GUY NORRIS / LOS ANGELES
General Electric is to inspect and modify GE90 engines after a series of recent incidents in which damaged low-pressure compressor (LPC) seals led to two in-flight shut downs on Boeing 777s, and an Air France aircraft experiencing a "stall event".
A Saudi Airlines 777 suffered engine vibrations after take-off from Jeddah on the 19 August. The crew shut down the engine and returned. GE says this incident was the second in-flight shut down to be caused by the suspected seal problem - the first being on an Asian-based aircraft on 31 March.
The crew of the Air France flight kept the engine running, but elected to land after the "stall event". GE says initial Snecma borescoping of the engine, which suffered a compressor stall on climb out from Jakarta on 18 August, appeared to show damage around the LPC stage-four toggle seal.
The seal is connected to the rotor adjacent to the stator vane where the clearance is, according to GE, "a little tight". The company says contact between the vane and the seal "liberated material", which led to the stall.
Following this incident, GE initiated a "control plan" to manage the problem in the field using a network of "quick-turn facilities" at GE90 overhaul sites.
The plan, covering 230 high-time, high-cycle engines, involves inspecting the toggle seal and replacing worn units. The corrective action scheme, which started on 1 September, involves trimming material from the stator vane to improve the clearance between the third and fourth stages in the LPC.
A longer term fix, based on a redesign of the stator vane, is under way says GE.
Source: Flight International
