SERVICE LETTER NO. L282 Australian Fuel Testing DATE: December 11, 2020 TO: Australian Robinson R22 and R44 Owners and Operators REASON FOR PUBLICATION: This Service Letter transmits information pertaining to recent engine testing performed on Avgas grades used in Australia and the United States.

DATE RELEASED: February 19, 2021 TITLE: YO-233-B2A Maintenance Manual DOCUMENT PART NUMBER: MM-YO-233 (Supersedes Maintenance Manual LM-YO-233, dated June 2012)

SERVICE LETTER NO. L283 Alternate Ignition System DATE: February 19, 2021 TO: All Owners and Operators of Lycoming YO-233 Series engines REASON FOR PUBLICATION: This Service Letter is announcing the availability of an alternate ignition system to replace the Champion Aerospace Electronic Ignition System (Lycoming P/N 66K26674-Y) on YO-233 Series engines. Installing this alternate ignition system...

SERVICE LETTER NO. L284 Blemish on Cylinder Barrel DATE: March 17, 2021 TO: All Owners and Operators of Lycoming O-235 Series engines REASON FOR PUBLICATION: This Service Letter is in response to reports of a blemish in the black oxide coating of P/N 16A26616 Cylinder Assemblies.

SERVICE INSTRUCTION NO. 1569 B DATE: April 21, 2020 SUBJECT: Installation, Operation, and Maintenance of Lycoming Electronic Ignition System (EIS) MODELS AFFECTED: Lycoming 4 and 6-Cylinder piston aircraft engines TIME OF COMPLIANCE: At the owner/operator’s discretion. REASON FOR REVISION: Revised the SUBJECT line. Formatted pages 4 through 18 to indicate separation between Installation, Operation...

Service Bulletin No. 642A Incorrect Piston and Ring Combination June 16, 2021 MODELS AFFECTED O-235-C, E & H series, and Factory Cylinder Kit P/N 05K23039 TIME OF COMPLIANCE Within the next 10 hours of operation or next scheduled maintenance event, whichever occurs first. REASON FOR REVISION: Deleted NOTICE “Only cylinders that …”. Added CAUTION and instructions for cylinder replacement before the...

SERVICE INSTRUCTION NO. 1280 D DATE: July 20, 2021 SUBJECT: Rotator Type Intake Valves MODELS AFFECTED: All Lycoming engines built with the conventional, large head intake valve No. 73117 including: IO-360-A, -C, -D; AIO-360-A, -B; HIO-360-A, -C; LIO-360, TIO-360-A, IO-720-A, -B, -C; VO, IVO, TVO, TIVO-540; IGO, IGSO-540, IO-540-A,B,E,G,K,L,M,P,S; TIO-540-A,F,J,N and LTIO-540-F,J,N. Engines...

SERVICE LETTER NO. L287 Increased Fuel Economy and Improved Manifold Pressure Stability DATE POSTED: August 17, 2021 TO: Owners and Operators of Lycoming TEO-540-C1A REASON FOR PUBLICATION: Announcement to TEO-540-C1A operators for the availability of the new ECU calibration and components to increase the fuel economy and improve the manifold pressure stability.

SERVICE LETTER NO. L285 Change in cylinder configuration for O-235-C, -E, and -H Series engines DATE: August 25, 2021 TO: All Owners and Operators of Lycoming O-235-C, -E, and -H Series engines REASON FOR PUBLICATION: Lycoming supplied cylinders for O-235-C, -E, and -H Series engines were previously plain steel, straight-bore cylinders. This design has been replaced with nitrided, choke-bore...