Turboshaft engines on helicopters flying low or hovering over the ocean and coastal and inshore regions ingest airborne salts that combine with the heat of their turbine sections to corrode blades and other components and increase exhaust gas temperatures. Missions that expose engines to salt-laden air include firefighting, offshore transport, search and rescue operations, anti-submarine and port security patrols, and vertical replenishment work. Exposure to these environments increases the need for aggressive engine washing, reducing aircraft availability; it also drives up maintenance and overhaul costs of the aircraft.
Donaldson, which for several years has investigated how salt ingestion affects helicopter engines, recently concluded a series of extreme tests that exposed an IBF-equipped engine to a high-volume sea water spray. The test used a wind tunnel with a sea water injection system coupled with an aerodynamic particle-size analyzer and a flame photometer to maintain and verify the size and concentration of salts in the airflow.
At the system's designed test airflow, more than 115 grams of salt was fed into the engine filter. Previous engine testing had demonstrated that the ingestion of 30 grams of salt could lead to a 9 percent increase in exhaust gas temperature. The recent testing showed that the oiled filter media in Donaldson IBFs - which today fly on thousands of civil and military helicopters worldwide - allowed 4.5 grams of salt to penetrate the IBF. This salt capture prior to turbine entry can reduce the damaging effects of salt ingestion on an engine.
The positive test results reinforce the benefits reported by many Donaldson maritime IBF operators worldwide over the years.
"Donaldson IBF systems can keep helicopter engines on a salt-free diet," said Eric Erickson, General Manager at Donaldson Aerospace & Defense in St. Louis. "This recent testing demonstrates our commitment to ensuring that Donaldson's customers can perform a wide range of critical missions reliably, affordably and safely."