Helicopter Destroyed in Hover Taxi Accident
Helicopter Destroyed in Hover Taxi Accident (Private Airbus AS350B N36033, Wolfsberg, Austria) On 20 July 2018 privately owned Airbus Helicopters AS350B N36033 was destroyed while attempting to hover taxi closer to a fuelling station at Wolfsberg airfield in Austria. The pilot suffered a minor leg injury. The Austrian air accident investigation body, the Sicherheitsuntersuchungsstelle des Bundes (SUB) issued their safety investigation report on 15 December 2020 (in German only). They explain that the pilot had departed the Adriatic town of Caorle, Italy at about 04:30 Local Time (approximately 50 minutes before sunrise) and arrived at Wolfsberg at about 06:20. The pilot intended to move the helicopter closer to the fuelling station after discovering the 11 m hose would not reach where the helicopter had landed. This required positioning the helicopter so the main rotor blades were c 4.25 m from the building. At the time the wind was from c 100º and 1-2 knots. After lifting into a 1 m hover there were “excessive pitching movements forwards and backwards” and the helicopter yawed approx 90° to the right. The pilot reported feeling turbulence from the side of the fuelling station building (a 5.2 m x 5.2 m, flat roofed, 3.2 m high building). While the pilot tried to stabilize the helicopter in hovering flight, the helicopter rolled to the right around its longitudinal axis and touched the ground of the unpaved movement area east of the refueling station with the main rotor blades. This indicates a c 50º bank angle. After the main rotor impact on the ground, the helicopter yawed to the left around its vertical axis and came to a standstill in the opposite direction… Fortuitously the helicopter remained upright as the filler cap had been removed on arrival and was in the cabin. The Safety Investigation The investigation revealed that pilot did not hold a valid licence and “there were no records or information available about the pilot’s flying experience”. When hovering in ground effect the air accelerated by the main rotor travels radially out across the ground. However, it can recirculate if there are obstructions, such as a building. The SUB determined the probable cause was: Loss of lateral control during hover in ground effect (HIGE). Probable factors were Excessive control inputs / Flight crew induced oscillations about the helicopter longitudinal axis (PIO) / Lack of corrective action to stop PIO Proximity of obstacles / Formation of ground effect air vortices (IGE) Safety Resources Air Ambulance Helicopter Downed by Fencing FOD Ambulance / Air Ambulance Collision Sécurité Civile EC145 Mountain Rescue Blade Strike Hanging on the Telephone… HEMS Wirestrike Norwegian HEMS Landing Wirestrike Austrian Police EC135P2+ Impacted Glassy Lake B206B Hit by Truck in Forced Landing after 16 Months of Operation with Unairworthy Engine Tragic Texan B206B3 CFIT in Dark Night VMC Fatal B206L3 Cell Phone Discount Distracted CFIT Time Pressures and Take-Off Trim Trouble When Habits Kill – Canadian MD500 Accident EC120 Forgotten Walkaround Fatal R44 Loss of Control Accident: Overweight and Out of Balance Final Report: AS365N3 9M-IGB Fatal Accident Fatal Helicopter / Crane Collision – London Jan 2013 Deadly Dusk Air Ambulance Bird Strike UPDATE 22 December 2020: Mid-Air Collision of Guimbal Cabri G2 9M-HCA & 9M-HCB: Malaysian AAIB Preliminary Report UPDATE 30 December 2020: AS350B3/H125 Bird Strike with Red Kite UPDATE 2 January 2021: A Short Flight to Disaster: A109 Mountain CFIT in Marginal Weather UPDATE 5 February 2021: Inexperienced IIMC over Chesapeake Bay (Guimbal Cabri G2 N572MD): Reduced...
