C208B Force Landing After Inadequate Maintenance Fault Finding
C208B Force Landing After Inadequate Maintenance Fault Finding On 12 May 2016 Cessna 208B Caravan N1114A of the Parachute Center was substantially damaged during a forced landing near Acampo, California, 1 minute into a skydiving flight. The aircraft ended inverted in a vineyard, the pilot suffered minor injuries, but the 17 passengers were all uninjured. According to the US National Transportation Safety Board (NTSB) in their safety investigation report: The pilot reported that…as the airplane passed 1,000 ft above ground level (agl), the engine lost power. The rear door had been opened for ventilation and “one of the jumpers called out there was fuel streaming past the door“. The pilot initiated a turn toward the airport, however, realized he was unable to make it, and landed in an open field. During the landing roll, the airplane exited the field, crossed a road [at about 30 knots], impacted a truck [with two occupants], continued into a vineyard, and nosed over. The accident was filmed from inside by one passenger. Safety Investigation Examination of the wreckage revealed: The fuel pressure line that connects the fuel control unit to the airframe fuel pressure transducer, Pratt & Whitney Canada (PWC) part number 3033981, was fractured below the fuel control unit fitting swaged seat. The supporting clamp, PWC part number 3006614, was fractured and was separated from its mating fuel pressure fuel line, PWC part number 3032010. In addition, the airframe P3 air line that provides air to the vacuum system exhibited a hole within the tube. The operator reported that they had replaced the fuel line, PWC part number 3033981, the night before the accident due to the original fuel line being fractured. They stated that the new fuel line had about 4 hours of operational time since the installation. Review of the maintenance logbooks revealed that an entry regarding the replacement of the fuel line was dated April 11, 2016 [sic], with no airframe, engine, or HOBBS meter times listed. The operator…stated that the clamp was attached at the time of the fuel line replacement. Both the new and old fuel lines and separated clamp were sent to the NTSB Materials Laboratory for further examination. Lab analysis showed that both fractured tubes “were found to exhibit features consistent with crack initiation due to reverse bending fatigue”. The orientation of the reverse bending fatigue cracks and the spacing of the fatigue striations on the tube fracture surfaces were consistent with high-cycle bending fatigue due to a vibration of the tube. The cushioned support clamp is designed to prevent such vibrations from occurring. However, if the clamp tab is fractured, it cannot properly clamp the tube and will be unable to prevent the vibration. The NTSB concluded that “the clamp most likely failed first, resulting in the subsequent failure of the tubes”: Since the clamp was likely fractured when the first fractured fuel pressure line was replaced, the clamp was either not inspected or inadequately inspected at the time of the maintenance. Other Safety Information It is reported that since 1999, 15 people have died jumping “from planes that took off from the parachute center”. The Parachute Centre was involved in a fatal parachute accident later in 2016. In September 2016, following that accident, 20 instructors at the centre were suspended and 120 others were told they needed to undergo more training after an investigation...
