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Which of the following statements are correct for turbo-prop powered aircraft? 1. The propulsion efficiency of turboprop is higher than that of turbo-jet and rockets for low speeds up to about 800 km/hr. 2. For the same thrust the turbine in the turbo-prop aircraft is smaller than in the turbo-jet aircraft 3. For the turbo-prop the flight velocity cannot exceed the jet velocity.

Which of the following statements are correct for turbo-prop powered aircraft? 1. The propulsion efficiency of turboprop is higher than that of turbo-jet and rockets for low speeds up to about 800 km/hr. 2. For the same thrust the turbine in the turbo-prop aircraft is smaller than in the turbo-jet aircraft 3. For the turbo-prop the flight velocity cannot exceed the jet velocity. Correct Answer 1 and 3 only

Concept:

Turboprop powered aircraft are suitable for low speed and low altitudes only. They are efficient because a large amount of thrust is obtained from the propeller run by a power turbine. Theoretically, the maximum speed obtained is equal to gas speed.

The size of the turboprop is higher than the turbojet because in the turboprop, the turbine runs propeller and compressor and 90% thrust comes from the propeller. While to turbojet main thrust comes from the jet and very little power is consumed by the compressor. So, for this little power, the turbine size is small. Hence only statements 1 and 3 are correct.

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