The National Transportation Safety Board (NTSB), the independent safety investigator of the US, has issued two urgent safety recommendations on General Electric GEnx engines, which power the latest generation of Boeing aircraft: Both the 787 Dreamliners and the Boeing 747-8s.
The GEnx-1B engines power the 787 Dreamliners that are the newest addition to Air India’s fleet. Among other users of the engine are Japan Airlines (JAL) and Ethiopian Airlines, with Qatar Airways set to join soon. The two other 787 operators, All Nippon Airways (ANA) and LAN Chile, have their aircraft powered by the Rolls Royce Trent 1000 engines.
The Dreamliner’s first commercial flight is scheduled to be on September 19. The GEnx-2B engines power the Boeing 747-8i of Lufthansa and the 747-8F freighters of many carriers.
The investigation of the GEnx engines began with the July 28 engine failure incident at Charleston, US, involving a Boeing 787 Dreamliner destined for Air India. Initial investigations had suggested a fracture failure of the fan midshaft (FMS). While that investigation is on-going, on August 31, NTSB had found similar signs in another GEnx-1B fitted on a yet-to-fly Boeing 787. The fan midshaft was removed from that engine for further inspection and examination. As a result of the investigative work to date, NTSB has determined that the fan midshafts (FMS) on the GEnx engines were fractured or cracked at the forward end of the shaft where the retaining nut was installed.
The NTSB has also expressed concern over a loss of power on the GEnx-2B engine of a Boeing 747-8F cargo flight, operated by Air Bridge Cargo, at Shanghai, China, during take-off. The airplane had accelerated through 50 knots when the engine's low pressure rotor speed dropped. The pilot aborted the take-off and returned to the ramp. Photographs of the low pressure turbine are said to have shown damage similar to the GEnx-1B engine from the Charleston incident involving a Boeing 787 bound for Air India.
NTSB Chairman Deborah A P Hersman said in a statement: "The parties to our investigation—the FAA, GE and Boeing—have taken many important steps and additional efforts are in progress to ensure that the fleet is inspected properly. We are issuing this recommendation today because of the potential for multiple engine failures on a single aircraft and the urgent need for the FAA to act immediately."
According to the NTSB, the engine manufacturer, GE, has developed a field ultrasonic inspection method to inspect the fan midshaft in the area where the fracture and crack occurred. This inspection can be done with the engine still installed on the airplane, thus saving operators a lot of money and downtime.
To date, all in-service and spare GEnx-1B engines have been inspected. In addition, all GEnx-2B engines on passenger airplanes have been inspected. However, as per the the NTSB, approximately 43 GEnx-2B engines mounted on 747-8F cargo airplanes have not yet been inspected, and this is a concern on potential fan midshaft failures.
Air India spokesperson could not be reached for comment.
