Monday, October 31, 2011

Helicopter Beginners Guide

Introduction

I should cover the basics of helicopter safety first, i wont go into flight safety, or pre-flight checks just yet. Just basic precautions to take on the ground whilst building or modifying your helicopter.


Specifically, until you are confident with the mechanics of the RC helicopter, and are in a informed position to start the mechanical set-up of the aircraft, do not connect the Li-Po battery to the helicopter. There are many reasons for this, but all will end in the helicopter trying to spin its blades at 2000 rpm, causing injury and/or damage. Once in a position to setup the helicopter mechanically, it is ok to connect the battery to the speed controller, but remove prior to this the three wires going to the motor, to prevent the helicopter trying to spool up.

The T-Rex 500 The T-Rex 500 with the front canopy removed

This is valid specifically for a electric helicopter, but is also valid for a nitro heli, except it is more difficult to accidently start a nitro heli. This guide is written in a fashion aimed towards electric helicopters, as this is what most new pilots will encounter. Most of the principles are the same, except the motor and speed controller is replaced by an engine and a servo. That is not to say electric helicopters are for beginners, its just a lot of the simple ready to fly sets are electric. Electric helicopters are available up to the 90 size IC range, and perform as well as, if not better than there IC counterparts.


I will cover the basics of all of the components in this guide as well, but i go into more detail about specific articles on other pages within this site. Also, see my subsequent articles on how to learn the basics of RC helicopter flight, and achieve a stable hover.


In this guide i will use the T-Rex 500 as the example, to guide you through the various components of the helicopter. I am not however recommending this as a beginners model. Under one-on-one tuition it is possible to learn on this aircraft, and in fact its flight characteristic can be set to be very docile and beginner friendly. But it is aimed more towards the mid to high end range and competition flight, they are also many times more expensive than a basic ready to fly box set, that a beginner should be aiming for.

Note

This section is essentially a glorified glossary of terms. I will go into detail on all of these subjects in other sections of the site. Such as radio setup, mechanical setup, flight training etc.Tthis is also a multipart series, so check back soon for more updates.

Helicopter Mechanics A modern carbon fiber helicopter airframe The frame serves as a support to the helicopters mechanics Airframe

Usually injection moulded. But also on more expensive models constructed from carbon fibre, and Aluminium. Providing a rigid frame to piece all of the components together, and transfer the power between the motor and rotor head. It also serves as a frame to hold the electronics. Modern pod and boom sport models, are semi exposed except for a fiberglass painted canopy that covers the first half of the airframe via some simple retaining clips. This aids in orientation of the aircraft whilst in flight, and helps to improve aerodynamics.

A belt driven tail drive unit Tail drive unit from above, we see the pitch slider and mixer arm Tail

Between the tail unit and main frame is the tail boom, it provides a route for the tail drive system and control linkages. It is necessary to have the rear rotor blades at a larger diameter than the main rotor blades away from the main frame. Usually there are also two support structures coming from the base of the helicopter frame, to a fixed point along the boom to aid structural rigidity. This is also where the horizontal stabilizer fins are located, a bit further towards the rear we find the vertical stabilizer connected to the tail drive unit. The power is normally transferred to the tail from the main motor via a belt drive, but it is also possible to have torque tube drives, that have a fixed drive shaft powering it. The rudder control on the radio controls the yaw of the helicopter via changes in pitch of the tail blades.

120 degree three servo swashplate 120 degree three servo swashplate connected to the cyclic servos Swashplate

This is one of the most important parts of a RC helicopter, it is how the movements from the servos are transferred to the rotor blades, and finally translated into a movement of the helicopter in the direction required. It allows the stationary helicopter frame and servos to apply movement to the spinning blades pitch. In order to produce propulsion in a certain direction, as the blades spin, at certain points along the circumference of the rotation, the pitch of the blade changes, thereby creating more lift on the left side than the right for example. This will then cause the helicopter to move to the right. This is the Aileron control on the radio, and produces a sideways banking motion. It is the same theory for the Elevator control, it rocks the swashplate forwards and backwards, like the Aileron moves it from side to side.

