Radio-controlled helicopter

A model helicopter (german radio- controlled helicopter, RC Helicopter short ) is a model aircraft, which was modeled on a man-carrying helicopter in form and function. It is held in a much smaller scale and can carry any person in most cases. Some models, however designed so that they can carry smaller loads; so there are, for example, special model helicopter equipped with camera systems, measuring instruments, loudspeakers, agricultural tools or even rescue equipment. Remote-controlled model helicopters thus find not only as a hobby, but also in the professional career spectrum use.

In contrast to the model helicopter made ​​of plastic or cast aluminum with high attention to detail to scale a model helicopter is airworthy and is usually remotely controlled, but need not necessarily be modeled on a great role model. A distinction is made between so-called scale models ( scale model of shape and color ), semi-scale ( largely scale replica with some detail changes ), Fun -scale models ( scale replica with Fantasiecolorierung that does not exist in reality ) and trainer versions (models, so do not exist in reality, but a pure training, sport or application function, such as rescue, camera work and measurements have ).

• 5.1 Takeoff weight
• 5.2 Flight times for electric models 5.2.1 Efficient Flying Project
• 5.2.2 Other Records

• 8.1 Germany

Development

The first commercially available model helicopters, a Bell Huey Cobra was presented in 1972 by Dieter Schlüter at the International Toy Fair in Nuremberg.

The distribution of model helicopters has received a significant boost in recent years. In addition to the opportunity to purchase an RC helicopter for small money, resulted in significant performance increases, new techniques and materials for drives and more reliability and easier usability for this phenomenon. In particular, the introduction of brushless electric motors (brushless ), lithium polymer batteries, gas turbines, carbon fiber reinforced plastic and fiberglass reinforced plastic models give high durability while reducing the take-off weight and provide a wide range of services available. Furthermore, there are constantly new designs, a low-cost mass production in Far Eastern countries such as China, Taiwan or South Korea.

Technical Details

The technique is based on man-carrying helicopters, differences are due to different physical conditions. As motorization come in either single-cylinder reciprocating engine on nitromethane or gasoline based, electric motors or small gas turbines. The greatly simplified technology in conjunction with much less take-off weight not only includes restrictions but also has advantages over the man-carrying model that present themselves as follows:

• Small size and weight: relatively stronger influence of aerodynamics and wind.
• Electric motors mean simplified gear and speed control compared to internal combustion engines, also less vibration.
• Electric drives ( tail rotor, coaxial, and others) are relatively inexpensive and efficient, although in larger models rather high cost of the batteries and their charging technology may apply, since the energy required for larger models is significantly higher.
• Gyroscopes and other stabilization systems allow automatic stabilization about one or more axes.
• Payload, transportation volume and range usually do not play a role.
• Reduced forces on the rotor allow, if necessary, the waiver of impact and swivel joints.
• The pilot needs a high motor ability to manage up to four control directions simultaneously via two joysticks can.
• Aerobatics including inverted flight (negative rotor angle of attack) is in some models relatively easy, what with some types and only under heavy load conditions of the mechanics and rotor blades is only possible with man-carrying helicopters.

Models

Surroundings are suitable models with programmable controllers. These provide both the mechanical construction as well as to specify sender-side or stabilization system-side software settings, the option to change settings in different ways. This can be a " beginner-friendly " setting for the initial flight tests and then later when the Modellheli can dominate in any normal flight attitude, a pretend " advanced " setting for the art or even 3D flight.

The very cheap models below 50 EUR have currently already a 3-channel controller. In addition to the height ( ' gas '), the rotation is controlled by the vertical axis and the ' Nick' forward drive. A classic helicopter but is really only fully equipped with at least 4 control axes and also controllable (height, pitch, roll, rotate ).

