ATR72 Survives Water Impact During Unstabilised Approach
ATR72 Survives Water Impact During Unstabilised Approach (Royal Air Maroc Express ATR 72-600 CN-COH) On 9 July 2018 Royal Air Maroc Express ATR 72-600 CN-COH struck the surface of the Mediterranean during an approach to Al Hoceima, Morocco. The aircraft was able to climb away and made a safe landing at Nador. The Safety Investigation The Morocco BEA issued their safety investigation report (in French only) on 12 July 2020. They explain that the aircraft had been operating Casablanca-Al Hoceima-Tangier-Al Hoceima-Casablanca. The 61 year old Aircraft Commander had recently converted to the ATR72 from the Boeing 737NG. He had around 194 hours on type and 13488 in total. The 25 year old Co-Pilot was a relatively new First Officer with 816 hours on type and 1063 in total. The crew had agreed the Aircraft Commander would fly the first sector and the Co-Pilot would be Pilot Flying for the next three. During the first sector the crew received a Terrain Avoidance and Warning System (TAWS) TERRAIN warning while at FL160 and a TERRAIN FAULT caution light. These disappeared after just over 6 minutes and were probably due to a GPS signal anomaly. During the subsequent (first) approach to Al Hoceima the crew conducted an RNAV approach to runway 17 over the sea. The Aircraft Commander, who was Pilot Flying, was unable to see the runway at the 1030 ft Minimum Descent Altitude (MDA) but continued below this height at descent rate of 1000 ft/min. The aircraft descended to just 60 ft, 1760 m from the threshold at a point it should have been at c 300ft. The ACSS TAWS activated with TERRAIN AHEAD PULL UP and AVOID TERRAIN messages at the aircraft descended to just 45 ft. The aircraft climbed to c 108 ft, which the crew maintained as they approached the airport and then landed. On their return to Al Hoceima later in the day the Co-Pilot was Pilot Flying. The crew decided on a VOR/DME approach, with a lower MDA (760 ft). the Aircraft Commander briefed however that if the runway was not in view at the MDA they would descend to 400ft, maintain that until the runway was visible, and if not, go around at 2 nm distance. The Co-Pilot suggested the TAWS should be turned off and after consulting the Dispatch Deviation Manual, the Aircraft Commander agreed. The rate of descent was reduced to 1,000 ft/min at 445 ft and the Aircraft Commander declared they would “continue”. The rate of descent was increased to 1800 ft/min as the aircraft passed through 310ft before being reduced to 1400 ft/min at 135 ft. The Co-Pilot determined the situation was “not normal…[and]…I’ll take it manual”, disengaging the autopilot at just 80 ft / 130 knots. While the Co-Pilot (the Pilot Flying) applied a nose up input, the Aircraft Commander (the Pilot Monitoring) applied a stronger nose down input. This continued for 9 seconds and 2 seconds later the Co-Pilot advanced the throttles. However, 1.4 nm from the threshold, the aircraft landing gear contacted the sea twice with 3.2 g and 3.9 g vertical decelerations. The Aircraft Commander reduced his control input and the Co-Pilot was able to climb the aircraft. The Aircraft Commander radioed they were diverting and subsequently reported a bird strike. On landing fuselage panels were found to be broken with stringers deformed. Water had been ingested through air inlets, leaving salt deposits. The landing gear had to be replaced due to being overloaded. The 58 occupants were all uninjured however. Within Royal Air Maroc Express non-stabilised approaches featured...
