Ambulance / Air Ambulance Collision
Ambulance / Air Ambulance Collision (Air Methods Bell 407GX N450AM) On 3 March 2019, at about 0013 Local Time, helicopter air ambulance Bell 407GX N450AM, operated by Air Methods Corp (doing business as Black Hills Life Flight), was damaged by a ground ambulance while rotors running after landing at the village of Union Center, South Dakota to pick up a patient. The Accident and Investigation The US National Transportation Safety Board (NTSB) explain in their safety investigation report (issued 10 August 2020) that: After landing, the pilot rolled the engine throttle to idle and briefed the…[medical personnel]…that they were clear to depart the helicopter. About 20 seconds into the “cool down” process the ground ambulance drove towards the helicopter and subsequently the main rotor blades impacted the top of the ambulance. The flight paramedic was thrown to the ground during the collision. The main rotor blades, tail boom, and fuselage sustained substantial damage. The ground ambulance driver saw the crew open the doors and get out of the helicopter, so he moved the ambulance forward to get closer to the helicopter. The ground ambulance driver stated that he did not realize “that the helicopter blades were still rotating.” Air Methods confirmed that the ambulance driver had received their training. A review of that training indicated that ground personnel are not to approach the aircraft until the blades had stopped rotation. The training also indicated that ground vehicle lights should be turned off while the helicopter is landing. An excerpt from the Air Methods General Operations Manual stated that ground personnel will not [sic] come beneath the rotor disk until directed to do so by the pilot in command; the pilot will use appropriate hand signals to do so. NTSB Probable Cause The ambulance driver’s failure to see the helicopter’s rotating main rotor blades in dark night conditions, which resulted in the ambulance’s inadvertent collision with the helicopter. Contributing to the accident was the ambulance driver’s failure to follow procedures when approaching the helicopter. A Drunken Prelude Bizarrely the very same helicopter was damaged while parked on the Regional Health Rapid City Hospital helipad in South Dakota on 3 August 2020. It was reported that a witness observed a car approaching the hospital helipad at 0340: The driver revved the engine and sped onto the pad before striking the tail end of a Black Hills Life Flight helicopter and driving away. Police found the suspect’s car a few minutes later thanks to a vehicle complaint. The car was driving on deflated tires along Sturgis Road. The car had damage to its roof and windshield, and it was clear to police that this was consistent with the helicopter’s damage. A 53-year-old male was arrested and later charged with: “driving under the influence (2nd), open container [of alcohol] in a motor vehicle, leaving the scene of an accident, and operating a vehicle on private property without permission”, but oddly not with damaging the air ambulance. Safety Resources The European Safety Promotion Network Rotorcraft (ESPN-R) has a helicopter safety discussion group on LinkedIn. Guidance on “Welcoming Helicopters” at emergency sites (in English and French). UPDATE 20 October 2021: A LifeFlight helicopter that was damaged on 18 October when it was struck by a slow-moving ambulance in Maine, US, could return to service by 20 October UPDATE 25 October 2021: Another HEMS/vehicle collision, which occurred to SAME MBB Bo 105CBS-4 LV-CVE at a toll plaza in Argentina on 23 April 2021, was captured on video: You may also...
