Investigators find evidence of fatigue as well as bird remains in powerplant of Ryanair Group jet.
US investigators have indicated that a single fan-blade from a Ryanair Group Boeing 737-800 detached and was thrown forward during July’s in-flight window loss over Greece.
Blade 10 of the right-hand CFM International CFM56 powerplant had fractured and separated below the blade platform, states the National Transportation Safety Board in preliminary findings.
Visual examination of the core showed “no evidence of radial uncontainment” through the engine cases, it says, but the inlet cowl – which is forward of the fan case – had evidence of punctures.
The inlet cowl inner barrel showed substantial impact damage, while the outer barrel had “radial penetration” which was “forward of the fan plane of rotation”, with punctures in two areas on the inboard side of the engine, each about 35cm by 25cm in size.
Bird remains, including feathers, were recovered from sections of the engine and have been sent to a Washington laboratory for identification.
Engine fragments struck the fuselage and right-hand horizontal stabiliser, penetrating through the passenger window at seat row 11 as well as lower fuselage skin behind the wing-body fairing.
As a result, the aircraft depressurised, and the passenger in seat 11F was “partially lodged” in the damaged window, receiving serious injuries, says the inquiry.
Although the event appears to parallel a Southwest Airlines 737-700 occurrence in 2018 – during which a passenger was fatally injured – investigators have not drawn any conclusions.
The inquiry acknowledges previous blade-out events with similar engines that have resulted in damage to the inlet or cowl, and fuselage structures.
But it states: “Determination of any relevant similarities or details between this accident and previous events remains under investigation.”
Operated by Ryanair’s Malta Air division, the aircraft had departed Thessaloniki on 10 July. It was climbing through 16,000ft, about 4.5nm south of the Greek-North Macedonia border, when the crew received a ‘high vibration’ warning for the right-hand engine.
Although the pilots reduced power and began running a checklist, the vibrations increased and the crew heard a “loud bang”. The flight, with 149 passengers and six crew members, turned back to Thessaloniki.
Analysis of the separated blade found it had fractured through the dovetail in the blade root, and the fracture surface showed features “consistent with fatigue”, says the inquiry.
Maintenance records for the engine state that the blades had undergone ultrasonic inspections in November last year and May this year, 253 cycles before the event, with no findings.
These inspections had been laid down in a service bulletin issued in the aftermath of the fatal Southwest 737 accident.
Investigators add that four suspected bird-strikes were reported by crews on the Malta Air jet’s right-hand engine over the 12 months prior to the blade fracture.
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