Model aircraft . Sport with a high scientific and technical component whose objective is to design, build and fly scale airplanes, as well as as exact replicas as possible of existing ones, designed exclusively for model airplanes or even test designs for future real airplanes.
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- 1 Varieties of Model Aircraft
- 2 Propulsion systems
- 1 Gliders
- 2 Rubber motor
- 3 CO2 engine
- 4 Internal combustion engine
- 5 Glow-Plug, Glow Plug or Simply Glow Motors
- 6 Diesel Engines
- 7 Spark Engines
- 8 Electric motors
- 9 brushed motors
- 10 Brushless motors
- 11 Turbine engine
- 3 Control of model aircraft
- 1 No control
- 2 Circular flight
- 3 Radio control
- 4 Issuer
- 5 Receiver
- 6 Servomotors
- 4 Category of aircraft
- 1 Coaches
- 2 Second level or next step
- 3 Acrobatic
- 4 FunFly
- 5 Mockup
- 5 FAI Categories
- 6 Model aircraft in Las Tunas Cuba
- 7 See Also
- 8 External links
- 9 Sources
Varieties of Model Aircraft
There are different types of model aircraft:
• Free flight : Pure towed models, launched by hand or with a rubber or explosion engine that glide without control or intervention of their owner.
• Circular flight , also called U-Control: Models that rotate around the pilot controlled by him thanks to a set of cables. Within this modality we find aeromodelling disciplines as different as acrobatics (F2B), models (F4B), racing (F2C), speed (F2A) and combat (F2D).
• Radio control (R / C): It is the queen category of model aircraft. In it we can find models or semi-models (according to their degree of similarity with respect to the real model), sailboats, motorsailers, etc., without counting helicopters, gyros and any flying monsters that work thanks to radio signals that transmit orders to servos that they act on the control surfaces of the models.
• Interiors: Models specifically designed to fly indoors, among which are radio-controlled helicopters, especially battery-powered, stand out for their low weight. Radio-controlled models have also recently been designed to fly indoors, such as gyms, large warehouses, etc. There are many stores in almost every country that specialize in selling these items for this hobby.
• [FPV]  : Comes from the English “[First Person View] ”. This is a new mode of model aircraft in which the pilot guides the model through wireless video. The images from the plane are transmitted live to the pilot through virtual reality glasses or monitors.
There are also clubs in many cities that hold competitions in the different divisions of model aircraft and help a lot to those who are new to this scientific sport.
Due to their propulsion or flight system, they can be divided into gliders, sailboats, rubber motors, internal combustion engines, electric or reactors.
Also known as sailboats. These models are characterized by a larger wing area, compared to the rest of the propulsion methods, due to the exclusive dependence of the wings for lift.
The lift is achieved thanks to the thermal updrafts, or the updrafts that occur on the slopes of the mountains and unevenness, in the same way as in a glider piloted from within. Like the rest of the models, they can be free flight, or radio controlled.
• Free flight models usually have a mechanical timer (also called a dethermalizer), in such a way that after a certain flight time has elapsed, it causes them to stall, thus descending to the ground. In this way, the loss of the model is avoided.
• Radio-controlled models use servos that control a transmitter that has two levers with which the model is directed and its flight is controlled.
This simple method of propulsion beam of rubbers that travels the axis of the fuselage of the model. Attached to the tail, and to the propeller, this bundle is twisted on itself manually, or with the help of a motor (not necessarily), thus remaining taut. Once the propeller is released, it begins to rotate as the tires loosen, thus advancing the model.
A pressurized gas capsule, inside the fuselage of the model, is filled from the outside with the help of a cylinder. The CO2 under pressure, released, exerts pressure on a piston in the engine cylinder, causing it to move in the same way as an internal combustion engine works. This linear movement of the piston becomes rotary, thus rotating the motor shaft, to which the propeller is attached.
Its main use is to motorize small interior models, especially Peanut size (approximately 20 cm wingspan). Model multi-cylinder star, in-line and V engines with more than 12 cylinders have been built. Currently, these motors are in disuse due to the appearance of electric motors and small batteries.