read moreBoeing 737-800 Engine Nacelle Strike and Continued Operation
Boeing 737-800 Engine Nacelle Strike and Continued Operation (Virgin Australia VH-YIW) On 23 April 2016 Virgin Australia Boeing 737-8FE VH-YIW was operating from Auckland, New Zealand to Faleolo Airport, Apia, Samoa. Unbeknown to the crew, the right engine nacelle made contact with the runway during the landing and been damaged. The damage was not detected for several days. The Serious Incident Flight The Australian Transport Safety Bureau (ATSB) explain in their safety investigation report (issued 30 June 2020) that the aircraft was expected to depart on the return sector before the arrival of approaching Tropical Cyclone Amos (TC Amos). At 2100 Coordinated Universal Time [UTC].about seven and a half hours before the planned take-off, the operator’s cyclone management team (CMT) reviewed the weather information…and determined that the flight could continue with additional risk mitigation in place. Specifically, the aircraft was required to carry maximum fuel, to allow for 60 minutes’ holding fuel at Samoa and for possible diversion to an alternate landing at Nadi, Fiji. Furthermore, engineering coverage was required at Samoa, or an engineer had to be carried on board from Auckland. The captain had a total of about 10,000 flying hours experience, c6,000 on type. The first officer had about 5,300 hours, c1,100 were on type. Both had operated to Apia many times, including at night and in rain. The flight departed from Auckland at 0433. The captain was the pilot flying and the first officer was the pilot monitoring. During the flight, the crew sought and received regular weather updates from the operator’s flight following service (flight following). While planning for the descent, approach and landing, the crew decided they would not commence the descent until they had received a weather report from the aerodrome tower controller. The flight crew were only able to make contact by HF radio and based on the feedback received decided they would conduct one approach and if unsuccessful they would divert. During the approach, the crew reported observing heavy rainfall on the aircraft’s weather radar display. The crew also reported that the conditions were not as turbulent as previously expected. On approach to land, the crew established visual reference with runway 08 at about 700 ft above ground level, and continued the approach. The captain disconnected the autopilot at 260 ft and then inadvertently activated the take-off/go-around (TOGA) function. He immediately realised, corrected this action and then deactivated the auto throttle as originally planned. The weather conditions remained within the aircraft’s operating limitations, and were therefore suitable, during the approach and landing. The flight crew were required to maintain a stabilised approach from 1,000 ft above the aerodrome elevation until touchdown. If the approach became unstable during this segment, the crew were required to conduct the missed approach procedure. The operator’s flight procedures stated that…”should it become apparent that the aircraft will touch down significantly short of the touch down aiming point, or beyond the end of the touch down zone (1000 m/3000 ft from the threshold or first third of the runway, whichever is less), the pilot flying shall initiate a go-around”. After about 20 seconds of manual flying on final approach, the aircraft started to drift left. The aircraft touched down about six seconds later. During those six seconds, both flight crew became aware of the aircraft’s left drift and the captain manoeuvred the aircraft to return...
read moreInadvertent Entry into IMC During Mountaintop HESLO
Inadvertent Entry into IMC During Mountaintop HESLO (Air Greenland Airbus AS350B3 OY-HGT) On 24 June 2019, during Helicopter External Sling Load Operation (HESLO) in Greenland inadvertent entry to Instrument Metrological Conditions (IMC) resulted in Air Greenland Airbus AS350B3 OY-HGT impacting the ground. The pilot escaped injury. The Accident The Accident Investigation Board Denmark (AIBD) explain in their safety investigation report that the helicopter was moving fuel with a 30 m long line from a barge to the mountaintop Telesite Dye One communication site. This waa at a former Distant Early Warning Line radar site at 4757 feet AMSL on Qaqatoqaq, near Sisimiut (formerly Holsteinsborg). The pilot recalled the wind was 210°, 5 knots, no turbulence and there were fog and cloud in the vicinity of the telecoms site. The pilot was 36, had flown 3037 hours in total and had “extensive firefighting and mountain flying experience”, including operating with longlines. The pilot was on a short term contract and completed their last Operator Proficiency Check (OPC) 4 months before, which included demonstrating a whiteout landing. They had also completed the operator’s HESLO check in March and had been observed for 2 days in line flying under supervision. The pilot had already successfully made 28 of the 30 planned movements of what appear to be 1000 litre IBCs, and the pilot had discussed with a Task Specialist (TS) at the barge the possibility of doing a second tasking before sunset. On the 29th lift, the helicopter started to climb, and… …at approximately 400-600 feet above the ground, along the mountain ridge and passing approximately 2200 feet Mean Sea Level (MSL), the pilot called a TS at the telesite station in order to obtain an opinion on the visibility and presence of clouds at the mountaintop. The TS reported that “actually only the telesite station itself was open, but the rest was foggy”. The pilot replied that he would “try to find his way up to the mountaintop”. After several turns during climb and at various airspeeds, the pilot at approximately 4900 feet MSL on a westerly track, approached the agreed-upon delivery point, which was a footbridge along the station buildings. The pilot was focused on the delivery point, a footbridge along the station buildings, and manoeuvring the helicopter. While not explained, this presumably made filling the site’s fuel tanks easier for workers at the site than if the fuel had been delivered to the lower helipad. While approximately 150 feet above the ground, due to clouds/fog the pilot lost external visual references and started feeling spatial disorientated. Fearing the fuel tank might hit ground personnel or structure, the pilot “abruptly started flying rearward” intending to release the load. In combination with various oscillating flight parameters, and an unstable external load, the pilot experienced partial loss of control of the helicopter. After further rearward, descending, oscillating flight, the fuel tank collided with rocky terrain. Approximately 30 m further downhill the pilot successfully released the load using the electrically operated release control on the cyclic stick. In a helicopter nose down attitude on a southerly track, at a high sink rate, and at a low height above the ground, the pilot regained partial visual references and noted that impact was inevitable. …approximately 100 meters downhill, the helicopter skids impacted with rocky terrain, and the long line entangled with rocks…. The helicopter ended up on its right hand side with the nose section facing towards Telesite Dye One....
