The NTSB has issued an “urgent” safety recommendation calling for a redesign of the Rolls-Royce RB211 Trent 800 Series engines in Boeing 777s after two separate reported incidents of thrust rollbacks due to ice accumulation on the engines’ fuel/oil heat exchanger (FOHE). The recommendation follows a revised FAA AD issued last week for Boeing 777-200s and -300s equipped with Rolls-Royce Trent 800 engines that mandates changes to step-climb procedures to reduce the chance that ice accumulation on the FOHE results in fuel blockage.
However, while the Safety Board acknowledged that the procedures can reduce the risk of a rollback due to FOHE ice blockage, the Board expressed concern that they add complexity to flight crew operations and exposure to other risks including rising terrain, hazardous weather and the inability of engines to achieve maximum thrust during a critical phase of flight, such as during a missed approach.
Rolls-Royce has already told authorities that it has begun a redesign of the FOHE, and that it expected to test, certify and install the modified parts within 12 months. The NTSB recommendation also asks aviation authorities to require operators of Boeing 777-200s powered by the Trent engines in question to install the redesigned FOHE “at the next scheduled maintenance opportunity or within six months after the revised FOHE design has been certificated, whichever comes first.”
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