read moreThe “Hold My Beer” Helicopter Accident
The “Hold My Beer” Helicopter Accident “Hold My Beer” is label applied on-line to video footage of many dangerous and/or ill-advised stunts, where the impending embarrassing and often painful failure is usually glaringly obvious before the end of the video. The US National Transportation Safety Board (NTSB) has reported on a helicopter accident that had a fatal alcohol fuelled ending. The Accident Flight On 12 June 2016 Robinson Helicopter Company (RHC) R44 II Raven N789MR impacted the ground during takeoff from the Classic Airstrip, near Jonesboro, Arkansas on a personal flight. The sole occupant, a 73 year old commercial licensed pilot, was fatally injured. The helicopter was destroyed by the impact and post-crash fire. A witness…reported that before noon, he saw the accident pilot drinking from a red cup that smelled like alcohol. The pilot refilled the cup 2 or 3 times during the next 2 or 3 hours. When the witness finished working on a task, he heard the pilot say that he was going to put on an airshow. The witness did say that ” I thought he was kidding “. However subsequently from a distance: The witness observed the helicopter lift off at a 45° angle backward and upward. The helicopter rose to about 125 ft and then descended out of sight behind hangars… The witness reported that he thought he “heard it hit”… The helicopter began to rise upwards above the hangars and it began to spin around. It appeared that the tail rotor was not working and the skids were bent as if it had hit the ground. The helicopter continued to rise to about the same height as when it lifted off. The helicopter then descended again, impacted terrain, and burst into flames in the middle of the west airstrip. The witness stated that another witness nearby called 911 and they waited for first responders to arrive. Medical And Pathological Information The autopsy indicated that the pilot’s cause of death was multiple blunt force injuries. A toxicology report indicated that the samples sustained putrefaction and listed the following findings: 418 (mg/dL, mg/hg) Ethanol detected in Blood 336 (mg/dL, mg/hg) Ethanol detected in Heart 309 (mg/dL, mg/hg) Ethanol detected in Lung 182 (mg/dL, mg/hg) Ethanol detected in Kidney 152 (mg/dL, mg/hg) Ethanol detected in Urine It should be no surprise to readers that: Ethanol is the intoxicant commonly found in beer, wine, and liquor. It acts as a central nervous system (CNS) depressant. After ingestion, at low doses, it impairs judgment, psychomotor functioning, and vigilance… The effects of ethanol on aviators are generally well understood; it significantly impairs pilots’ performance, even at very low levels. The NTSB note that: Federal Aviation Regulations prohibit any person from acting or attempting to act as a crewmember of a civil aircraft while having 0.040 gm/dl (40 mg/dl) or more ethanol in the blood. While ethanol can be produced in the body after death by microbial activity, the results indicate the pilot is likely to have been well over the regulatory limit. Diphenhydramine, a sedating antihistamine used to treat allergy symptoms and as a sleep aid, was also detected plus two other drugs that are considered ‘non-imparing’. NTSB Probable Cause The pilot’s failure to maintain helicopter control during takeoff. Contributing to the accident was the pilot’s impairment due to his combined use of alcohol and diphenhydramine,...
read moreInvestigators Criticise Cargo Carrier’s Culture & FAA Regulation After Fatal Somatogravic LOC-I
Investigators Criticise Cargo Carrier’s Culture & FAA Regulation After Fatal Somatogravic Loss of Control – Inflight (LOC-I) On 29 October 2014, Shorts 360 N380MQ, operated by SkyWay Enterprises as a Part 135 flight on contract to FedEx, crashed into the sea, shortly after a night time take-off from Sint Maarten in the Caribbean. The aircraft, which was was on a regular cargo flight to San Juan, Puerto Rico, was found on the sea bed 0.8 miles from the Princess Juliana International Airport, Sint Maarten (SXM). The two pilots, the only occupants, were both killed. The Sint Maarten Civil Aviation Authority (SMCAA) conducted an investigation into the accident. They raised safety issues that include: loss of situational awareness pilot monitoring duties loss of control / upset recovery crew resource management company safety culture FAA oversight and regulation of Part 135 operations and maintenance The Accident Flight The crew had reported for duty at 0845 in San Juan for the inbound flight to Sint Marteen, arriving at about 1130. The crew then had the day free, arriving back at the airport at about 1700. The SMCAA say that : The Captain observed the cargo loading and provided a cargo manifest to the ramp agent. A repetitive company flight plan was on file. The flight was approved for engine start by the Juliana Tower at 1817L. Area sunset was at 1742L and end of civil twilight at 1804L; night conditions and rain prevailed at the time… The flight commenced taxi to runway 28 at 1828L [and] was cleared for take-off at 1838L. At 1840L Tower personnel observed a normal take-off and initial climb. Then Tower personnel reported, [that upon] passing the departure end of the runway, the aircraft began descending both visually and on radar. There was no response to calls from the Tower…and the ATC data block for the flight no longer appeared on the airport radar screen. The first Coast Guard vessel was dispatched at 1900L. The sea and air search in the immediate hours of the crash confirmed aircraft debris in the area but there was no evidence of any flotation devices or survival equipment on the sea surface. The submerged wreckage was later located by divers. The operator had obtained the aircraft from American Eagle in 2000 and converted the aircraft to a cargo only configuration. In 2001 the GPWS, Rad Alt, CVR, FDR, attitude gyro, and TCAS were all removed. Part 135 only required these for passenger operations. However: A handheld GPS device was later recovered from submerged wreckage. …recorded data indicated the aircraft past the departure runway threshold on take-off and attained a maximum GPS altitude of 433 feet at 119 knots groundspeed at 18:39:30L. The two remaining GPS data points were over the sea and recorded decreasing altitude and increasing airspeed. A modification had been approved in 2005 that added an external antenna for this carry on GPS device. The Operator, its Safety Management and Safety Culture SkyWay Enterprises (SWE) was originally issued an FAA Air Carrier Certificate in 1979. They primarily operated cargo services within the Caribbean. When queried during the investigation both the DO [Director of Operations, who was also the company President] and the CP [Chief Pilot] stated that they had not been informed of any specific safety concerns nor had they seen the need to conduct safety meetings or distribute further information dedicated...