Simple electric models have been around for less than 100 EUR, they are characterized by a low weight (up to about 300 g ), and are now also recommended for the beginner, because these models take little damage due to the low weight of a fall, the case but then occurred but can be fixed inexpensively. In this Gewichts-/Preisklasse dominate the time Koaxialhelis, but it would be also increasingly by aerobatic pitch -controlled micro helicopter, as they can be flown unlimited and thus are of interest not only for beginners but also for advanced users. It is characteristic of these models, which are also known as RTF models, ARF models or BNF models that they are almost invariably offered as complete models that can be flown immediately with a mostly supplied remote control without major changes to the settings. RTF here means " Ready to Fly " ARF " Almost Ready to Fly", while BNF "Bind and Fly " means - that only a compatible remote control to the receiver of the model must be bound to the model fly. RTF models can - in theory - be flown out of the box, while ARF models minor modifications be made ​​and / or some parts need to be added and some adjustments need to be made at the transmitter BNF models.

There are at Glow, a division into classes ( 30s, 50s, 60s, 90s and 120s class ) as well as coach models a division into tail boom length classes (eg, 450 mm, 500 mm, 600 mm, etc. ), which is also in electrical models of is 250 mm to 800 mm Application. Turbine models are currently not divided into classes.

The market of slightly heavier models around 1000 g is very confusing. Here Finished models are just as kits which are supplied depending on the manufacturer in different degrees of prefabrication. In addition, most models are sold in different versions. So there are some providers that offer seven different versions of their model - from the basic model in plastic construction Easy way to tuned solid metal and carbon variant with colored anodized parts.

A price jump up to show the models over 1kg, because they need larger servos and E models also higher capacity batteries. These models would be due to their size and the associated relative stability against wind gusts and higher inertia in controlling also suitable entry-level models. But due to the high purchase price, they are usually flown only by advanced pilots, because in a crash the spare part prices are correspondingly high.

Another jump in price is given in Scale - models and models more than 5 kg. Since here with high quality mechanical and electronic components but the drive technology usually falls particularly significant and often mechanical special or even individual productions have to be assembled here are prices over 10.000, - € not uncommon. Therefore, these models require the utmost care and are therefore also only flown by professionals, especially since often multi-blade rotor heads ( three or more rotor blades) are used, which are without electronic aids is very difficult to master.

Typical constructions

Speed ​​controlled

In speed-controlled model helicopters (Fixed pitch in short, called FP ) control of buoyancy by changing the speed of the rotor blades is done. The FP of the collective pitch of the rotor blades is always the same, the control of the buoyancy and hence the height here solely on the rotor speed ( " gas "). This is regulated in electrically driven mini- model helicopters from a controller, which together with the receiver and the " Gyro" (see below) is most often combined in one module.

This design speaks carrier to send control commands to as the "pitch -controlled " version, but has the advantage of simpler mechanical construction, lighter weight and is also less sensitive to fall. It has proved itself particularly with small and cheap models below 500 g. There are also larger models in the range of 1.5 kg and especially sturdy with this rotor design, so that here, fewer parts are destroyed in case of accidental contact with the ground.

Non-coaxial with this model of the torque compensation and the rotation about the vertical axis of a rear-mounted engine is controlled. Since any change in speed of the main rotor produces a torque change, must necessarily also the yaw axis are constantly readjusted - what the model pilot and therefore difficult because the reference axis, unlike changes in a person sitting in the cockpit pilots in turning. Therefore, today most electronic angular rate sensors (so-called gyro, but rarely a real gyroscope) used, which regulate the yaw axis so that the orientation of the trunk does not change and it keeps the same.

The lateral ( vorwärts-/rückwärts- and sideways, and pitch and roll ) movement can be controlled by a swash plate, which is hinged by at least two servo motors. In very simple constructions is waived, it is only the altitude and the rotation controllable.

Pitch -controlled

As pitch is defined as the angle of a rotor blade with respect to the incoming air. The control of the lift is done classically by varying the collective ( joint ) angle of the rotors ( see swash plate ); however, the speed remains constant in the ideal case. It is controlled in the majority of cases with three servos to the swash plate, often in 120 degree arrangement in which the forces are evenly distributed on the servos, their movements must then be coordinated.

This vote of the linkages ( mixture ) can be done at the transmitter end by so-called Helicopter mixer or swashplate mixer. Meanwhile, there are also onboard systems (eg, the sensor-driven V-Bar or other similar systems ), which autonomously control the swashplate and tail rotor mixing and beyond also include a three-axis stabilization system. These systems are now so effective stabilizing, that completely on the auxiliary rotor plane (paddle ) waived on the rotor head and " flybarless " ( Flybarless), so it can be flown with a rigid ( = rigid ) rotor head. Thanks to these systems, flight speeds of over 250 km / h models are now available that can be difficult flown with the auxiliary rotor plane, since the model would thereby swaying heavily.

