The FAA ordered airlines to urgently modify engines on Boeing 787 Dreamliners, due to an icing problem that can cause a specific model of GE engine to shut down in flight. The problem affects 176 Dreamliners at 29 airlines, about 44 percent of the worldwide fleet.
The Federal Aviation Administration on Friday ordered airlines to urgently modify engines on Boeing 787 Dreamliners, due to an icing problem that can cause a specific model of GE engine to shut down in flight. The problem affects 176 Dreamliners at 29 airlines, about 44 percent of the worldwide fleet, the FAA said.
The FAA’s airworthiness directive follows a Jan. 29 incident in which one of the two engines on a Japan Airlines (JAL) 787 shut down in midair and couldn’t be restarted. The jet, flying from Vancouver, B.C., with 166 people on board, was about 90 miles from Tokyo’s Narita Airport when the right-hand engine failed.
According to data on that flight provided by aircraft-tracking firm Flightradar24, the pilots landed safely on one engine about half an hour later.
On planes with the same engine model on both wings, the problem could cause a potentially catastrophic dual shutdown of both engines.
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The FAA directive says “the potential for common cause failure of both engines in flight is an urgent safety issue.”
The rework ordered by the FAA has already started; GE issued a service bulletin on March 11. GE spokesman Rick Kennedy said rework on about 40 airplanes has been completed.
Airlines have until the first week of October to complete the rework on all their planes. In the meantime, pilots are required to follow a new ice-removal procedure in flight.
The FAA did not issue an emergency directive, its most immediate form of mandatory action. However, because of “the risk to the flying public,” the agency dropped its usual 30-day period for public comment before a directive takes effect.
The agency only regulates U.S. airlines, but government regulators elsewhere typically follow its lead.
The FAA directive, first reported Friday by The Wall Street Journal, states that the problem arises only in the latest upgraded model of the GEnx engine powering the Dreamliner, the GEnx-1B PIP2.
That upgrade, which was certified by the FAA and entered service in 2013, improved the fuel burn incrementally, in part by reducing the tiny gap between the tips of the engine’s large fan blades and the fan case.
In the January incident, ice had built up on the fan blades before the trouble occurred at an altitude of 20,000 feet as the plane descended.
When the ice abruptly shed, it caused the blades to move slightly forward and because of the contour of the fan case, this was enough to make the blade tips rub against the case.
The resultant heavy vibrations did so much damage that the engine shut down and could not be restarted.
Luckily, the GEnx engine on the other wing of the JAL Dreamliner was older and not the specific upgraded PIP2 design. The FAA directive says that second engine incurred only “minor damage during the icing event and continued to operate normally.”
However, some aircraft carry two engines of the upgraded PIP2 model type.
The fix GE has devised is to shave “less than 1/10 of an inch of the abradable seal material along the interior of the fan case which makes contact with the tips of the fan blades,” said Kennedy, the GE spokesman.
On all new PIP2 engines now being produced, this process is being done during the manufacturing process, increasing the fan-tip clearance to avoid the problem.
Jets already in service will have to be taken into maintenance facilities to have the work done.
“The process takes about 16 hours using a ‘fan grinding machine.’ All of the work is done on-wing with no engine removals,” Kennedy said.
He added that “because the shaving occurs in front of the fan blades, we expect almost immeasurable (fuel efficiency) performance impact” on the reworked engines.
This fix is being initially performed on all 176 airplanes in service that have two engines of this type. However, the FAA said it later may issue further directives to require rework of other affected engines.
Until airlines worldwide complete that work, the airworthiness directive mandates that 787 pilots be briefed on the problem and use a revised fan-ice removal procedure in flight.
When the system indicator in the cockpit lights up to indicate an ice buildup, or when ice buildup is suspected due to high engine vibration, the pilots are instructed to momentarily rev both engines close to full throttle every five minutes.
Kennedy said this latest icing problem is not related to an earlier engine issue that affected a series of GEnx-powered 787s in 2013, in which ice crystals built up inside the core of the engine at very high altitudes under certain unusual weather conditions. That issue was fixed by modifying the engine-control software.