AD 2021-22-16 Airworthiness Directives; Airbus Helicopters

Models named: EC 155B, EC155B1. Read the applicability below — it usually turns on serial or part numbers too.

This AD applies to Airbus Helicopters Model EC 155B and EC155B1 helicopters, certificated in any category.

Comply with this AD within the compliance times specified, unless already done.

(1) For helicopters with at least one Type Y planet gear assembly with a serial number (S/N) listed in Appendix 4.A. of Airbus Helicopters Alert Service Bulletin ASB No. EC155-05A034, Revision 5, dated December 4, 2018 (ASB EC155-05A034 Rev 5) or with at least one Type Z planet gear assembly with an S/N listed in Appendix 4.B. of ASB EC155-05A034 Rev 5 installed, within 10 hours time-in-service (TIS) after the effective date of this AD, and thereafter at intervals not to exceed 10 hours TIS, inspect the MGB magnetic plugs for particles. If there are any particles that consist of any scale, flake, splinter, or other particle other than cotter pin fragments, pieces of lock wire, swarf, abrasion, or miscellaneous non-metallic waste, and any of the planet gears have accumulated less than 50 total hours TIS, before further flight, inspect the MGB filter for particles. Thereafter, for 25 hours TIS, continue to inspect the MGB plugs for particles before each flight, inspect the MGB filter for particles at intervals not to exceed 25 hours TIS, and inspect the cumulative surface area of the particles collected from the magnetic plugs, the MGB filter, since last MGB overhaul, or since new if no overhaul has been performed. Note 1 to the introductory text of paragraph (g)(1): Airbus Helicopters service information refers to an MGB filter as an oil filter. (i) If the total surface area of the particles is less than 3 mm 2 , examine the particles with the largest surface area (S), greatest length (L), and greatest thickness (e). (A) If any (S) of all of the particles is less than or equal to 1 mm 2 , the (L) is less than or equal to 1.5 mm, and the (e) is less than or equal to 0.2 mm, inspect the MGB plugs for particles before further flight, and inspect the MGB filter for particles within 25 hours TIS. Thereafter: ( 1 ) For 25 hours TIS, continue to inspect the MGB plugs for particles before each flight and perform the actions required by paragraphs (g)(1)(i) and (ii) of this AD. ( 2 ) Inspect the MGB filter for particles at intervals not to exceed 25 hours TIS and perform the actions required by paragraphs (g)(1)(i) and (ii) of this AD. (B) If any (S) is greater than 1 mm 2 , (L) is greater than 1.5 mm, or (e) is greater than 0.2 mm, perform a metallurgical analysis for any 16NCD13 particles, using a method in accordance with FAA-approved procedures. (C) If there are any 16NCD13 particles, before further flight, replace the MGB with an airworthy MGB. (ii) If the total surface area of collected particles is greater than or equal to 3 mm 2 , before further flight, perform a metallurgical analysis for any 16NCD13 particles using a method in accordance with FAA-approved procedures. If there are any 16NCD13 particles, before further flight, replace the MGB with an airworthy MGB. (2) For helicopters with at least one Type Y planet gear assembly with an S/N listed in Appendix 4.A. of ASB EC155-05A034 Rev 5 installed, within 25 hours TIS after the effective date of this AD, inspect the MGB filter for particles. If there are any particles that consist of any scale, flake, splinter, or particle other than cotter pin fragments, pieces of lock wire, swarf, abrasion, or miscellaneous non-metallic waste, and any of the planet gears have accumulated more than 50 total hours TIS, before further flight, perform the actions required by paragraphs (g)(1)(i) and (ii) of this AD. (3) For helicopters with at least one Type Y planet gear assembly with an S/N listed in Appendix 4.A. of ASB EC155-05A034 Rev 5 installed, within 50 hours TIS after the effective date of this AD, replace the MGB or as an alternative to replacing an affected MGB, replace the epicyclic reduction gear module in the affected MGB in accordance with paragraph 3.B.2. of the Accomplishment Instructions of Airbus Helicopters Service Bulletin SB No. EC155-63-016, Revision 5, dated March 6, 2019 (SB EC155-63-016 Rev 5), except you are not required to contact Airbus Helicopters. (4) For helicopters without any Type Y planet gear assembly installed but with at least one Type Z planet gear assembly with an S/N listed in Appendix 4.B. of ASB EC155-05A034 Rev 5 installed, within 50 hours TIS after the effective date of this AD, or before any gear accumulates 1,800 total hours TIS, whichever occurs later, replace the MGB or as an alternative to replacing an affected MGB, replace the epicyclic reduction gear module in the affected MGB in accordance with paragraph 3.B.2. of the Accomplishment Instructions of SB EC155-63-016 Rev 5, except you are not required to contact Airbus Helicopters. (5) For helicopters with at least one Type Z planet gear assembly with an S/N listed in Appendix 4.B. of ASB EC155-05A034 Rev 5 installed, inspect the MGB filter for particles within the compliance times specified in Figure 1 to paragraph (g)(5) of this AD and inspect the oil sump for particles within the compliance times specified in Figure 2 to paragraph (g)(5) of this AD, based on the total hours TIS accumulated by the Type Z planet gear with the most total hours TIS accumulated since first installation in an MGB. If there are particles, before further flight, perform the actions required by paragraphs (g)(1)(i) and (ii) of this AD. Figure 1 to Paragraph ( g )(5) Total hours TIS accumulated Compliance time for initial inspection Compliance time for repetitive inspections Less than 400 total hours TIS Within 55 hours TIS after the effective date of this AD Within 55 hours TIS. 400 or more total hours TIS Within 25 hours TIS after the effective date of this AD Within 25 hours TIS. Figure 2 to Paragraph ( g )(5) Total hours TIS accumulated Compliance time for initial inspection Compliance time for repetitive inspections Less than 400 total hours TIS Before exceeding 400 hours TIS after the effective date of this AD Within 55 hours TIS. 400 or more total hours TIS Within 55 hours TIS after the effective date of this AD Within 55 hours TIS. (6) As of the effective date of this AD, do not install a type Y planet gear assembly with an S/N listed in Appendix 4.A. of ASB EC155-05A034 Rev 5 on any helicopter, and do not install an MGB with a Type Y planet gear assembly with an S/N listed in Appendix 4.A. of ASB EC155-05A034 Rev 5 on any helicopter. (7) As of the effective date of this AD, do not install a Type Z planet gear assembly with an S/N listed in Appendix 4.B. of ASB EC155-05A034 Rev 5 that has accumulated 1,800 or more total hours TIS on any helicopter, and do not install an MGB with at least one Type Z planet gear assembly with an S/N listed in Appendix 4.B. of ASB EC155-05A034 Rev 5 that has accumulated 1,800 or more total hours TIS on any helicopter. (8) As of the effective date of this AD, do not install any planet gear on any helicopter if the planet gear assembly type cannot be determined, and do not install any MGB on any helicopter if any of the planet gear assembly types cannot be determined.

This AD was prompted by the failure of a main gearbox (MGB) second stage planet gear. The FAA is issuing this AD to prevent failure of an MGB planet gear assembly. The unsafe condition, if not addressed, could result in failure of the MGB and subsequent loss of helicopter control.

None.