At the tail rotor designs come with a separate rear engine, with drive shaft and reversing gear or toothed belt used. In this way mechanically coupled tail rotor yaw axis through angle of attack of the tail rotor control what caused another servo. As the tail rotor controls the overall orientation of the model about the vertical axis of this, a particularly fast response time is required. For this reason are used to control the tail rotor servos ideally installed faster with shorter reaction times.

Coaxial rotor

As with man-carrying coaxial rotor helicopters two opposing, stacked rotors have the advantage that there is no tail rotor is needed for torque compensation. Especially thus unnecessary remaining in a tail rotor drift ( see there), which control where space is limited and indoors (indoor, eg halls ) very simplified. By the rotors are electronically controlled via two separate electric motors, rear-mounted engine and the tail servo can be omitted since the yaw axis is only controllable via differences in speed of the rotors. However, it reacts much slower than in models with private tail rotor, making it difficult to fly in the wind. The buoyancy control is mostly speed-controlled and only the lower rotor is partially controlled via swashplate for pitch / roll control. The design effort is therefore not higher than in the tail rotor design, but the control is to learn faster.

For simple structures is omitted entirely on the swashplate and the pitch regulated via a small acting perpendicular rear engine. At low airspeed also targeted flights are thus possible, while the weight of the model ( typically to about 50 grams) it is quite small and thus not suited for outdoor area because of the wind conditions.

Tandem rotor

The tandem configuration has already been used in the model. Two rotors are usually arranged in series. This means two independent rotor head and swashplate with a correspondingly high construction cost and high sensitivity. Since the flight performance of a model helicopter and in particular its payload rarely carry weight, the tandem design is usually only used to recreate an original as realistic as possible.

Flettnermodelle

In Flettnermodellen two intermeshing rotors are side by side, sometimes on two Ausliegern mounted. These models are very rare to find and usually self- constructions. The inter- meshing of the rotors at the same time also compensates for the torque, thereby ensuring a coordinated rigid gear level. The advantage of a Flettnermodells is an intrinsically stable flight and a space-saving mechanism.

A plural rotor

Taking a different approach designs with multiple rotors, usually four to eight Quadrocopter at the Octocopter. The control of all three axes is realized by means of different rotational speeds of the rotors. Since the materials are concentrated in the center, the inherent stabilization of the helicopter is missing. Therefore electronic accelerometer with Piezo technology or gyroscopes are used to stabilize the position mostly. By reacting quickly, from a microcontroller -controlled electric motors can here, unlike helicopters or large quadrocopters be dispensed sensitive rotor heads with pitch, which favors construction, weight and drop resistance. This design is increasingly used in drones and UAVs and is now even with safety authorities such as police and fire departments as well as in military applications.

Autogyro

Also auto gyros or gyroplane is built as models and flown. This is not helicopter in the strict sense, because the driving is done by a separate propeller, but as the buoyancy generated by a vane at the helicopter, which is held by the air flow to rotate. Due to these and by the moderate airspeed model gyrocopter are particularly easy to fly.

Einblatthubschrauber

Law rarely encountered are Einblatthubschrauber (also Engl. Single blade Helicopter) that have a single rotor head to which only a single rotor blade is also grown. The rotor blade has a small extension that protrudes beyond the rotor axis of the opposite side and also equipped with an appropriate counterweight, to avoid any imbalance and the entire system is developing bounce when starting or during operation.

Tiltrotorsysteme

2011 has been available the first Tiltrotormodell mass-produced in the form of a V-22 Osprey replica in Germany. Since the Kipprotortechnik for model scale is still quite expensive, the model was many times more expensive at its launch than comparable pitch or Koaxialmodelle in the same size class.

Frame information

Takeoff weight

The weight of a typical electric model helicopter is between 50 g ( micro helicopter with 20 cm rotor diameter ) and 5 kg ( about 1.50 m). But there are also miniaturized own designs and small commercial models from series production, the ready to fly even weigh less than 10 g and have a rotor diameter of less than 15 cm.

