque check on the main rotor mast assembly after the helicopter had flown 3 to 4 hours. Almost one hour was flown that day and several flights were intended on the day of the accident, intended to culminate in a return to Thruxton for the torque check. Before the first [55 minute] flight the pilot completed a walk-around, which included opening the engine cowlings and checking the fluid levels; he did not find any abnormalities. The engine oil level was showing as FULL on the sight glass. The pilot reported that the oil tank sight glass was clear and simple to read. By slightly nudging the helicopter he could clearly see the oil level moving. The oil level was still at FULL prior to the second flight, a private sightseeing flight from Wellsbourne Mountford Aerodrome, Warwickshire over the Malvern Hills. On board was the pilot and one passenger. Two witnesses noticed the helicopter as it was flying towards Wellsbourne (Witness 1 and 2). The first witness was just south of Bidford-on-Avon. He saw the helicopter flying towards him from the west and could see the helicopter clearly through his binoculars. He described seeing what looked like a “contrail” coming from above the cabin but below the rotor. He watched the helicopter as it passed overhead and flew to the east; the ‘contrail’ continued throughout this time. In the distance he saw it turn to the south but did not see the accident. The occupants were not aware of the ‘trail’ behind the helicopter The second witness, who was near Dorsington described seeing “white smoke” coming from the helicopter and took a couple of photographs. As it passed him, he heard a “popping noise”, saw the smoke turn grey and saw the helicopter descend to the ground near Long Marston. The helicopter was flying at approximately 1,800 ft amsl (approximately 1,700 ft agl) and 118 kt with the engine torque at 70 to 75%. The first indication in the cockpit of a problem was an amber [Full Authority Digital Engine Control] FADEC FAULT light on the Caution and Warning Panel (CWP). When the pilot checked the instruments, he saw the NR [Main Rotor Speed] was at 100% and the NP [Power Turbine Speed] was at 90%. In normal powered flight NP is equal to NR. He recalled looking at the torque and seeing a “5” but could not remember if it was fifty something percent or 5%, he did not recall the NG [Engine Gas Generator Speed]. The other engine instruments appeared normal. The pilot… …reduced the throttle slightly to match the throttle position to the NG then selected the FADEC mode to manual . He...
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