US safety board calls for action after high-altitude engine failures
The US National Transportation Safety Board (NTSB) has called for urgent action from the Federal Aviation Administration over a series of high-altitude, dual-engine flameouts on Beechcraft Beechjet 400 business jets.
The latest incident was in July, when a Beechjet 400 operated by Flight Options suddenly lost power while descending from 41,000ft (12,500m) to 33,000ft in instrument meterological conditions. The pilots were able to restart one of the Pratt & Whitney Canada JT15D-5s and land safely. In another incident, in November, another Beechjet 400 had to make a deadstick landing after total engine failure during a descent from 38,000ft.
There have been three incidents of simultaneous engine failure and one in which the left engine flamed out followed by the right engine 2s later. Initial concerns about de-icing fluid have been dispelled, with attention now focusing on engine ice forming when the aircraft were flying near convective storms.
The NTSB points to P&W's own investigation into the flameouts, which revealed that with engine anti-icing turned off it was possible for ice to build up on the leading edges of the low-pressure compressor stator, leading to compressor surge and/or flameout. The suggestion is that ice crystals melt as they enter the engine then re-freeze on the stator blades.
The NTSB has therefore recommended that the FAA immediately require Beechjet 400 pilots to switch on the engine ignition and anti-icing systems at high altitude or whenever they are in or near visible moisture or convective storm activity. It also wants Raytheon to incorporate the "valuable information" contained in its safety communiqué about anti-ice operation into the Beechjet 400 flight manual as well as the manuals of other JT15D-powered aircraft.
Finally, the NTSB wants the FAA "to work with engine and aircraft manufacturers" to "actively pursue research to develop an ice detector that would alert pilots to internal engine icing".
Source: Flight International