read moreOH-58C Crash After MRB Fatigue Crack
Ex-Military Agricultural OH-58C Crash After MRB Fatigue Crack (N139RD) On 1 November 2016 Bell OH-58C N139RD, on a Rotorcraft Development Corporation Restricted Type Certificate, operated by Helicopter Applicators, was substantially damaged during initial climb at Cameron, North Carolina. The pilot, who sustained minor injuries, was conducting a Part 137 agricultural ‘aerial application flight’, to spray herbicide, in the restricted-category ex-military helicopter. In their safety investigation report, released in November 2019, the US National Transportation Safety Board (NTSB) say: After loading the helicopter with herbicide, the pilot departed from the staging area; however, during the initial climb, as the helicopter was about 50 ft above the ground, the outboard portion of one of the two main rotor blades separated. The main rotor blades then struck the tailboom, and the helicopter entered an uncontrolled descent to the ground. Local TV news (VIDEO) Safety Investigation Metallurgical examination of the fractured [white] main rotor blade revealed a crack with fatigue features emanating from multiple origins in the area of the inertia weight attachment hole. Furthermore: According to FAA airworthiness records, the accident helicopter, serial No. 71-20396 was manufactured in 1971. It was originally owned and operated by the U.S. Army, and issued an FAA special airworthiness certificate in the restricted category for the purpose of agriculture and pest control on May 4, 1999. According to the FAA type certificate database, the accident helicopter serial No. and registration No. were listed in the approved serial number list under type certificate data sheet No. R00006DE. The original holder of this type certificate was Garlick Helicopters Inc., and the type certificate was transferred to Rotorcraft Development Corporation on February 2, 2009. Bell had published… …Military Alert Bulletin (MAB) USA-OH-58-87-1, revision B, originally dated August 12, 1987, and revised April 12, 2007. The purpose of the revised MAB was to notify military operators of model OH-58A, B, C and 206B-1 model helicopters with part numbers 206-011-250-003/113 main rotor blades to conduct initial visual inspections of the blades before returning them to service and subsequently inspect them at intervals of 8 hours or 32 flights, whichever occurred first. The inspection, to be performed with a 10x power scope was focused on the area of the inertia weight screw heads. Paint was to be removed prior to the first inspection, and a clear-coat finish was to be applied to facilitate subsequent inspections. On April 12, 2007, Bell also issued Operations Safety Notice (OSN) OSN-GEN-07-38, Revision A, to all OH-58 operators referencing the aforementioned MAB and providing a notification of changes incorporated in the revised MAB. Both the MAB and OSN noted that the inspection requirement did not apply to main rotor blades manufactured by Bell Helicopter identified with serial Nos. A-1 and subsequent. However, this OSN only applied to the aircraft serial numbers that Bell were responsible for. Bell were not responsible for ex-military helicopters where other organisations had successfully applied to the FAA to be the Type Certificate Holder. Rotorcraft Development was unaware of both the MAB and the OSN prior to the accident. The maintenance program created by Garlick Helicopters had also not specified inspecting the main rotor blade as per the MAB and OSN either. The NTSB say that: Performance of the recurrent inspection required by the MAB and the OSN likely would have detected the fatigue cracks on the main rotor blade before its failure during the...
read moreChallenger Damaged in Wind Shear Heavy Landing and Runway Excursion
Canadair Challenger Damaged in Wind Shear Heavy Landing and Runway Excursion (N813WT, Ox Ranch, TX) On 12 January 2019 Canadair CL-600-2A12 Challenger N813WT, operating a Part 91 corporate flight, was damaged in a hard landing, partial landing gear collapse and runway excursion at the Ox Ranch Airport (01TX), Uvalde, Texas, a private airstrip. The 9 occupants were uninjured. The Accident Flight The US National Transportation Safety Board (NTSB) explain in their safety investigation report (issued 29 June 2020) that the business jet had Fort Worth Meacham International Airport (FTW), Fort Worth, Texas to take the 6 passengers for a day of “actvities”* at the Ox Ranch. …after leveling off at flight level 280, the flight crew checked the weather conditions at nearby airports. There are no automated weather reporting stations on or near the airport. Based on the weather information that they had [Uvalde (UVA) and Laughlin (DLF)], the pilot planned for a visual approach… As the airplane neared the destination, the pilot flew over the runway and entered a left downwind visual traffic pattern to check if any animals were on the runway and what the windsock on the airstrip indicated. The pilot stated that they did not see the windsock as they passed over the runway. The pilot reported that there were turbulence and wind gusts from the hills below and to the west. The flight crew called their downwind and base legs over the airport’s common frequency. On base leg, the pilot had the copilot set the flaps to 30°. As the pilot turned the airplane onto the final approach for