Dramatic Loss of Control During AS350 Landing Practice
Dramatic Loss of Control During AS350 Landing Practice (AS350B3 N711BE at Palomar, California) Two people died in a horrific accident when a private pilot practised landing his newly acquired Airbus Helicopters AS350B3 helicopter N711BE on a wheeled landing platform (or tow dolly) at McClellan-Palomar Airport, Carlsbad, CA on 18 November 2015. The US National Transportation Board (NTSB) report that the pilot had practised several landings in a field before returning to the airport, “where the approach and hover taxi to the ramp were uneventful”. However: In the weeks preceding the accident, the pilot had expressed concern to multiple flight instructors that he was having difficulty adjusting to the flight characteristics of the helicopter. In particular, he found dolly-landings challenging. Although the pilot had many years of experience flying a Bell 407 helicopter, there were two significant differences between the Bell 407 and the accident helicopter. First, their main rotor systems rotated in opposite directions; therefore, the foot pedal inputs required to counteract changes in torque during takeoff and landing were opposite. (The pilot’s difficulty adapting to this difference was evidenced during most of the previous takeoffs captured by the onboard video when the helicopter yawed significantly after lifting off.) Second, the tips of the landing skids, which were used as a visual reference during landing, were forward of the pilot in the Bell 407 but just aft of the pilot in the accident helicopter. This change in visual reference would have been particularly significant during dolly landings, which require landing on a specific point directly below the pilot’s field of view. The pilot had received about 11 hours of flight instruction in the helicopter, and, despite the fact that his instructors advised him not to fly without an instructor, he opted to fly with a passenger…on the accident flight. Although the passenger held a helicopter rating, he was not an instructor or professional helicopter pilot and had about 180 hours total in helicopters. Furthermore, it was likely that he had little or no experience in the accident helicopter make and model. The NSTB say: The pilot made a landing attempt on a dolly but landed only partially on the dolly, which caused the helicopter to pitch nose up and strike the ground with its tail. The helicopter hit the dolly with such force that the dolly broke free from the chocks securing it and spun around. The helicopter climbed and spun upwards aggressively but stabilized after rotating 270° to the right. Ground crew personnel re-secured the dolly with chocks, and, after about 2 1/2 minutes, the pilot again attempted to land on the dolly, this time from the opposite direction. He made two unsuccessful attempts but was unable to maintain a stabilized approach each time. The pilot persisted: On his third attempt, he again landed partially on the dolly… …and the helicopter rocked back and forth striking the ground with its tailskid… …before violently climbing and pitching nose down, while rolling right. The helicopter spun 180° to the left and pitched up steeply… …and the tail rotor and vertical stabilizer struck the ground and separated. The helicopter hit the ground left side low, bounced, and rotated another 360° before landing hard on its belly. The main rotor blades continued to spin and the engine continued to operate; the helicopter spun on its belly at...