Top down image of the main rotor head Flybar support and mixer arms Rotorhead

Relatively simple compared to the swashplate, as most of the control mixing has been done there. The main components here are the blade grips, they are able to rotate to allow for the changes in pitch of the individual blade. Also on the rotor head is the flybar, this is to provide a mechanical form of stabilization to the inherently unstable aircraft. To provide control to the rotor head, we have a complex mixture of washout arms, bell crank arms, mixer arms, pitch control arms and flybar control arms. All working together to keep the helicopter in the air. I wont go into detail on these in this section, as the particular setup varies from one helicopter to another. I will however go into more detail in the mechanical setup section of this website.

Complete head unit removed from the helicopter and swashplate Mixer and bell crank arms connecting the swash plate to the rotors

A combination of rotor pitch and head speed gives the helicopter lift. When applying increasing pitch on both blades at the same time, this will produce lift, but also increased drag effects will reduce the head speed. On a modern transmitter, the throttle, and pitch are mixed to counter act this and keep a constant head speed, this is also where a engine governer comes into force on a nitro model.


To calculate head speed, we look at the rating of the motor, so a 3000 Kv motor will rotate at 3000 rpm per volt. So the T-Rex 500 runs at 22.2 v. This means the motor will spin at 66,600 rpm when the full voltage is applied, it then makes sense that at half throttle, we will have 33,300 rpm. It is then a simple case of working out the ratio between the teeth on the motor pinion and main gear to give us our head speed. So as an example, if for every one turn of the main gear, the motor turns 40 times, we would have a head speed of 1665 rpm.

Align 60A electronic speed controller The motor mounted on the helicopter Speed Controller and Motor

Unlike a nitro model where we have a mechanical mixture control and servo, on a electric helicopter we have a brushless motor and electronic speed controller [ESC]. The speed controller acts as many units in one. Supplying the appropriate voltage to the motor, providing power to the electronics, controlling headspeed, battery level warnings, and many more features. Most ESC's will have a built in battery eliminator circuit (BEC) to maintain the correct voltages to the receiver and ultimately the servos and gyro. If you have a nitro model, this will be a separate unit, and the helicopter electronics will have there own, smaller Li-Po batter pack. The ESC usually will connect to the motor via 3 cables, positive, negative and data. it is important when working on your helicopter on the ground, to disconnect the motor from the speed controller, to avoid accidental arming and spooling up.

Align GP750 servo Two of the three cyclic servos Servo's and Gyro

If you have a 120 degree swashplate you will have 3 servos mixed to control the swashplate movement. This is known as eCCPM, the controls are mixed on the transmitter, to allow the three servos to control the four directions of motion applied on the cyclic control. Some helicopters use 90 degree non-ccpm swashplates, but on the majority of current helicopters these are much less common. A quick visual inspection of your swashplate will allow you to identify easily which type you have.

Tail servo Tail pitch control unit

Lastly we have the tail servo, usually attached directly to the tail boom, or tucked away inside the main frame below were the tail boom interfaces with the frame. This provides the control for the pitch of the rear tail blades, to allow the model to yaw and rudder control. However, it is necessary to incorporate a gyro between the receiver and servo, to control the position of the tail. Due to the force of the tail rotor, it will generally always want to move. Also looking at the laws of motion, once moving it will want to continue on that path until operated on by an external force. So a gyro counteracts this. It keeps the tail locked steady in one position, when you give some left rudder, it moves left, but the moment you stop the control input the tail comes to sharp stop. Without this you would have to be constantly balancing the tail, and the other controls. No easy task.

The T-Rex 500 ready for action When not in use, keep the blades safe with the foam blade caddy Overview

So that completes are introductory lesson to the basics of remote control helicopters, this was meant as a simple overview, check back soon, and explore other parts of the site for more in-depth tutorials on RC helicopters. It may all seem confusing at first, but it will become second nature within no time at all.

