June 26, 2015 CFM56/GAU_004_15 

 

Subject: Subject: CFM International S.A. comments for FAA NPRM - Docket No. AA2015-0277; Directorate Identifier 2015–NE–05–AD, dated May 1, 2015. 

Airworthiness Directives; CFM International S.A. Turbofan Engines. 

To whom it may concern, 

CFM has reviewed the subject NPRM. Please find the related comments attached. 

Thanks and Best Regards, 

Gregory Uhler 

ODA RCE, EASA CVE 

GE Aviation 

Airworthiness and Certification 

T +1 513 552 3438 

M +1 513 275 8861 

gregory.uhler@ge.com
 

 

CFM Comments: Docket No. FAA-2015-0277; Directorate Identifier 

2015–NE–05–AD 

 

In “Summary” Section: 

Current: 

This proposed AD was prompted by reports of uncommanded in-flight shutdowns (IFSDs) on CFM CFM56–7B 

engines following rupture of the 73-tooth gearshaft located in the engine accessory gearbox (AGB). This proposed 

AD would require magnetic chip detector (MCD) inspection of the affected gearshafts until removal. 

To: 

This proposed AD was prompted by reports of one uncommanded in-flight shutdown (IFSD) on CFM CFM56–7B 

engines following rupture of the 73-tooth gearshaft located in the engine accessory gearbox (AGB). This proposed 

AD would require AGB/TGB magnetic chip detector (MCD) inspection of the affected gearshafts until removal. 

Reason: Clarification that there was only one un-commanded IFSD. Clarification as to which MCD to inspect. 

In “Discussion” Section: 

Current : We have received reports of uncommanded IFSDs on CFM CFM56–7B engines following rupture of the 

73-tooth gearshaft located in the engine AGB. 

To: We have received reports of one uncommanded IFSD on CFM CFM56–7B engines following rupture of the 73-

tooth gearshaft located in the engine AGB. 

Reason: Clarification that there was only one un-commanded IFSD. 

Current: The proposed AD requires enhanced MCD inspection until removal of the gearshaft.

To: The proposed AD requires enhanced AGB/TGB MCD inspection until removal of the gearshaft. 

Reason: Clarification as to which MCD to inspect. 

In “Relevant Service Information Under 1 CFR Part 51” Section 

Current: The SBs describe procedures for removal of affected 73- tooth and 41-tooth gearshafts. 

To: The SBs list the affected gearshaft serial numbers and describe procedures for removal of affected 73- tooth and 

41-tooth gearshafts. 

Reason: Expand definition of SB contents. 

In “Proposed AD Requirements” Section 

Current: This proposed AD would require an MCD inspection within 250 FHs since last inspection or within 25 

FHs after the effective date of this AD, whichever comes later. 

To: After the effective date of this AD, the proposed AD would require an AGB/TGB MCD inspection within 250 

FHs since last inspection or within 25 FHs, or before 3000 FHs since first installation for 73 tooth or before 6000 

FHs since first installation for 41 tooth whichever comes later.

Reason: Conform AD requirements to SB requirements regarding inspection times. 

In “Differences Between This Proposed AD and the Service Information” Section 

Current: CFM SB CFM56–7B S/B 72–0964, Revision 1, dated December 15, 2014, recommends performing a 

MCD inspection 250 FHs since last inspection or as soon as possible if the inspection was done more than 250 FHs 

ago. 

To: CFM SB CFM56–7B S/B 72–0964, Revision 1 (or later revision), dated December 15, 2014, recommends 

performing a MCD inspection 250 FHs since last inspection or as soon as possible if the inspection was done more 

than 250 FHs ago.

Reason: Include provision for later revisions of SB. 
 

 

In “PART 39—AIRWORTHINESS DIRECTIVES” Section 

(c) Applicablity 

Current: ... CFM Service Bulletin (SB) CFM56–7B S/B 72–0964, Revision 1, dated December 15, 2014. 

To: ... CFM Service Bulletin (SB) CFM56–7B S/B 72–0964, Revision 1 (or later revision), dated December 15, 

2014.

Reason: Include provision for later revisions of SB. 

(d) Unsafe Condition 

Current: This AD was prompted by reports of uncommanded in-flight shutdowns on CFM CFM56–7B engines 

following rupture of the 73-tooth gearshaft located in the engine AGB. 

To: This AD was prompted by reports of one uncommanded in-flight shutdown on CFM CFM56–7B engines 

following rupture of the 73-tooth gearshaft located in the engine AGB.

Reason: Clarification that there was only one un-commanded IFSD. 

(e) Compliance 

Current: For affected 73-tooth gearshafts, perform an MCD inspection within 250 flight hours (FHs) since last 

inspection, within 25 FHs from the effective date of this AD, or when the gearshaft accumulates 3,000 FHs since 

new, whichever comes later.

To: For affected 73-tooth gearshafts, perform an AGB/TGB MCD inspection within 250 flight hours (FHs) since 

last inspection, within 25 FHs from the effective date of this AD, or when the gearshaft accumulates 3,000 FHs 

since new, whichever comes later.

Reason: Clarification as to which MCD to inspect. 

(e) Compliance 

Current: For affected 41-tooth gearshafts, perform an MCD inspection within 250 FHs since last inspection, within 

25 FHs from the effective date of this AD, or when the gearshaft accumulates 6,000 FHs since new, whichever 

comes later.

To: For affected 41-tooth gearshafts, perform an AGB/TGB MCD inspection within 250 FHs since last inspection, 

within 25 FHs from the effective date of this AD, or when the gearshaft accumulates 6,000 FHs since new, 

whichever comes later.

Reason: Clarification as to which MCD to inspect. 

(e) Compliance 

Current : If any magnetic particles, including fuzz, are seen, determine with particles lab analysis if the particles are 

73-tooth or 41-tooth gearshaft material.

To: If any magnetic particles, including fuzz, are seen, determine with laboratory analysis if the particles are 73-

tooth or 41-tooth gearshaft material.

Reason: Conform AD requirements to SB requirements. 

(e) Compliance 

Current : 

(i) For affected 73-tooth gearshafts, perform an MCD inspection and particles lab analysis within every 500 FHs 

since the last MCD inspection until affected gearshaft is removed. 

(ii) For affected 41-tooth gearshafts, perform an MCD inspection and particles lab analysis within every 500 FHs 

since the last MCD inspection until affected gearshaft is removed. 

(iii) If any magnetic particles, including fuzz, are seen, determine with particles lab analysis if the particles are 73-

tooth or 41-tooth gearshaft material. 

To: 

(i) For affected 73-tooth gearshafts, perform an AGB/TGB MCD inspection and laboratory analysis within every 

500 FHs since the last MCD inspection until affected gearshaft is removed. 
 

 

(ii) For affected 41-tooth gearshafts, perform an AGB/TGB MCD inspection and laboratory analysis within every 

500 FHs since the last MCD inspection until affected gearshaft is removed. 

(iii) If any magnetic particles, including fuzz, are seen, determine with laboratory analysis if the particles are 73-

tooth or 41-tooth gearshaft material. 

Reason: Conform AD requirements to SB requirements and clarify which MCD is to be inspected. 

Additional Comment applicable to FAA NPRM and EASA PAD: 

If the Agencies include the CFM56-3 series engines in this proposed AD, CFM suggests that the affected part serial 

numbers be listed in the AD instead of the referencing the SBs, as CFM56-3 operators may not have access to the 

CFM56-7B Service Bulletins.. 

Reason: Provide Agencies with additional information regarding the CFM56-3.