Internal combustion engine
Just like how cars work, a fuel tank powers an engine with one or more cylinders. The combustion of the fuel inside the cylinder, moves the piston, which in turn turns the propeller. The engines most used in model airplanes are divided into three categories:
Glow-Plug, Glow Plug, or Simply Glow Motors
The fuel used in these model aircraft internal combustion engines is usually a mixture of oil, methanol and nitromethane in different percentages depending on the use and characteristics of the engine. The spark plug in the most common single cylinder two-stroke engines consists of a platinum resistance, which must be turned red hot before starting the engine.
To achieve this, electricity is passed through its resistance by means of a 1,2 or 2V electric battery (a device that in Spain is called a spark meter) or a voltage reducer coupled to a 12V battery called “Power panel”. Once started, the catalytic reaction of platinum with methanol keeps it incandescent long enough to wait for a new explosion. The displacement ranges from 0.4 cc to about 23 cc., Usually. It is the most used currently
The fuel used in these model airplane internal combustion engines is usually a mixture of petroleum, oil, ether and amyl nitrite in different percentages depending on the use and characteristics of the engine.
Unlike the Glow, the Diesel do not have any filament that must be turned red, the increase in temperature caused by the compression of the gases in the combustion chamber is enough to cause its self-ignition, for this, said chamber has an adjustable counter piston with a screw to increase or decrease the compression to achieve correct ignition and operation, the engine torque is much higher than that of the Glow due mainly to its much higher compression ratio, but, as it depends on the rpm at those that are going to work, it accepts very bad the operation to different regimes, reason why it is practically not used in radio control. The displacements range from about 0.8cc to 3.5cc., Usually.
The fuel used in these model aircraft internal combustion engines is usually a mixture of unleaded gasoline, normally 95 octane and oil in different percentages depending on the use and characteristics of the engine. They are engines, which are generally used from 1,700mm wingspan and greater than 20cc, easy to start and with much cheaper fuel than glow.
They are usually similar or equal to those of a chainsaw and the carburetor acts as a fuel pump thanks to the pressure produced by the crankcase, these are normally Walbro. The first used magnetic plate and switch to get the spark, but nowadays, they have CDI (electronic ignition) that works with a separate battery and the spark is produced when the propeller carrier (with a small magnet) passes through a sensor and sends a Signal to the CDI to produce the spark, this makes it much more reliable than a glow.
The spark plug is similar to that of a car or motorcycle but smaller. By means of this engine, the spark meter can be used, which is a device with two electrodes connected to each other.
Electric motors as a propulsion system for model aircraft have been used for many years, although it was not until the end of the last century when, thanks to the advances made in batteries, the true viability of these motors has reached or even exceeded to combustion engines.
DC motors with brushes was the logical beginning of this system, motors according to the “MABUCHI” standard were and still are widely used, especially in their sizes 200, 300, 400, 540 (from automotive models) and 600. Using these standards, they improved the characteristics using “rare earth” magnets (Cobalt, Neodymium, etc.)
At first, the motors were regulated with a switch actuated by a servo, and even a variable resistor, with which the speed of the motor could be regulated, although this system has a very low performance, and a lot of power is lost from batteries in the form of heat. soon a servo was created that replaced its motor with a relay that made the connection.
Subsequently, the reduction of prices of electronic components and the improvement of radio control equipment, achieved that the regulation of the motor was carried out by trains of pulses of variable width that, unlike a voltage variation, achieves the speed variation of the motor without excessively reducing the torque delivered. But, despite all these advances and improvements, they still have lower performance than “brushless” or brushless motors.
Of special relevance for model aircraft are the new high-performance, low-consumption three-phase or “brushless” motors. These motors are built in two ways
1- “Inrunner” or internal rotor, they were the first to be applied to model aircraft, in them, the winding is in the outer casing, while the rotor is inside, they are the ones that They have a smaller diameter and less torque but a higher turning speed, their main use, currently, is in EDF (Electric Ducted Fan) turbines and propeller propulsion with gear reducers, especially planetary ones.