read morePiper PA-30 Twin Comanche Accident After Unapproved Parts Failed
Piper PA-30 Twin Comanche Accident After Unapproved Parts Failed (ZS-ICB) On 29 March 2019, during a training flight to practise asymmetric circuits Piper PA-30 Twin Comanche ZS-ICB of Johannesburg School of Flying was destroyed at Hiltonia-Syferfontein Airport (FASY). The student and instructor escaped with minor injuries. The South African Civil Aviation Authority (SACAA) explain in their safety investigation report (issued 15 October 2020) that: After a successful touch down, the student pilot then applied full power to both engines for take-off, the aircraft accelerated to 80 knots (kts) before rotation. During rotation, the aircraft banked sharply to the right and the instructor took over control and feathered the right-side engine, but it did not respond as expected. The aircraft lost height and impacted the ground with the right-side wing before ground-looping and skidding, facing the opposite direction from which it had initially taken off. The aircraft came to a stop 120m from the edge of RWY 14. Examination of the number 2 (right hand) engine… …revealed that the throttle control cable end fitting was missing. It was later found in the wreckage and it was not the original equipment fitted by the manufacturer. On inspection of the logbooks, it was discovered that the throttle control cable end fitting was fitted on 24 July 2018. The AMO [also] did not follow the manufacturer’s SB 515 issued on 17 January 1977 which states that all Piper PA-30 Twin Commanche with serial numbers 30 – 1 to 30 – 2000 must be installed with a control cable ball joint retainer. The AMO which fitted [the] unapproved throttle control cable end fitting without a ball joint retainer had ceased operation on 31 October 2018. Safety Resources Helicopter Throttle Bracket Left Unsecured After Maintenance FAA Rules Applied: So Misrigged Flying Controls Undetected Critical Maintenance Tasks: EASA Part-M & -145 Change Misassembled Anti-Torque Pedals Cause EC135 Accident EC130B4 Accident: Incorrect TRDS Bearing Installation Fatal $16 Million Maintenance Errors Insecure Pitch Link Fatal R44 Accident Tree Top Autorotation for B206L1 After Loose Fuel Line B-Nut Leaks R44 Force Lands After Improper Repair Aerossurance worked with the Flight Safety Foundation (FSF) to create a Maintenance Observation Program (MOP) requirement for their contractible BARSOHO offshore helicopter Safety Performance Requirements to help learning about routine maintenance and then to initiate safety improvements: Aerossurance can provide practice guidance and specialist support to successfully implement a MOP. Aerossurance was to have run training workshops at the EHA European Rotors VTOL Show and Safety Conference in Cologne in November 2020 on a) Safety Culture and Leadership and b) Contracting Aviation Services: An Introduction to the Basics. Sadly due to COVID-19 the show has been postponed to 2021. 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 moreNH90 Caribbean Loss of Control – Inflight, Water Impact and Survivability Issues
NH90 Caribbean Loss of Control – Inflight, Water Impact and 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 near HMNLS Groningen. 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 report (in Dutch only) on 9 December 2020. This followed an ‘exploratory investigation’ and the Defence Safety Inspectorate (IVD) are expected to investigate further (UPDATE 2 December 2021: that follow-on report is now published and discussed below). The Accident Flight Holland-class offshore patrol vessel HMNLS Groningen was deployed to the Caribbean. The ship’s embarked NH90 had conducted a routine patrol flight around Aruba on 19 July 2020 and was undertaking a series of deck landings to keep the ship’s flight deck officer current. The NH90 is flown operationally single pilot in the Netherlands. The front left seat is occupied by the tactical coordinator, in the cabin there are the hoist and sensor operators. The pilot had 1679 hours of helicopter flight experience, 719 hours on type (306 hours as aircraft commander) plus 310 hours of NH90 time simulator. The deck practices were conducted in a standard way. After coming into a hover from the ship’s deck, the helicopter moved sideways to the left and then climbed away. On return the helicopter approach the ship from behind, came into a hover on the right side of the flight deck, and then moved sideways and landed. 