read moreCarb Icing Suspected in Fatal Aerial Photography Flight
Carb Icing Suspected in Fatal Aerial Photography Flight (Cessna 152, N24515) On 17 July 2018 Cessna 152 N24515 crashed near Fort Rice, North Dakota, during its second low-level aerial photography flight of the day from Mandan Airport, North Dakota. The pilot, the sole occupant, was killed. The Accident Flight and NTSB Safety Investigation The US National Transportation Safety Board (NTSB) explain in their safety investigation report (issued 13 July 2020) that the pilot (35 years old with c 750 hours total time) would take the photographs through the left-hand cockpit window. FAA radar surveillance data showed the aircraft had departed Mandan and flew to the target area to take photos of farms and ranches. The aircraft subsequently left the target areas and flew over the Missouri River. The NTSB say the aircraft then… …made several low-level turns over the river, most of which were to the left. The last recorded data point showed that the airplane at 1,700 ft. msl and a groundspeed of 49 knots. The airplane wreckage was found partially submerged in the river. The photographs from the pilot’s camera were extracted, and the last several images showed the river. The pilot died of blunt force chest injuries. No pre-impact anomaly was found with the aircraft. The NTSB comment that: Given the temperature and dew point at the time of the accident, the airplane was susceptible to serious carburetor icing at glide power settings. The airplane was equipped with a carburetor temperature system that was installed on the right side of the cockpit [i.e. opposite to the direction the pilot was looking]. The system had an “ice zone” warning light that illuminated before carburetor ice could form. It is likely that, during the low-level turns to the left over the river, the pilot was focusing on taking photographs through the airplane’s left window and did not see that the ice zone light had illuminated. After illumination of this light, a pilot was expected to apply carburetor heat. However, the airplane’s carburetor heat was found in the off position. Thus, given the ambient conditions at the time of the accident, it is likely that carburetor ice formed and resulted in a loss of engine power. Because the pilot’s attention was diverted to the photography mission, he likely did not notice the loss of airspeed, which resulted in the airplane exceeding its critical angle of attack, and a subsequent low-level aerodynamic stall. NTSB add that: Before the accident flight, a mechanic who assisted the pilot with refueling the airplane observed that the pilot kept rubbing his eyes. The mechanic surmised the pilot was fatigued. The mechanic suggested that the pilot that take a nap before continuing flight operations and the pilot replied that he can’t make any money if he isn’t flying, and subsequently departed for the accident flight. Evidence does not suggest that the pilot had a reduced sleep opportunity or circadian disruption during the days preceding the accident. However, at the time of the accident the pilot had completed one photo flight in the morning and was about 57 minutes into a second photo flight when the accident occurred. Although the pilot’s total flight time that day was not extreme, the single-pilot aerial photography flight required low level maneuvering and divided attention which could have been fatigue inducing from a workload and time-on-task perspective. However, there was insufficient...
