While conducting a survey flight at Ambalindum Station
(approximately 135 km north-east of Alice Springs, NT), the pilot
of a Robinson R22 Beta helicopter, registered VH-HZB, noticed
severe vibration of the main rotor assembly and cyclic controls.
The pilot landed the helicopter immediately, and a subsequent
inspection revealed that a length of aerofoil skin had peeled back
from the leading edge on the underside of one of the main rotor
blades.
A review of the current information surrounding Robinson
helicopter blade debonds found a number of previous incidents
involving a similar failure mechanism. Additionally, the issue of
main rotor debond had been addressed by a number of airworthiness
directives (ADs) issued by the Civil Aviation Safety Authority
(CASA) and the Federal Aviation Authority (FAA), along with a
number of safety alerts and service letters issued by the
manufacturer.
Debonding of the main rotor blade skin was considered to have
been influenced by extensive surface erosion observed around the
leading edges of the blade. Additionally, the investigation found
no evidence to suggest that the actions contained within the
current CASA Airworthiness Directive addressing blade debonding
issues (AD/R22/54) had been integrated into the helicopter's
maintenance routine. The logbooks and maintenance release documents
for the helicopter have since been updated to include reference to
AD/R22/54 Amdt 3.