AIRWORTHINESS DIRECTIVE For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section. Enstrom F-28 Series Helicopters AD/ENST 28/38 Main Rotor Hub Plates 3/2004 Applicability: Model TH-28 and 480 helicopters, with main rotor upper hub plate part number 28- 14280-1, and main rotor lower hub plate part number 28-14281-1, installed. Requirement: 1. Create a component history card or equivalent record for the upper hub plate part number 28-14280-1, and the lower hub plate part number 28-14281-1, and determine the total hours time in service. Thereafter, record the hours time in service for each hub plate and replace each hub plate upon accumulation of 5,000 hours time in service as follows: 1. Install hub plates, part number 28-14280-3 and 28-14281-3, on helicopters with main rotor damper part number 28-14375-8 installed. b. Install hub plates, part number 28-14280-5 and 28-14281-5, on helicopters with main rotor damper part number 28-14375-10 installed. 2. This Directive revises the Limitations section of the applicable maintenance manual by establishing a life limit of 5,000 hours time in service for the upper hub plate part number 28-14280-1, and for the lower hub plate part number 28- 14281-1. Note: FAA AD 2001-25-02 Amdt 39-12554 refers. Compliance: 1. Within 30 days after 18 March 2004, unless already accomplished. 2. From the effective date of this Directive. This Airworthiness Directive becomes effective on 18 March 2004. Enstrom F-28 Series Helicopters AD/ENST 28/38 (continued) Background: This Directive is issued in response to the related FAA AD, which was prompted by a reliability-based stress analysis that indicates a 5,000 hour life limit should be imposed on certain hub plates. The actions specified by this Directive are intended to prevent failure of a hub plate, loss of control of the main rotor, and subsequent loss of control of the helicopter. David Villiers Delegate of the Civil Aviation Safety Authority 4 February 2004 The above AD is notified in the Commonwealth of Australia Gazette on 25 February 2004.