AD/R22/36 Amdt 1 Main Rotor Blades 2 (Cth)

AIRWORTHINESS DIRECTIVE

On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/R22/36 and issues the following AD under subregulation 39.001(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.

Robinson R22 Series Helicopters

AD/R22/36 Amdt 1 Main Rotor Blades - 2 10/2005

Applicability:

All helicopters with MRB part numbers A016-1 and A016-2.

Requirement:

Conduct a close visual inspection of both main rotor blade upper and lower skins, looking for cracks originating in the vicinity of the trailing edge, in the general area from the trailing edge rivet (241 cm from the tip) to the blade station 30 cm outboard of the trailing edge rivet.

Compliance:

Inspect before reaching 500 hours component time in service, or before further flight after 24 August 1992, whichever is the latter, then repeat inspection at intervals not to exceed 25 hours component time in service.  Additionally, inspect before further flight if there has been any unusual vibration which may be related to the main rotor blades.

This directive shall be entered on the maintenance release as maintenance required. The required visual inspection may be performed and certified by a Pilot in Command who has been trained to do the inspection by an appropriately qualified person.

This Amendment becomes effective on 29 September 2005.

Background:

There was a report, in the early 1990’s, of one main rotor blade with both the top and bottom skins cracked, from the trailing edge, forward for 150mm in a chordwise direction, to the spar.  These cracks are believed to have initiated at a small corrosion pit on the aft edge of the main rotor blade trailing edge and propagated very rapidly, possibly in as little as a few cycles.  The corrosion that may cause these cracks is evidenced by small blisters in the paint on the trailing edge aft surface, and can be readily detected by sliding the fingers along the trailing edge bond line.

Note:  A more detailed inspection for corrosion in this area is part of the 100 hourly main rotor blade corrosion inspection and is therefore not specifically included in this directive.

This amendment is issued to exclude the Part Number A016-4 blade from the applicability, because the manufacturer, Robinson Helicopter Co, has advised that this blade has a stainless steel skin that is not susceptible to stress corrosion cracking. Only P/N A016-1 and A016-2 blades are affected.  There are no changes to the requirements or compliance in this amendment.

David Villiers
Delegate of the Civil Aviation Safety Authority

9 August 2005