Service difficulty reports (SDR)Piston 21 December-20 January 2020 By staff writers - Apr 22, 2021 463 PISTON LYCOMING IO540 AE1A5 – ATA 8520 RECIPROCATING ENGINE POWER SECTION – VALVE GUIDE – JAMMED. DR 612054591 Low rotor annunciator & horn. Engine guide valve seized a valve open. Share this article PrintemailFacebook0TwitterLinkedin