landing, the copilot lowered the landing gear. The airplane was 4.5 miles from the end of the runway at 2,500 ft agl and an airspeed of 170 kts. The copilot completed the “Before Landing” checklist. The pilot confirmed the thrust reversers were armed and called for the flaps to be set to 45°. At 2 miles from the end of the runway, the pilot checked his approach speed and confirmed the landing gear was down. The pilot reported there was turbulence and wind gusts from the hills below and to the west of them. As they passed 50 ft. and coming over the runway, the pilot reduced engine power to idle. The pilot reported they then encountered a windshear. Their airspeed dropped rapidly and the airplane “was forced down” to the runway. The pilot unlocked the thrust reversers, applied brakes, and reached to deploy the ground spoilers. As he deployed the thrust reversers, the pilot said it felt like the right landing gear collapsed. He applied full nose-left rudder and left-wing-down aileron, but the airplane continued to veer to the right. The pilot tried using the tiller to steer to the left with no response. A representative for the airport reported that the airplane on landing hit hard. About two-thirds of the way down runway 35, the airplane slid off the right side of the runway. The airplane proceeded through a ditch and struck a perimeter fence before coming to a stop. The airplane left the side of the runway and went into the grass, which resulted in substantial damage; the right main landing gear was broken aft and collapsed under the right wing. The tail was damaged by the perimeter fence. The 1983 aircraft appears to have been assessed as beyond economic repair. * The 18000 acre Ox Ranch offers over 60 varieties of animals to hunt, firing 0.5″ machine guns ($5 per round),...
read moreA Baffled Attitude Fuel Starvation Accident
HESLO Baffled Attitude Fuel Starvation Accident (Haverfield Aviation Hughes 369E N765KV) On 23 June 2017 Hughes (later MD) 369E N765KV, being operated by Haverfield Aviation for a Part 133 long line external load flight, was substantially damaged after a power loss near Dennis, West Virginia. The pilot was uninjured. The Accident Flight The US National Transportation Safety Board (NTSB) explain in their safety investigation report that: The pilot reported that he returned to the landing zone with a conductor attached to a long line. …during the accident flight, the conductor was not completely off the ground and was being dragged over terrain. To compensate for the dragging resistance, the pilot had the helicopter in an aft or left attitude, with a higher nose-up attitude than normal flight. The helicopter was in a 100-foot hover over the landing zone, while the pilot monitored a ground crewmember tasked to disconnect the conductor from the long line. The helicopter began to settle and the pilot raised the collective control; however, the helicopter continued to settle as a warning horn sounded and the engine noise ceased. The pilot then entered an autorotation and during the landing, a main rotor blade contacted the tailboom, which resulted in a tailboom separation. The pilot…estimated that the loss of engine power occurred 45 seconds to 1 minute after transitioning from the pull to a hover. Safety Investigation Postaccident wreckage examination, which included a successful test-run of the engine, did not reveal evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation. As is common with a Helicopter External Sling Load Operations (HESLO) flight the helicopter had been operating with a low fuel load. …when the helicopter was positioned nose up with the remaining fuel onboard (about 7 gallons in each tank), the low fuel light illuminated. The two fuel tanks were connected by an interconnect passage, and each tank had an internal baffle. The fuel pickup was located in the right front portion of the left fuel tank. Given that the low fuel light illuminated when the helicopter was positioned nose up, it is likely that the helicopter’s nose-up attitude during the long line operation led to the unporting of the remaining fuel, which resulted in fuel starvation. NTSB Probable Cause The unporting of fuel due to the helicopter’s nose-up attitude during long line operations, which resulted in fuel starvation and a total loss of engine power. Operator Safety Action The operator’s risk assessment form required that pilots land the helicopter with at least about 14.7 gallons of fuel remaining for long line operations. After the accident, the operator amended its risk assessment form to require the same fuel requirement as side pull operations (about 37 gallons of fuel remaining upon landing) for long line operations. Safety Resources Survey Aircraft Fatal Accident: Fatigue, Fuel Mismanagement and Prior Concerns Running on Fumes: Fatal Canadian Helicopter Accident UH-1H Fuel Exhaustion Accident Load Lost Due to Misrigged Under Slung Load Control Cable Keep Your Eyes on the Hook! Underslung External Load Safety EC120 Underslung Load Accident 26 September 2013 – Report Unexpected Load: AS350B3 USL / External Cargo Accident in Norway Unexpected Load: B407 USL / External Cargo Accident in PNG Load Lost Due to Misrigged Under Slung Load Control Cable Fallacy of ‘Training Out’ Error: Japanese AS332L1 Dropped Load Helicopter External Sling Load Operation Occurrences in New Zealand...
