In this article, you will learn how the main transmitting and receiving devices on board a UAV work, including GPS modules, telemetry modems, and video transmitters.
92 
The article describes the variety of types of UAVs, including multi-rotor systems and aircraft platforms, their advantages and limitations. It will consider key aspects of aerodynamics, such as lift, wing profile and thrust, which affect flight efficiency. It also highlights recommendations for detecting and combating drones, as well as flight planning features depending on weather conditions and the specifics of the device. This will help to better understand how to choose and effectively use a drone to perform specific tasks.
Artillery units, as the experience of this war shows, are a key force for the task of defeating the enemy with fire. Their effectiveness ensures 90% of the success of operations, because up to 75% of the enemy’s losses are due to artillery strikes. That is why close interaction with artillery is critically important, and its trust in you is a necessary condition. The rules for transmitting information about the target are quite simple: you need to provide an extract from the table or a photo from a UAV, coordinates and characteristics of the target.
If the object is moving and is not constantly in a given area, it is imperative to indicate the time frame. In the event of a “truce” regime being declared, it is worth asking to include your target in the list of planned ones. Work on such targets is usually carried out during fire in response to shelling of strong points.
For ease of understanding, we will not describe all the nuances of the creation and purpose of UAV systems that are in service and operated all over the world. This data can be easily found on the Internet. We will limit ourselves to an introductory lecture that will allow those who wish to independently find all the necessary information and answers to questions on the Internet.
First, let’s talk about the types of UAVs that are becoming more and more popular every day. One of the most common types is multi-rotor systems. They are also called multicopters, quadcopters, hexacopters or octocopters, depending on the number of propellers. Their main feature is a multi-engine design that works on a principle similar to a helicopter. The main advantages of these drones are the ability to take off and land without a special platform, the ability to hover in place and ease of control.
However, there are also disadvantages. The copters have a small range, are not suitable for operation in strong winds, are very sensitive to icing and require larger batteries than aircraft models.
Multi-rotor drones usually operate at a distance of up to 10 km (most – up to 4 km) and perform well in calm, calm weather. Their operating altitudes usually do not exceed 250–800 m, depending on the surveillance equipment. In urban areas, they are very effective, allowing you to look behind buildings or terrain. They are also indispensable in adjusting artillery fire, as they can hover over the target. They are often used to search for enemy DRGs near our positions at night, especially if the drone is equipped with a thermal imager.
The operating speed of such drones usually does not exceed 10 m/s, but small copters in manual mode can accelerate to 20 m/s.
The second most popular, but not the most effective type of UAV is the aircraft. The advantages of this system are a long range, greater energy efficiency compared to helicopters, and less dependence on the weather. The distance covered by an aircraft UAV of the simplest class – “battlefields” – is many times greater than the operating distances of helicopter systems. The disadvantages of an aircraft UAV are the need for a take-off and landing site, longer deployment and preparation time for departure, more complex control, and greater requirements for crew training. They are used for aerial photography during the day and night, and if the crew has the necessary skills, for adjusting artillery fire.
There are UAVs designed to perform RER, EW, and communications tasks. The operating speed range is from 1.5 to 30 m/s. Operating altitudes depend on the equipment and dimensions of the device, but always exceed 300 m. Usually this is a range of heights of 300 – 2000 m. There are several aerodynamic schemes of aircraft UAVs. The main aerodynamic schemes are classical and “flying wing”.
Quite often, questions arise: how to determine whether an enemy drone is working over our positions, or is it just a flyby of our UAV? How to distinguish a drone from a satellite, detect it and, if necessary, shoot it down? In this text, we will not consider special means of combating drones, but will focus on the basics that will help fighters on the front line.
Drones most often operate in the morning and evening, when the sun is low above the horizon and creates long shadows. The optimal conditions for their use are clear or slightly cloudy weather, no wind and fog. In a clear sky, a drone is difficult to notice, but against a background of clouds, its visibility increases significantly. Usually, the sound of a drone is heard first, and only then is it found in the sky.
It is difficult to predict the direction from which a drone will appear or the trajectory of its flight – it all depends on the level of training of the crew. Enemy UAVs act unpredictably: sometimes they follow all safety rules, and sometimes they completely ignore them. In the dark, the enemy uses drones with thermal imaging cameras, which most often appear closer to sunset. At night, drones filming positions never fly with their lights on. If a bright spot is visible at night, it is most likely a satellite, which makes no sense to shoot at.
Sometimes the enemy uses the “decoy” tactic: in a group of drones, one flies with a light, attracting attention and provoking fire, while the other drones fix the positions. Such groups usually operate at different heights and distances, which makes them difficult to detect.
