Italian Alps AW139 Mountain Rescue Hoisting Blade Strike
Italian Alps AW139 Mountain Rescue Hoisting Blade Strike (Vigili del Fuoco I-TNDD) On 7 October 2017 Leonardo AW139 I-TNDD of the Vigili del Fuoco fire and rescue service was conducting a hoist rescue mission at Monte Casale, near Trentino in Northern Italy, when it suffered a main rotor blade strike on a cliff face. The aircraft landed safely and an attempt was made to assess the damage while rotors running. The aircraft then made a further flight to Trento Mattarello Airport. The Accident Flight The Italian National Agency for Flight Safety (ANSV) explain in their safety investigation report (issued only 0n Italian on 8 September 2021) that the aircraft had been tasked at 08:14 after the fall of a young climber. The boy was near the base of a cliff at 2100 ft AMSL. The weather was good and the wind was negligible. On board the hoist-equipped helicopter were three crew (pilot, hoist operator and winchman) and two medical personnel. The single pilot had 5992 hours of experience, 715 on type and 3200 hours of HEMS / rescue flying. If a HEMS mission the hoist operator would have been sat next to the pilot as the HEMS Technical Crew Member (TCM) on the outbound flight. The unit at Trentino had two AW139s and an Airbus AS365N3. In 2016 it had carried out 2488 taskings and flew 1059 hours. The casualty was rapidly located and initially the winchman was lowered to assess the casualty. Then while hoisting down the two medical personnel from c 25-20 m AGL at 08:27 there was “a slight variation in the noise of the rotor itself is heard and consequently a slight oscillation of rotor revolutions and torque occurs”. The ANSV comment that only the pilot appeared to notice this. A few seconds later the pilot told the hoist operator that a blade strike had occurred and they had seen “a cloud of dust on the [cliff] wall, in the upper left”. The aircraft diverted to Pietramurata, about two minutes away. During that flight no abnormal vibration was felt. After landing, the rotor remained running as the hoist operator exited the aircraft to examine the rotor tips. Damage was evident but after discussion the decision was made to return to home base at Trento Mattarello Airport, influence by the lack of vibration. During that 6 minute 20 second flight, there was further discussion on the incident. The pilot believed they must have struck a well camouflaged outcrop having been convinced they had c 1.5 m of clearance. On shut down it was found that the helicopter suffered loss of 70 – 80 mm of each of the five main rotor blades and damage to the leading edge protection strips. Safety Investigation / Analysis The ANSV comment on the pilot workload when operating single pilot and note that… ….listening to the CVR shows the complexity of the rescue intervention… They comment that: It is reasonable to believe that the greyish-yellow background of the rock face…the helicopter was positioned orthogonally [from] did not help the pilot in determining the distance of the main rotor blades from the wall itself, taking into account that the blades, in the last part, are painted yellow to define the outer limit, however, blending in with the background of the aforementioned wall. The ANSV note that the helicopter was not equipped (nor was it required to be equipped)...
