Turboprops are engines that deliver jet thrust and move propellers. Turbos are added to the back of the engine, and the propeller is moved by a gearbox.
Turboprops work like turbojets, but instead of using a fan to compress the air, they use a turbine to do the job.
Turbojets produce more power than turboprops because they are much larger. Turbine engines use the heat of combustion to turn a shaft that spins a fan or drives a turbine.
This produces more thrust than a jet engine because there is less air resistance.
Turbos also have a higher efficiency rate because they do not need an afterburner to increase thrust. Let’s look at these fascinating machines in a bit more detail.
Turboprop engines move air in opposite directions. Air enters the engine through large intakes under the wing, then flows back toward the firewall. Then it turns around and flows forward again before entering the combustion chamber.
After passing the final axial-flow compressor stage, the air goes into a centrifugal-flow compressor stage. The air makes an additional 90-degree turn.
Combustors need to be designed to handle high-pressure air coming out of a compressor. The diffusers slow down the airflow, making it easier to start a flame.
Fuel nozzles send fuel into the air stream, making a fuel/oxygen mixture that can be burned.
Liners have many inlets, letting air into the combustion area. Igniters are the last part of the combustion process.
They start the fire by lighting up the fuel. They turn off once the flame starts. In the snow, they are used as a backup system (see also “Can Planes Fly In Snow?“).
Turbines produce thrust by turning blades around a central hub. When the blades turn, air moves over them creating pressure, pushing the plane forward. This process is called propeller thrust.
Reducing the rotation of the engine reduces the amount of power produced by the turbine. Thrust is generated when the blades rotate at high speeds.
Exhaust air isn’t used for anything useful. It’s simply redirected away from the engine and into exhaust pipes. Some planes show how much thrust is produced by exhaust gas alone.
This is usually very low compared to the rest of the engines’ output. Propellers still win!
Alan Arnold Griffith invented a new type of compressor, but it wasn’t used until after World War II.
During this time, Frank Whittle developed an entirely different type of compressor, which became known as the turbojet. This led to the development of turboprop aircraft.
Turbine engines were first tested in the 1930s. Jendrassik C-1, with a power of 1,000 hp, was designed by Hungarian engineer Jenö Jendrassik in 1939. He built an experimental engine in the Ganz works in Budapest.
This engine had 15 compressors and 7 turbines. The engine operated on compressed air. The compression ratio was 10:1. The combustion chamber was annular and first run in 1940.
Combustion problems limited the engine’s output to 400 hp and the engine was abandoned because of the war.
In 1945, the factory was turned over for conventional engine production. The first British turboprop engines were the Rolls-Royce R.B.50 Trent and the Pratt & Whitney Wasp Junior.
These two engines powered the first British turboprop aircraft, the Gloster Meteor EE227, which had two Rolls-Royce T.R.Dart engines.
This made the world’s first turbofan-powered aircraft. However, this test bed wasn’t intended for production.
The first turboprop aircraft was developed by the USSR. It was called NK-12. The NK stands for Nachalo Khimoy (Начало Химой).
The 12 means that this engine is a twelve-cylinder engine. This engine was used in the first four-engine turboprop aircraft. The first prototype of the NK-12 was flown on 16 July 1948. It was piloted by A.V. Smirnov.
A turboprop plane flies at a lower speed than a very light jet. This allows a shorter route. Flight times are similar. Medical evacuation by plane is an efficient method of transporting patients from remote areas.
The Pilatus PC12 is an excellent choice for this type of mission due to its performance, ability to land anywhere, and the fact that it can carry specific medical equipment.
Turboprops are more reliable than other kinds of engines because they don’t require oil or gas. Their reliability makes them cheaper than other engines.
Only aircraft not surpassing 700 km/h are equipped with turboprop engines. The speed of the airflow hitting the propellers creates supersonic shockwaves.
At 800 km/h, a third part of the length of the blade is hit, reducing the efficiency of the plane 50%. This makes flight impossible.
The Comfort Of Planes
Turboprop aircraft are being modernized. Modern aircraft, such as the Pilatus PC-12 NGX, now offer comfort similar to that of a Private Jet.
However, most propeller aircraft suffer from noise insulation problems and a lack of high tech tools on board.
Turboprops are luxury planes, but they aren’t as high-tech as jets. Their engines are more efficient than jet engines, but they also produce a lot of noise.
Turboprops are less powerful than jets, but they are also safer. The external propeller slows down the plane when it stops and they also have internal fan blades which slow down the plane even faster.
Turboprops have a longer range than jets, and they are cheaper to operate. In addition, Turboprop planes need less runway space than jets.
Turboprops are considered safer than jets because they use two engines instead of one. Piston planes are less safe than turbines because if one engine fails, then the plane is likely to crash.
Turboprop planes are designed to fly at lower altitudes and slower speeds than jet airplanes. This means that turbulence is less likely to affect them.
These planes also tend to stay below 30,000 feet. Planes flying above this altitude are more likely to experience turbulence.
So, we see that Turboprop engines are an innovative invention and being utilized the world over as an efficient and safe way to travel.