If you decide to shoot at a drone during the day, you need to take into account its height and speed, as well as the characteristics of your weapon. For example, a copter at an altitude of 400 m and a speed of 10 m/s will require a sight lead of about 5 m (or 10 lengths). This is without taking into account the wind, which can worsen accuracy. Such knowledge is usually sufficient for infantry.
The flight of heavier-than-air aircraft is possible because air has mass, inertia, and creates drag. If the shape of the aircraft is chosen correctly, some of this drag can be directed upwards, creating lift.
Most of the lift of an aircraft is created by the wing. Each wing has a span, chord, area, and profile. These basic parameters of the wing determine its capabilities. The span of a wing is the straight line distance between its extreme points, regardless of the shape of the wing and its swept shape. The span of a UAV wing is chosen by the designer as a compromise. Increasing the span improves the load-bearing properties of the wing, but reduces its strength, making it more difficult to maneuver such a device and its transportation.
The area of the wing is determined by its contours when viewed from above. The shape of the wing in plan is of great importance and depends on the purpose of the aircraft. The most commonly used are rectangular wings or trapezoidal ones with a taper. The taper is the ratio between the root chord of the wing (near the fuselage) and the end chord (at the ends of the wing). For a rectangular wing, the area is calculated as the product of the span and the chord.
The formula for the lift force of a wing has direct relationships: with an increase in the wing area, speed or air density, its carrying capacity also increases. However, an important parameter is the wing profile. The wing profiles of aircraft models, which often become the basis for combat UAVs, differ from those used in large aviation. These profiles require strict adherence to the shape, so drones with fiberglass rigid wings demonstrate better flight characteristics than models with foam plastic wings, which are easily deformed.
When repairing damaged wings, it is important to restore their profile as accurately as possible, because due to its special shape, air flows around the upper part of the wing faster than the lower part. This creates a pressure difference that generates lift.
It is this difference in pressure — above and below the wing — that creates the lift that keeps the plane in the air. The physical meaning of this picture is simple — the difference in pressure, and therefore, the lift, depends on the speed. There is no speed or the speed is insufficient — the plane falls. Today, a fairly large number of wing profiles have been created, which are systematized in special atlases indicating the aerodynamic characteristics and features obtained experimentally during blowing in a wind tunnel. When designing a UAV, designers choose the wing profile in accordance with the purpose of the aircraft. Wing elongation is also of great importance for the parameters of the UAV.
All other things being equal, a wing with a greater elongation has the best load-bearing properties. Wing elongation is the ratio of the wing span to its average chord.
Short-range UAVs usually have a wing aspect ratio of about 10 (Mara UAV, Kharkiv), while long-range UAVs can have an aspect ratio of up to 19 (MQ-1D Predator, San Diego). A wing with a large aspect ratio allows you to spend less energy on flight, and therefore fly further and longer, that is, an aircraft with such a wing has high aerodynamic quality.
Simply put, aerodynamic quality is the ratio of the distance that a UAV can fly with the engine off to the altitude that was lost. For example, if the aircraft descended by 1 km, it flew 20 km, which means that its aerodynamic quality is 20 km.
UAV operators are professionals who know that aerodynamic quality is more accurately defined as the ratio of the aircraft’s lift to its drag. If you treat a drone carelessly, its drag can increase significantly, which leads to a deterioration in aerodynamic quality. Stickers, edges of tape that flutter in the air flow, or GPS trackers wrapped around the outside with tape reduce the distance that the drone can cover. This can result in the drone not “reaching” its positions and falling into enemy-controlled territory, which will require explanations to the command.
After each flight, the UAV must be carefully inspected for damage and cleaned of dirt. For example, after landing in a ripening wheat field, the drone’s body may become covered with sticky sap, pollen, and insect remains. Therefore, the equipment set must necessarily include both wet and dry wipes for cleaning the device.
Aircraft centering is the location of the aircraft’s center of gravity relative to the wing chord. All loads on the UAV must be located in such a way that the centering does not exceed the range of permissible centerings for a particular aircraft. The range of centerings for classical aircraft is from 25 to 35% of the MAX. MAX is the average aerodynamic chord of the wing. For a rectangular wing, it is the chord, for wings of complex shape it is found by calculation.
UAV manufacturers usually indicate the location of the center of gravity for the convenience of the crews, often millimeters from the leading edge of the wing, and the most advanced ones put marks on the wing of the centering range. Raised on the fingertips placed on the centering marks, the UAV must be in a state of indifferent equilibrium. It is imperative to check the centering before each takeoff. For example, inaccuracy in installing the battery can significantly change the centering. This will cause either increased energy losses for stabilizing the UAV in flight, or even an immediate accident during takeoff.
Dynamic changes are constantly occurring in the atmosphere: horizontal air flows are intertwined with vertical winds of different strength and direction, forming vortices that interact with flows that bend the terrain. To safely pass through this “chaos”, the UAV must have a margin of stability.
