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Syllabus Dot Point
propulsion systems including
– internal combustion engines
– jet including turbofan, ram and scram
– turboprop
– rockets
Internal Combustion Engine
The internal combustion (IC) engine is the powerplant used on almost all light general aviation aircraft today. Electrical aircraft motors promise a new and cleaner aviation future but are still a way off, powering prototypes but, have not yet entered mainstream adoption.
Turbojet Engine
A jet engine is a gas turbine engine. A jet engine develops thrust by accelerating a relatively small mass of air to very high velocity, as opposed to a propeller, which develops thrust by accelerating a much larger mass of air to a much slower velocity. Part of the expansion of the burned gases takes place in the turbine section of the jet engine providing the necessary power to drive the compressor, while the remainder of the expansion takes place in the nozzle of the tail pipe in order to accelerate the gas to a high velocity jet thereby producing thrust.
What is the difference between a turboprop and a jet?
The main difference between a turboprop and a jet is that a turboprop is a jet engine turning a propeller. Turboprops are a hybrid of jet engines and the more traditional piston engine propeller that you see on smaller, lightweight airplanes.
Turboprops are reliable options and were designed to fill the gap between high speed, high altitude jets and low flying light airplanes.
Turboprop vs Jet Safety
Both turboprops and jets are powered by turbine engines, so they are essentially the same thing and thus, are considered to be equally as safe. The main difference is that turboprops have a propeller on the outside of the engine while jets have fan blades inside the engine housing.
One area where turboprops might get the nod is on smaller runways. Because of the drag propellers cause, they actually allow the aircraft to stop much more quickly than a jet. This is important because of something pilots call the ‘balanced field.’ The balanced field refers to how quickly you can stop during takeoff in the event something goes wrong. In this balanced field scenario, turboprops get the nod.
A more legitimate safety question is the safety factors between turboprops and jets vs pistons. Turboprops and jets are considered safer, and especially those with twin engines.
Ramjet
A ramjet is a form of airbreathing jet engine that uses the engine's forward motion to compress incoming air without an axial compressor or a centrifugal compressor. Because ramjets cannot produce thrust at zero airspeed, they cannot move an aircraft from a standstill. A ramjet-powered vehicle, therefore, requires an assisted take-off like a rocket assist to accelerate it to a speed where it begins to produce thrust. Ramjets work most efficiently at supersonic speeds around Mach 3 (3,700 km/h) and can operate up to speeds of Mach 6 (7,400 km/h). Ramjets can be particularly useful in applications requiring a small and simple mechanism for high-speed use, such as missiles.
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