Why Don’t Small Planes Use Turbine Turboprop Engines?

When it comes to small planes, one might wonder why they often rely on traditional reciprocating engines rather than turbine or turboprop engines. This article explores the reasons behind this preference and highlights the unique features of jet engines that make them more suitable for specific applications.

Introduction to the Colomban Cri Cri

One of the most striking examples of the integration of advanced propulsion systems in small aircraft is the Colban Cri Cri. Originally equipped with two 15 horsepower two-stroke engines, the Cri Cri is now capable of using even more powerful jet engines. This transformation demonstrates the potential for small planes to utilize high-thrust jet propulsion systems.

The Cri Cri's new jet engines operate at an astonishing idle speed of 50,000 rpm and can achieve a maximum speed of about 120,000 rpm. Despite these impressive figures, the plane can still fly with only one engine operational, showcasing the reliability and efficiency of these engines. However, the high fuel consumption rates of these jet engines cannot be overlooked. For instance, the Cri Cri can consume its 5 US gallons of jet fuel in just 25 minutes, compared to around 2 hours with its original piston engines.

Fuel Efficiency and Cost Considerations

Turbine engines, including turboprops, are known for their exceptional performance and reliability. However, they come with higher costs. These engines are significantly more expensive to purchase and maintain, which may not be justified for small private aircraft where affordability and simplicity are key considerations. Reciprocating engines, often referred to as gas engines, are substantially cheaper and often used in smaller, less expensive aircraft.

The type of aircraft that utilizes reciprocating engines typically includes smaller, less costly planes that do not require the high speed and altitude capabilities that turbine or turboprop aircraft offer. Therefore, users of small aircraft often opt for engines that are more economical and offer sufficient power for their needs.

Jet Engines in RC Planes

Jet engines also exist for radio-controlled (RC) planes, albeit in much smaller sizes. RC jet engines with low thrust (20N) can be found, most often for aesthetic and novelty purposes or for specific speed record projects. Many RC planes fly at speeds where a propeller would be more efficient, but they still use jet engines for practice and demonstration.

Advantages and Disadvantages of Jet Engines in Small Planes

While jet engines offer unparalleled performance, they come with several drawbacks. Small jet engines are expensive and require more frequent, complex maintenance. They also consume a significant amount of fuel, making their operation more costly. Additionally, jet engines necessitate long and hardrunways, which eliminates the convenience of operating from grass fields.

Furthermore, jet engines typically land at higher speeds, which requires more skilled pilots. Their use in small private aircraft is thus limited due to these practical and economic constraints. However, there are applications where small jet engines are indeed used, such as in target drones and small business aircraft like the Dassault Falcon or Grumman Gulfstream.

For small planes, the choice of engine depends on the specific needs of the aircraft and the preferences of the operator. Reciprocating engines remain a popular choice due to their cost-effectiveness and suitability for a wide range of small aircraft operations.