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Though they’re both powered by turbine engines, turboprops and jets are far from the same. Let’s look at turboprop vs jet engines to see which one is better.
A turboprop is a type of jet engine. All jet engines use a mixture of combusted fuel and air to produce exhaust. The main difference is how that exhaust is used. In a turboprop, the exhaust powers a propeller to generate thrust. In a standard jet engine, the exhaust gas is used to generate thrust.
While both turboprop and jet engines are two types of turbine engines, they operate in very different ways and one might be better than the other depending on the conditions and use of the airplane. In this article, you’ll learn what both engine types are, the differences between both, which one is safer, and which one is the better engine design.
When you visit SkyTough, our number one goal is to provide you with the best content on the web that explains everything you want to know about a given topic. With an article like this one, that requires extensive research on our end and input from other experts in the aviation industry. This way when you’re done reading, you’ll know all there is to know about turboprop vs jet airplanes!
What Is A Turboprop Engine?
As mentioned above, a turboprop engine is one of the types of turbine engines that power airplanes. In other words, you can think of a turboprop engine as a type of jet engine, even though that’s what we’re comparing in this article. A bit confusing, I know, but bear with me! You’ll be an expert on turboprop vs jet engines by the end of this article.
More or less, a turboprop engine is a crossover between a jet engine and a piston engine, since it combines the turbine technology from a jet while using a propeller as typically seen on a piston engine airplane. This is where the ingenuity of a turboprop comes into play
Instead of using the exhaust generated from the turbine as thrust to power the airplane, the rotational energy of the turbine is used to spin a propeller. This propeller then, as with piston engines, generates thrust. And since thrust is one of the four necessary forces for flight, this is what powers the turbopro through the skies.
Here’s a bit more detailed information on how a turboprop engine works.
Air enters through the front of the engine and runs through a compressor (or series of compressors) before entering the combustion chamber. Following combustion, the turbine begins to spin as the combusted mixture makes its way through the engine. The turbine spins a shaft that it’s connected to, which then runs into a gearbox.
The gearbox slows the rotation down to the necessary speed, and it’s output shaft spins the attached propeller at the front of the engine. This propeller then creates the aforementioned thrust needed to fly the airplane.
Turboprop airplanes, like other propeller-driven aircraft, typically work most efficiently at lower speeds and altitudes. This is why you usually won’t see turboprops flying at the same extreme speeds or high altitudes that most other types of planes do!
What Is A Jet Engine?
As mentioned above, a turboprop is just one specific type of jet engine. So before we start discussing the differences between the two, let’s take a look at what a jet engine actually is so that you can better understand the comparisons we make below.
A jet engine, often called a gas turbine engine, is one that uses a combination of air and fuel to produce exhaust gas. So far this is just like the turboprop. But what the engine actually does with the exhaust gas is where the magic happens. Let’s look at how jet engines really work to give you an idea of what we’re talking about.
Jet engines rely heavily on intake air, which enters through the front of the engine. As this air goes through the engine, it passes through a compressor (or series of compressors) that increases the pressure and temperature of the air. Following the compressor(s), the hot air enters the combustion chamber where it’s mixed with the specialized jet fuel that planes run on.
The exhaust gasses formed by this combustion then continue along through the engine through a set of turbine blades. These blades take some of the energy from the gasses and further spin the intake and compressor fans. Following the turbines,there is only one place left for the hot, fast-moving exhaust gasses to go.
The exhaust gas is accelerated through the engine and out the back through a tapered nozzle. As the hot exhaust gas escapes the engine at incredibly high speeds, significant amounts of thrust is produced which powers the airplane and enables it to fly through the skies. As you can see, this is entirely different from how a turboprop engine works.
The exhaust gas produces the thrust itself rather than relying on a propeller to generate enough thrust to fly. Since a propeller is no longer needed, jet engines are capable of operating at much higher speeds and altitudes, which is why jet engines are used in most supersonic aircraft.
Turboprop Vs Jet Airplanes: What Are The Differences?
Now that you have an idea of what both turboprop engines and jet engines are, let’s dive a little deeper and check out some of the key differences between the two. The four main areas of interest when comparing different types of airplane engines and how they work are: thrust generation, efficiency and limitations, performance, and safety.
So let’s get into it — turboprop vs jet engines.
If you read through the sections above detailing each engine type and how they work, then you most likely already picked up on the different ways that they produce thrust. So I won’t spend too much time going back through the details. Here’s a quick summary and comparison about how each engine produces the thrust necessary to fly.
Like all propeller airplanes, turboprops generate their thrust from the propellers themselves. To do this, the propeller needs to spin at very high speeds, which it does thanks to the spinning of the turbine inside the engine. Connected through a series of shafts and gears, the turbine directly spins the propeller at the front of the engine to produce thrust. The exhaust gas that leaves the engine is negligible and is not sufficient for any sort of additional thrust.
With a jet engine, the exhaust gas itself is used almost entirely for the production of thrust. As the cold intake air goes through the engine, its temperature and pressure are greatly increased. Once ignited during combustion, the hot exhaust gasses rush through a turbine and finally out of the engine through a tapered nozzle. As the exhaust velocity is increased through the nozzle, massive amounts of thrust can be generated.
In terms of pure power and the amount of thrust that each engine can produce, a jet engine has more capability than a turboprop.