read moreAW139 Brownout Accident with the Nigerian VP Aboard
AW139 Brownout Accident with the Nigerian VP Aboard (Caverton Helicopters, 5N-CML) On 2 February 2019 Leonardo Helicopters AW139 5N-CML of Caverton Helicopters crashed while landing at a football pitch at Kabba, Kogi State on a VVIP flight with Nigerian Vice President Oluyemi Oluleke “Yemi” Osinbajo on board. All 12 on board escaped without injury, though the aircraft was destroyed. The chartered commercial helicopter was being used because the Vice President was making an election campaign visit. The Accident Flight The Accident Investigation Bureau Nigeria (AIB Nigeria) say, in their safety investigation report (issued 28 July 2020), that the helicopter had positioned from Lagos to the capital, Abuja, that morning, landing at 10:00. The helicopter was refuelled and the flight crew prepared for the VIP charter flight. At about an hour before the planned departure, the flight crew received the coordinates for the temporary landing sites at Kabba and Okene, and they were thus able to finalize their flight planning for the mission. According to the weather report from the Nigerian Meteorological Agency (NiMet), the prevailing weather at the football field was good with visibility over 10 km and no clouds below 5,000 ft. The Kabba landing area was an unpaved area comprising a football field located in the centre with two spectator stands on each side of the field. The elevation of the area was 1,500 ft AMSL and…the field surface was characterized by scattered patches of grass and loose fine soil. Although the landing area was not an approved heliport, it was suitable as a temporary helicopter landing site. At about 13:46, the helicopter departed for Kabba as callsign NGR002. At 14:20 in cruise at 5000 ft AMSL, the Multi-Purpose Flight Recorder (MPFR) light came ON and the Crew Alerting System (CAS) displayed “FDR AND CVR FAIL”. The crew actioned the appropriate Quick Reference Handbook (QRH) checklist successfully and so the flight could continue. The flight crew stated that on initial approach, they carried out the pre-landing checks which included a landing brief for a ground helipad landing and a Landing Decision Point (or committal point) of 100 ft/20 kt indicated airspeed (IAS) based on the surrounding obstacles. Nigeria Police Force Bell 412EP 5N-PEJ was flying in advance of the AW139, landing at 14:30. The flight crew of NGR002 stated that they sighted the intended landing area as a result of the cloud of residual dust generated by the downwash of 5N-PEJ’s main rotor. The flight approached the landing area and the Pilot stated that he was able to take note of the area and the obstacles outside the landing area (spectators’ stands, football field goal posts, a car and people awaiting the arrival of the VIPs). After sighting the football field, the flight crew agreed on the selected landing area. NGR002 approached with the speed of 20 kt to about a 100 ft, and entered a hover to land. At about 50 ft above ground level, a brownout set in. The 2012 NATO RTO Technical Report TR–HFM–162 Rotary-Wing Brownout Mitigation: Technologies and Training describes brownout as “the condition where there is little or no out-the-cockpit window visibility caused by dirt and dust being stirred up by the rotor downwash and then re-circulated by the rotor blades of a helicopter during taking off or landing in an arid climate”. Brownout VIDEO. The report notes that “Since NATO has been operating in the arid climates (e.g., Africa and Afghanistan), Rotary-Wing...
read moreUS Dash 8-100 Stalled and Dropped 5000 ft Over Alaska
US Dash 8-100 Stalled and Dropped 5000 ft Over Alaska (Era Aviation N886EA) On 5 September 2012 Bombardier DHC-8-103 / Dash 8-100 N886EA, operated by Era Aviation as a Part 121 scheduled commercial flight with 12 passengers and 3 crewmembers onboard, stalled, rolled and made an uncontrolled descent when climbing through 12,000 feet. The aircraft dropped 5,000 ft before the crew recovered full control of the aircraft. The occupants were uninjured and the aircraft returned to Ted Stevens Anchorage International Airport (ANC), Alaska with minor damage. History of the Flight The US National Transportation Safety Board (NTSB) explain in their safety investigation report (issued only on 8 July 2020, 94 months later and after the operator [by then Ravn Alaska] and its owner had gone bankrupt!): The flight was cleared to a cruise altitude of 10,000 feet. Both pilots stated in interviews that the captain engaged the autopilot when the flight reached an altitude of about 1,000 feet agl. The captain stated that he engaged the indicated airspeed (IAS) button on the advisory display unit and set a climb speed of 150 to 160 knots. Between 7,000 and 8,000 feet, the airplane entered a cloud deck and began accumulating ice, and the captain turned on the de-icing equipment. The crew say the system was working but only clearing ice from the propeller spinners not the airframe. They requested ATC clearance to climb to up to 14,000 ft to avoid the icing. This was granted. While commencing the climb, the captain initially set 14,000 feet in the altitude alert controller. The captain stated that he engaged the IAS button when he initiated the climb out of 10,000 feet and that he did not use the vertical speed (VS) mode during the flight. He could not recall the position of the throttles during the climb from 10,000 feet, but he noted that he did not manipulate them once he initiated the climb. Although the airplane was equipped with [orange] fast-slow type speed control indicators on each pilot’s attitude director indicator (ADI), neither pilot reported looking at it. According to flight data recorder (FDR) data, during the climb, the initial airspeed was 170 knots, the climb rate was 850 feet/minute, and the engine power was not increased. The data showed a steady decrease in airspeed and a steady increase in altitude and pitch attitude for the duration of the climb. The captain stated that, during the climb, he was monitoring the icing indications. The first officer stated that he was monitoring the de-icing panel; looking outside to make sure the de-icing boots were inflating and deflating in the proper sequence; and looking at the propeller spinners, windshield wipers, and windshield. The first officer said he was also getting ready to communicate with the arrival station and taking care of paperwork in preparation for landing. Passing through about 11,500 feet, the flight began to emerge from the tops of the clouds, and the captain set the altitude alert controller to level at 12,000 feet. As the airplane began to level off, it began to shudder and the flight crew attributed it to an unbalanced condition of the propellers due to the uneven shedding of ice. This is when things developed rapidly: According to FDR data, the airplane lost lift at 1041:18 as the airplane was climbing through 12,192 feet...
