There has been a strong tendency in recent years to produce more and more specialised radios aimed at particular user groups such as aerobatics, gliders, helicopters, etc. This is fine for the dedicated contest flyer, or if the purchaser is only interested in one type of model, but there is clearly a demand for a general purpose radio which can suit all of the main interest groups. There have been attempts in the past to produce such a set using various types of plug-in modules, but these have never been popular due to their not being self-contained.
The advent of the microcomputer has made many things possible and several manufacturers are again turning their attention to multi purpose sets. JR's approach to the matter is to introduce the 'X-347', a name which is intended to convey that the equipment can cater for three types of model, has four model memories and seven channels.
Thanks to MacGregor Industries, I was able to examine a set over a period of some weeks which gave me ample time to find out just what it can do. There is no doubt that, while some compromises have been necessary, there is more available for each model type than the average flyer is ever likely to need. The helicopter functions, for instance, incorporate more than was generally available on any set until about three to four years ago. It also re-introduces a training or 'buddy box' system, a feature which has been absent from many recent sets.
The heart of the whole system resides in the transmitter and the airborne part of equipment is virtually identical to all existing JR sets, so we will not concern ourselves with that other than to mention that a new 7 channel PCM receiver is supplied. This means that PCM receivers are now available in 7, 8, 9 or 10 channel versions, all of identical size and weight.
The transmitter case follows the trend of all the new JR outfits and is very comfortably shaped to fit the hands. This particular case appears to be specifically designed for the 'X-347' and is not shared with any other model in the range.
Sticks are of the usual JR type with adjustable length and manual trims. The trim levers appear to incorporate the familiar overtravel device for extra movement but this has actually been discontinued and the moulding is now in one piece. As the computer allows you to have as much trim offset as you wish, this was obviously no longer necessary. Instead of the usual meter there is a large liquid crystal display which conveys all of the necessary information required when setting up. Information is fed in via six pushbuttons at the bottom of the front panel.
A useful feature is that the stick mode can be set to any one of four, via the computer, and the throttle ratchet and elevator spring are easily accessible for changeover. The four stick modes available are the usual 'mode 1' and 'mode 2', plus left handed versions of both of these. Stick tension can also be varied, as can the throttle ratchet tension. Trim levers now have a notch at the centre point so that you can identify this by feel.
A large handle on the rear serves as a convenient carrying device and also serves to prop the rear of the transmitter clear of the ground when laid flat. This gives some degree of protection to the plug-in RF module but may present difficulties if you use a transmitter tray. The aerial collapses inside the case making a very compact package for stowing in the car.
A removable panel at the lower rear of the case gives access to the battery. Also on the rear are two sockets for charging and direct servo control (DSC). This later socket is also used to connect two transmitters for training purposes.
The various minor controls are a little complicated to explain since most of them have more than one function. However, here goes:
There are three dual rate switches for aileron, elevator and rudder. The first two are located at top right and top left of the front panel and the third is at the front left of the case top. These can also be set to give an exponential response if required.
On the left, between the elevator dual rate switch and the display there is a knob which serves as a pitch trim in 'heli' mode or as auxiliary 2 in other cases. In similar fashion, between the aileron dual rate switch and the display there is a three position switch which serves as a pitch range switch in 'heli' mode (N, 1 or 2) or as a flap mixing switch (E>F, OFF, or F>E).
Completing the controls on the left hand side of the case top, there is a switch at the rear which operates the throttle hold in 'heli' mode and is a mix on/off switch for other uses. Further in there is a knob which serves as a hovering pitch trim or as a flap trim when flap/aileron mix is in use.
On the right hand side of the case top is a large spring-loaded toggle switch which operates the snap roll facility. If this is not in use, the switch can be used to operate the stop watch. It can also be used for the trainer system. A smaller switch in front of this can operate the retract function in any mode, or the invert function in 'heli' mode. It can also be used to turn a butterfly tail mixer on and off in the 'glider' mode. Finally, a knob between these two switches and the display serves as a flap control or as a hovering throttle in the 'heli' mode.