Sunday, October 30, 2011

E-Flite Blade RC helicopter review

Introduction

I thought i should give an overview of some of the more economical micro and sub-micro remote control helicopters out there. As i know these are popular routes into the hobby. One brand that has shown a great deal of excellent micro and small RC helicopters is E-Flite. These are typically fixed pitch or coaxial micro helicopters, small, cheap and fun. Such as the Blade mSR or the Blade CX2. Usually easy to control indoors, but much harder to master. E-Flite have a number of models in there range, but ill just cover a few of the most famous concepts here. Also note, Align are now entering this market, and they will be releasing their T-Rex 100 micro helicopter shortly.

Blade mSR micro helicopter Next step up from a coaxialReady-to-fly or bind-an-fly4 channelStable and responsive"Almost" indestructibleExcellent after market support

The Blade mSR is a super sub-micro RC helicopter that fits perfectly in the palm of your hand. It is a good choice after learning with a coaxial helicopter such as the MCX or the CX3. It is recommended over the 120 SR, as it is slightly easier to control and less expensive in a crash. It weighs in at an incredible 1 ounce, which is astonishing to be honest. Considering it crams in all the usual goodies such as gyro, servos, DSM2 receiver and motor ESC. Along with a selection of the other Blade helicopters it is available as either bind-an-fly or ready to fly variations. It uses a single, fixed pitch rotor, and is ideal for flying around the living room on a cold winters day. Also an excellent gift for a more experienced pilot, due to the "wow" factor of such a capable super micro machine.

Blade mCX micro helicopter Ultra-micro indoor flyingTest flown and factory assembledEverything needed to fly in one box1S 3.7V 110mAh Li-Po includedExcellent precision compared to other coaxials

A micro version of the CX/CX2 range. It is the entry level coaxial contra-rotating helicopter. A good choice for the beginner pilot, it is super stable and easy to control. Like the rest of the Blade range, it utilizes a Spektrum DSM2 receiver and can be teamed up with a compatible Spektrum controller, or the one provided in the ready to fly package. The package has everything required to get in the air for a single price. Parts are cheap, and due to the size and weight it is very crash tolerant. As usual for this type of helicopter, is is best suited to indoors flight.

Blade mCX2 micro helicopter All the best bits of the mCXUpgraded precision swashplateCoaxial counter-rotating headLED lights

In keeping with the original mCX, it is an updated version, with a few extra features for slightly more advanced flight. It is still easy to fly, and anyone can have a go. But for the more advanced pilot, the swash is now user controlled via various parameters, allowing some tuning of the flight characteristics. Larger motors, LED's and a bigger battery means more fun, and greater flights. Essentially an advanced coaxial remote control helicopter.

Blade 120-SR micro helicopter Smaller than micro sizeReady to FlyStability of a coaxial helicopter2.4GHz DSM2 receiver

The Blade 120 SR is a gorgeous little heli. It sits on the line between a small coaxial helicopter, and a sub-micro fixed pitch model. But, it uses only a single rotor. It achieves the stability of a coaxial, but with the agility of a single rotor. Which makes this a nice stepping stone up from a coaxial model. It is available as either a bind-an-fly, if you already have a spektrum DSM2 compatible transmitter. Or as a ready-to-fly unit complete with controller. It hares many similarities with the mSR, essentially just a bigger, faster, better version. If you have got to grips and are confident with a coaxial model, then either this or the mSR is a perfect choice.

Blade CX3 micro helicopter Heading lock gyroCoaxial stabilitySpektrum AR6100e receiver100% factory assembledBlade CX2 compatible parts

If you are after scale on a small budget, then this RC helicopter is for you. It is a faithful representation of a MD 520N Police helicopter, and it certainly looks the part. Utilizing a coaxial drive system for super stability, it will be hovering in minutes. The counter-rotating head means that almost anyone can pick up the controls and have a blast. Sub-micro servos allow full backwards, forwards and banking motions of the cyclic controls. The heading lock gyro means it will stay fixed on a rock solid course until you tell it otherwise. As a first heli, it is definitely recommended, and it is sure to give hours of fun.

Saturday, October 29, 2011

Aerial Photography: Maxi Joker 3

Minicopter, makers of the Joker 3

The Joker 3 is the latest model in a long line of field tested Joker helicopters. What began in 2000 with the Joker 1, the first high-end 90 class electric RC helicopter, has evolved over the years to become one of the most popular and universal models ever developed. The strength of the Joker in the beginning was it's enormous flexibility, whether as a beginner model, fitted to a scale fuselage, an aerobatic model, or simply a fun model to fly.