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. On the eighth practice flight did a lower circuit than before, less than 100 ft, as the plan was to take photos of the ship. As the helicopter passed down the right-hand side of the ship downwind… …the aircraft suddenly lost altitude very quickly and ended up in the sea with a bang. On impact, the tail broke off and the aircraft capsized, flooding the cabin. As a result of the impact, fuel immediately released around the aircraft. The floats automatically inflated and the helicopter continued to float upside down. The ship dispatched a fast rescue craft. The wreckage was located 2-9 August 2020 450 m below the surface. Salvage then occurred 7-8 September 2020 using multi-role subsea construction vessel Volantis of Deepwater, a DeepOcean Installer Remotely Operated Vehicle (ROV) NS a lifting cradle. Safety Investigation: Egress, Survivability and Rescue All the crew had done Helicopter Underwater Escape Training (HUET) in Den Helder. HUET video The sensor operator, who was sat on a box in the cabin was thrown forwards. The hoist operator was able to brace against the gun mount by the right-hand cabin door. Both were connected to the aircraft by a safety line. The immediate capsize resulted in disorientation. Having attempted but failed to open an exit they egressed via a push out window without injury. However, there were Aircrew Equipment Assembly (AEA) issues: Both men wore a personal vest of a type that had recently been introduced, but with which they had not yet trained. Using the new vests caused problems for the two men. There is a quick release a mechanism for disconnecting the safety line, to prevent falling from aircraft with the door open. Both crew members were unable to open the buckle on the front of the vest,...
read morePilatus PC-12 Pacific Ditching
Pilatus PC-12 Pacific Ditching (N400PW Ferry Flight) On 6 November 2020 Pilatus PC-12NGX N400PW ditched in the Pacific Ocean about 870 nm east of Hilo, Hawaii during a ferry flight. The two crew were rescued uninjured after 22 hours. The US National Transportation Safety Board (NTSB) explain in their preliminary report that… …the pilot-in-command (PIC), who was also the ferry company owner….and another pilot were ferrying a new airplane from California to Australia. The first transoceanic leg was planned for 10 hours from Santa Maria Airport (KSMX), California to Hilo Airport (PHTO), Hawaii. The manufacturer had an auxiliary ferry fuel line and check valve installed in the left wing before delivery. About 1 month before the trip, the pilot hired a ferry company to install an internal temporary ferry fuel system… The crew attempted the first transoceanic flight on November 2, but the ferry fuel system did not transfer properly, so the crew diverted to Merced Airport (KMCE), California. The system was modified with the addition of two 30 psi fuel transfer pumps that could overcome the ferry system check valve. The final system consisted of 2 aluminum tanks, 2 transfer pumps, transfer and tank valves, and associated fuel lines and fittings. The ferry fuel supply line was connected to the factory installed ferry fuel line fitting at the left wing bulkhead, which then fed directly to the main fuel line through a check valve and directly to the turbine engine. The installed system was ground and flight checked before the trip. The aircraft departed Santa Maria about 1000. The pilots each stated that the ferry fuel system worked as designed during the flight and they utilized the operating procedures that were supplied by the installer. About 5 hours after takeoff, approaching ETNIC intersection, the PIC climbed the airplane to flight level 280. At that time, the rear ferry fuel tank was almost empty, and the forward tank was about 1/2 full. The crew was concerned about introducing air into the engine as they emptied the rear ferry tank, so the PIC placed the ignition switch to ON. According to the copilot (CP), she went to the cabin to monitor the transparent fuel line from the transfer pumps to ensure positive fuel flow while she transferred the last of the available rear tank fuel to the main fuel line. When she determined that all of the usable fuel was transferred, and fuel still remained in the pressurized fuel line, she turned the transfer pumps to off and before she could access the transfer and tank valves, the engine surged and flamed out. The PIC stated that the crew alerting system (CAS) fuel low pressure light illuminated about 5 to 15 seconds after the transfer pumps were turned off, and then the engine lost power and the propeller auto feathered. The PIC immediately placed the fuel boost pumps from AUTO to ON. The CP went back to her crew seat and they commenced the pilot operating handbook’s emergency checklist procedures for emergency descent and then loss of engine power in flight. The crew attempted an engine air start. The propeller unfeathered and the engine started; however, it did not reach flight idle and movement of the power control lever did not affect the engine. The crew secured the engine and attempted another air start. The engine did not restart and grinding sounds and a loud bang were heard. The propeller never unfeathered and multiple CAS warning lights illuminated, including the EPECS FAIL light (Engine and Propeller Electronic Control System). The crew performed...
