Inspections have revealed premature exhaust valve and valve guide wear in a number of Robinson R22 and R44 helicopters used primarily in livestock mustering in northern Australia, according to Australia’s Civil Aviation Safety Authority (CASA).
In Airworthiness Bulletin (AWB) 85-025, issued earlier in December, CASA said that it is working with other government agencies and an industry working group to identify the cause of the problem, which has affected R22s with Lycoming O-360 engines and R44s with Lycoming O-540 engines. The focus has been on the way the helicopters are operated, possible fuel issues, carburetor set up and failure modes, CASA said.
“It has also been speculated that during extended ground operations at low manifold pressure and high rpm, the intake valve rocker arm oil is migrating down the …