Models with piston engines start at about 2 kg ( 30 - engine, about 5 cc, 1.30 m rotor diameter ), the widely used model helicopter with 90 engine ( 15 cc, 1.60 m rotor diameter ) weigh about 4-5 kg, Scale models with scale-like hulls are often at 6-12 kg, turbine-powered models also up to 25 kg.

Flight times for electric models

Flight time in electric models, depending on the used battery type and size of the battery pack 3-30 minutes. The used to improve the flight time lithium polymer battery (LiPo and Lilo ) have opposite NiCd or NiMh batteries have a higher specific energy, but have the disadvantage that they are considerably more expensive for the same capacity, allow less charge cycles and treated more carefully be need. LiFePo batteries of the latest generation have a similarly high specific energy as LiPo batteries can also be charged by nearly identical charging equipment, but are much less sensitive and allow for up to 600 charge cycles, so this technique is referred to by professionals as trendsetting.

Basically, it is advisable to let it cool down between flights operator mechanics, motor and controller, as this can become very hot depending on the flying style and potentially increases the risk of malfunction in omission. Conversely, these components work reliable if they can cool sufficiently after the flight or cooled according to the duration of the flight and thus can build any high temperatures.

Efficient Flying Project

New findings in terms of more efficient fly from electric helicopters were first series of measurements with corresponding equipment ( Eagle Tree data logger) in certain flight models: Thus, it makes much more sense for a balanced energy budget and for long flight times to fly at low speeds. At high speed, the flow resistance of the rotor blades at the same time grows worse werdendem efficiency rapidly, and thus wasted energy, the negative effect on the duration of flight and actually offers no gain when flying. The flight model should be as light as possible and kept must present a proper setup to bring optimum conditions for energy- efficient flying.

The competition pilots Matt Finke and Nico Niewind ( Heli Masters winner 2010) have thereby sought in 2009/2010 with different models in the context of several test flights with the inclusion of broad maneuvers a flying time of about 30 minutes. Considering previously mentioned aspects could both reach for models with up to 1.60 m rotor diameter unattainable translucent limit of 30 minutes of flight.

More Records

Outside the Efficient Flying Projects could 600 series model can be achieved with a modified logo of competition driver Timo Wendt country on 14 September 2013 at an FAI record flight competition in Ballenstedt a record time of 151 minutes. The 5.65 kg heavy model was equipped with a specially wound electric motor and a 33.8 Ah LiPo battery and made ​​the record flight with 800 blades at 600 rev / min on the rotor head.

The duration flight world record held since October 28, 2010, an electrically driven Quadrocopter, which could be held in the air more than 12 hours. The power supply for this record flight was thereby ensured by means of a signal emitted from the ground laser, which was focused on onboard solar cells on the flight model and thus maintained the drive power of the quadrocopter. In addition, the model was equipped with an on-board battery, so even a short interruption of the laser would have remained without consequences.

Flight times on models with internal combustion engines

Internal-combustion models, the flight time typically 20 minutes but this can be increased by a larger tank is. A higher weight of the tank and the amount of fuel carried may be, adversely affect the maneuverability and thus on the aerobatic capability. Meanwhile, however, also stands out in glow- a tendency to shorter flight times, since the engines are more efficient and therefore have a higher fuel flow rate.

Flight maneuvers

→ see main article maneuvers (Model Helicopter )

When aerobatic helicopter with the model a variety of maneuvers are possible, which can be achieved with any other aircraft. Pitch -controlled models are used for this application, since they react more quickly to control commands and allow aerobatic maneuvers with the backing sheets. In many countries and international championships are held.

When speed flight with the helicopter model is about the model extremely accelerate and achieve a high top speed. This type requires considerable skill and a good ability to assess the available space in the large-scale sharing fly, since the model can be flown only as far as it is clearly visible, but at the same time much space is needed to accelerate the model. Good results in the flight speed can be achieved by a nosedive, which is then transferred to a horizontal trajectory. In addition, a lot of fingers pointed feeling is demanded by the pilot, because small inputs on the transmitter at these speeds can have a big impact on the direction of flight and altitude.