read moreRLC B407 Reverses into Sister Ship at GOM Heliport
RLC B407 Reverses into Sister Ship at GOM Heliport (Bell 407s N662RL and N668RL at Paterson, LA) On 25 September 2021 Rotorcraft Leasing Company (RLC) Bell 407 N662RL was lifting off for departure from a heliport in Patterson, Louisiana when it drifted backwards into Bell 407 N668RL. Documents filed with the US National Transportation Safety Board (NTSB) state that N662RL was departing from pad D3 at the RLC Patterson heliport with one pilot and three passengers aboard. They were destined for a Gulf of Mexico offshore installation in Mississippi Canyon Block 194 (MC194) and then Ewing Bank Block 873 (EW873). The pilot had 1479 hours of flight experience, 255 on type. The tail rotor of N662RL contact the main rotor of N668RL that was rotor running with passengers aboard on pad D5. N662RL landed hard in a ditch. The three occupants of N662RL were uninjured and there are no reports of other injuries. Minimal information is in the NTSB Preliminary Report at time of writing. The RLC Patterson heliport is to the south of Harry P. Williams Memorial Airport, Patterson, an airport that features a runway and a seaway for floatplanes. The heliport has a typical non-ICAO Annex 14 compliant GOM heliport configuration and this accident highlights the challenges that some of the more fanciful Advanced Air Mobility vertiports will face. UPDATE 16 November 2021: The NTSB issued the following unhelpful statement as their probable cause: The pilot’s failure to maintain adequate clearance from a parked helicopter while hovering to reposition for takeoff. We consider this unhelpful as it is simply a self-evident statement of the circumstances, not an explanation of why the accident happened. Safety Resources The European Safety Promotion Network Rotorcraft (ESPN-R) has a helicopter safety discussion group on LinkedIn. You may also find these Aerossurance articles of interest: South Korean Fire-Fighting Helicopter Tail Rotor Strike on Fuel Bowser Ditching after Blade Strike During HESLO from a Ship US BSEE Helideck A-NPR / Bell 430 Tail Strike GOM Helicopter Ops 2000-2019: Single Engine Usage Plummets But Fatal Accident Rate Resistant Air Ambulance B407 Hospital Helipad Deck Edge Tail Strike During Shallow Approach Cessna 208B Collides with C172 after Distraction S-76C+ MLG Collapsed Due to Pothole Troublesome Tiedowns Troublesome Tiedowns: The Sequel UK AAIB Report on Two Ground Collisions Ground Collision Under Pressure: Challenger vs ATV: 1-0 Gazelle Caught Out Jumping a Fence S-92A Collision with Obstacle while Taxying Helicopter Destroyed in Hover Taxi Accident Pilatus PC-12 Collided with Pick-Up Truck During Dusk Take Off Air Ambulance Helicopter Downed by Fencing FOD Ambulance / Air Ambulance Collision Inappropriate Autorotation Training: Police AS350 Stabilised Hover Prevents Loss of Control Accidents Say FAA Hazardous Hangar Hovertaxy A Lethal Cocktail: Low Time, Hypoxia, Amphetamine and IMC Don’t Be a Sucker!: Cabri Canopy Implosion Mind the Handrail! – Walk-to-Work Helideck Hazard Impromptu Landing – Unseen Cable Alpine MAC ANSV Report: Ascending AS350B3 and Descending Jodel D.140E Collided Over Glacier Mid-Air Collision of Guimbal Cabri G2 9M-HCA & 9M-HCB: Malaysian AAIB Preliminary Report AAIB Highlight Electronic Conspicuity and the Limitations of See and Avoid after Mid Air Collision North Sea S-92A Helicopter Airprox Feb 2017 USMC CH-53E Readiness Crisis and Mid Air Collision Catastrophe Avoiding Mid Air Collisions: 5 Seconds to Impact Fatal Biplane/Helicopter Mid Air Collision in Spain, 30 December 2017 A319 / Cougar Airprox at MRS: ATC Busy, Failed Transponder and Helicopter Filtered From Radar Merlin Night Airprox:...
