The FAA has issued a requirement to fix 787-8 and -9 Dreamliners that are powered by General Electric GEnx-1Bs in order to prevent damage caused by fan ice shedding.
The requirement is for Boeing to repair aircraft utilizing this type of engine, along with revisions to the flight manual.
The FAA Airworthiness Directive (AD) follows a March directive that was prompted by a report of a “significant fan rub” event on a Boeing 787 equipped with the GEnx-1B performance improvement program engine (PIP) 2.
The event in-flight was caused by ice-shedding from the fan blades at 20,000 ft. causing a fan imbalance and protective shut-down of the engine.
The aircrafts other engine was the older-design GEnx-1B PIP 1 that reportedly sustained minor damage during the event, and continued to operate normally.
The FAA is said to be continuing the investigation with Boeing and GE; and it appears that the GEnx-1B PIP 2 engine appears to be susceptible to heavy fan blade rubs which causes the resulting damage.
The latest AD was published on April 22 2016 and became effective on May 9 2016. It is understood to require Boeing and GE make the required fixes, and Boeing provide pilots with a new ice-shedding procedure and briefing to reduce the potential likelihood of sustaining any fan-blade or engine damage due to icing.
The fix is required to complete within 150 days of issue of the directive dated May 9 2016.
The urgency of the fix stems from aircraft operating with two GEnx-1B PIP 2 engines operating in a similar environment to that of the aircraft which suffered the event. The risk is that neither engines suffer damage can cannot be restarted.
The AD cites 176 Dreamliner aircraft fitted with the GEnx-1B PIP 2 engines. It required all aircraft with two GEnx-1B PIP 2 engines fitted must have at least one engine fixed by the end of September.
The work does not involve removal of the engine, and thus all work can be conducted with the engine in situ.
The solution requires some of the surface of the fan case to be removed [taken back] in front of the fan blades, a process reported to take about 16 hours using a fan grinding machine to remove about one-tenth of an inch of material along the interior of the fan case, which makes contact with the tips of the fan blades.
For aircraft operators the news is that most of this work can be completed during aircraft ‘A’ checks.
The general Electric GEnx (General Electric Next-generation) engine is an advance dual rotor, axial flow, high-bypass turbofan engine produced for the Boeing 787 and 747-8. The engine features main composite flan blades with steel-alloy leading edges, and Titanium aluminide stage 6 and 7 low pressure turbine blades; as well a a composite fan case.
The GEnx-1B PIP 2 engine provides increased efficiency through reduced fuel-burn of 15-20%, features fan diameter of 111in / 2.8m as used in the 787-8, and provides reduced internal aircraft temperatures due to improved and more efficient cooling techniques.
Operators of VIP 787 aircraft should check directly with your aircraft management company, or directly with Boeing.