NDI Process Failures Preceded B777 PW4077 Engine FBO
NDI Process Failures Preceded Boeing 777 PW4077 Fan Blade Off (FBO) Event (United Airlines N773UA, Flight UA1175, 13 February 2018) On 13 February 2018 United Airlines Boeing 777-222 N773UA, suffered a fan blade off event and lost most of the inlet duct and both the left and right fan cowls of its No. 2 Pratt & Whitney PW4077 engine. Two small punctures were found in the right-hand fuselage just below the window line. This occurred over the Pacific Ocean shortly before top of descent when en route to Honolulu (HNL), Hawaii. The aircraft made a safe landing without injuries to the 374 persons on board. NTSB Safety Investigation FBO Event The US National Transportation Safety Board (NTSB) explain in their safety investigation report (issued 13 July 2020) explain that: The PW4000 112-inch engine fan blade is a hollow core, wide chord airfoil made of a titanium alloy with 6 percent vanadium and 4 percent aluminum as alloying elements. The fan blade is about 40.5-inches long from the base of the blade root to the tip of the airfoil and about 12.5- and 22.25-inches wide at the blade root and blade tip, respectively. A fan blade weighs a maximum of 34.85 pounds. During the accident flight while in cruise at flight level (FL) 360, the flight crew heard a loud bang, followed by a violent shaking and warnings of a compressor stall. The flight crew shut down the engine, declared an emergency, and proceeded to HNL without further incident. On examination of the engine it was found that… The fan blade in position No. 11 was fractured transversely across the airfoil about 1.44-inches above the fairing at the leading edge and slightly below the surface of the fairing at the trailing edge. There was a piece of fan blade found up against the leading edges of the fan exit guide vanes at about 4 o’clock. This piece of fan blade was about 15-inches wide chord wise, 23-inches long radially, and had a fracture surface on the inner end that corresponded to the fracture surface on blade No. 11. Laboratory examination of fan blade No. 11 revealed a low cycle fatigue (LCF) fracture that…initiated from a subsurface origin in a region of micro texturing consisting mostly of primary alpha crystals on the interior surface of the hollow core fan blade. The examination also revealed that the fan blade’s material conformed to the specified titanium alloy’s requirements. …fan blade No. 10…the adjacent trailing blade, was fractured across the airfoil at about midspan. The engine / fan history: According to United Airlines’ maintenance records, the No. 2 engine had accumulated 77,593 hours time since new (TSN) and 13,921 cycles since new (CSN) and 8,579 hours and 1,464 cycles since the last overhaul. The engine was installed on the airplane on October 18, 2015 [and] had operated 8,579 hours and 1,464 cycles since it had been installed. The entire fan blade set, including fan blade No. 11 had last been overhauled by P&W’s Overhaul & Repair (O&R) facility in July 2015. As part of the overhaul process, the blades underwent a fluorescent penetrant inspection (FPI) and a thermal acoustic imaging (TAI) inspection. P&W developed the TAI inspection process in about 2005 to be able to inspect the interior surfaces of the hollow core PW4000 fan blade. The records for the TAI inspection in July 2015...
read moreVortex Ring State: Virginia State Police Bell 407 Fatal Accident
Vortex Ring State (VRS): Virginia State Police Bell 407 Fatal Accident (N31WA, Charlottesville, Virginia) The US National Transportation Safety Board (NTSB) have concluded the Virginia State Police (VSP) Aviation Unit Bell 407 helicopter, N31VA, that crashed during surveillance of a violent ‘white nationalist‘ rally in Charlottesville, Virginia on 12 August 2017 had entered a Vortex Ring State (VRS). The helicopter impacted the ground, there was a post-crash fire. The pilot and the observer were fatally injured. The Accident Flight The NTSB explain in their safety investigation report (issued 13 July 2020) that: …the purpose of the flight was to provide the VSP command center with a continuous video downlink of the public demonstrations that were occurring in Charlottesville. The helicopter departed Charlottesville Albemarle Airport (CHO) about 1600. The helicopter arrived over the area of the demonstrations at 1604 and remained there until 1642 when the flight crew was tasked to provide overwatch for the Governor of Virginia’s motorcade. At 1643, the flight crew advised the VSP command center that the helicopter was heading directly to the motorcade and was about 30 seconds away. Radar data indicated that the helicopter was flying at an altitude of about 2,200 ft mean sea level (msl) in the area of the motorcade before it began to turn to the right and descend rapidly. Radar data also indicated that, about 30 seconds later, the helicopter was descending through 1,450 ft msl at a groundspeed of 30 knots. Shortly afterward, the helicopter descended below the area of radar coverage, and radar contact was lost. About 1649, a crewmember aboard a Fairfax County Police Department (FCPD) helicopter observed the accident helicopter descending upright into trees at a high rate of descent… The FCPD helicopter pilot…landed near the accident site to render aid. The other two crewmembers exited the helicopter and proceeded to the accident site. Upon reaching the accident site, the crewmembers encountered heavy black smoke and fire. The NTSB Safety Investigation The NTSB say that: Video from a security camera…captured the helicopter…descending vertically at a constant acceleration and with increasing negative vertical speed until ground impact. Photographs of the accident helicopter that were taken by a ground witness revealed that, about the time that the helicopter began its vertical descent, the helicopter was yawing to the right at a rate between 87° and 97° per second. Toward the end of the flight, the helicopter’s low forward airspeed while descending was consistent with the helicopter entering Vortex Ring State (VRS). As the helicopter approached 2250 ft of altitude the speed slowed to about 20 kts calibrated airspeed. At 16:48:06 the aircraft’s speed increased to 30 kts and at 16:48:12 it climbed from 2225 to 2275 ft while the speed again slowed to near 10 kts. The aircraft’s final descent began at 16:48:18. Examination of data from the Rolls-Royce 250 engine control unit… …revealed a sharp increase in torque, from 54% to 104% immediately before the helicopter’s descent. Insufficient left pedal input with increasing torque can result in a right yaw that can develop into a spin. Bell Helicopter provided the NTSB with the area of predicted vortex ring state for a Bell 407 with a gross weight of 4,633 lbs at sea level. [The graphic below] shows this predicted area with the aircraft’s forward speed and average vertical speed overlaid. The blue shaded area represents combinations of forward speed and vertical speed...
read moreATR72 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...
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