read moreImpromptu Landing – Unseen Cable
Impromptu Landing – Unseen Cable (Skogsflyg Cassel Aero R44 SE-JIT) On 8 November 2019 Robinson R44 SE-JIT of Skogsflyg Cassel Aero landed hard at Unkervatnet in Norway while conducting reindeer herding task for a Sami village in the Tärnaby area of Sweden. The Accident Flight The Swedish Accident Investigation Authority (SHK) explain in their safety investigation report (issued on 2 July 2020 in Swedish with an English summary) that on-board were the pilot and a mission specialist, a reindeer owner from the Sami village. The 25-year-old pilot was relatively low time (455 hours in total and 355 hours on type). The reindeer were further west than expected and their tracks went inside Norway. The pilot [had] followed the valley west and tried to contact the Norwegian air traffic service to file a flight plan in the air if possible. The regulations do allow this in some cases but not when the flight crosses a national border. The regulations stipulate that an flight plan must be submitted at least 60 minutes before take-off if the flight involves crossing a national border. No contact was obtained with the Norwegian air traffic service and the flight [had] continued…about 15 km into Norway. The pilot decided to land to contact the operator’s flight manager in order to clarify the conditions for flying in Norway. The Swedish operator’s Operations Manual did cover flying in Norway from an ATC perspective but not from a permit perspective: [In fact] the company has an authorization issued by the Swedish Transport Agency to conduct commercial specialized aviation operations of a high-risk nature in Sweden and also in Norway, but lacked a low-flying permit in Norway and a “Traffic Permit per Assignment” to fly in Norway. Having decided to land: A turning area at the end of a forest road was identified as a suitable landing site and the pilot relied on the assessment he did from a high altitude. The approach along the forest road towards the turning area meant that there were backlight conditions during the landing. Just before the turning area, there was a telephone line crossing the road. During the accident site investigation, it was found that the height of the line is half the height compared to the height of the surrounding trees on the north side of the forest road. On the south side, the height of the line is about 2/3 of the height of the surrounding trees. The lead poles on both sides of the forest road were obscured by surrounding trees. When the pilot detected the line, he made an evasive manoeuvre. However, the rear end of the helicopter hit the line and was damaged. The pilot made an immediate but hard landing, resulting in further damage. SHK Conclusions The SHK comment that the cause of the accident was the inadequate landing site reconnaissance (from high rather than low altitude). Contributory factors were: The backlighted conditions The pylons being hidden in trees The change in circumstances resulting in uncertainty, needing consultation with base and a previously unanticipated landing. Safety Actions Cassel Aero decided on 14 November 2019 to suspend all the company’s flight operations and at a flight safety meeting on 18 November 2019, the company management decided that the flight operations would not be resumed until all corrective measures had been taken. [T]he company has introduced an extra training program for the 2020 season, which includes training in the risk identification checklist (RIC), training in crossing national borders and practical...