2- “Outrunner” or rotating casing, They take as a model the motors used in computing, in which the permanent magnets are arranged in a ring around a group of coils arranged radially, these motors are larger in diameter, the torque It is much higher, and they work at regimes that allow the direct use of the propellers, even with diameters large enough in relation to the weight of the set to apply them to any specialty of model aircraft.
To dose the power of these electric motors, specific inverters are used, which generate a three-phase current that varies in frequency.
These motors are powered by batteries that should be independent of the power supply of the other electrical devices within the model aircraft such as receivers and servos, although almost all general-purpose drives have a power system based on the batteries of the model. motor, and is responsible for, by lowering the voltage of the batteries when discharged, cut the power to the motor while maintaining that of the radio control equipment.
Depending on the nature of the batteries, the regulation system changes to avoid damaging them, thus a regulator for Ni-Cd or Ni-Mh batteries cuts with lower voltages than LiPo The latter, due to their low weight and high charge density, They are the most commonly used, however, in model airplane specialties where a very intense and short discharge is necessary, nickel batteries still have a field of application.
As in manned aircraft, the turbo jet engine works the same way, even generating a very similar sound. Engines of this type are much more expensive and generate a lot of power, turning an airplane into a real rocket reaching speeds of up to 550 km / h
Control of model aircraft
Out of control
In the so-called free flight model aircraft, they must be freestanding, that is, once launched, the aircraft does not have any system to control its destination, although, to avoid losing it, they sometimes have a timing system. To radically change your flight attitude by making you descend, these systems are usually clockwork mechanical or as simple as a fuse that burns a device that changes your flight attitude. There are pure gliders and motorized models to reach the height of flight to later continue planning.
The models describe a circular path around the pilot located in the center, who holds the plane by means of cables, usually made of steel, which, depending on the size of the plane and the flight mode, are between 16 and 21 meters high. length.
In its basic form, two cables are used that together with the depth control allow the model to make any figure that can be drawn on the surface of a hemisphere. In the case of certain specialties such as Carrier (aircraft carriers), three cables are used, or in the case of models, more than 5 cables are used to operate the different elements of the model, such as accelerators, flaps, retractable trains, gates. , etc.
The different official specialties are included in the FAI regulations, although there are more flexible regulations for non-official and initiation competitions.
Radio-controlled (RC) models use a transmitter or radio controlled from the ground by the pilot, and a receiver inside the aircraft that controls a series of servos that transmit through a mechanism of rods or similar movement to the different control surfaces of the model aircraft as They can be ailerons, flaps, speedbrakes, rudder and depth. In this way, your flight is controlled.
This controls yaw angles, pitch and bank. In models equipped with a motor, if it is an internal combustion engine, another servo controls the accelerator, if it is an electric motor, a variator is used giving more or less speed to the motor. As many servos can be placed on the aircraft as the size of the model and the capacity of the radio station allow.
There are radios with a capacity from 2 channels to 14, with the same or greater number of servos. These can be used for a greater number of operations inside the aircraft, such as adjusting the flaps, raising and lowering the retractable landing gear, expelling smoke in the aircraft, lights, etc.
It is the device that is in charge of acting as an interface between the pilot and the controls of the plane. This device is commonly called a radio or radio control. The operation of this device consists of interpreting the movements that the user exerts on their “sticks”, push buttons or switches and converting them into a radio signal, in order to be transmitted to the plane.
There are many types of radio controls of different brands, but normally there are at least four channels, these four channels are controlled by “sticks”, which are a kind of springs that can move proportionally in the four directions. There are radio controls that apart from the 4 basic channels have a higher number of channels, to control other functions of the plane, there are also models that incorporate electronic mixes or different computer tools that make the flight more complete.