The Joker 3 complete with a basic aerial photo setup

Technology pushed things further, and with the advent of the first lipo batteries in 2004 there was a need to protect the very expensive batteries by creating a chassis that protects the valuable contents in the event of a crash. From this need the Joker 2 was born, primarily in the iteration of the Maxi-Joker. Because of its (smooth flying characteristics) and extremely low vibration it has become, and remains one of the world's most popular photo helicopter. As an aerobatic model, the Joker 2 was the first 12s battery powered helicopters.

The industry has shifted in recent years, the development of Flybarless electronics and falling prices of Lipo batteries coupled with an increase in reliability have brought many changes to the RC heli industry. Scale Heli flyers desired a drive shaft to be able to integrate the mechanics into lighter hulls. Aerobatic pilots wanted more maneuverability and less weight without compromising the chassis strength.

The Joker 3

It is precisely this basic idea of the expensive components of a helicopter in a compact, stable, and protective carbon chassis that has remained a design requirement. This typically yields around 200 grams more weight when compared to extreme lightweights on the market but costs from crashes are significantly reduced. The guiding principles of a joker are: low cost, low wear and long life.

Thus, all components of the joker are lovingly created in small batches with very tight tolerances. The same techniques are also used in the new model, the Joker 3. Concept The basic concept of the Joker 3 is to once again increase the quality. The Joker 3 in contrast to its predecessor gets a freewheel unit on the main rotor shaft and a split drive gear. Additionally the rigid tail rotor drive allows for a perfectly easy running gear, both in flight and autorotation. The freewheel on the Joker 3 is a 15mm(!) strong clamping body that allows for a total weight of up to 20kg. An additional feature is the main and tail rotor are decoupled from each other by a second freewheel, this led to increased smoothness on the 3DD and was carried over to the Joker 3.

The Joker 3 mechanics

"The very good and quiet running primary drive belt has carried over to the Joker 3. Of course the increased use of such a mechanism brought about increased manufacturing costs. A basic requirement of Joker kit must be that it costs less then 1000 euros, a requirement that they have stuck to to date. The solution to this problem was called value analysis. This is a process to optimize cost intensive production processes. A principle of our production was and is a mixture of self-manufacturing and suppliers of manufactured parts from precision oriented shops in Germany. Of course the lion's share has always been produced in house. Manufacturing process have been partially broken down to several companies and, above all, the in house manufacturing processes have been optimized. Thus it became possible to only incrementally increase the cost of the Joker even though commodity prices rose sharply in some instances."

So with the Joker 3 compared to the Joker 2 you get almost the same price for more helicopter. The good news is that the total weight of the Joker 3 is 200 grams lighter then Joker 2.

Features A fully kitted out Joker 3 aerial video unit Extremely stable and rigid chassisIntegrated host of Flybarless electronics in a well protected chassis.Compartments for components above the flight battery as well as optimum antenna position.Integrated battery slot for up to 12s/5000 mAh BatteryEngine mount acts as a cooling plate for the ESC, a small buffer battery can be mounted above the esc.Additional freewheel clutch between main-and tailrotor, an easy to mount and remove torque tube driveEasily removable tail boom for transportation and maintenance purposesPrecision scissor linkage on the tail rotor featuring 9 (!) bearingsPrecision swashplate with double ball raced swash holder and swash drive with 8 bearings.Direct CCPM linkages to the swashplate without the old push-pull linkages.Robust flybarless rotor damping with different hardnesses.Product family As the basic models we offer five alternatives: Joker 3 with belt driven tailrotorJoker 3 with TT driven tailrotorMaxi-Joker 3 with belt driven tailrotorMaxi-Joker 3 with TT driven tailrotorJoker 3 fuselage mechanic without main- and tail rotor and specific trainer attachments.

