General Electric

Following a thorough review of NPRM FAA-2007-27687, proposing an AD for GE CF34-1A, CF34-3A, CF34-3A1, CF34-3A2, CF34-3B, and CF34-3B1 engines resulting from an updated analysis, GE proposes the following items for consideration: 1. Paragraphs (h), (i), (k), and (l) provide instructions for initial and recurrent inspections of specific fan disks identified by SN as Tier 1 (paragraph (h) and (k)) or Tier 2 (paragraph (i) and (l)) but do not explicitly state these fan disks must be removed from service by September 30, 2018. The referenced GE S/B CF34-AL S/B 72-A0252 and GE S/B CF34-BJ S/B 72-A0235 recommend removing the affected fan disks from service by September 30, 2018 and this is included in the proposed AD as Mandatory Terminating Action in paragraph (o). For further clarity, GE recommends adding removal instructions as new paragraphs in each section as follows: (h)(3) For Tier 1 fan disks, listed by P/N, SN, and Tier in Table 1 of GE ASB CF34– AL S/B 72–A0233, Revision 04, dated October 27, 2008, remove fan disks from service no later than September 30, 2018. (i)(3) For Tier 2 fan disks, listed by P/N, SN, and Tier in Table 1 of GE ASB CF34– AL S/B 72–A0233, Revision 04, dated October 27, 2008, remove fan disks from service no later than September 30, 2018. (k)(3) For Tier 1 fan disks, listed by P/N, SN, and Tier in Table 1 GE ASB CF34– BJ S/B 72–A0212, Revision 04, dated October 27, 2008, remove fan disks from service no later than September 30, 2018. (l)(3) For Tier 2 fan disks, listed by P/N, SN, and Tier in Table 1 GE ASB CF34– BJ S/B 72–A0212, Revision 04, dated October 27, 2008, remove fan disks from service no later than September 30, 2018. 2. Paragraph (j)(1) provides instructions for inspection of Tier 3 parts not previously inspected using GE S/B CF34-AL S/B 72-A0233 R3 or prior revision and says: “Use paragraph 3.A of the Accomplishment Instructions of GE ASB CF34–AL S/B 72–A0253, Revision 04, dated October 27, 2008.” This appears to be a typo as there have been no revisions to S/B 72-A0253. GE recommends the SB reference be changed to read as follows: “Use paragraph 3.A of the Accomplishment Instructions of GE ASB CF34–AL S/B 72–A0233, Revision 04, dated October 27, 2008.” 3. Paragraph (k) provides instructions for Tier 1 parts in business jet applications. The paragraph reads: “For CF34–1A turbofan engines with fan drive shaft, P/N 6036T78P02, and airworthiness limitation section life limit of 15,000 CSN, CF34–3A, CF34–3A2, and CF34–3B turbofan engines with Tier 1 fan disks listed by P/N, SN, and Tier in Table 1 of GE ASB No. CF34–BJ S/B 72–A0212, Revision 04, dated October 27, 2008, do the following:” The CF34-3A1 application has been omitted from the description, and the fan drive shaft life limit distinction has been applied to the CF34-1A model. This could be misleading for operators, so for accuracy GE recommends the paragraph be modified to read as follows: “For CF34–3A1 turbofan engines with fan drive shaft, P/N 6036T78P02, and airworthiness limitation section life limit of 15,000 CSN, and CF34–1A, CF34–3A, CF34–3A2, and CF34–3B turbofan engines with Tier 1 fan disks listed by P/N, SN, and Tier in Table 1 of GE ASB No. CF34–BJ S/B 72–A0212, Revision 04, dated October 27, 2008, do the following:” This same correction would also apply to paragraph (l) for Tier 2 parts and paragraph (m) for Tier 3 parts. 4. Paragraph (k)(1)(i) provides instructions to “Perform a TEV inspection, FPI, and ECI on the Tier 1 fan disks within 350 CIS after the effective date of this AD. Use paragraph 3.A of the Accomplishment Instructions of GE ASB CF34–BJ S/B 72–A0212, Revision 04, dated October 27, 2008, to perform the TEV inspection.” For clarity, GE recommends the end of the above paragraph be modified to read as follows: “…to perform the TEV inspection, FPI, and ECI.” 5. Paragraph (l)(1)(i) provides instructions for inspection of Tier 2 fan disks operating in business jet applications. The compliance instructions in (l)(1)(i) are written as: “Perform a TEV inspection, FPI, and ECI on the Tier 2 fan disks within 2,000 CIS after the effective date of this AD, or within 3,500 CIS after September 12, 2007, or by March 19, 2012, whichever occurs first.” For consistency with the GE risk assessment GE recommends that “…3,500 CIS after September 12, 2007…” be amended to read “… 3,500 CSN….” This is consistent with the GE SB instructions and prior communication with the operators. 