AD/ENST 28/9 Amdt 4 - Main Rotor Mast (Cth)

AIRWORTHINESS DIRECTIVE For the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/ENST 28/9 Amdt 3 and issues the following AD under subregulation 39.1 (1) of CAR 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 28/9 Amdt 4

Main Rotor Mast 10/2002 DM

Applicability: Model F-28, F-28A, F-28C, F-28F, 280, 280C, 280F, and 280FX helicopters.

Requirement: 1. Determine the part number of the main rotor transmission, and the radius of the upper fillet of the shaft as specified in Figure 1 of Enstrom Helicopter Corporation Service Directive Bulletin (SDB) No. 0094 Revision 2, dated 15 February 2002.

2. For Model F-28C, F-28F, 280C, 280F, and 280FX helicopters, replace any transmission having a small radius shaft fillet with a serviceable transmission having large radius fillet as specified in Table 1 of SDB No. 0094 Revision 2.

3. For Model F-28, F-28A, and 280 helicopters:

(a) If the transmission has a shaft with a small radius fillet and the transmission part number is not listed in Table 1 of SDB No. 0094 Revision 2, replace the transmission with a serviceable transmission specified in Table 1 of SDB No. 0094 Revision 2.

(b) If the installed transmission is part number 28-13101-1 or -1-R, or part number 28-13101-3 or -3-R, and has a small radius shaft, visually inspect each transmission for a crack in the shaft upper fillet using a 10X or higher magnifying glass.