Also for this type there are now competitions (Speed ​​- Cups). It can be reached speeds in excess of 277 km / h.

Training for pilots

The control of a model helicopter requires intensive training. Since helicopter not intrinsically stable fly ( except Koaxialhelis and helicopters that are equipped with electronic flight aids), constant corrections are required, the overwhelm the beginner to start. Since flight errors are thus connected in the worst case with a crash and repair costs, there are now numerous simulation programs that greatly facilitate the entry and thus prevent costly repairs for crashed models. In addition, there are flight schools, where a flight instructor can correct with his communicating with the student teacher transmitter transmitter flight error. In addition, an RC pilot should study appropriate literature and relevant websites and forums in order to acquire the relevant theoretical knowledge relating to the commissioning of a model helicopter before he makes the first flight tests. In addition to training landing racks that will facilitate in particular the difficult for beginners takeoff and landing phase of flight and prevent overturning of the model on the ground or ground contact of the rotor blades, there are now but also technical means of balancing the control error and by means of a emergency button on the transmitter, the model into a favorable attitude to return or even make a separate emergency landing.

As a good beginner's environment, the fly has been found in a closed room ( indoor flight or indoor flying). Most of this gyms are used with small models is also flying in a living room possible. Due to lack of weather -related disturbances such as wind flying is improving, but maximum altitude and walls or other obstacles at the same time must be observed. In smaller rooms caused by the rotor downwash turbulence in the air that can cause an irregular flight. In addition, crashes in the hall because of the hard soil properties can lead to considerable damage model.

Special attention is at the first flight tests while the ground effect, downwash or even hovering in ground effect ( HIGE ) called to bestow. This occurs when you hover at low altitudes (up to about 1.5 times the rotor diameter ) and manifests itself in a very unstable flight condition, as the helicopter on his own rotor wash as it is on a ball and constantly changes its position. Therefore, frequent corrections when flying are necessary.

FPV ( Immersionflight )

Increasingly, the FPV flying established (English: First Person View), also called immersion flies, in the scene, so the fly from the onboard perspective. Here is a oriented in the direction of flight small camera on board the model and transmits it to the RC helicopter pilots located at the bottom of a video signal, which makes this small of a monitor or video goggles for itself visible. Based on the video image of the pilot moves the model in the desired direction, so that the otherwise applicable sight barrier, in which the model can be only so far flown, like the model from the ground in the air is visible - can theoretically be - exceeded and only the range of the video signal or the range of the remote control to limit the flight. Even if the aircraft should get out of range of the remote control or the video signal receiver, there are some more expensive models now GPS -assisted flight modes, which enable the flight model in this case in an autopilot mode and return it back to the pilot and even land may, without the pilot input or the model is lost. In Germany, it is not allowed in the FPV according to current legislation, to fly out of sight of the model.

Law and compulsory insurance

Germany

The rise of flight models, including model helicopters is regulated in § 16 LuftVO. Accordingly, it requires a special license from the competent Land authority, if the models

• Heavier than 5 kg are,
• To be flown with a combustion engine within less than 1.5 km from residential areas or
• Less than 1.5 km from boundaries of an aerodrome to be flown away.

The climb to airfields further requires the approval of the air supervisory body (eg German Air Traffic Control - DFS) or the flight line. The rise may be prohibited according to § 29 LuftVG when operational risks to the safety of air transport and for public safety or order of the operation of model aircraft out.

Other restrictions may result to be obtained by the consent of a property owner or other authorized users, if you want to fly on his property. In addition, there are areas about which there may be flown (eg on nuclear power plants, military security areas and nature reserves). Planes may also be flown within towns generally not. The private use of model aircraft must always be such that no one is endangered, harassed or compromised.

In addition to compliance with the general regulations and additional insurance must ( § 102 LuftVZO ) to be completed, which must be designed for both the operation of the model in the open and in closed rooms or halls for the operation of the model. It must be completed for all airplanes a Aviation liability insurance.

This insurance for model aircraft is special and far-reaching as a private liability insurance - hence the operation of model aircraft can not be covered by the private liability insurance. The legislature is not to conclude a liability insurance policy, as a crashing or runaway model helicopter can cause serious personal injury or damage that may lead to corresponding compensation claims to.

References / Comments