An in-flight, uncontained, engine failure not only trashes that particular engine, but can also send shrapnel into potentially vulnerable areas of the aircraft (wing fuel tanks for example). The aircraft may still be able to fly without that engine but the effects of shrapnel are potentially lethal.
Rolls Royce had its share of teething problems with its Trent 900 engine for the Airbus A380 (Trent 900 failures) and had to spend at least $300 million to replace faulty engines. There are only two engines from two manufacturers available for the A380 (Trent 900 from Rolls Royce and the GP7200 from the Engine Alliance – a 50/50 JV between GE and Pratt & Whitney), and competition is limited. Whereas the A380 has 4 turbofan engines, Boeing’s 787 Dreamliner has only two. Again competition is limited between Rolls Royce’s Trent 1000 and GE’s GenX.
But the Trent 1000 is having erosion/corrosion problems which are causing blades to crack. Blade failure is particularly nasty since the entire engine downstream of the failure can be easily wiped out. Worse, a broken blade or its fragments travel at high speed and can be ejected through the engine casing creating the “uncontained failure”. Vibration induced failures usually show up relatively quickly but corrosion/erosion induced failures can take a few thousand hours of operation to show up. In any event, the Japanese airline ANA has five affected engines but is replacing all 100 engines on its 50 aircraft.
The Guardian:The Japanese airline ANA has said it will replace all 100 Rolls-Royce engines on its fleet of Boeing 787 Dreamliners after three engine failures in 2016 caused by corrosion and cracking of turbine blades.
The world’s largest 787 operator said all 50 of its 787s would receive engines fitted with new blades, a process that could take up to three years.
ANA had five engines that currently needed repairs “but we will replace all the 100 engines for enhanced safety measures”, the company said, adding that it had already repaired three engines.