read moreA Saab 2000 Descended 900 ft Too Low on Approach to Billund
A Saab 2000 Descended 900 ft Too Low on Approach to Billund (Darwin Airlines HB-IZW) On 10 December 2015 Saab 2000 HB-IZW of Darwin Airline (branded Etihad Regional but operated for on behalf of Air Berlin), that had earlier departed from Berlin Tegel, Germany, suffered a serious incident on approach to Billund, Denmark. During this approach, the aircraft descended steeply and below the minimum safe altitude prompting a Terrain Avoidance and Warning System (TAWS) warning. The aircraft diverted back to Berlin and landed safely. History of the Accident Flight The Swiss Safety Investigation Board (SUST) explain in their safety investigation report that the Aircraft Commander had 8022 flying hours experience (but only 170 on type) and the co-pilot had 12100 hours experience (1022 on type). The weather in Billund that afternoon was overcast with a 600ft cloud base. After an uneventful cruise flight, the pilots noticed problems with the glideslope indication during the approach to Billund Airport. At an altitude of 800 ft above ground and 250 ft below the minimum altitude stipulated for this position, the pilot flying [PF – the Aircraft Commander] initiated a go-around. Because of the problems with the glideslope indication, the pilots decided to perform a non-precision approach using the localiser for the second approach. The safety investigators report that: During the [second] descent, the PM [Pilot Monitoring] tried to calculate the reference altitude for the correct glide path for a specified distance. He was not able to calculate this because he wanted to use the DME distance but could not find any DME information on the approach chart. He did not communicate that he was unable to come to a result and hence was not monitoring the vertical flight profile. When the aircraft was at a DME distance of 5.5 NM and an altitude of 1240 ft AMSL, the auto-callout ‘one thousand’ sounded, meaning that the aircraft was 1000 ft above ground. According to their statements, the crew noticed at this time that something was not right, but they did not realise what was wrong. 19 seconds later, the enhanced ground proximity warning system (EGPWS [i.e. a Honeywell TAWS]) sounded for one second with a glideslope warning. The investigators comment that: According to their statements, the crew was convinced that something was wrong when the auto-callout ‘five hundred’ sounded another 12 seconds later. 7 seconds later, at an altitude of 757 ft AMSL or 404 ft AGL, the PF decided to initiate a go-around. At approximately the same time, the EGPWS ‘terrain ahead, pull up’ warning sounded. The PF flew the normal go-around procedure and, one second after the EGPWS warning, the go-around mode was active. The lowest altitude during the go-around was 700 ft AMSL or 346 ft AGL. After they had completed an analysis of the problem, the crew decided to return to Berlin…as the weather in Berlin allowed for a visual approach. The remainder of the flight was uneventful. The investigators say that after the flight: After…the crew concerned made a telephone call to the company to inform them that they had to execute a go-around during the approach to Billund Airport due to receiving a false warning from the EGPWS. The aviation company’s safety manager only realised that the incident had been a serious incident during the routine flight data monitoring (FDM) of the day’s operations and reported...