read moreFatigue Featured in Anchorage Alaska Air Ambulance Accident
Fatigue Featured in Anchorage Alaska Air Ambulance Accident (Bering Air Beechcraft King Air 200 N363JH) On 21 October 2017, at c0530 Local Time, Beechcraft King Air 200 N363JH, operated on a Part 135 Air Ambulance flight by Bering Air, was damaged in an unintentional gear-up landing at the Ted Stevens Anchorage International Airport (ANC), Alaska. The pilot, two flight medics and medevac patient were uninjured. History of the Accident Flight The US National Transportation Safety Board (NTSB) explain in their safety investigation report (issued 29 June 2020) that the aircraft had departed for Anchorage from the Nome Airport, Nome (OME), Alaska, about 0320 on a inter-hospital patient transfer flight. The pilot started his duty day on October 20, at 1830 at the company headquarters at OME. The medical evacuation flight was on a weather hold for several hours and the pilot got permission from the company director of operations (DO) to rest at his home about 5 minutes away. The pilot arrived at his home about 2130 and went to sleep about 2140. At 0113 on October 21, he awoke with a telephone call from the company dispatch center for a medical evacuation flight. The pilot described his sleep during the approximate 3.5-hour nap as good and added that he was “sleeping a real deep sleep.” The pilot reported back to the company headquarters, completed his preflight duties, and the airplane departed from OME without incident. The flight from OME to the ANC Class C airspace was without incident. The pilot reported that after being handed off from the Anchorage Air Route Traffic Control Center to the Anchorage Approach Control, he received clearance to descend to 6,000 ft mean sea level (msl) followed with a vector heading and a descent clearance to 2,000 ft msl. As he was descending through about 4,000 feet msl, he visually confirmed the airport and requested a visual approach. He reported the air traffic controller didn’t respond to his request, and he requested a visual approach again. The controller responded back with a vector for the instrument landing system (ILS) runway 7 right approach. The pilot reported his groundspeed was about 210 kts indicated airspeed, he joined the final approach course, and was cleared to land. He reported he believes he was given a vector heading that was too close to the final approach fix and the airplane went through the final approach fix. The pilot then received another heading and he re-established himself on the final approach course. For the landing, the pilot selected the approach flaps setting. He reported he failed to visually check and confirm for the three-landing gear down and locked indication lights in the cockpit. Upon touchdown on the runway with the landing gear not extended, the airplane skid on the pod installed on the underside of the fuselage along with the two engine nacelle assemblies on each wing. During the landing sequence, the metal 4-blade Hartzell HC-E4N-3G propellers for each engine separated about midspan due to runway impact damage… The right side forward fuselage sustained minor damage from various separated propeller blade debris impacts. The airplane came to rest on the runway, and the occupants egressed without further incident. The airplane was recovered and transported to secure location for a comprehensive damage assessment. The airplane sustained substantial damage to the right engine mount… The...