Particular emphasis was placed on the Joker 3 to give it the most flexibility possible. So in addition to the basic models you can also choose between the following alternatives:

Belt driven tail rotorMFS II main rotor instead of the paddle-less "V" rotor headBeginner Kit with specially tailored parts such as rotor blades, shorter tail boom, belt drive of the tail rotor and full upgradability to full-sized joker (8s-operation).Enlarged sub-chassie for enthusiasts of Li-ion or LiFe cells.Stabilizer or bracket for the rear strutsPlatform for gyro, or flybarless system that will not fit between the upper chassis plates.Technical data: Rotor diameter: up to 1.60 m (Maxi-Joker to 1.80 m)Weight without battery: 3250 gramsFor engines with 6mm or 8mm shaftTail rotor diameter: 290 mm (Maxi-Joker 330 mm)Reduction: Engine to main rotor: - depending on the Motor between 1:9 and 1:13,6 (7 levels)Main rotor to tail: - 4,8:1Recommendations for extreme performance Maximum: Engine: Kontronik Pyro or Köhler actro 32-3Control: Kontronik Jive 80HVLipo: SLS ZX 12s/3700 to 12s/5000 mAhBlades: Radix 690 or 710 mmTail Rotor Blades: Radix 105 mmFlybarlesselektronik: AC-3XServos: powerful digital servosReceiver: 2.4 GHz

View the original article here

Friday, October 28, 2011

Helicopter Pitch and Throttle Curves

Pitch and Throttle curves. People get to easily confused by this subject. It is mostly because they look for other peoples settings to use as there own, and don't truly understand the mechanics behind them. So when they don't work, they are unsure of what to adjust to rectify the problem, for instance if you are suffering from a low headspeed and "wagging" RC helicopter.


This subject is in fact very easy, and it just requires a little careful planning to get the perfect pitch and throttle curves for your RC helicopter. I will also briefly look at idle up pitch and throttle curves for the budding 3D pilot. My blog will list the latest RC helicopter guides and tutorials.

RC Helicopter Servo End Points

A little digression first, if you followed my previous guides, and in particular the mechanical setup guide. You will have seen we set the end points for the servo travel on the helicopter. It is useful to just spend a few minutes understanding how curves fit within those end points. When we have the servo travel set at 100%, we can increase or decrease that value, which then restricts or increases the servo travel. The pitch and throttle curves work within these pre-set end-points. So 100% at point 5 on a throttle curve corresponds to 100% servo movement if it is set to 100% as the end point, or 125% if set to this in the end point menu.

Graphical Helicopter Throttle Curve Menu

So remember, pitch and throttle curves work within your end points. When we initially set up the radio system, we gave the pitch a linear curve. Normally most radios use a 5 point pitch and throttle curve, but some more advanced radios use a much higher granularity allowing for a higher resolution curve. So in a linear curve we have the 5 points corresponding to the 5 stick positions in a linear fashion. P1=0%, P2=25%, P3=50%, P4=75% and P5=100%.


How this information is displayed will depend on your particular hand-set. Some will display it as a visual graph, and also as you move the throttle stick, will also update the relative position on the graphs axis. Others will just list them as text, so P1, P2 and so on.

Pitch Curves

After the mechanical setup, we arrived at a ±11° pitch range, with a linear curve this then means at P1 we have -11° pitch, and +11 degrees at P5, with a linear change between the two points. Crossing P3 at zero degrees pitch. It is possible to change these points to tailor how the pitch changes as we move the throttle stick. In normal mode we most certainly don't want -11° of pitch at zero throttle. But we do want this kind of pitch curve in idle up for 3D flying and upside down antics, but more on that later.

Graphical Helicopter Pitch Curve Menu

Getting back to end-points again briefly, we can use the throttle and pitch curves to set "fake" end points. So for instance if P1 is changed to 30% rather than 0%, then low stick now starts at a 30% value of the linear curve. So we will not get the full travel distance. This can be very useful. So with the pitch curve for normal mode flying you would make a higher starting point to make less pitch range between bottom and centre stick.


Changing P1 and P2 of the linear pitch curve, will allow us to reduce the negative pitch range of the helicopter. We are after a linear curve between P1 and P3, the same for the curve between P3 and P5, but at a different rate of increase. Ideally -3°, or -2° for P1, this means we wont slam the helicopter into the ground when trying to land, but also we need negative pitch to be able to bring the heli down in high winds.


