Calls For Main Rotor Inspections To Address Delaminating
Issues
Earlier this week, the National
Transportation Safety Board made 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)
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