read moreHoist Assembly Errors: SAR Personnel Dropped Into Sea
Hoist Assembly Errors: SAR Personnel Dropped Into Sea (NASC UH-60M NA-703) On 30 June 2017 Sikorsky UH-60M Black Hawk helicopter NA-703 of the Taiwanese Ministry of the Interior National Airborne Service Corps (NASC) was conducted a Search and Rescue (SAR) training mission off Taichung Harbour, Taiwan. During the third hosting operation the hook assembly separated from the hoist cable, causing two rescuers to fall into the sea. The two were recovered by a surface craft. One sustained minor injuries but the other was seriously injured. The Aviation Safety Council (ASC) of Taiwan has released its final report on their investigation in Chinese only. The helicopter was fitted with a Breeze-Eastern BL29900-30-1 hoist. On 28 June 2017, ‘bird caging‘ had been detected on the hoist cable (a phenomenon where several outer strands become loose). The cable was replaced by NASC maintenance personnel. The ASC determined that the hoist hook had been inappropriately assembled doing that maintenance. ASC Findings Related to Cause During hoist cable replacement maintenance, an unknown external force may led the bearing [to be] moved and stuck in the bearing housing when the hook assembly was disassembled When assembling the hook assembly, the mechanic could not properly bottom the bushing nut to the bearing housing due to the bearing stuck in the bearing housing. A 1.5 mm gap was created between the lower flange bottom surface of the bushing nut and top surface of the bearing housing. The above gap caused the locking screws [to] not properly engage into the castled slots on the bearing housing. The inspector did not properly check whether the two locking screws were engaged into the castled slots on the bearing housing prior to the completion of the hoist cable replacement. Due to the two locking screws were not properly engaged into the castled slots on the bearing housing, therefore the bearing housing did not lock with the bushing nut. Without lock mechanism, the bearing housing was loosening from the screw threads of bushing nut and separated from the hoist assembly when hook assembly swivelled during hoist retrieving process. ASC Findings Related to Risk The mechanics and the inspectors neither understood and followed the procedures correctly during assembling nor visually inspected the locking screws were properly engaged into the castled slots on the bearing housing. They misunderstood that the locking screws were properly seated in the castled slots once the cotter pin holes could be seen. The NASC did not assign a proper quality inspector to perform the hoist maintenance for the occurrence helicopter. The inspector who performed the inspection of the hoist maintenance did not complete the type hoist maintenance training, had limited understanding of the hoist manufacture maintenance manual, and failed to conduct the vital point inspection correctly. Most maintenance manuals adopted by the NASC are in English. The NASC did not establish the English ability requirement and evaluation system of their mechanic[s]. The NASC did not have proper process to integrate/control both technical information from hoist manufacturer and technical manual from aircraft manufacturer regarding the hoist maintenance. The different understanding of how to use the manual existed in NASC different department that disadvantaged the NASC mechanic to use the manual correctly and conduct the training properly. The NASC did not record inspection results of vital point onto rescue hoist maintenance log as required by the hoist manufacturer maintenance manual. There are neither...
read moreMan Hit By Aircraft During Arctic Nuclear Sub Exercise
Man Hit By Aircraft During Arctic Nuclear Sub Exercise (UPDATED 19 Dec 2019) Often headlines disappoint. Well this story is exactly what the headline says. On 20 March 2018, de Havilland Canada (now Viking Air) DHC-6 Twin Otter N716JP struck an individual during take-off from a remote sea ice airstrip (‘Ice Camp Skate’), about 140 miles north of Deadhorse, Alaska (the flight’s destination). The US National Transportation Safety Board (NTSB) report that the casualty suffered serious head and neck injuries and the aircraft received substantial damage to the left wing and left aileron. The Part 135 VFR flight was operated by Bald Mountain Air Service as part of a contract for logistical support of ICEX 2018, a 5 week exercise with three US Navy and Royal Navy nuclear submarines (USS Connecticut, USS Hartford and HMS Trenchant) operating beneath the frozen Arctic Ocean. The Accident Flight The aircraft commander reported clear skies with ice pack haze. The airstrip was lined with snow berms on both sides. The take-off was to the North at 19:45 LT and he noted that: …the sun was low on the horizon, resulting in shadows on the airstrip, and that flat light conditions made it difficult to discern topographical features. The injured person, an employee of the Arctic Submarine Laboratory, who operated the site, made a statement that he had informed the aircraft commander that he would position himself alongside the runway to photograph the departure, behind the 3-4 ft tall snow berm. The aircraft commander reported that… …just before the takeoff roll, he and the first officer saw a pedestrian standing near the left side of the departure end of the airstrip. The aircraft commander stated that… As the takeoff roll continued, the airplane became airborne, so the captain lowered the nose to remain within ground effect and gain airspeed before initiating a climb. The captain added that, as the airspeed increased, he started to climb the airplane and then initiated a left turn. Both pilots reported that, during the turn, they heard a loud thump, which was immediately followed by an aileron control anomaly. The captain initiated a left turn back toward the airstrip and subsequently made an emergency landing. After landing, both pilots saw the pedestrian lying near a snow berm on the left side of the airstrip. The captain reported that he did not remember if it had been prearranged to have the pedestrian stand near the departure end of the airstrip during the departure. The pedestrian reported that…as the airplane’s takeoff progressed, it did not climb as quickly as it had during previous departures and that the last thing he remembered before the collision was seeing the left wing getting lower to the ground as the airplane began a left turn and flew toward him while continuing to accelerate. A security video camera recorded the accident sequence, and the recording supported the pedestrian’s account of the sequence of events. Although the captain reported that he climbed the airplane before initiating a left turn, the review of the video revealed that the flight crew operated the airplane at a low altitude and along a flightpath that placed it in dangerous proximity to the pedestrian (which was inconsistent with federal regulations) and left no margin to avoid the collision with him. The next thing the injured person remembered was waking up in the medevac helicopter. The aircraft was equipped with a...
read moreKing Air 200 Smoke and Fumes From Windshield Electrical Fault
King Air 200 Smoke and Fumes From Windshield Electrical Fault Privately owned Beechcraft King Air B200 JA01EP was climbing from FL150 to FL200 en route from Gifu to Takamatsu in Japan on 6 April 2017 when smoke and a burning smell appeared in the cockpit. The whole right windshield inner pane cracked “like a spider’s web”. The crew declared an emergency and diverted back to Gifu, making a safe landing. The Japan Transport Safety Board (JTSB) say in their safety investigation report that burn marks were subsequently found at and around the terminal block of the right windshield. The JTSB say: [The] right windshield terminal lug was loose and there was gap of 0.05mm between the screws and the terminal lugs. …it is probable that the smoke was generated by overheating the terminal block and the surrounding parts and components were burned out, because the electrical resistance at the contact points of the terminal block junction was increased, due to the loosened screws of the terminal block. Due to a previous partial delamination, the windshields had been replaced by a 3rd party maintenance organisation in January 2012. The JSTB note that: The description concerning the replacement of windshield in the maintenance manual do not include any reference to tightening torque for screws of terminal block, therefore, the screws were tightened using standard torque value (20 to 25 in-lbs). While inspections of the windshield are required every 200 flight hours for cracks and sealant deterioration, there is no requirement to check the power connection. As no subsequent problems were reported, no further maintenance had been conducted in this area in the subsequent 5 years The JTSB concluded that loosening of the screws likely occurred due to the vibration “because the tightening torque of the screws was not sufficient when replacing the windshield”. Safety Resources UPDATE 1 October 2020: JTSB have issued their report into a serious incident that occurred on 30 October 2019 to Bombardier CL-600-2C10 (CRJ100) JA11RJ of IBEX Airlines which suffered arcing and a cracked windshield. Professor James Reason’s 12 Principles of Error Management Back to the Future: Error Management Safety Performance Listening and Learning – AEROSPACE March 2017 Maintenance Human Factors: The Next Generation Airworthiness Matters: Next Generation Maintenance Human Factors 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 is pleased to sponsor the 9th European Society of Air Safety Investigators (ESASI) Regional Seminar in Riga, Latvia 23 and 24 May 2018 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 moreIndian King Air Take Off Accident: Organisational & Training Weaknesses
Indian King Air Take Off Accident: Organisational & Training Weaknesses Beechcraft King Air 200 VT-BSA of the Indian Border Security Force (BSF) Air Wing crashed on 22 December 2015 after a Loss of Control – Inflight (LOC-I) shortly after take off on a flight from New Delhi to Ranchi. There were ten persons on board, all of whom were fatally injured. The Accident Flight In their report the DGCA India say: Shortly after take-off and attaining a height of approximately 400 feet AGL, the aircraft progressively turned left with simultaneous loss of height. It had taken a turn of approximately 180º and impacted some trees before hitting the outside perimeter road of the airport in a left bank attitude. Thereafter, it impacted ‘head on’ with the outside boundary wall of the airport. After breaking the outside boundary wall, the wings impacted two trees and the aircraft hit the holding tank of the water treatment plant. The tail portion and part of the fuselage overturned and went into the water tank. There was post impact fire and the portion of the aircraft outside the water tank was destroyed by fire. The weather at the time of accident at Delhi was foggy with visibility reported as 800 meters and winds of 3 knots. The previous METAR which was available with the flight crew mentioned visibility of 600 meters. The visibility was marginal and it is inferred that the marginal visibility was a contributory factor to the accident. The safety investigators explain that: As per the Pilot Operating Handbook procedure…the autopilot should be engaged only after attaining the height of 500 feet AGL… …however conversation recorded on the CVR indicates that… …the Autopilot was engaged just after the aircraft had lifted off (even the landing gear had not been retracted). This hurried and non-standard action by the flight crew…reveals their eagerness to let the aircraft be flown by the autopilot… Engagement of the autopilot without engaging the Heading Mode resulted in the aircraft turning left probably due to the existing left bank or inadvertent manual input by the flight crew at the time of engagement of the autopilot. The bank angle increased progressively and beyond 45º , a situation the flight crew could not decipher because of their disorientation. Organisational Factors and Culture The safety investigators make the point that: An Organisation may look compliant vis-a-vis the mandatory requirements but may still be seriously deficient in discharging its duties safely and efficiently. We would add, that they may even be compliant but effectiveness may be weak. The investigators elaborate: Therefore deeper analysis of the Organizational Structure & Procedures (if existing), and those practised is required to find out the answer to the circumstances leading to the accident. The safety investigators then note that: Civil Aviation Requirement Section 3 – Air Transport Series C Part X Issue I, gives the minimum procedural requirements for the issue of permission to undertake aircraft operations by State Governments or Public Sector Undertakings of the Central/ State Governments. Unlike in some other nations, this requires a Safety Management System (SMS) for such operations. However they determined that the Safety Department and SMS “was practically non-existent” (similar to a prior 2015 Indian offshore helicopter accident): From the discussions with the Officers who were designated as the Chief of Flight Safety in the present and past, it was noted that as and when any...
read moreSignificant Twin Otter NLG Crack
Significant DHC-6 Twin Otter NLG Crack A significant crack was found in the Nose Landing Gear (NLG) of a Viking DHC-6 Twin Otter according to a Service Difficult Report (SDR) submitted to the Civil Aviation Safety Authority (CASA) in Australia. The SDR states: During maintenance inspections, a crack was detected at the upper end of the nose landing gear outer cylinder. It was found that other operators had also experienced similar failures and…previous investigations had found that the crack originated from a corrosion pit found under the upper bearing installed on the outer cylinder. This is because the upper bearing migrates up and allows the moisture to penetrate. As a result a pit forms and thus results in the propagation point for a crack. Safety Resources Eclipse 500 Landing Gear Production Defect “Shoulda gone around”: B727 Landing with NLG Retracted Poor Painting Prevents Proper Performance: Shorts Sherpa NLG Collapse B1900D Emergency Landing: Maintenance Standards & Practices A Lufthansa MD-11F Nose Wheel Detached after Maintenance Error ATR72 VH-FVR Missed Damage: Maintenance Lessons B747 Landing Gear Failure Due to Omission of Rig Pin During Maintenance When Down Is Up: 747 Actuator Installation Incident Lost in Translation: Misrigged Main Landing Gear Maintenance Human Factors in Finnish F406 Landing Gear Collapse S-92A Nose Landing Gear Incidents UPDATE 28 April 2020: Beech 99A MLG Collapse 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 moreUSAF F-16C Crash: Engine Maintenance Error
USAF F-16C Crash: Engine Maintenance Error Improper assembly of the Main Engine Control unit caused a USAF Lockheed Martin F-16C Block 30H 87-0306 to be destroyed in a crash SW of Joint Base Andrews, Maryland, on 5 April 2017, according to the USAF Accident Investigation Board. The pilot ejected safely 10s before impact. The F-16C was from the Air National Guard 113th Wing, 121st Fighter Squadron at Joint Base Andrews and was one of four departing on a basic surface attack training mission. During take off the aircraft experienced an uncommanded GE F110-GE-100C engine acceleration, followed by a loss of thrust and engine fire and so the pilot jettisoned the external fuel tanks (one landed between two houses and the other landed in a wood, fortuitously neither hitting anything) and then shut the engine down. A severe engine overspeed and engine over-temperature had occurred, followed by the engine fire and, ultimately, a catastrophic engine failure. The AIB found… …the cause of this mishap was the incorrect assembly of the main engine control (MEC) differential pressure pilot valve, which was missing a required 600-degree retaining ring and the anti-rotation pin. The misassembled differential pressure pilot valve caused the MEC to malfunction and to incorrectly meter abnormally high fuel flow to the engine. A substantially contributing factor to the mishap was the 552d Commodities Maintenance Squadron, MEC Overhaul Shop, Oklahoma City, Air Logistics Complex, lack of an adequate procedural requirement for MEC parts accountability. The loss to the US Government was valued at $22 million. Maintenance History and MEC Investigation The MEC is designed to regulate fuel flow and the variable stator vane position of the engine. The MEC senses the engine core speed and adjusts fuel flow as necessary to maintain the desired engine speed in accordance with pilot input via the throttle. The MEC overhaul process consists of complete disassembly, solvent wash, and inspection. After inspection and any ncessary component replacement, the MEC is reassembled and tested. After overhaul, the MEC of 87-0306 underwent test on 31 January 2017 but failed to meet acceptance criteria. It was re-inspected and found to have a fuel cam spline misaligned. That error was corrected and it was retested on 16 February 2017. It again failed test, being rejected with comments “check FDT [fan discharge temperature] spring and VSV [variable stator vane]; VSV not repeating”. The MEC was again returned to the overhaul shop. The FDT spring was found serviceable, the governor servo valve was changed due to a broken tang, and O-ring foreign object debris (FOD) was found in the VSV. The MEC passed a third test on 8 March 2017. The MEC was fitted to the engine of 87-0306 the day before the accident on 4 April 2017 in unscheduled maintenance. When stripped at Woodward Governor after the accident the MEC was found to contain FOD (a piece of backing ring) that potential prevented sealing of the unit, an incorrect Vitron seal (rather than the specified fluorosilicone seal) and the absence of both the 600-degree retaining ring and anti-rotation pin. The investigation found that the personnel involved were appropriately trained and there were no “major” documentation errors. However, USAF Technical Order (TO) 6J3-4-131-3 requires “parts accountability and emphasizes the critical importance of such procedures” but “does not specify a methodology for parts accountability”. The investigators found: During on-site observation of the MEC overhaul shop, it was observed that gaps exist in...