6. Paragraph (m) provides instructions for the inspection of Tier 3 fan disks operating in business jet applications. Paragraph (m)(2) covers the Tier 3 parts which have previously been inspected to GE SB CF34-BJ S/B 72-A0212 R3 or prior revision. The compliance time instructions in this paragraph differ from those provided in the GE SB and also for the comparable instructions for the regional jet applications (paragraph (j)(2)). GE recommends the paragraph be modified to read as follows: “For Tier 3 fan disks, listed by P/N, SN, and Tier in Table 1 of GE ASB No. CF34– BJ S/B 72–A0212, Revision 04, dated October 27, 2008; already inspected using GE ASB No. CF34–BJ S/B 72–A0212, Revision 03, dated June 27, 2007, or earlier issue, perform a TEV inspection and an ECI on the Tier 3 fan disks within 3,500 CSLI, but no later than March 19, 2012 at the next shop visit. Use paragraph 3.A of the Accomplishment Instructions of GE ASB CF34–BJ S/B 72– A0234, dated October 27, 2008, to perform the TEV inspection and ECI.” The March 19, 2012 compliance date will force a repeat inspection on these Tier 3 parts, which have already been inspected previously to GE SB CF34-BJ S/B 72- A0212 R3 or prior, before repeat inspection of previously inspected Tier 1 and Tier 2 fan disks. Removing the date and changing the compliance to be “at the next shop visit” will ensure that the recommended actions for the Tier 3 parts are not elevated to a higher level than that for the Tier 1 and Tier 2 parts. This is consistent with the risk assessment for the field program. The affected parts have already been inspected in the most critical areas and compliance with SB CF34- BJ S/B 72-A0234 at next shop visit will ensure they get the enhanced inspections that were introduced in CF34-BJ S/B 72-A0212 R4. 7. SB CF34-AL S/B 72-A0233 R4, CF34-AL S/B 72-A0252 and CF34-AL S/B 72-A0253 apply both to regional jet operators and also to a small number of business jet operators who fly under the RJ manual. These business jet applications may include both CF34-3B1 and CF34-3A1 models. The proposed AD distinguishes between regional jet and business jet applications based on engine model and, in the case of the CF34-3A1 model, the life limit of the fan drive shaft, P/N 6036T78P02. For consistency between GE service bulletin instructions and the proposed AD, GE recommends that another method of separating the CF34-3A1 model into the appropriate population be used for enhanced clarity. GE recommends the following suggestions for consideration. A. GE recommends the use of aircraft model and version number. The business jet operators who fly under the RJ manual are operating CL-600-2B19 aircraft (versus business jet operators who fly under the BJ manual and are operating CL- 600-2B16 aircraft). The engines on the CL-600-2B19 can be either CF34-3A1 or CF34-3B1 engines and include the Corporate Jet Liners (converted regional jet aircraft), Challenger 850SE, and Challenger 850 aircraft. The aircraft with the early CF34-1A engines were certified as CL-600-2A12 and then they moved to CL-600- 2B16 (these are the CL601-3R, CL604 and CL605). The pertinent paragraphs would then read as follows: (h) “For CF34–3A1 engines with fan drive shaft, P/N 6036T78P02, and airworthiness limitation section life limit of 22,000 CSN, or CF34–3A1 engines with fan drive shaft, P/N 6036T78P02, and airworthiness limitation section life limit of 15,000 CSN that are operating on a CL-600-2B19 certified aircraft and CF34–3B1 turbofan engines with Tier 1 fan disks listed by P/N, SN, and Tier