The FAA and Pratt & Whitney Canada believe they have found the cause of three high-altitude double engine flameouts on Pratt & Whitney Canada JT15D-5-powered Beechjets between mid-2004 and mid-2006. An investigation by the FAA, NTSB, P&WC and Raytheon Aircraft (now Hawker Beechcraft) led to modified operating procedures for the Beechjet in late 2006, but a proposed Airworthiness Directive issued on Friday reveals that the problem could affect other JT15D-powered aircraft, including Mitsubishi Diamonds, 500-series Cessna Citations and Hawker 400XPs. According to the FAA, its investigation into the Beechjet incidents revealed that the engine’s fuel control hydromechanical unit (HMU) P3 servo can be exposed to excessive moisture and freezing and can subsequently cause a flameout. To preclude P3 servo freezing, P&WC issued a JT15D alert service bulletin to reroute compressor delivery air to the HMU and improve moisture separation. The FAA’s proposed rule would mandate the fixes for aircraft with affected JT15D-5 engines within 200 flight hours after the AD’s effective date or by December 31, whichever occurs first.