read moreDon’t Be a Sucker!: Cabri Canopy Implosion
Don’t Be a Sucker!: Cabri Canopy Implosion (Swiss Helicopter Guimbal G2 HB-ZDQ) On 1 July 2020 Swiss Helicopter Guimbal Cabri G2 HB-ZDQ was conducting a training flight near Vaulruz in Switzerland when the helicopter’s canopy shattered. The Swiss Transportation Safety Investigation Board (STSB) explain in the safety investigation report (in French) that both student and instructor suffered minor injuries to their face, hands and legs. The Flight The serious incident occurred during an exercise to demonstrate handling at close to Vne (Velocity, Never Exceed) at c119 kt at a pressure altitude of 5500 ft. While passing the indicated speed of 110 kt, the plexiglass canopy suddenly burst. Due to the high relative wind, a lot of debris ended up in the cockpit, the headsets and glasses of the two crew members were torn off. The instructor decreases the speed, puts on his second pair of prescription glasses which is in his trouser pocket and decided to land as quickly as possible. The implosion was significant enough to trigger the Emergency Locator Transmitter (ELT). The helicopter landed safely on a football field about 5 minutes later. The Safety Investigation The one-piece plexiglass Capri canopy is 2 mm thick and glued to the fuselage around its perimeter. The investigators note that the “canopy has been designed to withstand aerodynamic stresses” and that these are highest at high speed. At the site of the serious incident, it was observed that a suction cup attachment was installed on the canopy. Such an installation makes it possible to fix an on-board camera, for example, but it was not provided for by the manufacturer and can generate additional stresses on the one-piece canopy and consequently weaken it. Safety Action Guimbal issued Service Letter, SL 20-001 A which advises owners not to attach items to the canopy with a suction cup mount. The investigators note that Airbus Helicopters has also recently issued safety promotion notice 3587-P-00, encouraging the wearing of a helmet. Safety Resources The European Safety Promotion Network Rotorcraft (ESPN-R) has a helicopter safety discussion group on LinkedIn. You may also find these Aerossurance articles of interest: AS350B3/H125 Bird Strike with Red Kite Safety Lessons from a Fatal Helicopter Bird Strike USAF HH-60G Downed by Geese in Norfolk, 7 January 2014 Deadly Dusk Air Ambulance Bird Strike Swedish Military NOE Helicopter Bird Strike Power of Prediction: Foresight and Flocking Birds looks at how a double engine loss due to striking Canada Geese had been predicted 8 years before the US Airways Flight 1549 ditching in the Hudson (which was just days after a Louisiana helicopter accident). Hanging on the Telephone… HEMS Wirestrike A Short Flight to Disaster: A109 Mountain CFIT in Marginal Weather Gazelle Caught Out Jumping a Fence Fatal B206L3 Cell Phone Discount Distracted CFIT Austrian Police EC135P2+ Impacted Glassy Lake A Lethal Cocktail: Low Time, Hypoxia, Amphetamine and IMC Mid-Air Collision of Guimbal Cabri G2 9M-HCA & 9M-HCB: Malaysian AAIB Preliminary Report AAIB Highlight Electronic Conspicuity and the Limitations of See and Avoid after Mid Air Collision RLC B407 Reverses into Sister Ship at GOM Heliport 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 moreA Lethal Cocktail: Low Time, Hypoxia, Amphetamine and IMC
A Lethal Cocktail: Low Time, Hypoxia, Amphetamine and IMC (R44 N744TW Utah) On 17 May 2019, private Robinson R44 N744TW was destroyed in an accident near Alpine, Utah. The pilot and passenger both received fatal injuries. The Accident The US National Transportation Safety Board (NTSB) safety investigation report, published on 15 October 2021, explains that the 32-year-old pilot had just 145 hours total flight time, 32 on type. He had “started an oil fracking company” and had rented the R44 from Utah Helicopters, where he had been trained (mostly on R22s). He had departed Myton, Utah, at 09:30 with his wife, intending to fly to South Valley Regional Airport (U42), West Jordan, Utah, to pick up a second passenger before proceeding to Phoenix, Arizona. A witness stated “it was raining lightly at that time.” There was no record of the pilot receiving any preflight weather information from an access-controlled source. During the flight the pilots mother received several texts from the pilots wife and at 10:27 a video… …showing the helicopter above a thick cloud layer with no discernible horizon. Some of the cloud tops appeared above the helicopter. The NTSB explain that: Radar data provided by the Federal Aviation Administration (FAA) revealed a target correlated to the accident helicopter first appear on radar at 0956 at an altitude of 10,400 ft mean sea level (msl), on a heading of 309° about 44 miles west of [Myton]. The helicopter continued generally on a west-northwest course… The airspeed initially varied from 37 to 88 knots ground speed but stabilized to about 85 knots for most of the flight. The helicopter climbed to 13,000 ft msl at 1007 and remained between 12,700 and 13,000 ft ft msl until about 1030, when it descended below 12,500 ft msl. The helicopter was not equipped with a supplemental oxygen system, nor were any supplemental oxygen provisions found