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/R44/18 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 R44 Series Helicopters


AD/R44/18 Amdt 1

Main Rotor Blades

5/2006
 
Applicability:
All R44 Series Helicopters.
Requirement:
Perform the following inspection on the entire leading edge (from blade root to tip) of both main rotor blades: (a)   Visually inspect the upper and lower skin-to-spar seams (See figure 1 for the skin-to-spar seam location) for: (i)    Cracks in paint; (ii)   Evidence of sections of blade skins bulging up during flight; or (iii)   Any other indication of skin separation, such as opening up of the skin-to-spar seam. Note:  A wedge or triangular shaped section of bare metal with its leading edge at the bond seam, is a possible indicator of skin disbonding. (b)   Tap test the 0.50 inch bond joints which are situated aft of the upper and lower skin-to-spar seams (See figure 1 for bond joint location).  Inspect skins carefully for any evidence of bulging or skin disbonding in this area. (c)   If the visual or tap test in (a) and (b), respectively, indicates that the skin has disbonded, immediately remove the blade from service and quarantine the blade.  A Major Defect Report form specifying the blade serial number, total time in service and a detailed description of the extent of the damage, must also be submitted to CASA. Note:  The “Tap test” in (b) is to be performed in accordance with standard maintenance practices for bonded metallic structures, taking appropriate care not to cause new or additional disbonding.
 
 
Figure 1: Main Rotor Blade Cross Section showing inspection locations.
Compliance:
Unless already accomplished, immediately before further flight and thereafter every 25 flight hours, or if rotor vibration develops suddenly or progressively during a flight or over several flights. This Directive shall be entered on the Maintenance Release as maintenance required. The required visual inspection and “tap check” may be performed and certified by a Pilot in Command who has been trained to do the inspection by an appropriately qualified person.  In this case, a copy of this Directive is to be carried in the aircraft.
 
This Amendment becomes effective on 11 May 2006.
Background:
Main Rotor Blade skin disbond and separation at the skin-to-spar seam have been found on the tip of two R44 Main Rotor Blades.  If not detected, skin disbond and separation may lead to catastrophic failure of the rotor blade.  The original issue of this Airworthiness Directive was intended as an interim action until the investigation was completed and the disbond mechanism was better understood. This amendment relaxes the compliance time from “At each daily inspection” to “every 25 flight hours” and adds a requirement to perform the inspection immediately, if main rotor vibration increases over a short period.  A review of cases of skin disbond found since this AD was first released in April 2003, has revealed that there have been two additional cases of skin disbond detected and reported.  Given the apparent infrequency and moderate growth rate of these skin disbonds, an inspection every 25 hours will be sufficient to detect a disbond before it becomes serious.  The inspection must also be carried out if main rotor vibration increases over 1 or more flights, anytime between the mandatory 25 hourly inspections.  Significant disbonds and blade skin leading edge lifting will be indicated by increased rotor vibration that is not able to be corrected by a blade track and balance.
     
 
The original issue of this Airworthiness Directive became effective on
28 February 2003.
David Villiers
Delegate of the Civil Aviation Safety Authority 31 March 2006