read moreNTSB on LA A109S Rooftop Hospital Helipad Landing Accident
NTSB on Los Angeles A109S Rooftop Hospital Helipad Landing Accident (N109EX of Helinet Aviation Services / Prime Healthcare at USC Kerk) The US National Transportation Safety Board (NTSB) have published their preliminary report on Leonardo Helicopters AW109S N109EX of Helinet Aviation Services which crashed onto the University of Southern California (USC) Keck Medical Center (USC Keck) rooftop helipad in Los Angeles, California on 6 November 2020. UPDATE 28 January 2023: NTSB have now published further factual information (see below) that puts attention on the tail rotor and past inspections. The helicopter was making a Part 135 helicopter air ambulance flight, with a donor heart for a transplant operation aboard. The pilot suffered minor injuries and the two passengers were uninjured. The Los Angeles Fire Department (LAFD) retrieved the organ from the wreckage and the hospital says “the heart was successfully transplanted following the crash, and the transplant recipient is recovering well”. The Accident The US National Transportation Safety Board (NTSB) explain in their preliminary report that: The pilot reported that he established the helicopter in a steep approach, to land on the rooftop helipad of a multi-story medical building [approaching in a northerly direction over Hazard Park according to videos of the accident]. The pilot had offset his heading to the left to gain greater visibility to the landing zone. He observed the absence of any wind indication from the windsock and no movement on nearby trees. When the helicopter had decelerated to about 45 knots, he increased the engine and rotor RPM to 102%. About 40 feet above the helipad, the pilot noticed a slight yaw to the right that continued despite full left pedal application. He thought to fly away from the helipad when the helicopter aligned in the direction he just approached from. As the helicopter rotated to about 90° from his approach heading, it suddenly and very violently made a dramatic increase in right yaw. Realizing the helicopter was going to be uncontrollable, the pilot “dumped the collective” and tried to stay over the helipad. He stated that after the helicopter struck the helipad, it rolled left and continued spinning on its side, and eventually came to a stop. The pilot shut down the engines and all three occupants exited unassisted. The NTSB say that: A review of a witness video, (See figure 1), taken from an adjacent building, revealed the helicopter approached the rooftop helipad while slowly rotating clockwise about the vertical axis. The helicopter stopped descending and rotated 360°. The helicopter then descended while rotating an additional 180° and rolled to the left before impacting the helipad. The main rotor blades contacted the helipad, followed by the left main landing gear and the fuselage. The helicopter descended out of view of the camera. The helicopter came to rest on its left side, on the helipad. The four composite blades of the main rotor system fragmented and separated, spreading debris throughout the rooftop and down to the ground. The tail rotor and 90° gearbox separated and were found on the rooftop. The left main landing gear separated and remained near the attachment points of the fuselage. UPDATE 28 January 2023: NTSB Safety Investigation Factual Report: Focus on Tail Rotor Ring Nut NTSB investigators have revealed that the tail rotor assembly rotating control ring nut was separated from the thrust sleeve assembly. No other pre-impact defects were found. Examination of the tail rotor assembly and 90° gearbox by the NTSB...