read moreTool Bag Takes Out Tail Rotor: Fatal AS350B2 Accident, Tweed, ON
Tool Bag Takes Out Tail Rotor: Fatal AS350B2 Accident, Tweed, ON (UPDATED 30 Oct 2019 with Final TSB Report) Four died when a tool bag came loose and struck the tail rotor of a helicopter carrying workers of an electricity utility company. The accident involved Airbus Helicopters AS350B2 C-GOHS operated by Ontario’s Hydro One Networks need Tweed, ON on 14 December 2017. The Transportation Safety Board of Canada (TSB) say in an initial report on 21 December 2017 that a single pilot and three Hydro One linesmen were on board, supporting maintenance on high-power electricity transmission lines: As part of the work being conducted, a few bags used for carrying tools and supplies were carried externally on a platform extending out of the right side of the fuselage. These bags, when carried externally, are normally attached with double-lock carabiners. Shortly before the accident, the pilot picked up the 3 linemen at the base of a tower and was transporting them to a nearby staging area. While nearing the staging area, one of the bags that was being carried externally blew off the platform and, along with its attached carabiner, struck the tail rotor. Shortly thereafter, while the pilot was attempting to land, the helicopter departed from controlled flight, all 3 passengers became separated from the helicopter while it was still airborne. The helicopter subsequently crashed nearby. We have found a heavily damaged white canvas bag, with a damaged carabiner attached, and the tip of a tail rotor blade over 600 meters away from the crash site. Two of the three linesmen were not wearing seat belts. Safety Advisory TSB have issued a safety advisory: Cargo must be adequately secured at all times, to prevent it from shifting or departing the helicopter during flight. Passengers who do not wear seat belts risk serious injury or death in the event of an emergency. TSB Final Report Issued 30 October 2019 TSB report that: At 1144 Eastern Standard Time, the pilot picked up a crew of 3 power line technicians near the bottom of a tower for a return flight to the staging area. It had become common practice for power line technicians to attach tool bags and other small items to the external platform for flights to and from work sites. In line with this practice, the technicians attached a few items to the platform while boarding the helicopter, and then took their seats in the aft cabin. TSB also note that while there were specific procedures for stowage and securing bags when workers board from a power tranmission line in the hover via a helicopter ‘Air Stair‘ eternal platform… …when boarding from the ground, there were various practices relating to the storage and securement of the preform bags [ a 4‑foot‑long canvas supply bag]. The practice of carrying external loads attached to the platform was not a formalized procedure at the company and, as a result, adequate controls were not in place to ensure that these objects were properly stored or secured. Consequently, an empty canvas supply bag with an attached carabiner that was being carried on the platform was not adequately secured before the helicopter departed for the return flight to the staging area. The pilot was likely unable to confirm that the load was stored inside the cabin because he was occupied with controlling the helicopter during the...
read moreSeason’s Greetings from Aerossurance
Aerossurance sends its Season’s Greetings to all its customers, partners, suppliers, colleagues and friends. We also wish you all a safe and prosperous 2018! For aviation advice you can trust, contact Aerossurance at: enquiries@aerossurance.com Follow us on LinkedIn and on Twitter @Aerossurance for our latest...
read moreIrish Air Corps Order Pilatus PC-12s
Irish Air Corps Order Special Mission Pilatus PC-12s The Irish Air Corps (IAC) signed a contract on 19 December 2017 for three special mission Pilatus PC-12NG aircraft, mission equipment and support services worth €32 million. The IAC originally issued a Request for Tender (RFT) in May 2017 for 3 CS-23 certified Fixed Wing Utility Aircraft. These had to be of an in production type with military experience too. It is expected that the Cessna 208B Caravan would have been offered in the competition too. These aircraft are intended for use in Intelligence, Surveillance, Target Acquisition and Reconnaissance (ISTAR) roles in addition to other utility support (including logistical support, passenger transport and MEDEVAC / air ambulance roles). They will replace the Air Corps’ five Cessna FR172H, which entered service in 1972. The requirement included the provision of a full mission solution including the aircraft, role equipment (including an electro-optical/infrared [EO/IR] turret and communications equipment, plus the ability to fit a LifePort PLUS), training, tools and a logistical support package. The first two aircraft will be delivered in 2019 and the third in 2020. The aircraft are expected to have a 