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Report: Saab 340B veered off snowy runway after long and fast landing in Finland
11 December 2019
NTSB: fan blade failure cascaded into cowl failure and loss of cabin pressure on Southwest Flight 1380
The U.S. NTSB determined that a fractured fan blade from a CFM-56-7B engine, on a Southwest Airlines Boeing 737-700, led to the engine inlet and fan cowl separating and subsequently damaging the fuselage, resulting in a rapid cabin depressurization.
One passenger died and eight others suffered minor injuries on April 17, 2018, when the fractured fan blade impacted the fan case, causing fan cowl fragments to strike the airplane’s fuselage near a cabin window. The window departed the airplane, and the cabin rapidly depressurized. The accident happened after Southwest Airlines flight 1380 departed New York’s LaGuardia Airport, bound for Love Field, Dallas, Texas. The flight crew conducted an emergency descent and diverted to Philadelphia International Airport. There were 144 passengers and five crew members aboard.
The NTSB noted, as part of its probable cause, the accident occurred when portions of the fan cowl separated in flight after a fan blade, which had fractured due to a fatigue crack, impacted the engine fan case at a location that was critical to the structural integrity and performance of the fan cowl structure. The NTSB found that the separated fan blade impacted the engine fan case and fractured into multiple fragments. Some of the fragments traveled forward of the engine and into the inlet. The impact of the separated fan blade with the fan case also imparted significant loads into the fan cowl through the radial restraint fitting, which is what caused the fan cowl to fail.
As a result of the investigation, the NTSB issued seven new safety recommendations. These recommendations address the need to ensure the structural integrity of the fan cowl on Boeing 737 next-generation airplanes and assess whether other airframe and engine combinations have critical fan blade impact locations, the importance of having flight attendants secured in a jumpseat during emergency landings, and guidance for mitigating hazards to passengers affected by an in-flight loss of seating capacity.
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Report: Unstable approach, failure to go-around leads to a hard landing of ATR 72 at Canberra, Australia
The ATSB is highlighting the importance of adhering to standard operating procedures following the release of a final investigation report into the hard landing of an ATR 72 airliner resulting from an unstable approach.
On 10 November 2017, ATR 72-700 VH-FVZ operating as Virgin Australia flight VA646 was arriving at Canberra Airport, Australia in conditions of light turbulence. On the flight deck were the captain (who was also a training captain), the first officer (who the captain had previously trained), and a check captain. The check captain was conducting a routine annual operational line check of the captain and a six-month operational line check of the first officer over four flights on the day. The occurrence flight was the last of these flights. In the main cabin were two cabin crew members and 67 passengers.
During the landing approach the first officer, who was the pilot flying, assessed that the aircraft was overshooting the desired approach profile. In response, at a height of 118 feet above the runway, he reduced engine power to idle, but this resulted in an abnormally high descent rate.
The aircraft captain, who was the pilot monitoring, identified that power was incorrectly set, and twice called for an increase in power before subsequently intervening and increasing power himself. This intervention, however, occurred too late to arrest the high rate of descent.
Four seconds prior to touching down, the aircraft was descending at a rate of 784 feet/minute, already greater than the design limit of the undercarriage and above the normal descent rate for the approach of about 575 feet per minute. At that time, the aircraft was subjected to a significant change in the wind from a 10 knot headwind component to a 2 knot tailwind component. This resulted in a further loss of lift, and the captain later stated that he felt the aircraft drop out from under him.
Consequently the aircraft reached a recorded 928 feet per minute descent rate at touchdown, resulting in a 2.97 G hard landing on the main landing gear, tail skid and underside of the rear fuselage, resulting in substantial damage.
The aircraft subsequently required inspection of landing gear components, reskinning of sections of the fuselage underside, and replacement of the tail skid and a drain deflector mast before it could return to service.
ATSB recommends mandating PW4170 engine modification after incident
The ATSB has issued safety recommendations to the FAA and engine manufacturer Pratt & Whitney calling for them to maximise a modification that would prevent a component failure of the PW4170 series engine which powers some Airbus A330 airliners.
The recommendations follow an ATSB investigation into a 18 January 2018 incident where a Malaysia Airlines Airbus A330-300, which was operating a scheduled passenger flight from Sydney to Kuala Lumpur, Malaysia, diverted to Alice Springs due to a malfunctioning left engine.
Subsequent disassembly and inspection of the affected engine, a Pratt & Whitney PW4170, identified that, as a result of exposure to elevated temperatures, a segment of the third stage outer transition duct (OTD) had distorted and fractured. The large fractured section caused a blockage within the engine that created turbulent airflow, partially blocking a low pressure turbine vane inlet stage and causing an increase in exhaust gas temperature. That in turn led to low pressure turbine blade failure, high vibration and compressor stall/surge events.
The ATSB investigation established that there has been a total of 16 similar events globally within the past four years, all attributed to the ‘Advantage 70’ increased thrust modification for the PW4000-100 series engine, including five involving Malaysia Airlines aircraft. The modification increased the engine outer duct gas path temperature, which led to the distortion and liberation of the outer transition duct segments.
Pratt & Whitney, which had ceased production of PW4000-100 series engines for the Airbus A330 in July 2017, has now redesigned the engine’s OTD to withstand higher temperatures. The newly designed hardware will be available for retrofit from November 2019 and service bulletins will recommend installation of the new ducts at the operator’s discretion.
Report of easyJet birdstrike accident at Murcia, Spain, not to be published
Spanish investigators have finished the investigation into a bird strike accident at Murcia, but will not publish the final report because the accident happened at an airport owned by the air force.
The accident occurred on March 27, 2018, when an easyJet Airbus A319 aborted the takeoff at Murcia-San Javier Airport, Spain, after suffering a bird strike. Birds (reportedly seagulls) were ingested in both engines. Since Murcia Airport is owned by the Spanish Air Force, a joint civil-military investigation was carried out by the CIAIAC (civil) and CITAAM (military).
The CIAIAC reported on its website that the investigation has been completed, however: “taking into account the characteristics of the treatment of information in the military field and the obligations to inform the parties in the civilian field, it has been agreed that the publication and public dissemination of the Final Report will be restricted.”
EasyJet Airbus A319 G-EZMK (photo: Anna Zvereva / CC:by-sa)