Stability determines the ability of a drone to maintain a given flight mode without operator or autopilot intervention. If stability is insufficient, the aircraft requires frequent manual intervention to correct the course with ailerons or elevators. This leads to increased energy consumption and reduced flight range. In case of excessive stability, the device becomes less maneuverable, which creates additional difficulties for the operator.
Therefore, during design, designers choose a compromise margin of stability that provides a balance between stability and maneuverability. The overall stability of a UAV consists of three components: longitudinal, transverse and directional.
All efforts to ensure the stability of an aircraft are reduced to the combination of the center of pressure of the aircraft and its center of gravity. The center of pressure of an aircraft is the point of application of the sum of all aerodynamic forces acting on the aircraft. With any deviation of the center of pressure from the center of gravity, the aircraft begins to rotate around the center of gravity, and this feature is used to control the flying aircraft. The main thing is to move the center of pressure in the right direction and by the right amount. For this, the aircraft has control surfaces: rudder, elevator, ailerons. When any rudder is deviated, the center of pressure moves and the aircraft changes its position in the air.
In addition to the above aerodynamic control surfaces, flaps are installed on many UAVs. Flaps are used to reduce the landing speed of the aircraft.
The thrust of an aircraft is the ratio of the thrust developed by the power plant to the weight of the aircraft. That is, if the thrust of the propeller is 2 kg, the take-off weight of the UAV is 2 kg, then the thrust of such an aircraft is 1. Modern powerful electric motors and batteries easily allow a UAV to have a power output of more than 1, that is, such an aircraft can take off vertically like a rocket. But the use of excessively powerful power plants on UAVs is impractical, primarily from an economic point of view. Every gram of propeller thrust costs money.
A propeller creates thrust on the same principle that a wing creates lift. The profile of the propeller blades is similar to the profile of a wing, and the amount of thrust is affected by the diameter of the propeller, pitch, rotation speed and air density. The profile of the blades depends on the type of engine.
For internal combustion engines (ICE), propeller blades are usually thicker because they withstand significant shock loads. Wooden propellers are most often used with single- or twin-cylinder internal combustion engines because of their ability to withstand uneven rotation and avoid fatigue failure.
Propellers for electric motors have a thinner profile, which allows you to make the most of the advantages of an electric drive – smooth operation, high power and speed of rotation. Plastic propellers of complex design further reduce drag during flight when the engine is turned off.
Both wooden and plastic propellers can be dangerous to careless operators, causing serious injuries. The folding blades of the propeller open into the operating position under the action of centrifugal force and fold when pressed by the oncoming air flow.
The diameter of a propeller is the diameter of the circle formed during rotation. Larger diameter propellers make less noise, reducing the visibility of the UAV. The pitch of a propeller is the distance along the axis of rotation that the propeller would travel in one revolution if it were screwed into a solid medium.
The maximum speed of the propeller should ensure that the speed of the blade tips does not exceed 280 m/s. Exceeding this figure leads to undesirable effects, since the speed of the blade tips approaches the speed of sound. This causes a sharp decrease in the efficiency of the propeller.
In addition, changes in air density due to weather or seasonal conditions can reach up to 20%. In such adverse circumstances, the thrust of the propeller can decrease significantly, which is especially important to consider during UAV takeoff.
Some manufacturers advise adapting the propellers to seasonal conditions, using different models for summer and winter, to ensure maximum efficiency in any climatic conditions.
Of the variety of aerodynamic schemes, there are several main ones that are most popular for UAVs: the classic scheme with a pulling propeller, the classic scheme with a pushing propeller, the flying wing with a pushing propeller, the flying wing with a pulling propeller.
Flying wings have a number of advantages compared to the classical scheme. They are more technological, easier to transport and less vulnerable to damage during inaccurate landings. However, the absence of a fuselage and tail makes such devices less stable in pitch and course, since the control surfaces have a shorter shoulder relative to the center of gravity.
A flying wing is more difficult to launch by hand, as can be done with a UAV of the classical scheme. For its reliable start, a more powerful engine is required. In turn, drones of the classical scheme, although they require more careful transportation, provide better stability and flight qualities, which is important for the correct operation of optical equipment.
Regarding the type of propeller, a pulling propeller has significant advantages over a pusher propeller. It operates outside the aerodynamic shadow created by a pusher propeller and provides additional blowing of the wing, increasing its load-bearing properties and the overall stability of the device.
The material in this article is only a basic foundation that will help the UAV operator form his own understanding of the processes that occur with the device during flight. Deeper and more diverse knowledge will always be useful! It will allow an experienced operator to accurately assess and predict the success of flights, plan them correctly and choose the best conditions for departure.
92 
56