20 year service life. The IAC are already a Pilatus customer as they operate the PC-9M. Read more here. UPDATE 2 June 2018: The first aircraft has flown at Stans. UPDATE 26 March 2019: It appears that the first delivery has slipped to 2020. UPDATE 2 June 2019: The first two are being fitted out in the US. UPDATE 4 October 2019: The last of its remaining FR172H aircraft are retired. UPDATE 16 December 2019: Department of Defence has announced the acquisition of two Airbus C295 medium airlifters in a maritime surveillance configuration to replace the CN235s in service. UPDATE 18 January 2020: Test and evaluation is expected over the next 4 months. UPDATE 1 April 2020: A 4th PC-12 is being delivered direct from Switzerland and is expected to support COVID-19 taskings initially. UPDATE 2 April 2020: It is reported the 4th aircraft was previously HB-FXT (msn 1898). The original three PC-12’s ordered for the Air Corps are currently being fitted out at the Pilatus factory in Denver Colorado. They are currently registered as civilian aircraft N280NG (msn 1795), N281NG (msn 1834) and N282NG (msn 1844). Some crew have already undergone training in Colorado, in fact all three aircraft have been noted flying in the last month. UPDATE 10 May 2020: Busy First few weeks for Air Corps PC12 UPDATE 10 September 2020: The three aircraft modified in the US have been ferried across the Atlantic to Baldonnel. Aerossurance has extensive air safety, operations, 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 moreBell V-280 Valor Tilt Rotor First Flight
Bell V-280 Valor Tilt Rotor First Flight Bell Helicopter made the first flight of their V-280 Valor tilt rotor on 18 December 2017. The aircraft hovered during the short flight at Amarillo, Texas. Unlike the earlier Bell-Boeing V-22 Osprey the V-280, targeted to cruise at 280 kts, does not tilt its engines (two GE T64s) only its rotors. This eliminates engine lubrication complexity and reduces the hot efflux effects on the ground. To achieve this engine power is transmitted through a spiral bevel gearbox that transfers power to the proprotor gearbox. This rotates on two spherical bearings. Bell are clearly sensitive about the design solution as both video and photographs have been altered to blur the mechanism and preserve the Valor’s modesty. In the event of an engine failure, power is transmitted by a cross-shaft, similar to that on the V-22, from the operative engine to the opposite proprotor. The V-280 had previously conducted ground runs on a test stand at Amarillo, TX: It features a triple-redundant fly by wire (FBW) control system. UPDATE 26 February 2018: The V-280 has now flown for 9 hours and been rotors running for 56 hours. The first US Army pilot flew it 7 February 2018. UPDATE 15 May 2018: V-280 has now completed a transition to forward flight and achieved 190 kts. UPDATE 20 June 2018: Bell’s V-280 Valor shows off agility, speed in first public flight demo UPDATE 18 December 2018: V-280 Reducing Risk For Future Army Tiltrotor, Bell Says https://youtu.be/LM4EGT_a0Xc UPDATE 9 January 2019: Flying the Bell V-280 Valor: Tru Simulation Technical Demonstrator UPDATE 29 January 2019: Bell to roll back V-280 funding until US Army competition Bell plans to make no more significant investments in its V-280 Valor tiltrotor until the US Army makes a commitment to Future Vertical Lift Capability Set 1 or Capability Set 3 programmes. After the V-280 reached its 280kt (519km/h) speed goal on 23 January, Bell believes that it sufficiently demonstrated the tiltrotor technology. UPDATE 21 May 2019: V-280 Passes Key Agility Test JMR-TD and FVL The Bell V-280 Valor program is part of the Joint Multi Role Technology Demonstrator (JMR-TD) initiative, started in 2013, which runs into 2019. Construction of the V-280 began in June 2015. The JMR-TD program is the R&D precursor to the Department of Defense’s Future Vertical Lift () programme that will be the basis for the replacement of the majority of US military rotorcraft and undoubtedly reshape the US rotorcraft industry. V-280 would be offered to replace Sikorsky H-60s and Bell H-1s under the Army/Marine Corps FVL-Medium or Capability Set 3 programme. Team Valor The V-280 program brings together Bell Helicopter, Lockheed Martin, GE, Moog, IAI, TRU Simulation & Training, Astronics, Eaton, GKN Aerospace, Lord, Meggitt and Spirit AeroSystems (who make the fuselage) – collectively referred to as Team Valor. SB>1 Defiant Team Valor’s main rival for FVL is a team of Sikorsky (now part of Bell’s team-mate Lockheed Martin!) and former Bell V-22 partner Boeing, who joined forces to develop the SB>1 Defiant. This combines a coaxial rotor with a pusher propeller. UPDATE 26 December 2018: The 30,000lb (13.6t) prototype SB>1 has been rolled out and is due to fly early in 2019. UPDATE 21 March 2019: The SB>1 flies. Other Bidders Karem Aircraft and AVX Aircraft are validating their FVL concepts using non-flying test hardware. FLRAA Contract Award (UPDATE 5 December 2022) Just short of 5 years...