at the accident site. At 1031, the helicopter began a right descending right turn that continued until radar contact was lost at 1033 at an altitude of 9,200 ft msl and groundspeed of 108 knots, about 1,650 ft from the accident site. The data revealed that the helicopter completed about 2.5 360° turns before radar contact was lost. NTSB Investigation & Analysis The wreckage was highly fragmented, consistent with a high-speed impact. Examination of the airframe and engine revealed no evidence of any preaccident mechanical failures or malfunctions. Weather radar imagery above the accident location between about 8,600 ft and 14,200 ft msl identified reflectivity consistent with light rain in an area that included the accident site. The helicopter was likely operating in visual meteorological conditions above the clouds until its initial descent from about 13,000 ft, at which point the helicopter likely entered and remained in instrument meteorological conditions for the rest of the flight. Although the altitude and duration of the flight did not meet regulatory requirements for supplemental oxygen use, it is likely that the pilot may have been experiencing some early effects of hypoxia, including euphoria, which may have exacerbated the effects from his use of multiple drugs. Toxicology testing revealed a blood level of amphetamine (around 300 ng/ml) and the presence of phenylpropanolamine, indicating that the pilot was most likely using a street preparation of the drug. Generally, levels above 200 ng/ml are the result of mis-using amphetamine to maximize its psychoactive effects. Testing also identified phenylpropanolamine and oxycodone in blood and urine, and oxazepam in urine. The…pilot had reported no medical conditions and no use...
read moreSouth Korean Fire-Fighting Helicopter Tail Rotor Strike on Fuel Bowser
South Korean Fire-Fighting Helicopter Tail Rotor Strike on Fuel Bowser (Heli Korea Sikorsky S-76C+ HL9661) On 25 April 2020, fire-fighting Sikorsky S-76C+ HL9661 of Heli Korea suffered a tail rotor strike on a fuel bowser landed at a forward operating base at the edge of the Yeongsan River, South Korea. There were no casualties of loss of containment of fuel but the helicopter received substantial damage. The Korean Aviation and Railway Accident Investigation Board (ARAIB) safety investigation report was published on 29 June 2021 (in Korean only). The Accident Flight The flight crew of two had been on duty since 08:30 at the forward operating base. One licenced aircraft engineer and a fuel bowser driver were also on site. The pilots had gone for lunch at 11:35, but they were called out at 11:52 to tackle a mountain forest fire. The helicopter took off at 12:12 and was on scene at 12:25. After an hour of fire-fighting with an underslung fire-fighting bucket the crew decided to return for fuel. At the operating base, the wind was 35 knots gusting 45. Due to the wind direction the approach was in the opposite direct to normal. The helicopter flew over the fuel bowser and placed the fire-fighting bucket on the ground next to the engineer and bowser driver. The accident investigators then suggest the wind caused the helicopter to drift backwards, although it seems reasonable to expect that after placing the bucket on the ground the helicopter would manoeuvre aft to land with the bucket and sling ahead of the nose. What is known is that the aircraft commander “felt the aircraft’s nose turning to the right with a thump and quickly lowered the collective”. The tail rotor had in fact contacted the upper deck of the bowser. The helicopter rotated 450° before coming to rest. Fragments of broken tail rotors were widely scattered around the site. The ARAIB Safety Investigation There is no mention of any flight data recorder data being available. The investigators note that in Heli Korea’s procedures: There was no information about the parking location of the feeling vehicle [and] here was no information about the [aircraft] parking position when a refuelling vehicle, which is fundamentally important for operational safety, was waiting for refuelling. The investigator state the co-pilot should advise the aircraft commander of obstacles, and mention the importance of Crew Resource Management (CRM) but then say rather harshly in this case “it is judged that there was no active action or advice” by the co-pilot. They also complain of the weeds growing on landing site. However, matters not discussed in the accident report: The approach briefing The decision to pass over the bowser rather than an offset approach and crab sideways Communications with the ground crew before or during the approach The positioning of the ground crew (which may have influence where the bucket was laid down) A recent prior accident involving the operator: On 18 March 202o Heli Korea Bell 214B1 HL9171 crashed into trees in strong winds during firefighting. with one fatality Another accident that occurred prior to the report being published: On 21 April 2021 Heli Korea S-76C+ HL9285 crashed into a lake during firefighting. with one fatality ARAIB Conclusions The cause of the accident was landing in strong winds, and unable to maintain position the helicopter was pushed backwards, and the tail rotor impacted the top of...
