**3. Analysis of the future trends for aviation power units improvement**

Modern power units have a high level of performance, and for ordinary people, the question is why they need to be improved. There are several reasons that can answer

### **Figure 14.** *APU location onboard of an aircraft [16]: 1—Main engines; and 2—APU.*

this question. First of all, the aviation industry is the leader in engineering because it requires the highest possible performance, which can provide more higher efficiency of this transportation industry. The second reason is the environmental impact. In recent years, society demands a stronger approach to environmental safety. And the aviation industry has to make its own contribution. So, these two reasons push aviation engine engineers to improve the power units.

A number of ways are used to increase the range and altitude, speed, cargo capacity, also to improve the take-off and landing performance of aircraft and reduce the environmental impact.

## **3.1 Thrust and power improvement**

Required thrust P, measured in [N] or [kg], and power N, measured in [W] or [h.p.] of the power unit.

Maximum airspeed is determined by the following equations:

• for (bypass) turbojets or turbofan engines

$$\mathcal{V}\_{\text{max}} = \sqrt{\frac{2 \cdot P}{\mathcal{C}\_{\text{Da}} \cdot \mathbb{S} \cdot \rho\_H}},\tag{1}$$

where CDa is an aerodynamic drag coefficient; S is a wing area; ρ<sup>H</sup> is the atmospheric density at a given altitude H;

• for piston and turboprop engines

$$\mathcal{V}\_{\text{max}} = \sqrt{\frac{2 \cdot N \cdot \eta\_p}{\mathcal{C}\_{\text{Da}} \cdot \mathbb{S} \cdot \rho\_H}},\tag{2}$$

where η<sup>p</sup> is propeller efficiency factor.

As an example of the efficiency of modern engines, it is possible to explain the maximum performance of different types of engines:

