NTSB Takes On Beechjet Flameouts

The National Transportation Safety Board (NTSB) last month formally made four safety recommendations to the FAA concerning recent dual flameouts of engines powering Raytheon Beechjet 400-series airplanes, in part requesting the agency to help educate pilots on the realities of high-altitude engine icing. The recommendation letter [PDF] highlights four separate events — three in U.S. airspace and a fourth over Brazil — in which both Pratt & Whitney Canada (P&WC) JT15D-5 turbofan engines powering the incident aircraft failed at high altitude and their crews were unable to perform restarts in a timely manner. In one incident, the airplane was successfully deadsticked onto a runway at Jacksonville, Fla., while only one engine could be restarted in two of the other events. According to the NTSB, “the ice is believed to be building up on the compressor stator airfoils deep within the engine.”

In its letter, the NTSB formally recommended that the FAA:

• Immediately require Beechjet 400 pilots to activate the engine ignition and anti-ice systems at high altitude whenever they are in or near visible moisture, or near convective storm activity, or before any power reduction.
• Require Raytheon to incorporate previously published information regarding anti-ice operation and ice formation into the Beechjet 400 airplane flight manual.
• Expand the second recommendation, above, to incorporate anti-ice operation and ice formation data into the airplane flight manuals of other JT15D-powered airplanes.
• Actively develop an ice detector that would alert pilots to internal engine icing and require that it be installed on new production turbojet engines and retrofitted to existing turbojet engines.

The NTSB noted what it called “a general perception” among turbine airplane pilots that ice is not a threat at higher altitudes because it is too cold. While that may be true for airframe icing, ambient air has a habit of being heated as it enters a turbine engine, melting any ice. High-altitude power reductions — which seem to be involved in each of the four incidents the NTSB cited — apparently allows that liquid to refreeze, sometimes shutting down the engine.