read moreEmergency S-76D Landing Due to Fumes
Emergency Sikorsky S-76D Landing Due to Fumes (Air Ambulance N761AF of Arkansas Children’s Hospital) The US National Transportation Safety Board (NTSB) has recently (5 Oct 2021) opened the public docket on an accident that occurred to Sikorsky S-76D air ambulance N761AF of Arkansas Children’s Hospital on 15 May 2019. The helicopter received substantial damage after an event that occurred in the cruise flight near Morrilton, Arkansas. None of the 6 occupants were injured. NTSB have since issued their probable cause so we have updated the article below. The Accident Flight The NTSB safety investigation report explains that 43 minutes into the flight the pilot experienced fumes in the cockpit. He turned off the environmental control system and commenced a descent. He recounted that: Within approximately 10 seconds, system visual and aural warnings indicated smoke within the aft baggage compartment so I initiated an emergency descent and landing to the [Morrilton Municipal] KBDQ airport declaring an emergency…[and]…requesting crash/fire/rescue from the town managing KBDQ be dispatch to the uncontrolled airport. I alerted the Arkansas Children’s Hospital communications center of the situation and made a landing and shutdown at KBDQ without further complication. The Safety Investigation The NTSB explain that… …examination of the helicopter by a FAA inspector revealed that the exhaust duct from the No. 2 engine was disconnected and not in its seated position. Exhaust from the No. 2 engine entered the compartment containing the tail rotor drive shaft and resulted in heat damage to drive shaft and surrounding areas. The exhaust ducts are attached using two bolts secured at 110 ft-lbs of pressure. Upon inspection of the No. 1 engine, as well as the operator’s second helicopter, all bolts were found partially disengaged and not tightened to the specified torque value. Lock wire is not required to be applied to these fasteners. The NTSB concluded that: The maintenance history of these components was not determined, but given the available information, it is likely that they were improperly secured, which resulted in their loosening and subsequently allowed the exhaust duct to become unseated. NTSB Probable Cause The improper securing of the exhaust duct bolts, which resulted in the duct becoming unseated and substantial heat damage to the tail rotor drive shaft. While this doesn’t explain why, the NTSB have classified this accident: Aircraft Fasteners – Incorrect service/maintenance Aircraft (general) – Incorrect service/maintenance Personnel issues (general) – Maintenance personnel Another Exhaust Duct Accident – A More Dramatic Outcome (Agusta A109A G-DNHI, 9 October 2006) The UK Air Accidents Investigation Branch (AAIB) report that Agusta A109A G-DNHI was also in the cruise when… …an engine exhaust duct separated from the helicopter and struck the tail rotor assembly, causing the tail rotor gearbox to also separate. After an initial yaw to the right, the pilot regained limited control. However, a further sudden yaw, possibly associated with a partial structural failure of the upper vertical stabiliser, prompted an immediate autorotative descent, which culminated in a successful forced landing. The investigation established that a [Mormon / U-band] clamp attaching an exhaust duct to the left engine had failed, due to stress corrosion cracking, allowing the duct to disconnect from the engine. Two AAIB safety recommendations were raised. Safety Resources The European Safety Promotion Network Rotorcraft (ESPN-R) has a helicopter safety discussion group on LinkedIn. You may also find these Aerossurance articles of interest: Ungreased Japanese AS332L Tail Rotor...