read moreHESLO AS350B2 Dropped Load – Phase Out of Spring-Loaded Keepers for Keeperless Hooks
HESLO AS350B2 Dropped Load – Phase Out of Spring-Loaded Keepers for Keeperless Hooks (PDG AS350B2 G-PDGF) On 3 March 2020 Airbus Helicopters AS350B2 G-PDGF of PDG Aviation Services inadvertently dropped a 700 kg underslung load while conducting Helicopter External Sling Load Operations (HESLO) near Glencoe in Argyll, Scotland. The pole broke into two when it impacted a hillside about 200 m from a minor public road, but clear of any third parties. HESLO AS350B2 Dropped Load – The Incident Flight G-PDGF was being used to transport 47 wooden poles over 2 days to work sites alongside an electricity powerline which was being refurbished. Prior to starting the task the pilot of met the ground handler, who also worked for the operator, and three client employees. The UK Air Accidents Investigation Branch (AAIB) explain in their safety investigation report (issued 9 July 2020) that: The client’s employees had previously attended a training course on helicopter operations, which covered lifting underslung loads. The ground handler briefed the employee who would be hooking on the loads at the storage facility. The ground handler’s task was to assist and oversee this operation but also to refuel the aircraft at a separate refuel site. This meant that, whilst the ground handler was at the refuelling site, the client’s employee would be left unsupervised to ‘hook on’ the loads. During the afternoon of day one, after successfully transporting several loads…G-PDGF arrived to pick up a 700 kg pole whilst the ground handler was away from the storage facility. The pilot manoeuvred the helicopter to allow the client’s employee to attach the load to the hook. The design of the hook consists of a load bearing beam which, when electrically actuated by the pilot, causes the beam to rotate around a pivot allowing the load to be released before then re-closing. Once the load was attached the pilot climbed G-PDGF to lift the pole off the ground. He transitioned to forwards flight whilst…cross-referencing the engine instruments and checking the load in a mirror as he increased airspeed in 10 kt increments. He stabilised the helicopter at 60 kt and 200 ft agl, as opposed to his usual transit speed of 80 kt, for the short flight to the work site. However, after about 6 km the pole began to develop a spinning motion, which rapidly increased in intensity, and which the pilot could feel through the airframe. Immediately, he lowered the collective and applied rear cyclic to bring G-PDGF rapidly to the hover but, before he could complete this manoeuvre, the pole fell from the helicopter. The pilot immediately returned G-PDGF to the refuel site and shutdown. He inspected the undamaged hook, which was found in the closed position, and the strop that was later recovered from the hillside was also undamaged. The Operator’s Analysis Four causes for the loads release were considered by the operator’s safety investigation: the inadvertent release of the electrically-operated hook by the pilot; the release of the hook due to an electrical malfunction; and two causes, similar in nature, that could cause the spring-loaded keeper to be forced open during flight. The operator considered it unlikely that the load was released inadvertently by the experienced pilot because the release system requires two independent switches on the cyclic to be depressed simultaneously to command a release. The hook and its release system were electrically checked by the operator’s...
read moreNDI Process Failures Preceded B777 PW4077 Engine FBO
NDI Process Failures Preceded Boeing 777 PW4077 Fan Blade Off (FBO) Event (United Airlines N773UA, Flight UA1175, 13 February 2018) On 13 February 2018 United Airlines Boeing 777-222 N773UA, suffered a fan blade off event and lost most of the inlet duct and both the left and right fan cowls of its No. 2 Pratt & Whitney PW4077 engine. Two small punctures were found in the right-hand fuselage just below the window line. This occurred over the Pacific Ocean shortly before top of descent when en route to Honolulu (HNL), Hawaii. The aircraft made a safe landing without injuries to the 374 persons on board. NTSB Safety Investigation FBO Event The US National Transportation Safety Board (NTSB) explain in their safety investigation report (issued 13 July 2020) explain that: The PW4000 112-inch engine fan blade is a hollow core, wide chord airfoil made of a titanium alloy with 6 percent vanadium and 4 percent aluminum as alloying elements. The fan blade is about 40.5-inches long from the base of the blade root to the tip of the airfoil and about 12.5- and 22.25-inches wide at the blade root and blade tip, respectively. A fan blade weighs a maximum of 34.85 pounds. During the accident flight while in cruise at flight level (FL) 360, the flight crew heard a loud bang, followed by a violent shaking and warnings of a compressor stall. The flight crew shut down the engine, declared an emergency, and proceeded to HNL without further incident. On examination of the engine it was found that… The fan blade in position No. 11 was fractured transversely across the airfoil about 1.44-inches above the fairing at the leading edge and slightly below the surface of the fairing at the trailing edge. There was a piece of fan blade found up against the leading edges of the fan exit guide vanes at about 4 o’clock. This piece of fan blade was about 15-inches wide chord wise, 23-inches long radially, and had a fracture surface on the inner end that corresponded to the fracture surface on blade No. 11. Laboratory examination of fan blade No. 11 revealed a low cycle fatigue (LCF) fracture that…initiated from a subsurface origin in a region of micro texturing consisting mostly of primary alpha crystals on the interior surface of the hollow core fan blade. The examination also revealed that the fan blade’s material conformed to the specified titanium alloy’s requirements. …fan blade No. 10…the adjacent trailing blade, was fractured across the airfoil at about midspan. The engine / fan history: According to United Airlines’ maintenance records, the No. 2 engine had accumulated 77,593 hours time since new (TSN) and 13,921 cycles since new (CSN) and 8,579 hours and 1,464 cycles since the last overhaul. The engine was installed on the airplane on October 18, 2015 [and] had operated 8,579 hours and 1,464 cycles since it had been installed. The entire fan blade set, including fan blade No. 11 had last been overhauled by P&W’s Overhaul & Repair (O&R) facility in July 2015. As part of the overhaul process, the blades underwent a fluorescent penetrant inspection (FPI) and a thermal acoustic imaging (TAI) inspection. P&W developed the TAI inspection process in about 2005 to be able to inspect the interior surfaces of the hollow core PW4000 fan blade. The records for the TAI inspection in July 2015...
