AD 2025-02-12 Airworthiness Directives; Austro Engine GmbH Engines

Makes named: austro. Models named: E4, E4P. Read the applicability below — it usually turns on serial or part numbers too.

This AD applies to Austro Engine GmbH Model E4 and E4P engines with an engine serial number (ESN) listed in Tables 1, 2, 3, and 4 of Austro Engine GmbH Mandatory Service Bulletin No. MSB-E4-039/3, Revision 3, dated November 22, 2023 (Austro MSB-E4-039/3).

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

(1) For all affected engines, within the applicable compliance times specified in table 1 to paragraph (g)(1) of this AD, perform an oil analysis in accordance with paragraph 2., Technical Details, Engine Oil Analysis of Austro MSB-E4-039/3, and do not return the engine to service until the results of the oil analysis have been determined. Table 1 to Paragraph ( g )(1)—Oil Analysis for All Affected Engines Engine group Compliance time Interval Group 1 and Group 3 engines that do not have an ESN identified in table 2 to paragraph (g)(1) of this AD Within 15 flight hours (FHs) from December 11, 2023 (the effective date of AD 2023-20-03) Before exceeding 50 FHs since last oil analysis. Group 1 and Group 3 engines that have an ESN identified in table 2 to paragraph (g)(1) of this AD Within 15 FHs from the effective date of this AD Before exceeding 50 FHs since last oil analysis. Group 2 and Group 4 engines that do not have an ESN identified in table 2 to paragraph (g)(1) of this AD Within 25 FHs from December 11, 2023 (the effective date of AD 2023-20-03) Before exceeding 100 FHs since last oil analysis. Group 2 and Group 4 engines that have an ESN identified in table 2 to paragraph (g)(1) of this AD Within 25 FHs from the effective date of this AD Before exceeding 100 FHs since last oil analysis. Table 2 to Paragraph ( g )(1)—Affected ESNs Not Included in AD 2023-20-03 Engine group ESN ESN ESN ESN Group 1 E4-A-06367 E4-A-06248 Group 2 E4-C-06249 E4P-C-06185 Group 3 E4-A-05072 E4-A-05074 E4-A-05075 E4-A-05078 Group 3 E4-A-05079 E4-A-05080 E4-A-05081 E4-A-05082 Group 3 E4-A-05083 E4-A-05084 E4-A-05085 E4-A-05086 Group 3 E4-A-05087 Group 4 E4-C-00559 E4-C-05089 E4-C-05090 E4-C-05091 Group 4 E4-C-05092 E4-C-05093 E4-C-05094 E4-C-05096 Group 4 E4-C-05098 E4-C-05099 E4-C-05100 E4-C-05101 Group 4 E4-C-05102 E4-C-05103 E4-C-05104 E4-C-05105 Group 4 E4-C-05106 E4-C-05107 E4-C-05108 E4-C-05109 Group 4 E4-C-05110 E4-C-05111 E4P-C-06073 (2) Thereafter, repeat the oil analysis required by paragraph (g)(1) of this AD before exceeding the applicable interval specified in table 1 to paragraph (g)(1) of this AD. (3) Following each repetitive oil analysis, the engine may be returned to service for no more than the applicable interval specified in table 1 to paragraph (g)(1) of this AD, until receipt of the oil analysis result. (4) If the result of any oil analysis required by paragraph (g)(1) of this AD indicates the aluminum content of the oil is greater than the limit specified in paragraph 2., Technical Details, Engine Oil Analysis, Table 5—Oil check analysis Aluminum PPM allowable; of Austro MSB-E4-039/3, before further flight, replace the pistons, piston rings, con-rods assembly, and crankcase, or replace the engine core in accordance with paragraph 2., Technical Details, Engine core replacement; or Pistons, piston rings, crankcase and con-rod assy replacement; as applicable, of Austro MSB-E4-039/3. (5) For Group 3 and Group 4 engines, within the applicable compliance times specified in table 3 to paragraph (g)(5) of this AD, replace the pistons, piston rings, and con-rods assembly, or replace the engine core in accordance with paragraph 2., Technical Details, Engine core replacement; or Pistons, piston rings and con-rod assy replacement, as applicable, of Austro MSB-E4-039/3. Table 3 to Paragraph ( g )(5)—Replacement for Group 3 and 4 Engines Engine group Compliance time Group 3 engines that do not have an ESN identified in table 2 to paragraph (g)(1) of this AD Before exceeding 900 FHs since new, or within 15 FHs after December 11, 2023 (the effective date of AD 2023-20-03), whichever occurs later. Group 3 engines that have an ESN identified in table 2 to paragraph (g)(1) of this AD Before exceeding 900 FHs since new, or within 15 FHs after the effective date of this AD, whichever occurs later. Group 4 engines that do not have an ESN identified in table 2 to paragraph (g)(1) of this AD Before exceeding 1,000 FHs since new, or within 25 FHs after December 11, 2023 (the effective date of AD 2023-20-03), whichever occurs later. Group 4 engines that have an ESN identified in table 2 to paragraph (g)(1) of this AD Before exceeding 1,000 FHs since new, or within 25 FHs after the effective date of this AD, whichever occurs later. Note 1 to paragraph (g)(5): FHs since new indicated in table 3 to paragraph (g)(5) of this AD are FHs accumulated by the engine since first installation on an airplane or since last overhaul as of December 11, 2023 (the effective date of AD 2023-20-03) for Group 3 and 4 engines that do not have an ESN identified in table 2 to paragraph (g)(1) of this AD, or as of the effective date of this AD for Group 3 and 4 engines that have an ESN identified in table 2 to paragraph (g)(1) of this AD.

This AD was prompted by reports of piston failures and the determination that certain batches of pistons were manufactured with a dimensional deviation in the piston pin bore and piston diameter. The FAA is issuing this AD to prevent piston failure. The unsafe condition, if not addressed, could result in loss of oil, loss of engine power, and reduced control of the airplane.

This AD replaces AD 2023-20-03, Amendment 39-22562 (88 FR 76104, November 6, 2023) (AD 2023-20-03).