read moreInvestigation into Secretive Surveillance Aircraft Accident in Malta 24 Oct 2016
Investigation into Secretive SA227 Surveillance Aircraft N577MX Accident in Malta 24 Oct 2016 The French BEA-D (Le Bureau Enquêtes Accidents Défense – Air, UPDATE: renamed the BEA pour la sécurité de l’aéronautique d’État [BEA-É] in 2018 in recognition of its role in all state aircraft) issued a progress report in late 2017 into the loss of US registered SA227 AT Merlin IVC surveillance aircraft N577MX of Luxembourg based CAE Aviation operating from Malta for an unspecified agency of the French Government on 24 October 2016. During the initial climb, 4 seconds after rotation, the aircraft pitched nose up, then rolled right around 150 degrees, reaching just over 260ft above ground level, before descending about 3 seconds later. The aircraft rolled to the left prior to impact with the ground, 130 meters to the right of the take-off axis and approximately mid-runway. https://youtu.be/9OubF4h6ozw?t=38 The flight lasted about 10 seconds. There was a post crash fire. All 5 on board died. Background N577MX had been modified from March 2015 to March 2016 and was officially owned by a company registered in Missouri. Different photographs in the BEAD-Report show an aircraft with a FLIR/EO sensor turret (though we believe this to be a US Air National Guard Bureau stock photo of a C-26) and another of N577MX two belly small radomes and a blade antenna. In its modified state the aircraft had a total of 6 seats. The aircraft was owned and operated by CAE Aviation, a company formed in 1971, who conduct aerial surveillance and airborne geophysics operations as well a providing aircraft for parachute training. It is said to be unrelated to the Canadian company CAE but is an agent for Wescam. CAE Aviation are said to also operate N919CK (registered to a trustee in Delaware) in Malta. The flight crew were employees of CAE Aviation. The Commander was aged 30 and the Co-Pilot aged 70. Both had FAA licences. The rear crew consisted of a Tactical Coordinator and two Systems Operators aged between 32 and 52. The organisation that employed them is not revealed but press reports claim they worked for a French intelligence agency and the aircraft was conducting missions off the coast of Libya. Analysis The aircraft was not fitted with a Flight Data Recorder. A acoustic spectral analysis of ground based video recordings shows that during the taxy out the rotational speeds of the two engines are identical. In flight at least one of the two propellers was operating at at rated speed until impact. The BEA-D eliminated the possibility that one of the flight crew seats may have come unlocked at rotation (and so resulted in an inadvertent nose up pitch input as it slid aft). They do note that once the nose was 11 degrees above the horizon the ground ahead would not be visible. Turbulence from the preceding 757 or from buildings was rejected as a possible cause due to a 3 minutes separation and the low wind on the day respectively. No bird debris was found and no evidence of birds was seen in the surveillance videos or report by witnesses. The Warning and Caution panel had 7 indicators lit (shown in red or green below), 22 off (in black) and 11 that so far have not been determined (in white). The one red light was for the SAS (stall avoidance system). Investigation is ongoing in this area. Glare from the sun is a...