read moreAir Ambulance A109S Spatial Disorientation in Night IMC
Air Ambulance Helicopter Spatial Disorientation in Night IMC (North Memorial Healthcare Leonardo A109S N11NM, Minnesota) On 28 June 2019, at about 0040 Local Time Leonardo Helicopters AW109S N11NM, an air ambulance operated by North Memorial Healthcare, was destroyed at Brainerd Lakes Regional Airport (BRD), Minnesota. The pilot and flight nurse died at the scene. The flight paramedic was seriously injured. The helicopter had been approaching the airport in dark night instrument meteorological conditions (IMC) after delivering a patient to the North Memorial Medical Centre and was just commencing a missed approach. This was the operator’s second night A109S accident in less than three years. The previous one, non-fatal, involving N91NM on 17 September 2016 was discussed in this Aerossurance article: HEMS A109S Night Loss of Control Inflight, issued on 29 September 2018. That also involved a missed approach and NTSB determined in the first accident that “the pilot’s excessive cyclic input…resulted in a loss of control and spiralling descent into terrain”. The Safety Investigation The US National Transportation Safety Board (NTSB) explain in their safety investigation report (issued in November 2020) that N11NM was… …equipped with a 2-axis autopilot for lateral (roll) and longitudinal (pitch) control. The autopilot provided for limited yaw dampening, but no yaw control. Minimum airspeed to comply with IFR handling quality requirements for the helicopter [Vmini] was 55 knots. The pilot had 3376 hours total, 533 on type and 2294 as Pilot In Command. The pilot’s most recent Part 135 competency/proficiency check occurred on March 12, 2019. During the 90 days before the accident, the pilot logged 27 landings at night, 16 instrument approaches, 1 flight hour of actual instrument time, and 57 hours of simulated instrument time. The pilot’s total actual instrument time flown was 41 hours. BRD was located in a rural area with few ground lights, and there was no moon illumination at the time of the accident. Airport personnel stated that several lakes near BRD would often generate patchy fog and visibility could vary significantly at different locations on the airport. Another pilot working for the operator told the NTSB: I’ve experienced some weird things at Brainerd… I’ve seen it in both directions, where it’s worse than it says it is, and I’ve seen it where it’s way better than it says it is. History of the Accident Flight The flight was returning to BRD after delivering a patient to North Memorial Heliport (MY77), Robbinsdale, Minnesota. An onboard Appareo Vision 1000 device recorded flight data, cockpit imagery, and audio of the flight. The helicopter departed MY77 at 2348, and the pilot received an instrument flight rules [IFR] clearance from air traffic control (ATC) to climb to 6,000 ft mean sea level (msl) and fly direct to BRD. At 2356, while holding an iPad, the pilot stated on intercom to the paramedic and/or flight nurse that visibility at BRD was “1 mile, looks good.” The pilot requested the instrument landing system runway 23 (ILS RWY 23) approach and informed the controller that he had obtained the current weather at BRD. At 0028, the pilot selected the BRD automated surface observing system (ASOS) frequency. The ASOS transmission included a ceiling of 200 ft above ground level (agl) and 1/4-mile visibility with fog. The controller cleared the helicopter for the ILS RWY 23 approach. Shortly thereafter, the ASOS transmitted weather included 1/2-mile visibility with haze, and the pilot stated “awesome, 1/2 we’re legal” on the intercom. The pilot subsequently activated the runway lights. At 0034:35, the helicopter began a descent on the ILS glideslope with the autopilot coupled. About 5 seconds...
read moreAlaskan AS350B3e Accident: Botched Autorotation Practice?
Alaskan Airbus AS350B3e Accident: Botched Autorotation Practice? (N907PL) On 28 September 2018 a private Airbus Helicopters AS350B3e (H125) N907PL was destroyed in an accident in Glacier Bay National Park, near Lituya Bay, about 60 miles NW of Gustavus, Alaska. One person died, 2 remain missing presumed dead and one was seriously injured. The US National Transportation Safety Board (NTSB) explain in their safety investigation report that: The private pilot [aged 42, 1,129 flying hours total, 26 on type and president of Anchorage’s Davis Constructors and Engineers] had just purchased the helicopter… He had done a AS350B3e factory course in Texas with 3 hours of flight time and 1 hour of simulator time. He had then done 18.3 hours of flying an AS350B2 in Alaska, and another 6 hours on the AS350B3e in Texas, before embarking on the delivery flight from Texas to Alaska. The trip began on September 25, 2018, and included more than 30 stops for sightseeing, fuel, and rest. The left seat safety pilot [aged 53, 15,350 flying hours total, 4350 on type, who had flown with the owner for 11.4 hours in an AS350B2 previously] was onboard for insurance coverage purposes and was acting as a safety pilot. The safety pilot was the owner, director of operations, and chief pilot for two different commercial helicopter operators in Alaska that operated several AS350B2 model helicopters. The right seat pilot-in-command [the owner] planned to drop off the safety pilot in