An extract from Blakmax's posted link
In addition, the bond joints between the spar and skin of the fractured main rotor blade
from the Fiji accident helicopter contained adhesive fracture features in many isolated areas of
the leading edge of the skin, indicating a weak bond. A weak bond in this area could allow the
leading edge of the skin to lift above the blade surface so that airflow during main rotor rotation
could peel the skin back further. If peel damage to the skin is minor, the main rotor blade will
vibrate irregularly, indicating that the helicopter must be landed immediately. However, if the
degraded bond on the main rotor blade is significant when the skin begins to peel, a large portion
of the skin may peel back suddenly, resulting in catastrophic fracture of the blade and complete
loss of control of the helicopter.
The Safety Board has determined that the adhesive fractures in the main rotor blade from
the Fiji accident helicopter propagated from the blade tip and leading edges and cannot rule out
the possibility that the in-flight breakup was initiated by a bond failure at the tip of the blade.
The indications of deteriorated bond strength uncovered in the main rotor blades highlight the
need for RHC and the Federal Aviation Administration (FAA) to address durability testing and
inspection of adhesive bonds in RHC helicopter blades.
So in addition to the suspect head design, you have suspect blade manufacture. when the crucial parts of your helicopter are held together by glue, you have to be bloody sure you have got the glue process 100% right.