in Table 1 of GE ASB No. CF34–AL S/B 72–A0233, Revision 04, dated October 27, 2008, do the following:” The same addition would apply to paragraph (i) for Tier 2 part and paragraph (j) for Tier 3 parts. Incorporating this recommended change as well as that from item 3 above, paragraph (k) would then read: (k) “For CF34–3A1 turbofan engines with fan drive shaft, P/N 6036T78P02, and airworthiness limitation section life limit of 15,000 CSN that are operating on a CL- 600-2A12 or CL-600-2B16 certified aircraft, and CF34–1A, CF34–3A, CF34–3A2, and CF34–3B turbofan engines with Tier 1 fan disks listed by P/N, SN, and Tier in Table 1 of GE ASB No. CF34–BJ S/B 72–A0212, Revision 04, dated October 27, 2008, do the following:” The same addition would apply to paragraph (l) for Tier 2 part and paragraph (m) for Tier 3 parts. B. If use of the certified aircraft model is not feasible, GE then recommends the use of the model designation and service bulletin number engraved on the engine name plate. The life limits for CF34 engine models are established on the basis of the model designation and, for 3A1/3B1 engines operating under the Regional Jet manual, the service bulletin number engraved on the engine name plate. Service bulletin CF34-AL S/B 72-0146 and CF34-AL S/B 72-0147 cover the use of CF34- 3A1/3B1 engines in regional jet and business jet applications, respectively. These bulletins define the appropriate life limit chapters to be used. Incorporating this change, the pertinent paragraphs would then read as follows: (h) “For CF34–3A1 engines with fan drive shaft, P/N 6036T78P02, and airworthiness limitation section life limit of 22,000 CSN, or CF34–3A1 engines with fan drive shaft, P/N 6036T78P02, and airworthiness limitation section life limit of 15,000 CSN that are in compliance with GE SB CF34-AL S/B 72-0147, and CF34– 3B1 turbofan engines with Tier 1 fan disks listed by P/N, SN, and Tier in Table 1 of GE ASB No. CF34–AL S/B 72–A0233, Revision 04, dated October 27, 2008, do the following:” The same addition would apply to paragraph (i) for Tier 2 part and paragraph (j) for Tier 3 parts. Incorporating this recommended change as well as that from item 3 above, paragraph (k) would then read: (k) “For CF34–3A1 turbofan engines with fan drive shaft, P/N 6036T78P02, and airworthiness limitation section life limit of 15,000 CSN that are not in compliance with GE SB CF34-AL S/B 72-0147, and CF34–1A, CF34–3A, CF34–3A2, and CF34–3B turbofan engines with Tier 1 fan disks listed by P/N, SN, and Tier in Table 1 of GE ASB No. CF34–BJ S/B 72–A0212, Revision 04, dated October 27, 2008, do the following:” The same addition would apply to paragraph (l) for Tier 2 part and paragraph (m) for Tier 3 parts. C. If the above recommendations are not acceptable, at a minimum, the addition of CF34-AL S/B 72-A0233 R4 as a reference in paragraphs (k), (l) and (m) is recommended to allow business jet operators who fly under the regional jet manual to determine whether they have any of the affected fan disks installed. These operators may not have ready access to SB CF34–BJ S/B 72–A0212 R4 and would have difficulty determining whether they are affected by the proposed AD. Incorporating this recommended change as well as that from item 3 above, paragraph (k) would then read: “For CF34–3A1 turbofan engines with fan drive shaft, P/N 6036T78P02, and airworthiness limitation section life limit of 15,000 CSN, and CF34–1A, CF34–3A, CF34–3A2, and CF34–3B turbofan engines with Tier 1 fan disks listed by P/N, SN, and Tier in Table 1 of GE ASB No. CF34–BJ S/B 72–A0212, Revision 04, dated October 27, 2008, or alternately, listed in Table 1 of GEAE SB CF34–AL S/B 72–A0233, Revision 04, dated October 27, 2008, do the following:” The same addition would also apply to paragraph (l) for Tier 2 parts and paragraph (m) for Tier 3 parts. Modifying the proposed AD to reflect these changes would more clearly identify affected populations and still meet the FAA’s purpose in issuing the Airworthiness Directive.