COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 107 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Propellers - Variable Pitch - MT AD/PMTV/1 Blade Root Lag Screws 4/99 DM Applicability: MTV-3-B-C/L250-21 and MTV-9-B-C/CL250 or /CL260-27 model propellers manufactured prior to 31 December 1998 and installed on Vedeney M-14-P or M-14- PF engines. Requirement: Check lag screw torque in accordance with MT-Propeller Service Bulletin (SB) 17, Revision A, dated 5 March 1999. Incorporation of new blade root lag screws in accordance with SB 17, Revision A, constitutes terminating action for this check. Note 1: LBA ADs 1999-081/2 and 1999-082/2 also refer. Note 2: Propellers inspected per the original issue of SB 17 satisfy the intent of this Directive. Compliance: Unless previously accomplished, prior to next flight after effective date of this airworthiness directive. Thereafter at intervals of 100 hours time in service or 12 months, whichever occurs first. This Airworthiness Directive becomes effective on 17 March 1999. Background: This airworthiness directive is prompted by reports of broken blade root lag screws in certain models of MT propellers installed on aerobatic aircraft. Lag screw breakage is attributed to loss of torque. Fractured lag screws can lead to blade separation and loss of control of the aircraft.