The legal broadcast band in Spain is between 35,060 and 35,200 Mhz in 10 Khz intervals, but in other countries 27 or 72 Mhz is also used. Now the radio controls that emit in pcm are being extended, compared to the traditional ppm of recently, in addition to new types of modulation that are being extended notably and that work on the 2.4GHz frequency, just added to the current communications regulations for aeromodelling.
These systems avoid the problem of interference existing in the other frequencies that commonly occurs when a second radio control is turned on with the same frequency as another that is in use, producing in the worst case the loss of control of the model aircraft.
It is a small device housed in the plane that is responsible for decoding the signals it receives from the radio control and converting them into electrical impulses that will make the corresponding servos move. To receive the signal corresponding to your station, it must have a quartz crystal installed (like the station), which defines the working frequency.
This frequency has to be the same in both the radio control and the receiver, for the whole to work. Obviously, both the receiver and the transmitter have to work in the same emission system, either ppm (fm) or pcm.
Commonly called servos. These devices are responsible for producing mechanical force to move the different systems of the plane. They are usually small in size, but they can exert a great force (the standard ones over 3.5 kg / cm). They consist of a small motor, with its bearings, and a sensor to know the position of the servo.
They range from microservos weighing less than 3 grams but exerting almost a kilo of force to large servos that can exert a force of 25 kg / cm. They usually work with voltages between 4.8 and 6v, and can be found in an analog or digital version, the latter being generally faster and more precise (they are often used for drift control in helicopters, although their use is spreading rapidly).
Airplanes of this type are built in such a way that the flight is the simplest for beginners, with ample capacity to glide due to the long and wide wings located on the upper part of the plane, in addition they usually have dihedral (wings in the form of “V “), which make it very stable in air. They are not good for stunts and speed flying.
Second level or next step
The airplanes include an improvement in the leading edge of the wing and in the position of this one, improving the speed and the aerobatic capacities but they remain airplanes to learn to fly. They can have variants in their landing gear, which can be a tricycle or a tail skate.
Generally there are monoplanes or biplanes, they are characterized by responding quickly to any order from the radio station and can reach higher speeds. They become particularly unstable at low speeds, causing inexperienced pilots to lose control, on the contrary in the hands of an expert the maneuvers they can perform are unimaginable. Within these is a category of flight that was born not long ago, called 3D flight.
These are aggressive maneuvers, with high angles of attack and speeds close to or lower than stall. These models are motorized and are equipped with large mobile surfaces that allow them to maneuver at low speeds, for this also propellers with a larger diameter and less pitch are used, in this way we can make the plane fly slower and respond better to the controls. at low speeds as we increase the air flow .
This new type of Airplane is a variant of the acrobatic one, since with it all kinds of maneuvers can be performed. The main difference with these is the weight; These aircraft, being much lighter than conventional aerobatics, can perform a certain number of maneuvers that aerobatics, due to their wing loading, cannot perform. These planes (as the name suggests) are fun to fly, although to some extent, they are not suitable for beginners. They are usually cheaper than conventional acrobats.
Model making in model aircraft is divided into two branches: models and semi-models. The models are reproductions of the original plane, with a specific scale and a physical design faithful to the real plane. Semi-models can be defined as non-complete models, in the sense that they do not have the same detail as a model. The semi-model is designed to be an economical type of aircraft, easier to fly than the model, and within the reach of the average citizen’s pocket.