read moreGazelle Caught Out Jumping a Fence
Gazelle Caught Out Jumping a Fence (N505HA) On 5 September 2018, a privately owned Airbus Helicopters (formerly Aérospatiale) SA341G Gazelle N505HA crashed while hovering at Kortrijk-Wevelgem International Airport (KJK/EBKT) near Wevelgem, Belgium. The Accident The Belgian Air Accident Investigation Unit (AAIU) explain in their safety investigation report, issued on 22 June 2021, that: On the day of the accident, the pilot wanted to bring 3 friends for a lunch in Valenciennes (France). The helicopter was parked between two hangars located landside approximately 86 m north of the airfield perimeter, which is delineated by a 1.8 m high fence. The Gazelle main rotor diameter is 10.5 m (D value is 12). After the pre-flight inspection and the boarding of the passengers, the helicopter took off vertically to an altitude of 25 ft AGL, a little higher than the roof of the hangars. At the end of the vertical climb, when the pilot slightly pushed on the cyclic to gently move forwards, he felt twice a yaw movement of the helicopter and, after a quick check on the instrument panel, he noticed that the red ALARM warning light was on. He immediately lowered the collective pitch control and pushed the cyclic control further forwards to gain some forward velocity, before flaring and trying to land the helicopter on the grass area bordering the airport fence. A witness…heard the characteristic sound of an engine surge (a loud bang) before the helicopter moved down. The helicopter landed very hard on the grass strip between the circulation road and the airport fence, breaking the skids upon impact and causing significant belly damage. One blade of the main rotor hit one of the fence poles and sent it 50 m away, on the runway. The helicopter finally came to rest on its left side with the engine still running. The pilot shut down the engine, closing the fuel shut off valve. Despite a significant loss of fuel through the vent lines of the fuel tank, there was no post-crash fire. Three occupants were uninjured and one had only minor injuries. The Belgian AAIU Safety Investigation: The Engine Surge The helicopter was technically in good working condition, airworthy with no technical condition having directly caused the crash. The pilot-owner stated that he had washed the helicopter exterior the day before the crash. However, the engine’s air intake was found to be particularly dirty. To start up the engine, the pilot moved the FFC lever forward, but the lever was not latched in the notch during take-off. The slight friction between the FFC lever and the panel, and the extinguishing of the red ‘ALARM’ warning light, may have influenced the pilot from moving fully forward and latching the lever. The pilot was probably not aware of the crucial importance of latching the lever… The improper setting of the fuel flow control (FFC) lever and the dirty airpath of the engine air intake would have eroded the surge margin of the engine. When transitioning from the hover to forward flight…the engine compressor surged. The light tailwind and the rotor downwash hitting the surrounding buildings and so disturbing the airflow may have been a contributing factor. The AAIU note that: Moving the helicopter from the hover in ground effect (HIGE) to forward flight demands the most power during take-off. To avoid a compressor surge, the Flight Manual therefore instructs to slightly increase...
