CASA warns about R44 exhaust systems

Operators and maintainers of Robinson R44 helicopters are being warned in a new airworthiness bulletin of the dangers of engine exhaust system failures.

CASA has received a number of reports of collapsed R44 engine exhaust mufflers inside the cabin heater shroud, as well as severely burnt cabin heating hoses.

These failures pose a danger because if cabin heating is selected when a muffler has collapsed inside the heater shroud, carbon monoxide can enter the cabin putting the pilot at risk of incapacitation.

Investigations of the muffler failures have found a number of contributing factors.

These include magneto timing problems, mixture equipment malfunctions and incorrect exhaust muffler cooling rigging.

A new airworthiness bulletin provides details about how to address these three issues.

CASA also points out that Robinson considers the installation of a carbon monoxide detector in the R44 cabin to be mandatory because engine exhaust gases can enter the cabin in certain circumstances even if the exhaust system is working properly.

R44 helicopters that were not equipped with a detector must be retrofitted.