AD 2003-08-52 Airworthiness Directives; GE Aircraft Engines CT7-9B Turboprop Engines

This AD applies to GEAE CT7-9B turboprop engines. These engines are installed on, but not limited to Saab Aircraft AB 340B airplanes.

Compliance with the requirements of this AD is required as indicated unless already done. Determining Compressor VG Rigging Schedule (f) Determine which schedule was used to rig the compressor VG. The serial numbers (SNs) contained in Table 1 of this AD are known to have been rigged to VG schedule N1. Engines with SNs that are not listed in Table 1 might be rigged to VG schedule N1. You must review the engine records to determine if the engines are rigged to VG schedule N1 using GEAE Service Bulletin (SB) No. CT7-TP S/B 72-0241, dated April 6, 1990. Table 1 follows: Table 1.—SNs of Engines Known to Have Been Rigged to VG Schedule N1             785102 785104 785106 785107 785109 785111 785112 785113 785117 785118 785125 785128 785129 785131 785133 785136 785138 785148 785150 785151 785152 785154 785160 785185 785188 785211 785231 785232 785234 785235 785237 785239 785241 785257 785259 785265 785266 785275 785322 785325 785326 785334 785375 785391 785400 785459 785460 785462 785465 785474 785476 785477 785480 785481 785487 785499 785506 785534 785538 785554 785569 785591 785592 785598 785603 785700 785759 Rigging the Compressor VG to Schedule N (g) If the compressor VGs of both engines on the airplane are rigged to VG schedule N using GEAE SB CT7-TP S/B 72-0328 dated June 9, 1992 or GEAE Alert Service Bulletin (ASB) CT7-TP S/B 72-A0328, Revision 1, dated April 8, 2003 no further action is required. (h) If the compressor VGs on both engines on the airplane are rigged to VG schedule N1, do the following: (1) Within 30 flight hours (FH) or 3 days after the effective date of this AD, whichever occurs later, rig the compressor VG on one engine to VG schedule N in accordance with 3.A.(1) through 3.A.(12) of the Accomplishment Instructions of GEAE ASB No. CT7-TP S/B 72-A0328, Revision 1, dated April 8, 2003. (2) Within 100 FH or 10 days after the effective date of this AD, whichever occurs earlier, rig the compressor VG on the remaining engine to VG schedule N in accordance with 3.A.(1) through 3.A.(12) of the Accomplishment Instructions of GEAE ASB No. CT7-TP S/B 72-A0328, Revision 1, dated April 8, 2003. (i) If the compressor VG on one engine on the airplane is rigged to VG schedule N1, within 100 FH or 10 days after the effective date of this AD, whichever occurs earlier, rig the compressor VG to VG schedule N in accordance with 3.A.(1) through 3.A.(12) of the Accomplishment Instructions of GEAE ASB No. CT7-TP S/B 72-A0328, Revision 1, dated April 8, 2003. Installation of Engines With VG Schedule N1 (j) After the effective date of this AD, do not install any CT7-9B turboprop engine that is rigged to VG schedule N1 on to any Saab Aircraft AB 340B airplane. Alternative Methods of

This AD was prompted by reports of 12 compressor stall events that occurred over a six month period. The actions specified in this AD are intended to prevent a dual-engine in-flight shutdown or power loss due to a compressor stall during deceleration from takeoff power to climb power.