Hong Kong Aircraft Engineering Co. Ltd.

Reference: A AD2011-02-07 B AD 2010-12-10 C AD 2010-06-15 For B747/CF6-50, the AD( Ref.A) deficiencies/queries as follows: 1. HPT1-2B BSI a/ Inspect for signs of impact ,cracking ,burning, damage, or distress on any areas of the blade airfoil. No acceptance limits is given in Ref.A. Does it means any findings, even well within AMM limits is rejectable and a FPI must be performed before next flight? Would USI per SB72-1312R01 considered an acceptable equivalent to FPI? b/No AMM reference quoted. Is it “AMM 72-00-00,601or B72-1307R01”? c/Ref C requires “ Actions required whenever the HPT rotor blade cumulative airfoil material loss is 50% of a blade or more”. It is more restrict than current AMM 72-00-00,601 limits. Is it purposely deleted in Ref. A and now use AMM limits for engine acceptance instead? 2. EGT thermocouple probe inspection. a/No AMM reference quoted. Is it “BSI for TMF Liner clocking per AMM 72-00-00,601 and 72-52-00 or SB72-1307R01 ”? b/Recent GE Webex meeting mentioned the probes must be removed for GVI. Is it required for AD Ref.A compliance? 3. EGT System resistance check inspection. a/No AMM reference quoted. Is it “AMM-21-00,601 or SB72-1307R01”? 4. Ultrasonic Inspection of the LPT rotor stage 3 disk forward spacer arm. a/No mention of shop credit. Is it SB 72-1309R00 (FPI or USI)? FPI equivalent to USI? 5. Engine core vibration survey a/The reference SB72-1313R01 is a one time vibration check only. Would it be revised to reflect the repetitive 350FC requirement and include the AD reference? b/FPI would be required if failing the vibration survey. Could we perform the on- wing USI per SB1312R01 instead?