read moreEC120 Forgotten Walkaround
EC120 Forgotten Walkaround Maintenance, which included a compressor wash and an ‘A’ check, had been conducted on privately owned Airbus Helicopters EC120B G-SWNG. After the maintenance, according to the UK Air Accidents Investigation Branch (AAIB) report “the pilot left the helicopter for a short period of time” on 17 August 2017. The pilot stated that when he returned to the helicopter, contrary to his normal practice, he forgot to complete a walkaround inspection of the helicopter before commencing the flight. On approach to Wellesbourne, Warwickshire, an unusual noise was heard, and the pilot landed immediately. Examination of the helicopter showed that the lower forward edge of the right engine cowling was damaged, the forward cowl latch assembly was missing and the centre latch had been damaged. Damage was also observed on the inboard sections of all the main rotor blades. The main rotor blade damage was caused by contact with the right engine cowling. The AAIB explain that the engine cowls hinge upwards and are held closed by 3 latches: Closing the main lever of each latch places the latch hook under tension, securing the cowling to the structure and locks the main lever in the closed position. The secondary lever will not close if the main lever is not in the locked position, providing a positive indication of an unlocked latch. When the secondary lever is closed a spring can then be moved over the tip of the secondary lever to prevent it from opening. Inspection of the remaining two cowling latches confirmed that there was no evidence of unusual wear or damage to the latch hooks or the parts of helicopter structure where the hooks engage. There was no evidence of distortion or adverse wear to any of the springs used to retain the secondary latch levers. The manufacturer issued Safety Information Notice No 2339-S-53 in June 2016 after previous in-flight cowl opening events: This highlighted the need to inspect the condition and function of the cowl latches during the Daily Inspection. In addition, the notice also advised that, for helicopters with a predominantly red colour scheme, the inside faces of the lock levers should be painted in a contrasting colour to the helicopter’s colour scheme, to provide an increased visual cue of an unlocked cowl latch. The inner faces of G-SWNG’s engine cowling lock levers had been painted in this manner. AAIB Conclusions In view of the maintenance activity immediately before the flight it is reasonable to conclude that the right engine cowling latches had not been correctly locked when the ‘A’ check was completed. Given that the inner faces of the latches had been painted in a contrasting colour to the helicopters paint scheme it is probable that this condition would have been observed by the pilot during a pre-flight walkaround inspection. The fact that the pilot left the helicopter for a short period of time before takeoff, coupled with the recent completion of routine maintenance, probably introduced sufficient interruption and distraction to the pilot’s normal pre-flight routine to cause him to forget to carry out a pre-flight walkaround inspection. Other Safety Resources In a recent article Flawed Post-Flight and Pre-Flight Inspections Miss Propeller Damage we noted that the Australian Transport Safety Bureau (ATSB) highlighted Flight Safety Foundation (FSF) guidance that after interruptions/distractions have been recognised and identified, the next priority is to re-establish situation awareness as follows: Identify:...
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