Wasilla, Alaska, then proceed to Anchorage with the [two] passengers [the young sons of the pilot owner]. N907PL was equipped with a Genesys Aerosystems HeliSAS autopilot and stability augmentation system. The NTSB comment that in an interview after the accident the survivor, a 14-year-old boy, stated that… …the safety pilot did not seem recently familiar with the B3e model and the options that were installed on the accident helicopter. The safety pilot asked a lot of questions about the B3e, and the [owner] pilot appeared more familiar with the helicopter systems than the safety pilot. This may have course have been the safety pilot checking the owner pilot’s understanding. Although not mentioned by the NTSB, the survivor also commented that both pilots were aware of a past accident where an object in the cabin caught on flying controls and were very alert to that hazard. During this trip the helicopter departed Juneau, Alaska that morning bound for Yakutat, Alaska. It proceeded west over the mountains st 3000-4000 ft AMSL, then north-west along the coast at about 500 to 700 ft AMSL. Video from the cockpit image recorder [an Appareo Vision 1000] indicated that the pilot, seated in the right seat, was manipulating the flight controls from takeoff until the accident occurred [there is no mention of the NTSB of any analysis of the audio data recorded]. The surviving passenger stated that, while en route, the pilot indicated that they would be landing on a beach in order to stretch their legs. The recovered data showed the helicopter flying about 500 to 700 ft over water when the pilots began conversing and pointing toward the shore. The safety pilot, whose hands were on his lap, then raised his right hand in a manner that appeared that he was guarding the cyclic control in anticipation that his assistance or intervention might be required. Shortly thereafter, the pilot twisted the collective twist grip throttle from FLIGHT to IDLE; data from the engine data recorder (EDR)...
read moreAOA Anomalies on Successive B737-800 Flights
AOA Anomalies on Successive Transavia Boeing 737-800 Flights (F-GZHO) Transavia France Boeing 737-800 F-GZHO suffered Angle of Attack (AOA) anomalies and alerts during take off from Norwich, UK on 7 February 2018 and then on 8 February 2018 after take off from Paris Orly, France. The French Bureau d’Enquêtes et d’Analyses pour la Sécurité de l’Aviation Civile (the BEA) explain in their safety investigation report, issued on 16 November 2020, that the first flight was a ferry flight after a base maintenance C-Check at KLM UK Engineering with just 3 persons on board and then the second a revenue flight with 180 persons on board. Aircraft Systems Context BEA explain that: IAS DISAGREE, AOA DISAGREE and ALT DISAGREE messages are generated by the DEU [Display Electronics Units] 1 and 2 based on the data provided by the two ADIRUs [Air Data Inertial Reference Units]. These messages are displayed in amber on the PFD without an audio warning. The conditions for the activation…are the following: The IAS DISAGREE message is displayed on the two PFDs when there is a difference of more than 5 kt for at least 5 seconds between the left and right indicated airspeed values. The AOA DISAGREE message is displayed on the two PFDs when there is a difference of more than 10° for at least ten seconds between the angle of attack values measured by the left and right sensors. The ALT DISAGREE message is displayed on the two PFDs when there is a difference of more than 200 ft for at least 5 seconds between the left and right altitude values. The 737 is equipped with two AOA sensors installed on the forward fuselage…. The external part of the sensors consists of a heated vane which positions itself in the air flow bed. The rotary movement of each sensor is transmitted to two electric resolvers, located in the body of the sensor, by means of internal gears. The resolvers transform the rotary movement into an electrical voltage value which is proportional to the angle of attack. Within each sensor, resolver 1 sends its electrical data to the SMYDC [Stall Management Yaw Damper Computer] and resolver 2 to the ADIRU which generates the air and inertial data of the aeroplane. Resolvers 1 and 2 are mechanically linked by a gear. Thus, when the AOA sensor functions nominally, the angular positions of the two resolvers change at the same rate. An angle of attack measurement error thus affects the indicated airspeed and altitude displayed on the PFD on the side of the erroneous measurement. …in addition to the indicated airspeed and altitude display errors, the various computers situated on the same side as a malfunctioning AOA sensor receive false input data. These dysfunctions may result in an increased work load for the crew along with difficulties in controlling the aeroplane. During a C-check one… …inspection required the two AOA sensors to be manually turned by 30°. The technicians who had carried out this operation had not noticed any anomaly. Flight on 7 February 2018 The aircraft took off at 18:40 in night Visual Metrological Conditions (VMC). The captain was Pilot Flying (PF). …at roughly the moment when the captain carried out the rotation, the IAS DISAGREE alert message appeared on both PFDs. The crew called out the appearance of the alert and quickly saw that the right PFD [Primary...
