Saab 340B Compressor Stalls Lead To Emergency AD

 - October 16, 2007, 6:49 AM

Emergency AD 2003-08-52 was issued last month for the GE CT7-9B turboprop in response to 12 compressor-stall events in Saab 340Bs over a six-month period. The stalls occurred when pilots throttled back from takeoff power to climb power. Nine of the events involved engines that had the compressor variable geometry (VG) rigged to N1, one of two allowable rigging options that affords slightly higher performance at the expense of stall margin. Since 1992 GE has recommended that operators use only N, which provides more margin on older engines that are inherently more susceptible to stalling due to wear or deterioration. Under the AD, operators flying aircraft with either one or both engine compressors rigged to VG N1 must reset at least one of the compressors to N.