read moreFrench Cougar Crashed After Entering VRS When Coming into Hover
French ALAT Cougar Crashed After Entering VRS When Coming into Hover On 15 April 2020, a French Army ALAT (Army Light Aviation) Airbus Cougar NG AS332M1e 2336 of the 5th Combat Helicopter Regiment (5e RHC), based in Pau, was destroyed during a hoist training flight northeast of Tarbes. Two occupants died, two were seriously injured and three suffered minor injuries. History of the Flight Investigators of the BEA-Etat (BEA-E) explain in their safety investigation report, issued in French only on 20 September 2021, that the student pilot has just 77 flight hours on Cougar and 592 hours in total. He was a former Puma pilot who started his conversion onto the Cougar in November 2019. The instructor pilot had 2,060 hours on type and 3,251 hours in total. The crew had completed the hoist training and the instructor pilot had commenced an emergency drill exercise involving a simulated failure of two alternators while hovering. The BEA-E explain that the instructor intended to demonstrate that after a double alternator failure the helicopter would need to accelerate forwards as a peculiarity of the Cougar is that N1 is restricted to 85% after a double alternator failure. They note that no double alternator failure had ever occurred in reality on the ALAT Cougar fleet and there was no formalised emergency procedure for this event, yet this emergency exercise was a common one within the ALAT Cougar community. The investigators also note that the student pilot was now manually flying the helicopter, while the autopilot had been coupled for the earlier exercises. Main rotor pitch reduced, the aircraft lost altitude and crashed vertically in a field with a slight nose-up attitude. Just before impact, in ground effect, the rotor became effective again and the helicopter briefly returned to a hover. This occurred with very high torque that resulted in a loss of directional control and during this the helicopter yawed and tipped on to its right hand side. There was a post crash fire, believed to have been due to hydraulic fluid leaking onto hot engine components after the firewall suffered impact damage. As is all too common in helicopter accidents the Emergency Locator Transmitter (ELT) did not signal as the wiring to the antenna was severed. Survivability was adversely affected because: Only one in seven crew members wore a flight suit. Army culture favours the wearing of combat fatigues, including in flight. These fatigues were not flame retardant. Furthermore only the flight crew were seated in crashworthy seats. Injuries to the flight engineer were also consistent with being unstrapped, a necessity to reach some controls. The BEA-E Safety Investigation The helicopter was not equipped with any crash-protected flight recorders (although the ALAT Cougar fleet is expected to have these in incorporated in the future). The embodiment had been delayed because an audio mixer component had become obsolescent. The helicopter was fitted with SIT-ALAT (French Army Light Aviation Terminal Information System) which provides a moving map display and saves GPS data. Unfortunately this unit was destroyed in the fire. A reconstruction of the trajectory was however possible with the assistance of specialists iwiation Gmbh. The flight path was reconstructed based on eyewitness video information (although trees obscured the decent). Just prior to coming into the hover the helicopter was at c 300 ft AGL, at a heading of 310º. The witness video shows that the helicopter is moving at a ground speed of 47 kt. This means the crew...
read moreFuel Starvation During Powerline HESLO
Fuel Starvation During Powerline HESLO (Haverfield Aviation Hughes 369D/500D N9159F) On 25 April 2020 Hughes 369D (aka 500D) N9159F of Haverfield Aviation, was substantially damaged in an accident near Pylesville, Maryland. This occurred while conducting a Part 133 helicopter external sling load operation (HESLO) at a power line work site. The pilot was uninjured. The Accident Flight The US National Transportation Safety Board (NTSB) safety investigation report, published on 15 July 2021, explains that the 34-year-old pilot had 12549 hours total flight time, 8736 on type. While… …he was performing human external cargo (HEC) long line operations, he heard on the radio that ground personnel were having difficulty moving a conductor power linenearby. He proceeded to the landing zone, which was about 300 to 400 ft from the area requiring assistance, and dropped off the HEC. Then, while hovering, he picked up a conductor hook via the long line (with assistance from ground personnel) and continued to the area that needed support. This was a change in category of load, to what the FAA defined as a Class C operations (“a jettisonable external load where a portion of the load remains in contact with land or water”). [A]fter the hook was attached to the conductor wire, he began maneuvering for about 10 to 15 seconds to move the wire a short distance laterally, as a crane was supporting the weight of the wire. [W]hile maneuvering, he applied “slight aft and up pressure” to move the conductor wire and there was no lateral banking. He believed the pitch attitude during the maneuvering was about 5° to 10° nose up. After the conductor wire was moved to the desired area, the pilot maneuvered to remove the hook from the wire, but before the hook was free, the helicopter entered a left yaw and the engine began “spooling down.” The pilot…subsequently heard the “engine out alarm” and entered an autorotation by “slamming the collective down.” The…loss of engine power occurred about 150 ft above ground level (agl) and [the pilot] immediately pulled the ‘belly band’ release lever—one of two levers needed to release the long line. A belly band is secondary retention method used by the operator for HEC operations to provide redundancy in the event of an inadvertent release of the cargo hook while carrying a human load. The pilot explained that “removing the belly band constantly throughout the day for human vs non-human line operations could lead to an installation error” and so it “normally remains installed throughout a day’s work, regardless of whether a person is on [the] line”. To release the belly band, the pilot would need to pull an estimated 8 to 12 inches. The handle is located near the pilots left hand, and the pilot would need to remove their left hand from the collective to pull the handle the 8-12 inches. The pilot stated that he did not have sufficient time to pull the second (mechanical release) lever on the cyclic control to release the long line. Significantly: He reported that as part of his recurrent training, he routinely practiced autorotation’s, but had never practiced an autorotation while also having to pull the belly band handle and the main cable emergency release. As the helicopter entered the flare, the pilot pulled the collective up to complete the autorotative landing, but the long line, which remained attached to the helicopter and conductor wire, became taut and caused the helicopter to roll onto its left side. The main...