read moreVortex Ring State: Virginia State Police Bell 407 Fatal Accident
Vortex Ring State (VRS): Virginia State Police Bell 407 Fatal Accident (N31WA, Charlottesville, Virginia) The US National Transportation Safety Board (NTSB) have concluded the Virginia State Police (VSP) Aviation Unit Bell 407 helicopter, N31VA, that crashed during surveillance of a violent ‘white nationalist‘ rally in Charlottesville, Virginia on 12 August 2017 had entered a Vortex Ring State (VRS). The helicopter impacted the ground, there was a post-crash fire. The pilot and the observer were fatally injured. The Accident Flight The NTSB explain in their safety investigation report (issued 13 July 2020) that: …the purpose of the flight was to provide the VSP command center with a continuous video downlink of the public demonstrations that were occurring in Charlottesville. The helicopter departed Charlottesville Albemarle Airport (CHO) about 1600. The helicopter arrived over the area of the demonstrations at 1604 and remained there until 1642 when the flight crew was tasked to provide overwatch for the Governor of Virginia’s motorcade. At 1643, the flight crew advised the VSP command center that the helicopter was heading directly to the motorcade and was about 30 seconds away. Radar data indicated that the helicopter was flying at an altitude of about 2,200 ft mean sea level (msl) in the area of the motorcade before it began to turn to the right and descend rapidly. Radar data also indicated that, about 30 seconds later, the helicopter was descending through 1,450 ft msl at a groundspeed of 30 knots. Shortly afterward, the helicopter descended below the area of radar coverage, and radar contact was lost. About 1649, a crewmember aboard a Fairfax County Police Department (FCPD) helicopter observed the accident helicopter descending upright into trees at a high rate of descent… The FCPD helicopter pilot…landed near the accident site to render aid. The other two crewmembers exited the helicopter and proceeded to the accident site. Upon reaching the accident site, the crewmembers encountered heavy black smoke and fire. The NTSB Safety Investigation The NTSB say that: Video from a security camera…captured the helicopter…descending vertically at a constant acceleration and with increasing negative vertical speed until ground impact. Photographs of the accident helicopter that were taken by a ground witness revealed that, about the time that the helicopter began its vertical descent, the helicopter was yawing to the right at a rate between 87° and 97° per second. Toward the end of the flight, the helicopter’s low forward airspeed while descending was consistent with the helicopter entering Vortex Ring State (VRS). As the helicopter approached 2250 ft of altitude the speed slowed to about 20 kts calibrated airspeed. At 16:48:06 the aircraft’s speed increased to 30 kts and at 16:48:12 it climbed from 2225 to 2275 ft while the speed again slowed to near 10 kts. The aircraft’s final descent began at 16:48:18. Examination of data from the Rolls-Royce 250 engine control unit… …revealed a sharp increase in torque, from 54% to 104% immediately before the helicopter’s descent. Insufficient left pedal input with increasing torque can result in a right yaw that can develop into a spin. Bell Helicopter provided the NTSB with the area of predicted vortex ring state for a Bell 407 with a gross weight of 4,633 lbs at sea level. [The graphic below] shows this predicted area with the aircraft’s forward speed and average vertical speed overlaid. The blue shaded area represents combinations of forward speed and vertical speed...
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