The different categories into which model aircraft are subdivided are determined by the International Aeronautical Federation (FAI) and are defined by a letter that in model aircraft is always “F” followed by a number and another letter to determine the different specialties within that category. . Let’s see what they are:
Category F1 – Free Flight
- F1A – Sailboats without motor
- F1B – Sailboats with rubber engines
- F1C – Piston Engine Sailboats
- F1D – Indoor Models
- F1E – Hillside sailboats
- F1F – Helicopters
- F1G – Models with rubber engine
- F1H – Gliders (Class A-1)
- F1J – Models with piston engine
- F1K – Models with CO2 engine
- F1L – Indoor Models (EZB)
- F1M – Indoor Initiation Models
- F1N – Indoor Gliders Thrown by Hand
- F1O – Hand Thrown Outdoor Gliders
Category F2 – Circular Flight
- F2A – Speed models. This specialty is, without a doubt, the most technological in model aircraft. In it, the laws of aerodynamics are taken to their limit, using asymmetric airplanes (they usually have only the inner wing and only the outer stabilizer, the wing is metallic, the propeller only has a blade, they use very high quality materials and use not usual in other specialties (Titanium, Magnesium …) the engines rotate at more than 40,000 rpm thanks to the use of tuned resonator exhausts and reach speeds of more than 300 km / h
- F2B – Acrobatics models. Although these models have varied over time, they have done so less than in other specialties, they are models with a large surface area for both the wing and the elevator, a short tail moment that, when using the ailerons in the opposite direction to the Elevator rudders, allows maneuvers with minimum turning radii.
This allows maneuvers such as square and triangular “loops”, while being able to make wide turns with constant radius. The use of “Uniflow” tanks allows that the operation of the engine is not influenced by the level of fuel. The engines are slightly greasy carburettors, so that, when the model rises, it accelerates slightly with respect to horizontal flight, and, when it descends, it also slows slightly, with this the maneuvers are carried out at a practically constant speed, with which the effect it is much more aesthetic.
- F2C – Racing models. The races are the F1 of model aircraft, in the case of circular flight races three athletes fly their models in the same circle in order to complete 50 or 100 laps (The model aircraft would complete 5 or 10 kilometers of flight depending on whether they are classifications or the final race).
Due to the capacity limitation of the tank by regulations, pilots must land their models to carry out refueling and engine starting operations, these tasks are carried out by their mechanical counterparts. The term in English is “Team racing”, that is, team racing because it is in the synchronization of the team where the most important advantages are obtained, reaching a refueling in less than 3 seconds from when the mechanic touches the model until it is loose. The model aircraft reach speeds close to 220 km / hour, which forces the pilots to maintain a good physical condition and good reflexes. In addition, the preparation of the models, engines, propellers is quite important.
- F2D – Combat Models. They are of a very different design from the rest of the model aircraft, called Combat Wings, this describes them perfectly, it is a wing with a built-in stabilizer and a support for the motor, they have a string attached that in turn holds Due to the extreme maneuvers, both to cut and not to be cut, it is very common for one or both of the participants to crash, but, as the competition is by time, it is allowed to change the model.
- F2E – Combat models with diesel engine (Provisional class). Also called slow combat, it is similar to combat, but the speed reached by the combat wings is lower, the maneuvers that can be performed are also limited, it was prepared to improve the new pilots’ access to a specialty that had become excessively difficult to start in. It requires the use of normal motors and commercial propellers.
- F2F – Racing models with diesel engine and profiled fuselage (Provisional class). Called Carreras 15 and Carreras 30 depending on the size of the models and their displacement, as in the case of slow combat, it allows an approach to the races without the need for a very high expense, using both simpler aircraft to build like flying. It requires the use of normal motors and commercial propellers.
Category F3 – Radio Controlled Flight
- F3A – Acrobatics
- F3B – Thermal gliders
- F3C – Helicopters
- F3D – Pylon Racing
- F3F – Hillside sailboats
- F3G – Motorsailers
- F3H – Race gliders
- F3I – Aerial Trailed Gliders
- F3J – Thermal sailboats
F3P – Indoor acrobatics with Depron models
Category F4 – Models
• F4A – Free flight models
• F4B – Circular flight models
• F4C – Radio control models
• F4D – Indoor free flight models with rubber engine
• F4E – Indoor free flight models with CO2 engine or electric
• F4F – Indoor free flight models (Peanut Formula)
• F4J – Gas turbine powered flight models
Category F5- Models with electric motor
• F5A – Acrobatic
• F5B – Motorsailers
• F5C – Helicopters • F5D – Pylon
• F5E – Solar planes
• F5F – Electric gliders (up to 10 elements)