read moreDrone / Helicopter Mid Air Collision over LA City Hall ‘Probable’ Say NTSB
Drone / Helicopter Mid Air Collision over Los Angeles City Hall ‘Probable’ Say NTSB (Airbus AS30B2 N71HD) On 4 December 2019 Airbus AS350B2 N71HD was being operated by Helinet Aviation Services as an electronic news-gathering flight for ABC7 News in Los Angeles under Part 91 and visual flight rules, within Class G uncontrolled airspace. The US National Transportation Safety Board (NTSB) explain in their safety investigation report (issued 29 June 2020) that the pilot… …reported colliding with an unknown object at 1,100 feet above mean sea level (msl) in the vicinity of Los Angeles City Hall. The pilot conducted a precautionary landing at a nearby helipad. Post-flight examination revealed minor damage to the right horizontal stabilizer and tail rotor blade. The helicopter was equipped with a SpiderTrax [sic] flight following system, which indicated the helicopter passing northeasterly in the vicinity of LA City Hall at 7:15 pm at 1,104 feet msl (approximately 828 above ground level (agl)). The pilot and operator reported that no visible evidence of a bird strike was apparent, and believed that the aircraft collided with a small unmanned aircraft (sUAS, or drone). The three occupants were uninjured. There was a small round dent which partially punctured the leading edge of the horizontal stabilizer. Further dents and scuff marks were approximately 6 to 8 inches outboard of the round dent on the leading edge and along the upper surface. One of the tail rotor blades exhibited a small gouge in the composite surface approximately mid-chord. The horizontal stabilizer and tail rotor were sent to the NTSB Materials Laboratory for examination. Visual examination was consistent with an inflight hard-body impact. The dent and scuff marks were compared to the dimensions of common small drones and were consistent with the distance and orientation between the motor and center fuselage/battery compartment. Ultraviolet light inspection revealed no evidence of biological material. The dented region exhibiting material transfer was examined using Fourier-transform infrared spectroscopy (FTIR). The white and gray areas were probed, and the data were contrasted with an area of the painted stabilizer skin surface away from the impact zone. In subtracting out the spectrum peaks from the control area away from the impact zone, several peaks consistent with a different or foreign material were noted. These peaks were consistent with a polycarbonate polymer. Examination of an exemplar popular drone indicated the primary construction material is polycarbonate. (Polycarbonate plastics are used in many other common items, such as safety glasses or light lenses). Under magnification, inside the round dent, a small circular indentation was noted of approximately 0.125 inches (~3 mm) in diameter, exhibiting tears and cracking around its circumference. These features were consistent with fore-to-aft impact with a hard, cylindrical object. The propeller shafts on many common small drones are approximately 3 mm in diameter. The damaged portion of the horizontal stabilizer was sent to the National Institute for Aeronautical Research (NIAR) impact dynamics lab (part of the FAA UAS Center for Excellence). NIAR scanned the damaged component and created a finite element model (FEM) of the stabilizer. The FEM was entered into their impact kinematics simulation with a representative model of a common small drone. The resultant damage was similar to that of the incident, although the calculated relative speeds were higher than those reported by the helicopter pilot. NIAR researchers noted that the collision model they...
