THIS paper on helicopter gas turbines is divided into two parts. The first compares the performances of two helicopters, one powered with a two-shaft free turbine and the other with a single-shaft fixed turbine. The second part considers the engine and rotor control problems associated with each type of powerplant.
Part one of the paper discusses helicopter performance advantages arising from the flexibility of the free turbine. Also, several modes of helicopter operation for each turbine are considered in two flight plans. Advantages in helicopter hovering time and range for various methods of turbine operation are assessed on the basis of steady-state engine performance.
Part two of the paper considers the transient behavior of the two types of powerplants under several control actions. Anticipated helicopter maneuvers during a flight plan are studied. Various combinations of powerplants, powerplant schedules of operation, control systems, and helicopter maneuvers, are used to indicate control problems.