1AD/HILLER 12/24 Amdt 4 - Main Rotor Blade Doubler & Honeycomb Areas

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY

SCHEDULE OF AIRWORTHINESS DIRECTIVES

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Hiller UH-12 Series Helicopters

AD/HILLER 12/24

Amdt 4

Main Rotor Blade Doubler & Honeycomb Areas

3/87

Applicability: All models UH-12D, UH-12E, UH-12E4, OH-23F and OH-23G.

All models converted by STC 178WE and STC 177WE fitted with main rotor blades assembly P/N 53200-03.

Requirement: 1. (a) Visually inspect the main rotor blades root doubler area for evidence of delamination. This includes all doublers on the leading and trailing edge surface, upper and lower, from the fork attachment plate to the tip of the outboard doubler.

(b) Visually inspect the main rotor blades for bond separation and voids along the entire length of the blade as shown in Hiller Aviation SB UH-12-51-7 Fig 1 and 2.

2. Inspect and test the main rotor blades for delamination and bond separation, (Tap test), IAW Hiller Aviation SB UH- 12-51-7 and SL 51-3A.

Compliance: 1.(a) & (b) before each flight.

Note: This Directive shall be entered on the Maintenance Release as maintenance required. These inspections may be performed by the pilot in command, in which case certification is not required. A copy of this AD shall be carried in the aircraft.

2. At each scheduled inspection for Maintenance Release issue.

Background: Bond separation has been detected in main rotor blades at the root doubler area and at the tip extending inboard for 24 inches and separation growth has been found to be very rapid on some blades. Amendment 4 to this Directive consolidates the inspections to a visual at each pre-flight inspection and aligns the additional checks with the Maintenance Release issue.