The best way to set P1 and P2 is to use a pitch gauge. Attach it to the blade, and set P1 to when you read approx -3°/-2° of negative pitch. P3 will still be at zero degrees pitch, so set P2 halfway between the two. This is now your normal pitch curve Leave P3,P4 and P5 the same to match the idle up settings for these points. As the idle up switch is flipped whilst in the hover, so they need to match, usually at around 5°/6°. This normally corresponds to around ¾ stick for the hover.

Throttle PositionExample Normal Pitch ValuesNormal Pitch curveThrottle Curves

In a RC helicopter, the motor doesn't always provide power in a linear fashion, especially electrics, the power band is normally quite high. If it was linear curve, it would match the pitch change exactly, which wouldn't work. If the rpm is low on the headspeed for the given pitch, we need a higher motor rpm to increase the head speed. As our pitch values are now set. (curve rising steeply then plateau). A symptom of low head speed is oscillating in the hover, we now adjust the throttle curve to give the correct headspeed at the appropriate stick position.


The idea now is to match the power band to the correct pitch, so at 11°, we need the maximum motor rpm, again we are in normal mode, so we need a curve with a high power band. Rising fast, and then levelling out, to provide the maximum power as loads are applied to the blades, and drag becomes a factor.


Ill give a "text book " example here, what we are looking for is for the throttle to ramp up sharply then flatten out. So this would be P1=0%, P2=50%, P3=80%, P4=90% and P5=100%. Remember as the throttle stick moves we are going through two curves, pitch and throttle. Both have an effect on lift, but our pitch values are fixed, so the throttle values are the ones that need "tweaking" in order to maintain the correct headspeed of the helicopter.

Throttle PositionExample Normal Throttle ValuesNormal Throttle Curve

So, now for the scary bit (although, it really isn't that scary!) idle up! So, eventually you will want to fly upside down. If you try that in normal mode you will have an expensive repair bill, and dented pride. So we need to adjust our pitch and throttle curves to take this into account, remember, we set the helicopter up mechanically to be able to fly upside down, but we did not allow for this in our normal flight mode. Luckily, modern computer radios allow you to have a second, and even sometimes a third set of curves, that you can swap to at the flick of a switch.

Idle Up: Pitch Curve

So what we are looking for is the same amount of pitch but negative in the bottom half of the throttles travel as we have in the upper half for positive pitch, so lets say ±11°. This is simply our original mechanical linear pitch curve, this will allow for an equal amount of positive and negative pitch at the extremes of the stick movement. Set the idle up pitch curve to these numbers.

Throttle PositionExample Idle Up Pitch ValuesIdle Up Throttle CurveIdle Up Compared to Normal Throttle CurveIdle Up: Throttle Curves

So as I said, we need/want to fly upside down, and as pulling back on the throttle is now negative pitch, a linear curve on throttle would give zero throttle. We most definitely don't want this to be happening, in fact we want an increase in the motor to pull out from our manoeuvres as we press on through increasing negative pitch values.


This equates to a throttle curve looking like a "V" as we need the correct power from the engine at the appropriate pitch value. At mid stick, P3, we do not want 100% throttle, as there will be no load on the blades at zero degrees pitch, so we reduce the throttle here to stop the headspeed increasing like a banshee, we apply a linear increase either side of this, with P2 and P4 to match a linear curve. Similar to the normal mode, these values may need "tweaking" in order to get the correct head speed. We could also use a "U" shape, but the same theory applies and for this example we will concentrate on the linear increase either side of centre stick.


With these settings we will get an increase in rpm when the idle up switch is engaged, this is normal, and also the way it is normally kept. If this is unnerving, the throttle curves can be adjusted so at the ¾ stick position of the hover, when we engage idle up, they match to stop the slight and sudden jump in the helicopter.

Throttle PositionExample Idle Up Pitch ValuesIdle Up Pitch CurveIdle Up Compared to Normal Pitch CurveConclusion

So if you have followed the mechanical setup, radio setup, blade balancing, and blade tracking guides this should be the final step in the setup of the helicopters rotor head. The above examples are suitable for a wide range of RC helicopters, some may differ slightly, if in doubt, always refer to the manual, or a reputable on-line forum. You will find the members of this community more than willing to help you. Thanks for reading.