read more17 Year Old FOD and a TA-4K Ejection
17 Year Old FOD and a TA-4K Ejection (Draken International Skyhawk N140EM, Las Vegas) On 18 August 2016 an ex-RNZAF Douglas TA-4K Skyhawk of Draken International, registered N140EM, was destroyed following a loss of engine power shortly after entering the traffic pattern at Nellis Air Force Base (LSV), Las Vegas, Nevada. The pilot ejected and sustained minor injuries. The aircraft, which impacted the ground near Las Vegas Motor Speedway, was operated as a Public Aircraft supporting the 57th Adversary Tactics Group, USAF with Dissimilar Air Combat Training (DACT). Public Aircraft are effectively the FAA equivalent of a civil ‘State Aircraft’, to use ICAO terminology. Exercise Red Flag 16-4 was under way at the time, and a pair of Draken A-4s had been exercising with 4 USAF F-16s. The Accident Flight The US National Transportation Safety Board (NTSB) explain in their safety investigation report (issued 28 May 2020) that: According to the pilot, he was the lead airplane of a flight of two aggressors, returning to LSV after completion of their Weapons School support flight in the Nevada Test and Tactics Range. He led the formation to the overhead pattern, and shortly after the break to downwind, the engine lost power. The engine did not respond to throttle movements. The pilot started a turn toward the airport; however, he realized that he was unable to make the runway, so he turned left away from the runway toward a field and then successfully ejected from the airplane. The pilot estimated that his parachute canopy fully opened approximately 100-150 feet above the ground. The pilot was a former USAF F-16 pilot and also a current Southwest B737 pilot. Airlines A review of surveillance video shows the airplane flying wings level at a low altitude and descending. A few seconds later, the ejection sequence was initiated and two chutes (one from the unoccupied back seat) were observed deployed. A couple of seconds later, the airplane impacts terrain…at a relatively shallow angle… After impact, the airplane continued to slide forward on the ground for about 30 ft and then struck and breached a concrete wall. The airplane continued to slide forward for about another 45 ft before coming to rest on its right side against a berm. A post-crash fire ensured, and the debris was mostly contained from the concrete wall to where the airplane came to rest. Safety Investigation: Engine Shop Component Overhaul Build Debris The TA-4K aircraft flight manual stated: ejection is mandatory “when an engine flameout occurs below 1,500 ft agl and 250 kias,” except when unusual circumstances clearly dictate otherwise. The A-4 series was equipped with Douglas Escapac ejection seats. The TA-4K had the IG3 variant. The ejection sequence appeared to function normally, and no anomalies were observed with the equipment. A review of the ejection seat assembly revealed that all inspections and time change requirements were current, with the exception of the separation rocket motor inspection, which were due on both ejection seats in July 2015. However, an extension of the inspections, was approved by the FAA, with the manufacturer’s assessment memorandum. Investigating the power loss… No anomalies were noted during the initial airframe and engine examination that would have precluded normal operation. However, examination of the main fuel control (MFC) revealed foreign object debris (FOD) from a nonmetallic material inside the MFC unit. The material was identified as a nylon 6/6 material that was consistent with other seal material in the...
read moreMaintenance Issues in Fire-Fighting S-61A Accident
Maintenance Issues in Fire-Fighting S-61A Accident (Croman, N1043T, Oregon) On 19 August 2015 fire-fighting Sikorsky S-61A N1043T, operated by Croman Corp, experienced a partial loss of power to the No. 2 engine and subsequently forced landed and rolled over on a mountainside near Ironside, Oregon. One pilot sustained minor injuries and the other was uninjured. The Accident Flight The aircraft was working the Eldorado Fire 8 miles SE of Unity, Oregon. According to the US National Transportation Safety Board (NTSB) safety investigation report (only released 13 April 2020), the crew: …picked up 4,000 pounds of water from a pond then made a climbing left turn to the east towards the fire. About 20 ft above the ground, there was an engine power loss and a drop in RPM. The pilot dumped the water from the bucket at the end of the longline and attempted to gain airspeed and altitude as they entered a small valley. The pilot was keeping the bucket clear of the ground and obstacles when he attempted to release the longline, but it would not fully release from the helicopter fuselage. …they continued to lose engine RPM and rotor RPM. With the terrain rising, they found the flattest accessible spot and began to slow the helicopter. The pilot landed the helicopter as level as possible, however, the helicopter rolled onto its right side. Before touchdown, the longline and bucket had impacted brush and trees and the bucket became entangled in a fence, which likely hindered the pilot’s ability to successfully land the helicopter. The Safety Investigation Examination of the longline revealed… …the fuselage belly hook released the longline as intended; however, one of the two hydraulic quick-disconnect couplings failed to release the longline. A safety wire was used to connect the fitting on the quick-disconnect mechanism to the coupling. The use of the safety wire did not allow the quick-disconnect mechanism to function as intended and release the longline. The wire broke on impact with the ground. Examining the failed engine… …revealed metallic debris on all four magnetic plugs. Removal of the pinion gear assembly from the accessory gearbox revealed that the pinion gear, which mates with the bevel gear, exhibited wear on the gear teeth and some metal smearing along the tips, which is consistent with gear disengagement. Disassembly of the pinion support assembly revealed roller ball, bearing cage, and race damage to the upper support bearing and wear to the bevel gear teeth consistent with that observed on the mating pinion. When the bevel and pinion splines disengaged, the fuel and oil pumps were no longer being driven, so fuel and lubrication to the engine were cut and the engine lost power. Aluminum oxide particles were embedded in the cage pocket and inner races of both bearings and likely contributed to the bearing wear that eventually caused bevel and pinion gear disengagement. According to the manufacturer, aluminum oxide is not present in any T58-GE-402 bearing or component within the oil lubrication system pathway. Historically, aluminum oxide has been inadvertently introduced into the engine during the engine overhaul/repair process. Aluminum oxide is abrasive and once it is embedded into the bearing it can cause uneven wear and accelerated failure. The last engine light overhaul was completed about 1 year before the accident, and it is likely that the aluminum oxide was introduced at that time. NTSB Probable Cause A loss of power to the No. 2 engine due to the...
