Focus on CFM56-7B Inspection Procedures
The effectiveness of required, routine inspection techniques is emerging as a key focus in the investigation of the April 17 CFM56-7B engine failure involving a Southwest Airlines Boeing 737-700, the National Transportation Safety Board said in a May 3 update on the probe.
The fan blades on the failed engine, including the fractured one, underwent detailed fluorescent penetrant and visual inspections as well as full overhauls in November 2012—10,700 cycles before the accident, investigators discovered. The engine had accumulated more than 30,000 cycles since new.
Links between the April accident—which required an emergency landing in Philadelphia and caused the death of one passenger—and a non-fatal August 2016 accident that also involved a Southwest 737-700 are becoming more apparent. In each instance, a No 1. engine failure was linked to a cracked fan blade, with fatigue cracking within the dovetail-shaped blade root—where the blade is attached to the hub—identified as the likely cause.
Following the 2016 accident, which led to an emergency landing in Pensacola, Florida, CFM revised its overhaul procedures, adding eddy current inspections, the NTSB says. CFM also issued a service bulletin in 2017 recommending inspections of all blades at 15,000 cycles since their last overhaul.
Days after the most recent accident, CFM revised its inspection recommendations, urging ultrasonic inspections for blades with at least 30,000 cycles since new. Both the European Aviation Safety Agency and the FAA mandated the checks, giving operators until May 10 to perform the inspections on the 680 affected engines.
Each CFM56-7B has 24 fan blades. The blades are made of a titanium alloy, and the root’s face is coated with a copper-nickel-indium alloy. The NTSB says the fan blade that fractured during the April incident, mounted in position No. 13, separated at the root, with the dovetail remaining installed in the fan disk. Two other pieces, a 12-in. fragment and a 2-in. fragment, were recovered from within the engine, between the blades and outlet guide vanes.
Inspection of the blades revealed signs of fatigue cracking within the dovetail. “The origin area was located outboard of the dovetail contact face coating, and the visual condition of the coating appeared uniform with no evidence of spalls or disbonding,” the NTSB says. An examination by electron microscope revealed “striations consistent with low-cycle fatigue crack growth,” the board adds.
ST Aerospace and Vietnam Airlines Sign Parts JV
ST Aerospace has signed a memorandum of understanding with Vietnam Airlines to set up a joint venture to provide component MRO.
The joint venture, to be headquartered at Noi Bai International Airport in Hanoi, will start with support for a wide range of aircraft systems including pneumatics, hydraulics and electrical components, before potentially increasing collaboration to include aerostructure and airframe MRO.
According to both parties, the joint venture will leverage Vietnam Airlines’ maintenance subsidiary, Vietnam Airlines Engineering Co.’s (VAECO) existing facilities in Hanoi and Ho Chi Minh City, while ST Aerospace will use its MRO expertise to help VAECO develop its facilities and capabilities.
In addition to the joint venture, the two companies have also entered into a 14-year component maintenance-by-the-hour contract to support 58 Airbus A321ceos and 20 A321neos.
Avocet Aviation Services, Florida, secured a 321 Precision Conversions contract to perform its Airbus A321 prototype conversion at Orlando Sanford International Airport. It is initially assigned to work on a cargo door conversion prototype with as many as five more aircraft to follow.
Taby Air Maintenance of Sweden selected C&L Aviation Group to market its Saab 340B cargo conversions as an approved sales and installation center in the Americas out of Bangor, Maine. The converted freighter can carry 1,280 ft.3 of cargo.
Belavia selected Embraer to provide a component support program for three E175s and four E195s.
Eastar Jet of South Korea selected Lufthansa Technik to provide Total Component Support for its Boeing 737NGs.
Pratt & Whitney added Turbine Controls, StandardAero, Twin MRO, ACMT and Lewis & Saunders to its Geared Turbofan (GTF) Engine Repair Supplier Network, which now comprises 10 members.
Pratt & Whitney secured a 15-year EngineWise service agreement with JetBlue Airways to maintain geared turbofan engines for 85 A320neo family aircraft.
Rolls-Royce was selected by Jackson Square Aviation to provide its LessorCare support service for Trent engines.
Royal Jordanian selected Spairliners to provide component supply and management for three Embraer 175s and two 195s.
SR Technics secured a 10-year HK Express contract to provide component maintenance, pool access and logistical services out of Kuala Lumpur for 20 A320ceos and 12 A320neos. As part of the deal, SR Technics is setting up an A320 component pool in Hong Kong.
ST Aerospace was selected by Air Canada to perform Airbus A330-300 interior reconfigurations to harmonize with its Boeing 787 fleet.