Thursday, October 27, 2011

Helicopter Scale Turbine Engines

Jetcat Scale Helicopter Turbines Jetcat PHT-3 Turbine

If you are building the ultimate scale model, you will want the ultimate scale power source. That will be a turbine engine, based upon the full size equivalents running from kerosene, and spinning at up to 100,000 rpm, enough to power even the largest RC helicopters. They are not for the beginner however, these are very complex and dangerous units if mishandled, and not to mention highly expensive. They are however essential if you desire the perfect scale model. There is nothing quite like the sound of a jet turbine starting.

Jetcat PHT-2 Turbine

One of the main turbine engine producers for helicopters is Jetcat, and in particular the very popular Jetcat PHT-3 model, which incorporates the mechanics for the main and tail gear into the unit. The specifications are as follows:

Jetcat PHT-3 Turbine Starting Equipment Gear stage: Rotor RPM: 1,260Tail rotor RPM: 5,880Torque: 28 NmPower output: 3kW/4HP (electronically limited)Weight: Turbine and gear 2.7 KgPeripherals: 550g (ECU/pump/valves/battery)Features: Centrifugal clutch, Jet-tronic ECU for autos tart, integrated RPM regulator Idle RPM: 33,000Max RPM: 85,000Fuel consumption: 60-160 ml/minResidual thrust: 1,5-10NEGT: 340-550CFuel: Kerosene, JetA1Lubrication: 5% oil mixed with fuel Fully automatic turbine start up by a command from the R/C transmitter without external connections. No compressed air. No starting equipment.Turbine starts without compressed air or fans. Automatic cooling down when the turbine is shut down.Precision ceramic ball bearings for low maintenance.High performance turbine wheel which is fully tested.Integrated glow driver with a separate function to check the glow plug.Turbine supervision and regulation assisted by measurement of RPM and exhaust gas temperature.Multi-stage electronic system to ensure reliable operation.Connection to the R/C system via 1 receiver channel. A second switched channel is required to operate air speed sensor or smoke system.Rapid throttle response time.Programmable minimum and maximum RPM within the allowable range.The fully automatic start up and running procedure minimizes operator handling faults that could result in damaging the turbine.Plain text display of the current running parameters including: exhaust gas temperature, RPM, fuel consumption, remaining fuel, last run time, total run time, battery voltage, turbine condition, reason for last shut down etc. Options: Active rotor brakingRS232 Computer interfaceAir speed sensorJetcat turbines

We are pleased to announce that we will also be shortly offering a build service for these engines, in conjunction with the scale build service for Vario fuselages. So if you are keen to get in the air, but not so keen on the many hundreds of hours some models can take to create, then we will be your best option. It means you can take the guess work out of the equation when dealing with £3,000+ jet turbine engines.

Wednesday, October 26, 2011

Helicopter Radio Setup

Introduction

Computer helicopter radios do a lot of the hard work for us now in flying a radio controlled helicopter. But they need to be setup carefully and accurately. You will normally require a 6 channel radio for a RC helicopter. These are, elevator, aileron, rudder, gyro, throttle and pitch. A computer radio will mix the cyclic servos to control the swash for you. It will also mix the throttle and pitch, dependent on your settings.


Some of the options can be overwhelming. Below you will find the main options that you need to know about, and what there purpose is. We will add at a later date some "Ideal" settings for particular helicopter/transmitter combinations. However, we encourage you to make your settings unique to yourself, this will allow for greater understanding of the operation of the helicopter, and for a more responsive and well behaved helicopter.

Revolution Mixing The Spektrum DX6i helicopter radio

If you have installed a Heading Hold gyro, you will want to inhibit this option, as the gyro will take care of it for you. If not you will have to do some trial and error getting this setting just rite.


Basically, as you increase the throttle of the RC helicopter, the torque is increased, meaning the tail will want to move in the opposite direction to the main rotor. What revolution mixing does is mix the throttle channel to the rudder channel. There by compensating for this movement.

