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Overview of the PT6 Engine

  • The PT6 engine is a widely-used turboprop engine that powers over 100 different aircraft types.

    • Engine models produce varying levels of power.

Power Ratings

  • PT6 A Dash 21 (used on King Air C90): 550 horsepower

  • PT6 A Dash 68 B (used on Pilatus PC 21): 1600 horsepower

  • Turbo shaft versions for helicopters: 900 to 1970 horsepower

Engine Type

  • The PT6 is a type of gas turbine engine, specifically categorized as a reverse flow free turbine turboprop.

    • Reverse Flow: Air enters at the back, flows forward, and exits at the front.

      • This design allows for a shorter power shaft, which results in a lighter structure and fewer vibrations.

    • Free Turbine: The power turbine operates on a separate shaft from the compressor turbine.

      • Advantages include:

        • Different rotational speeds for compressor and power turbine.

        • Easier start-up process, as only the compressor shaft needs to be turned to start.

Engine Components

  • Gas Generator: Comprises the compressor, combustion chamber, and compressor turbine.

    • Purpose: Produces high-pressure, high-temperature gas to drive the power turbine.

Airflow Process

  1. Air Intake: Air enters through the intake at the back of the engine.

  2. Compressor:

    • Consists of 3 or 4 axial stages and a single centrifugal stage.

    • Rotor blades provide kinetic energy, while stator vanes convert kinetic energy to pressure.

  3. Combustion Chamber (Burner):

    • Fuel is injected and burned, raising the air temperature at approximately constant pressure.

  4. Compressor Turbine:

    • A single-stage axial flow turbine extracts energy from the compressed air.

    • This allows the compressor and turbine to be mounted on the same shaft, spinning at the same rate.

  5. Power Turbine:

    • Contains 1 or 2 axial stages depending on the engine model.

    • Extracts energy for the power output.

Power Transmission

  • The power from the power turbine is transmitted through a 2-stage planetary gearbox:

    • High rotation rate and low torque are converted to lower rotation rate and higher torque for the propeller.

Exhaust Process

  • Exhaust gases are vented through a nozzle, still containing residual energy.

    • This residual energy provides a small amount of jet thrust.

Additional Resources

  • Mention of a free course titled "A Brief Introduction to Aviation" covering:

    • Theory of flight

    • Meteorology

    • Flight instruments

    • Enrollment links available in the video description.