read moreBrake Failure Causes PA-31 Runway Excursion During Taxi
Brake Failure Causes PA-31 Runway Excursion During Taxi (PR-RCS) On 22 February 2019 privately owned Piper PA-31-325 Navajo PR-RCS suffered a runway excursion when taxiing to the end of the runway at Londrina-14 Bis Airport in Brazil for what was to be its first flight in 7 months. The aircraft suffered substantial damage. The pilot, the sole occupant, as unharmed. The Accident The Brazilian accident investigation agency CENIPA issued their safety investigation report in Portuguese (only) on 21 July 2021. They explain that while some inspections and engine runs had been conducted prior to the return to service, there was no evidence in the maintenance records of any storage checks having been carried out. When the aircraft taxied out for take off… …about 300 meters from the threshold and with the aircraft at reduced speed, braking was started, which occurred normally up to 150 meters before the threshold, when the right brake began to show abnormalities. When trying to stop the aircraft, the right brake failed and the aircraft left the runway, falling into a ravine. CENIPA Safety Investigation In order to identify possible abnormalities in the braking system, some functional tests were carried out. Repeated movements were applied to the pedals of the pilot and co-pilot brakes of the right and left wheels of the main landing gear in order to pressurize the system and then a continuous force was applied. Seconds later, it was observed that the copilot’s right pedal began to give way, remaining a few centimeters in front of the left one , As a result, a visual inspection was carried out on the aircraft’s brake system, in order to detect possible brake fluid leaks, when a leak was found in the set of brakes on the right wheel. Thus, the right brake assembly brake piston assembly, PN 551 719 (Piper Parts Catalog, PA-31-325, Section IV, page 1J8, fig. 41, item 1) was removed [and] it was found that there was a leak in the lower piston, PN 755 838, piston (Piper Parts Catalog, PA-31-325, Section IV, page 1J8, fig. 41, item 3). The set of right brake pistons, brake assembly, PN 551 719, was removed and the pressure line to that set was plugged. Then, the brake activation test was performed. Again, repeated movements were performed on the pilot and co-pilot pedals of the right and left wheels of the main landing gear, followed by a continuous force. However, both the pilot and co-pilot pedals remained in the same position, thus eliminating the possibility of another system leak. Then, the set of right brake pistons, brake assembly, PN 551 719, was disassembled, when it was found that there were signs of wear (grooves) in the gasket PN 755 838, O ring (Piper Parts Catalog, PA-31-325 , Section IV, page 1J8 fig. 41, item 4). Wear was found on the inside of the lower piston housing, PN 753 968, cylinder – brake (Piper Parts Catalog, PA-31-325, Section IV, page 1J8, fig. 41, item 2). There was dirt accumulation on the oil at the bottom of the right brake piston assembly, brake assembly, PN 551 719 (Piper Parts Catalog, PA-31-325, Section IV, page 1J8, fig. 41, item 1). CENIPA Conclusions CENIPA determined that “the wear of the gasket and piston housing, and the accumulation of dirt and oil in the housing and lower piston of...
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