NTSB makes safety recommendations to FAA.
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Press Release Summary:
National Transportation Safety Board recommends that FAA revise Advisory Circular AC-27 Certification of Normal Category Rotorcraft and AC-29 Certification of Transport Category Rotorcraft, to include long-term durability testing of adhesive bond joints for helicopter blades to ensure safe operation. It also recommends that FAA require Robinson Helicopter Corporation to develop nondestructive inspection technique capable of consistently detecting bonding defects.
Original Press Release:
NTSB Safety Recommendations A-08-25 through -29
The National Transportation Safety Board makes the following recommendations to the Federal Aviation Administration:
Revise Advisory Circular (AC)-27, "Certification of Normal Category Rotorcraft," and AC-29, "Certification of Transport Category Rotorcraft," to include long-term durability testing of adhesive bond joints for helicopter blades to ensure safe operation throughout their design life in all environments and operating load spectrums that the blades will experience and to set service life limits accordingly.
(A-08-25)
Require Robinson Helicopter Corporation to develop a nondestructive inspection technique or combination of techniques capable of consistently detecting bonding defects, such as voids, debonds, and weak (kissing) bonds, in bond areas between the skin and spar at the tip of the blade and between the skin and tip cap for R22 and R44 model helicopters. (A-08-26)
Require that all Robinson Helicopter Corporation main rotor blades be inspected using the effective and reliable nondestructive inspection method(s) developed in response to Safety Recommendation A-08-26 at intervals appropriately less than 596 hours time in service (TIS), which investigations have shown to be the earliest known TIS at which debonding occurs, to evaluate the bond joints between the skin and spar at the tip of the main rotor blade and between the skin and tip cap to find bonding defects. (A-08-27)
Amend Airworthiness Directive 2007-26-12 and add requirements that the main rotor blades are to be inspected for crack(s) in the paint layer at the skin-to-spar bondline. Main rotor blades that contain a crack in the paint layer at the skin-to-spar bondline should be removed from service. (A-08-28)
Review the manufacturing processes and continued airworthiness requirements for blades manufactured by companies other than Robinson Helicopter Corporation, and, for those using adhesive bonding, determine if sufficient durability testing and inspections of adhesive bonds are in place to ensure the safe operation of the blades without failure throughout their designed life expectancy in all environmental and operating load spectrums that the blades will experience. (A-08-29)