read moreUnited Airlines Suffers from ED (Error Dysfunction)
United Airlines Suffers from Fan Cowl ED (Error Dysfunction) We have previously discussed a long running series of around 40 events when Fan Cowl Doors (FCD) were lost from Airbus A320 series aircraft, including: A319 Double Cowling Loss and Fire – AAIB Report ANSV Report on A320 Fan Cowl Door Loss: Maintenance Human Factors Tiger A320 Fan Cowl Door Loss & Human Factors: Singapore TSIB Report In each case the cowls had inadvertently been left unlatched and this had not been subsequently detected before flight. Airbus introduced a modification that would prevent the cowls being opened without inserting a mechanical ‘key’ attached to a long red streamer, that would normally be stowed on the flight deck and that could only be removed when the cowls were fully locked. But remarkably a US airline fought the proposed Airworthiness Directive (AD). United Airlines Responses to FAA NPRM The airline responded as follows for the FAA Notice of Proposed Rulemaking (NPRM) to adopt the exiting EASA AD (AD 2016-0053 on IAE V2500 powered A320s had been issued in March 2016 and was followed by AD 2016-0257 on CFMI CFM56 powered A320s): United Airlines (UAL) stated that it strongly disagrees with making the new latch keys installation mandatory. UAL stated that each one of the fan cowl door losses during takeoff can be attributed solely to human error. The implication is that no design improvement is needed after 40 occurrences. UAL explained that the mechanics are not correctly latching the fan cowl after maintenance and the flight crews are not checking that the latches are secured before departure. This is undoubtedly true, but in a surprisingly they go on to say: …instead of mandating the modification, UAL stated that more emphasis should be placed on addressing the root cause—not the design, but human error. James Reason, Professor Emeritus, University of Manchester wrote in his classic 1997 classic Managing the Risks of Organizational Accidents that among some of the problems with error management are: Focusing on the active failures (of people) not the latent conditions Not being informed by current human factors thinking regarding error and accident causation Human error is not itself a cause, but merely the start of a human factors investigation, as explained by Sidney Dekker in The Field Guide to Understanding Human Error – A Review (discussed in this book review The Field Guide to Understanding Human Error to the RAeS). United are disappointingly focusing on what Reason called ‘the human condition’ and hoping to change it, something he argued was futile, but that “we can change the conditions under which people work“. Perhaps United have never heard of the Murphy’s Law from the 1940s either. United went on to complain that: …adding another loose piece of equipment to be maintained and stored on the airplane would lead to operational complications. That is true but in the scheme of operation of a modern airliner it is neither a disproportionate or novel complication. According to the FAA: UAL also noted that additional time would be added to accomplishing routine tasks after incorporation of the modification. UAL contended that additional time would be required to access the cockpit, retrieve the key, and open the fan cowls, which would expose personnel and the airplane to further damage or harm. They don’t specify what further damage / harm this could involve as non of these tasks are again unique. More telling: Mandating the modification, UAL...
read moreCrossed Wires: Online Maintenance Human Factors Training Video
Crossed Wires: Online Maintenance Human Factors Training Video In need of inspiration for your maintenance human factor continuation training? Why not use this free CASA HF video?: ‘Crossed Wires’ The 8.5 minute video from 2013 portrays the incubation of an incident at the fictitious Perfect Twins maintenance organisation. As part of a workshop activity participants could note down the human performance influencing factors and risk inducing behaviours as they occur. Then discuss these as a group afterwards and consider what controls your organisation has (or hasn’t!) got in place. The video supports the CASA Safety Behaviours: Human Factors for Engineers resource kit that includes a detailed HF guide, facilitator’s guide and participant workbook, with other ideas to exploit the video. It can be followed by this, admittedly slightly idealistic, shorter video on how things could be at Perfect Twins Maintenance in which the maintenance manager in particular demonstrates safety awareness, safety leadership, improved communications skills and assertiveness: https://www.youtube.com/watch?v=prHWy2MNN8s Extra Maintenance Continuation Training Resources For further inspiration see our articles: Critical Maintenance Tasks: EASA Part-M & -145 Change Airworthiness Matters: Next Generation Maintenance Human Factors James Reason’s 12 Principles of Error Management Back to the Future: Error Management The Power of Safety Leadership: Paul O’Neill, Safety and Alcoa an example of the value of strong safety leadership and a clear safety vision. Aircraft Maintenance: Going for Gold? looking at some lessons from championship athletes we should consider. Plus this book review The Field Guide to Understanding Human Error by Dekker, presented to the RAeS in 2006: The Field Guide to Understanding Human Error – A Review There are also these free case studies, already used by other maintenance organisations for continuation training, you can discuss: Misassembled Anti-Torque