read moreJapanese Jetstar Boeing 787 GEnx-1B Engine Biocide Serious Incident
Jetstar Boeing 787-8 VH-VKJ General Electric GEnx-1B Engine Biocide Serious Incident near Kansai On 29 March 2019 the No 1 General Electric GEnx-1B engine of Jetstar Airways Boeing 787-8 VH-VKJ, flying from Cairns, Australia to Osaka Kansai International, Japan, fell below idle during the descent at an altitude of about 16,000 ft for 8 seconds. The No 2 engine then fell below idle too for 81 seconds. The aircraft safely landed at Kansai International less than 30 minutes later. The Japan Transport Safety Board (JTSB) explain in their safety investigation report (issued 25 June 2020) that engine rpm oscillations had been recorded during the incident. In fact oscillations had been recorded by the FDR since a fuel biocide treatment had occurred on 27 March 2019. However, these oscillations had been so small as not to have been noticed until the descent on 29 March 2019 when “ENG FAIL L” and “ENG FAIL R” EICAS messages also appeared. During the subsequent investigation… ….a residue, primarily composed of magnesium salts was observed in multiple locations (fuel filter, fuel metering valve [FMV] spool, fuel splitting valve [FSV] spool, variable bleed valve [VBV] spool and high pressure turbine [HPT] active clearance control [ACC spool]). Testing showed that up to 320 times more force was needed to move the control servos with the residue. The JTSB therefore concluded that when fuel pressure was low when descending at flight idle, “the FMV spool and FSV spool had restricted freedom of movement” and that the engines had dropped below idle due to the FSV sticking. JTSB say: It is probable that biocide treatment inside fuel tanks conducted two days before the serious incident was involved in the accumulation of [the] residue…because the composition of the residue were similar to the Kathon FP1.5. Biocide treatment is used to prevent microbial growth that can cause corrosion and damage fuel and engine systems. The Aircraft [had been] ferried to Auckland International Airport, New Zealand to borrow facilities of other company to conduct biocide treatment inside all three fuel tanks (left, center and right) because the Operator did not have their own facilities. …biocide treatment is conducted by connecting biocide treatment cart to a certain position of fueling hose to mix biocide with fuel for loading into fuel tank. AMM stipulates that biocide of either Kathon FP1.5 or Biobor JF is used, and the Operator used Kathon FP1.5. Kathon FP1.5 (MIL-S-53021A) composition is: Glycol: 90.0%, Water: 5.85%, Magnesium salts: 2.65%, 5-Chloro-2-Methyl-4-Isothiazolin-3-one: 1.15% and 2-Methyl-4-Isothiazoliln-3-one: 0.35%. The magnesium salts contained in Kathon FP 1.5 are insoluble in fuel but will dissolve into water if a water phase is present in the fuel. When Kathon FP1.5 is used, biocide and fuel are loaded to make concentration ratio inside fuel tank 100 ppm (parts per million) by volume. Therefore, in the event that fuel remains in aircraft, fuel and biocide to be loaded require adjustments to obtain a higher concentration ratio for loading into aircraft so that the final concentration ratio inside the tank can be 100 ppm. After completing fuel loading, biocide treatment is completed by soaking fuel for 12 to 24 hours keeping concentration ratio inside fuel tank at 100 ppm. The certifying staff involved had not recorded details of the biocide quantity added. JTSB comment that “It is desirable to keep these records because they are considered to be important for traceability of maintenance work.”. JTSB determines that the actual concentration was 250 ppm in...
