Tuesday, August 18, 2015

GE presses to lift icing limits on 787, 747-8 engines

GE Aviation plans to roll out a new software upgrade that could finally remove the last of the operating restrictions imposed two years ago on one of the engines that power the Boeing 787-8.

The pending release of software version B185 for the engine’s full authority digital engine control (FADEC) system represents GE’s latest attempt to resolve the ice crystal icing (ICI) problem for the GEnx engine family.

Several GEnx engines – including GEnx-2B models powering the 747-8 – experienced power loss after ingesting tiny crystals as aircraft flew into strong tropical thunderstorms at high altitude.

In hopes of fixing the problem, GE has since rolled out FADEC software versions B178 and B180.
After building up on fan blades, the ice crystals eventually begin to shed, potentially entering the compressor and extinguishing the combustor. The software allows the FADEC to detect the conditions when shedding is likely.

At that point, the FADEC commands a set of variable bleed valve doors – normally used to scoop up foreign objects swallowed by the engine during take-off – to open, allowing ice crystals to shed harmlessly into the bypass air flow around the engine core.

The US Federal Aviation Administration had previously barred aircraft powered by the GEnx-1B or GEnx-2B from flying within 50nm of a storm that had the potential of producing high-altitude ice crystals.

But the release of software versions B178 and B180 prompted the FAA to relax the restrictions, allowing the 787 to operate below 37,500ft in such conditions and the 747-8 to fly below 35,500 without changing their routes.

The latest B185 software is almost ready and could convince the FAA to remove the operating restrictions entirely, GE says. GE validated the software modfications after analyzing more than 12,00 hours of GEnx flight data and conducting tests at the company’s cold-temperature facility in Winnipeg, Canada.

(Stephen Trimble - Flightglobal News)

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