Pedals Cause EC135 Accident EC130B4 Accident: Incorrect TRDS Bearing Installation and Misrigged Flying Controls: Fatal Maintenance Check Flight Accident which shows how the incident at Perfect Twins Maintenance could have turned out UPDATE 19 May 2018: Too Rushed to Check: Misrigged Flying Controls and another… UPDATE 25 August 2018: Crossed Cables: Colgan Air B1900D N240CJ Maintenance Error On 26 August 2003 a B1900D crashed on take off after errors during flying control maintenance. We look at the maintenance human factor safety lessons from this and another B1900 accident that year. UPDATE 19 April 2019: FAA Rules Applied: So Misrigged Flying Controls Undetected in an accident to a Cessna 172 in Bermuda. UPDATE 31 May 2019: The Portuguese accident investigation agency, GPIAAF, issued a safety investigation update on a serious in-flight loss of control incident involving Air Astana Embraer ERJ-190 P4-KCJ that occurred on 11 November 2018. The aircraft was landed safely after considerable difficulty, so much so the crew had debated ditching offshore. GPIAAF conformed that incorrect ailerons control cable system installation had occurred in both wings during a maintenance check conducted in Portugal. GPIAFF note that: “By introducing the modification iaw Service Bulletin 190-57-0038 during the maintenance activities, there was no longer the cable routing and separation around rib 21, making it harder to understand the maintenance instructions, with recognized opportunities for improvement in the maintenance actions interpretation”. They also comment that: “The message “FLT CTRL NO DISPATCH” was generated during the maintenance activities, which in turn originated additional troubleshooting activities by the maintenance service provider, supported by the aircraft manufacturer. These activities, which lasted for 11 days, did not identify the ailerons’ cables reversal, nor was this correlated to the “FLT CTRL NO DISPATCH” message.” GPIAFF comment “deviations to the internal procedures” occurred within the maintenance organisation that “led to the error not being detected...
read moreSwedish NH90 CFIT: Pilot Experience and Skating on Frozen Lake
Swedish NH90 CFIT: Pilot Experience and Skating on Frozen Lake The Swedish Accident Investigation Authority (SHK) has issued their report (in Swedish but with an English summary) on a serious incident at Lake Gilten, south of Namsos, Norway on 27 February 2016. A Swedish Air Force NH90 helicopter (designated HKP14D), serial number 1080 (052), came in contact with the ground when low flying, during the preparations for an international exercise in Norway. The helicopter was number two in a two-ship formation consisting of two NH90s. They had transported Swedish soldiers from Vaernes (Trondheim) to an exercise location and were headed back toward their temporary base at Namsskogan. The impact left a 20 m long, 50 cm deep track in the snow and ice on the frozen lake, without injury or serious damage to the helicopter. …visibility was estimated about 800-1,000 meters. The crews followed the sloping terrain down to the lake. At the same time they reduced the height and the speed was reduced. The lake was snowy which one caused few external references, which in turn made it difficult distance estimate in relation to the snow surface. Distance to others side of the lake was about 500 meters. The view was sufficiently sufficient for the crews to see the forest there. Approaching lake high rate of descent developed say the SHK, from an initial altitude of around 730ft. Radar altitude reduced from 185 feet to 0 feet in 18 seconds while airspeed fell from 48 to 17 knots. The crew were not monitoring radar altitude. The radalt was bugged to warn at just 30 ft and was also subject to a delay before activation. One audio warning came in the form of a two-tone signal two seconds before ground contact. Analysis The SHK comment that the crew “could not fly to the extent that they would have needed and also had planned to do before the exercise” their time on type was low and they had not “fully educated themselves on the current helicopter type”. The Commander had 347 hours on type but just 15 in the last 90 days. The co-pilot had just 93 hours on type, 17 in the last 90 days. The SHK opine that: Pilots are particularly at risk during their first 1000 flight hours, and in particularly during the first 500-600 flight hours. The same applies even experienced pilots who change airplane or helicopter. The first about 500 flight hours on a new type exhibit a markedly increased risk of accident frequency They base this view on the following references: FAA Study (Knecht 2012), ICAO-ADREP data base (1990), Killing Zone (Graig 2001), U.S. Naval Safety Center (Borowsky 1986), Aviat. Space Environ Med. (1992 Jan; 63 (1): 72-4, 2008 NALL Report (AOPA) and NTSB Safety Alert (SA-040, March 2015) This concept is also examined in The “killing zone” revisited: Serial nonlinearities predict general aviation accident rates from pilot total flight hours The low experience levels were identified by a prior risk assessment: The analysis apprehended a number of risks and contained several measures and limitations to mitigate the risks. However, the measures decided were not fully taken. Furthermore, according to SHK, the measures would only have been sufficient to reduce the risks to an acceptable level, if the crews [were suitably experienced on type]. Though, it is possible that the incident could have been avoided if the measures had been taken according to the plan. The fact that no one reacted upon this within...