read moreMyanmar National Embraer 190 NLG Jam: Maintenance Error? We’re Not Convinced!
Myanmar National Embraer 190 NLG Jam: Maintenance Error? We’re Not Convinced! (XY-AGQ, Mandalay) On 12 May 2019 Myanmar National Airlines Embraer 190 XY-AGQ suffered damage to its forward fuselage during the landing in Mandalay, on a flight from Yangon, after the Nose Landing Gear (NLG) failed to extend. The 89 occupants were unharmed. A maintenance error narrative was accepted without question by the technical press. We aren’t convinced! https://youtu.be/Jl5xXzj8n64 Safety Investigation The Aircraft Accident Investigation Bureau of Myanmar (AAIBM) issued their safety investigation report on 16 June 2020 (after just 13 months). They explain that analysis of the Flight Data Recorder (FDR), and the weight-off-wheels switch signal in particular, showed that as the NLG retracted the shock strut had compressed enough to disengage a self-centring cam which keeps the nose wheels central as the NLG enters the bay. The nose wheels turned and became offset by about 20°. Any more that 8° offset means the wheels will jam when the NLG is lowered, which is what happened. On 23 previous flights the weight-off-wheels switch signal had also changed from ‘WOffW=True’ to ‘WOffW=False’ during the retraction. The investigators concluded that a similar event could have occurred on those flights. The aircraft had previously undergone fault-finding to try to rectify a failure message relating to the weight-on-wheels system, first observed on 8 May 2019. The engineer involved stated that the aircraft had… …encountered a Landing Gear WOW System fault just after take-off from Yangon and returned to Yangon and the Pilot-in-command entered a Landing Gear WOW System fault message into the Technical Logs book. The engineer said that the maintenance action performed was cleaning the Nose Landing Gear sensors, connector and targets according to Fault Isolation Manual (FIM) (32-61-00-810-890-A00). After that he checked CMC [Central Mainteance Computer] of the aircraft, that there were no WOW SYS fault messages active. The aircraft was put back into service that day but on 11 May 2020, the crew felt the NLG vibrating during take-off and gear retraction. They recorded in the Technical Log records that “Nose Wheel Tension is Stronger than Normal During Take off and Landing Rolling”. Maintenance was performed that night, with the engineer stating that the task performed… …was the Nose Landing Gear shock Strut N2 Chamber Servicing, according to Aircraft Maintenance Manual (AMM) 12-12-09-600-804-A. He also stated this condition, was not included in FIM. Therefore, he decided on the appropriate maintenance action for this fault based on his experience. After that he checked the Dimension H of sliding tube of Nose Landing Gear based on the temperature 30ºC , it was within limit in the graph of (AMM) 12-12-09-600- 804-A. The accident occurred on the next flight. The AAIBM Conclusion The investigators concluded: Maintenance actions were not properly done as per the fault isolation manual in rectifying the intermittent Weight off Wheels System Fail fault and in addition, poor workmanship in performing the Nose Landing Gear Strut N2 servicing. Our Observations and Warnings on WYLFIWYF and the FFP Fallacy However, disappointingly, the investigators actually provided no evidence for their conclusions! They identify no omission or error by the first engineer. They don’t comment on the dilemma the second engineer faced, namely the absence from the FIM of the oddly phrased problem reported nor do the investigators assess the adequacy of the maintenance instructions in general. The investigators also do not identify why the N2 Chamber servicing was either incorrect or, indeed if correct, may have contributed to the jam on the 24th flight. There are also...
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