Efficiency and Limitations
Notice in the section above, we had to qualify the final sentence by saying a jet engine has the capability to produce more thrust overall than a turboprop. This is because a turboprop is much more efficient with its propulsion than a jet engine in some circumstances, and vice versa. So now let’s take a look at each of the engine’s efficiency and any sort of limiting factors on their capabilities.
The limiting factors on a turboprop’s efficiency and capability to generate more and more thrust are the propeller speed and blade area. The propeller needs to be able to spin fast enough to create thrust while the blade area needs to be large enough as well. In short, the propeller blade area must increase to proportionally increase the engine’s power output. This can be done by increasing the number of blades, adding chords to the blades, or increasing their lengths.
Jet engines, on the other hand, of course have no limitations when it comes to propeller speed since, well, they don’t have propellers to begin with! Instead, these engines are usually limited only by the internal temperatures inside the engines and the nozzle design. Similarly to how a propeller can only ever spin so fast, a nozzle can only ever speed the exhaust gasses up enough to produce thrust.
So in short, both engine types are limited mostly by speed in one way or another — propeller speed for turboprops and exhaust velocity for jet engines. But what does this really mean in terms of efficiency?
For the most part, turboprop engines thrive at lower speeds, which is where they are most efficient. In fact, turboprops are the most efficient type of gas turbine engine at most subsonic speeds (at least up until nearly 500 mph). At these lower cruising speeds, the turboprop engine produces incredibly high power to weight ratios, which makes it ideal for smaller private planes or bush planes that won’t be traveling nearly as fast or as far as other types of planes.
On the flip side, a jet engine becomes more and more efficient as speed increases, even past the speed of sound. Since the amount of thrust (power) produced is directly related to the amount and velocity of intake air, jet engines are very inefficient at lower speeds, often less than half as efficient as a turboprop.
But when a turboprop’s efficiency drops substantially as it nears 500 mph, a jet engine is just starting to hit its stride and will continue to increase in efficiency more and more. This is why most commercial airplanes and military aircraft use jet engines instead of propeller-driven ones — they are far more efficient at the high speeds these planes operate at.
Similar to the previous section, turboprops and jet engines are limited by many of the same factors that limit their efficiency. This is because efficient operation and overall performance are closely tied to one another and usually rely on many of the same factors. So I won’t waste time going into the details of what limits each engine’s performance. Instead, let’s look at some actual performance measurables from these types of engines.
In terms of power output, a jet engine is far more capable than a turboprop. It’s difficult to compare apples to apples because jet engines are measured in thrust and turboprops are measured in horsepower, but it’s not even really close at the maximums.
The most powerful jet engine in the world is the GE90-115B, capable of producing a whopping 127,900 lbf (pound-force) of thrust. For what it’s worth (though not a direct comparison), the most powerful turboprop ever was the Kuznetsov NK-12 with its 15,000 shaft horsepower.
As you can likely imagine since jet engines can produce far more power, jet airplanes are also capable of far faster speeds than turboprops. This is clearly evidenced with the fact that the fastest plane ever, the Lockheed Martin SR-71 Blackbird, used jet engines to reach its record-setting speeds.
Moreover, recall from above that turboprop engines operate at their best at lower speeds. If these planes were to approach the speed of sound, the engines would be operating so inefficiently it’s almost never worth the effort and strain.
Again, you can probably guess which engine wins out in this category — the jet engine. Due to its ability to create far more power and operate more efficiently at higher speeds and altitudes, planes equipped with jet engines are typically capable of flying far higher than turboprops.
This is also evidenced by looking at how high planes fly and seeing the record-setting altitudes. All of which were achieved using jet engine-powered airplanes.
Range and Fuel Burn
The range and fuel burn of each engine is really dependent on how the plane is being used and what the goals for the plane are. This is because for shorter flights, a turboprop is almost always going to be the better option due to the extreme efficiency at lower speeds.
But for longer flights, a jet engine is the best option since the planes can fly faster and carry more cargo and passengers. In terms of nothing but fuel burn, a jet engine bruns significantly more fuel than a turboprop. There is a crossover point at which this accelerated fuel burn becomes more fuel-efficient than that of a turboprop.
For all intents and purposes, turboprops and jet engines are more or less equally safe. This is because the underlying technology — the gas turbine in both of them — undergoes roughly the same thermodynamic processes and stresses. So neither one has inherently more failure possibilities than the other.
That said, for airports with shorter runways, a turboprop may be considered the better option. This is because at the low speeds used during takeoff, a turboprop produces significant power to weight ratios and can get the airplanes up and off the ground in typically 3,200ft or less compared to the standard 5,000ft runways needed for jet airplanes.
Turboprop Vs Jet Airplanes: Which One Is Better?
If you’ve read this far, then you probably already know the answer to this question — it depends entirely on what the plane is being used for and what you’re hoping to get out of the aircraft. Depending on the circumstances, either a turboprop or a jet airplane could be the better option.
For example, if you’re going to be chartering small amounts of cargo or smaller amounts of people a short distance, then the fuel-efficient turboprop will be the best choice. But if you are concerned with maximum payload and speed, then a jet airplane is almost always going to be a better option.
So take the information in this article and decide what your goals and aspirations for the airplane are. With that in mind, you should be able to decide which of these gas turbine powered planes are right for you!