read moreShort Sling Stings Speedy Squirrel: Tail Rotor Strike Fire-Fighting in Réunion
Short Sling Stings Speedy Squirrel: Tail Rotor Strike Fire-Fighting in Réunion (Hélilagon Airbus AS350B3e / H125 F-OFML) with Video On 24 January 2019 Airbus Helicopters AS350B3e (H125) Squirrel F-OFML of Hélilagon suffered a tail rotor failure during fire-fighting with an underslung bucket at Grand-Brûlé, Sainte-Roseon on the Indian Ocean island of Réunion. The French Bureau d’Enquêtes et d’Analyses pour la Sécurité de l’Aviation Civile (the BEA) explain in their safety investigation report (issued only in French) that the pilot (who had 10,129 hours of flying experience and 4,198 on type) had been flying for four days fighting fires on the eastern side of the Piton de la Fournaise volcano. This was by both by direct water drop and replenishing temporary reservoirs set up by ground fire-fighters using pumps and hoses. The helicopter had an underslung 820 litre Type 1821 Bambi Bucket on a short 5 m sling (so the bottom of the bucket was c 9.7 m below the helicopter in the hover) to do both tasks. Having dropped water on the main front of the fire at 2,200 ft AMSL (location 2 the graphic below), the helicopter was returning to collect more water from a point about 2 nm away, on the lower slopes of the volcano at 385 ft AMSL (location 1 below). Wind was north-easterly, gusting 30 knots. During that leg while descending through at 930 ft AMSL at 13:48:17 (location 3), the pilot heard a high-frequency noise at the same time as feeling a slight jerk to the left. The pilot then perceived a loss of effectiveness of the rudder pedals. After a MAYDAY call, the pilot continued flying with the intention of finding a suitable area for an emergency landing. This part of the flight was captured on the early part of the VIDEO. The pilot was not able to find a location suitable for a run on landing. When airspeed was reduced, the helicopter started to rotate around its yaw axis and made two and a half turns before a hard landing at 13:52:45 (in location 4 at 315 ft AMSL) on a lava flow from 2002, near the coast road. The helicopter was shutdown. On egress the pilot discovered the cables of the fire-fighting bucket were entangled with the tail rotor and the tail rotor blades were broken at 3/4 length. The right skid was broken in several places and there was impact damage from the underslung load on the tailboom. A local news report contained close-up images. Closer examination revealed that the Tail Gear Box (TGB) casing had fractured around its circumference. The BEA determined this was due to overload when the blades struck the underslung load. The BEA observe that flight and wind parameters derived from the two independent onboard recording systems (an Appareo Vision 1000 and a Helisafe system) “show that the helicopter was operating in a very turbulent air mass”. This is likely due to be a combination of the wind and the Volcano topology, supplemented by heat from the fire. When the underslung load hit the tail rotor the helicopter was flying at an indicated speed of 97 kt, with a rate of descent of 1,230 ft/min in a “particularly turbulent environment”. The BEA note that the manufacturer’s manual for the fire-fighting bucket can only be complied with if the bucket is connected directly to the cargo hook (with no sling) or by using a sling of at least 15 m. The manual also states airspeed with the bucket fitted should not...
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