Following the launch of Pratt & Whitney's investigation into the cause of mysterious surges on newly modified PW4000s, the US Federal Aviation Administration has issued an airworthiness directive (AD) requiring affected operators to limit the number of engines with the revised design to one per aircraft. The AD prohibits further modifications on other engines with the revised "cutback" stator design.
The move follows two surge incidents on Boeing 747-400 and 767-300 aircraft powered by PW4000 engines recently modified with the high pressure compressor (HPC) cutback stator module (Flight International, 24-30 October).
P&W meanwhile is running the suspect engines in its Wilgoos test site in Connecticut to evaluate what caused the surges.
Source: Flight International