read moreCoking Causes Power Loss: Australian AS350BA
Coking Causes Power Loss: Australian AS350BA On 2 November 2015, Airbus Helicopters AS350BA VH-SFX of GBR Helicopters was performing a low-altitude aerial weed spotting operation over dense forest in the Whyanbeel Valley, QLD. On board the pilot, a navigator and two aerial spotters. The Australian Transport Safety Bureau (ATSB) explain in their safety investigation report that: …during the fourth flight of the day, the helicopter momentarily yawed twice within a short period in an uncommanded and unusual way. The pilot, concerned with the uncommanded movements, ceased the operation, climbed and increased the helicopter’s forward airspeed. The pilot then elected to head back towards the base of operations (approximately 11km away) and, if required, land along the way if a suitably safe area along the flight path presented. Shortly after, the chip detector light illuminated…prompting the pilot to search for a suitable landing area. As the helicopter continued to climb through approximately 200 ft, the engine stopped producing power… which required the pilot to conduct an autorotation and emergency landing. …the emergency landing was handled in a competent and proficient manner. …the helicopter landed heavily with the skids digging into the uneven terrain and breaking off. The navigator in the front seat received minor injuries and the pilot received serious back injuries from the impact forces. The ATSB comment that: The pre-departure briefing gave the passengers the necessary knowledge to prepare for the emergency by adopting the brace position and exiting the helicopter only when it was safe to do so. The Engine Failure The helicopter was powered by a Turbomeca (now Safran Helicopter Engines) Arriel 1B. The ATSB say: …the aircraft lost power due to a front bearing failure in the turbine module. The failure was due to an accumulation of coke particles in an oil jet. Coking is an artefact from exposure to abnormally high temperatures that leads to oxidation and chemical breakdown of the oil. The observed coking of the front bearing and its oil jet duct was likely a result of the engine oil exposure to abnormally high temperatures in the area. While there were clogging inspection procedures of the power turbine rear bearings, no preventative maintenance actions existed that allowed for the identification of coking within the front bearing. There is… …published guidance for the thermal stabilisation of engines at shutdown. The guidance involved throttling the engine back until the engine was at ground idle for at least 30 seconds prior to shutdown. [This] allows for the temperature to reduce and thermally balance, while maintaining sufficient oil-scavenging capability and oil flow rates to minimise the potential for coke formation. Non-compliance with the manufacturer’s stabilisation recommendations may lead to coking. In the period January 2000 to September 2015, there were 13 cases of Arriel engine deterioration in the power turbine shaft front bearing due to oil jet clogging. However, this is the only accident that has resulted in the failure of the turbine shaft. The ATSB was unable to specifically determine why the coke particles had formed. The severity of the engine failure was increased through the fracture of the power turbine shaft and the subsequent separation of the turbine disc. This was due to a lack of adhesive on the splined nut that was threaded to the rear of the power turbine shaft. The engine manufacturer had intended...
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