Digital trims

To set this, you will want to be in a stable hover, increase the throttle and take note of the amount of movement. After landing again, change the setting by a percent or two, hover, and repeat, until an increase in throttle has little or no effect on the helicopters tail.


Allows you to choose between a 90 or 120 degree swashplate, dependent on your helicopter.

Revolution mixing

Controls the movement of the cyclic servos in response to stick movements. This is used in combination with a mechanical setup to get the swashplate level at all ranges of pitch.

Throttle Curve

The throttle curve maps pre-defined values of throttle power to your collective stick. Linear by default, this means that when your collective is at zero, your throttle will be at zero. Equally, when at 50% and 100% collective, your throttle will be at 50% and 100% respectively.

Swashplate selection

99% of the time however, you will not want a linear line, it will be curved, as the aim is to maintain a constant headspeed with a combination of this setting and the pitch curve (See below) The exact numbers for the throttle curve will depend on your flying style and helicopter.

Pitch Curve

Similar to the throttle curve, the pitch curve controls how many degrees of pitch your blades are exhibiting when the collective stick is at any particular position. Unlike the throttle curve, a good starting line for this is linear (0/25/50/75/100) for the five collective positions. You can make changes to this to change the sensitivity of the helicopter in hover for example, but you will also need to adjust the throttle curve to maintain that magical constant head speed.


Again trial and error to set up, and not needed if you have a heading hold gyro. This allows for different trims at different rpm modes (Idle up etc, more on this later).

Channel Reverse

As simple as it sounds, it allows you to make changes to the travel directions of the different servos.

Swash mixing

Like we all learned in mathematics, an exponential curve, increases or decrease at an ever increasing rate. So applying this type of setting to your helicopter cyclic controls means the area around the center of the sticks will be less sensitive than the extremes of the sticks. This will help in the hover, but allow for agile flight characteristics when chucking the model around in an aerobatic attempt.

Gyro Gain Servo reverse

The sensitivity of your gyro is controlled from this option. It may take a few hovers to get it spot on. But the tell tail sign of to much gain, is wagging of the tail on the horizontal plane. To low and the tail will be very sloppy, not holding position as well as it should be. Fine tune this for the ultimate tail hold.

Idle Up Exponential

The "switch of doom" as it is more commonly know, this has been known for more crashes than i care to mention. If you do not intend on using this and/or you are a beginner, make sure this is inhibited.


Essentially it allows you to set multiple options to different values at the flick of a switch. As an example, in normal flight, hovering etc a pitch curve giving 0 - 6 - 10 degrees of pitch is perfect, and with this a reasonable calm throttle curve. Now that we are coming out of the hover, and want to try out some 3D routines, we require some negative pitch, so having pre-set our idle up throttle and pitch curves, we can switch to a constant throttle value, and a pitch range of (-10) - 0 - 10. Meaning that just above centre stick we have a few degrees of positive pitch, and good throttle value for hovering. We can now flip the model and hover inverted, as we can use the lower half of the collective travel for negative pitch.

Gyro gain control

This is similar for a lot of the other values, including the gyro gain, these can all be set to a different value for idle up. Some radios will also have a idle up 2, it is the same thing, but allows for 3 separate settings.

Throttle Hold

If you ever need to do an emergency autorotation, this allows you to set a specific pitch curve, and access it at the flick of a switch, to allow you to glide your helicopter down safely.

Travel Adjust Servo travel limits

It allows you to set up how far the servos travel with a given stick movement. It allows you to set end points, so your servo doesn't keep moving when it should be stopping due to mechanical limitations.

Trainer (Switch)

Whilst held, allows for a second, connected helicopter radio to take over your flight controls. However, once released the controls are back in your hands.

Hover Pitch and Throttle (Adjustable dial)

Allows you to fine tune the pitch and throttle values whilst hovering. You should be aiming for around 1,600 rpm on the throttle and 6 degrees of positive pitch in the hover.


That just about wraps up our guide to radio setup. Check back soon for some pre-made settings for popular combinations, and a more in-depth look at some of the advanced functions and mixing possibilities.