GEnx "Bleedless" (B787) & GEnx "Bleed-Air" (B747-8)

Jeannot a écrit:Cher Admin

Vous remarquerez sans aucun doute que je n'ai jamais dit que le souci aurait été lié au GEnx. J'ai simplement dit qu'il semblait que le souci devait provenir du 789 et que le constructeur aurait imposé que la puissance ne dépasse pas les 75.000 lbs alors qu'un des motoristes aurait voulu pouvoir monter jusqu'à 76.500 lbs afin d'être certain de pouvoir faire décoller l'animal et le voir remplir les missions pour lesquelles ils était prévu.

A new modification for the most advanced version of the GEnx-1B engine alters one of the fuel-saving features added to the Boeing 787 propulsion system.
Despite the required design change, manufacturer GE Aviation says the closely scrutinised fuel burn performance for the Boeing 787 fleet will not be affected.
“No performance impact [is] expected,” GE tells Flightglobal.
GE engineers are shaving about one-tenth of an inch from a layer of abradable seal material surrounding the ring of fan blades.
GE issued a new service bulletin recommending the design change on 11 March. The US Federal Aviation Administration (FAA) followed up a week later with an urgent proposal to make the change mandatory on all GEnx-powered 787s.
The change was prompted by an in-flight shutdown caused by ice build-up on the fan blades. When the ice abruptly sheds from the blades, the sudden change causes an imbalance in the fan. As a result, the blades rub too hard against the abradable seal, causing so much damage inside the engine that it could not be restarted in flight.
An investigation determined that the problem was unique to the most advanced version of the GEnx-1B engine – the performance improvement package (PIP)-2, which allowed GE to meet Boeing’s fuel burn targets on the 787.
One of the fuel-saving PIP-2 features included tightening the space between the blades and the abradable seal material, reducing air flow leakages that make the engine less efficient.
But that change also appears to have made the engine more susceptible to damaging rubbing between the blade and the abradable seal.
“Reduced fan clearance, if not corrected, could result in engine damage and a possible in-flight, non-restartable power loss of one or both engines,” the FAA says in a proposed airworthiness directive.

Poncho a écrit:ou un 3 ème arbre mais c'est moins sûr)

An Air India Boeing 787-800, registration VT-ANR performing flight AI-315 from Hong Kong (China) to Delhi (India) with 154 passengers, was enroute at FL380 over Myanmar about 500nm east of Kolkata (India) when the crew reported an engine (GEnx) problem, drifted down to FL260 and diverted to Kolkata for a safe landing about 100 minutes after leaving FL380.

The action is mandated by an FAA Airworthiness Directive (AD), which, according to GE, will require rework on 336 GEnx-1B Performance Improvement Package-2 (PIP) engines that are “twinned” on 168 787-8 and 787-9s. The work, scheduled to be completed by September, does not require removal of the engines from the wing, but will entail up to 16 hr. of grinding per powerplant.
The AD was prompted by an inflight shutdown that occurred after an aircraft flew through icing conditions at 20,000 ft. on Jan. 29. The FAA said the engine encountered “a significant fan rub event . . . apparently caused by partial fan ice shedding and a resulting fan imbalance that in turn caused substantial damage to the engine and an inflight non-restartable power loss.” The agency added: “The urgency of this issue stems from safety concerns over continued safe flight and landing for airplanes that are powered by two GEnx-1B PIP2 engines.”