The most famous Free Power Turbine Engine ever produced is the PT6. The major benefits of a free power turbine are the following:
1. Nil Negative torque feedback. With direct drive turbines in fixed wing , NTS (negative torque sensing) is required as rapid decelerating can cause what is called prop loading especailly on descent.
2. Less moving parts ease of servicing.
3. More robust less suseptible to F.O.D. ie centrifugal compressors commonly used.
Dissadvantages:
1. There is s delay in using reverse pitch as the turbine needs to accerate before the propellor actuator can become effective. Some aircraft call for high idle prior to landing in reverse required landings.
2. cant think of another but there are more .
Anyone care to elaborate?
Sheep