Airworthiness directives › 2021-21-05
AD 2021-21-05 Airworthiness Directives; General Electric Company Turbofan Engines
Applicability*9
This AD applies to General Electric Company (GE) GEnx-1B64, GEnx-1B64/P1, GEnx-1B64/P2, GEnx-1B67, GEnx-1B67/P1, GEnx-1B67/P2, GEnx-1B70, GEnx-1B70/75/P1, GEnx-1B70/75/P2, GEnx-1B70/P1, GEnx-1B70/P2, GEnx-1B70C/P1, GEnx-1B70C/P2, GEnx-1B74/75/P1, GEnx-1B74/75/P2, GEnx-1B76/P2, GEnx-1B76A/P2, GEnx-2B67, GEnx-2B67/P, and GEnx-2B67B model turbofan engines.
Compliance
Comply with this AD within the compliance times specified, unless already done.
Required actions
(1) For all affected GEnx-1B model turbofan engines, within 120 days of the effective date of this AD, revise the operator's existing FAA-approved minimum equipment list (MEL) by incorporating into the MEL the dispatch restriction specified in Figure 1 to paragraph (g)(1) of this AD, as a required operation or maintenance procedure. Note 1 to paragraph (g)(1): Specific alternative MEL wording to accomplish the actions specified in Figure 1 can be approved by the operator's principal operations or maintenance inspector. ER23NO21.189 (2) For all affected GEnx-2B model turbofan engines, within 120 days of the effective date of this AD, revise the operator's existing FAA-approved MEL by incorporating into the MEL the dispatch restriction specified in Figure 2 to paragraph (g)(2) of this AD, as a required operation or maintenance procedure. Note 2 to paragraph (g)(2): Specific alternative MEL wording to accomplish the actions specified in Figure 2 can be approved by the operator's principal operations or maintenance inspector. ER23NO21.190 (3) For all affected engines, before the EEC reaches 11,000 cycles since new, replace the EEC MN4 microprocessor using an approved overhaul procedure. (i) If the number of accumulated cycles on the EEC MN4 microprocessor cannot be determined through operator maintenance logs or FADEC International shop visit reports, before the EEC exceeds 12 years since entry into service (EIS) for affected GEnx-1B model turbofan engines or 14 years since EIS for affected GEnx-2B model turbofan engines, replace the EEC MN4 microprocessor using an approved overhaul procedure. (ii) [Reserved] (4) Thereafter, replace the EEC MN4 microprocessor before accumulating 11,000 cycles since the last replacement.
Unsafe condition
This AD was prompted by an in-service occurrence of loss of engine thrust control resulting in uncommanded high thrust. The FAA is issuing this AD to prevent dispatch of the airplane when certain conditions caused by degradation of the MN4 microprocessor in the electronic engine control (EEC) are present. The unsafe condition, if not addressed, could result in loss of engine thrust control and reduced control of the airplane.
Affected ADs
None.
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