When you switch on the transmitter you will be presented with a display which shows a letter (C or F) which indicates the type of modulation selected (PCM or PPM), the battery voltage and the timer (either stopwatch or countdown). In this state, only the timer can be operated and this is done by means of the '+', '-' or 'CLR' keys.
To program(me) the various functions you have two options:
a) Turn the transmitter off, hold down the two keys marked 'UP' and 'DN' together and switch the transmitter back on. This gives access to the 'System Setting Mode'.
b) With the transmitter turned on, press the above two keys together, this gives access to the 'Model Program Mode'.
The 'System Setting Mode' allows you to set the overall characteristics such as the model type, model name, modulation type, the stick mode and allows you to copy information from one model number to another (not, alas, from one transmitter to another). It also allows you to set the swashplate type ('Heli' mode), wing type ('acro' mode) and 'V' tail/flapperons ('glid' mode).
The 'Model Program Mode' allows you to set up all of the individual parameters for each model.
It must be said here that the method of actually setting and displaying of the various programmable functions for a model aircraft is controlled very much by the amount of money that the modeller is prepared to spend. The more simple and logical that the entry system is and the more clear and graphic that the display is, the higher the cost. It follows from this that a budget system will necessarily involve a fair amount of learning on the part of the owner. If the equipment also has to cater for many needs, then the result will involve even more compromise. Because of this, the 'X-347' has what might appear to be a very complex and confusing entry system which is made more difficult to learn by the restricted amount of information that can be displayed. Nonetheless, it is all there and it is up to the owner to use it. The writer is a firm believer in the adage, "if you really need it, you will learn to use it.
Where the consumer may perhaps have a justifiable complaint lies in the fact that virtually every new model (even from one manufacturer) seems to have a different programming system. However, those of you who are familiar with computers will be aware that this problem is not restricted to the radio control industry!
Having said all that, there is little point in going through all of the programming options, in detail, for each type of model. The following is, therefore, only a brief summary of what is available.
These apply to any type of model and include servo reversal on all channels and adjustable end point in each direction (maximum 150%). A 'Sub Trim' facility allows you to offset the neutral point of any channel by up to 125%. This means that you can reset the stick trims to the centre for all models and don't have to remember where they should be for each model. If over-used, this can limit the throw in one direction, so use with caution.
Both positions of the dual rate switch can be set to any value between 0 and 125%. You can also set up exponential throw on both dual rate switch positions. The maximum travel will remain at the figure set by the dual rate facility and the exponential can be from 0 to 100%.
There are 4 programmable mixers (only 1 in 'heli' mode) which can be used to mix any two channels on a master/slave basis. The mixers can be switched in and out in several ways. Mixing ratios are adjustable (they are also influenced by the end travel settings) and can be in any direction (right or left rudder can apply up elevator).
Failsafe can be set to hold the last position or go to a programmed setting (PCM receivers only).
The training system allows two transmitters to be coupled together and allows control of any of the four main flying controls to be retained by the instructors transmitter when control is passed to the student. This means that the student can learn one or more controls at a time.
Several timers are included. An integrated timer keeps track of the time that the transmitter is switched on (it must be reset after charging) and a second timer can be used either as a stopwatch or as a countdown timer. At the end of the countdown period, there is an audible alarm.
As previously noted, there are four model memories which store all of the various values and any of these can be set to any of the three model types. In other words, you can have one for glider, one for a power model, one for a helicopter and one more of any type. To help you to remember which is which, the model name can be displayed too (up to 7 characters). Obviously, there is only so much that the computer can do for you and you have to remember what each minor control does in each model mode. However, they are all suitably labelled with all of their functions in abbreviated form.
Elevator/flap mixing can be switched in or out via the flap mix switch. Flaps can move from 0 to 125% of the elevator movement (up and down set separately) and can be in either direction.
Flap/elevator mixing sets any required trim change of the elevator when the flaps are lowered. This can be set up to operate automatically at a predetermined throttle position (Auto Landing System).
The snap roll switch can be set to simultaneously drive the aileron, elevator and rudder servos to their maximum movement deflection in any required direction to cater for left, right, inside or outside snap rolls.
By using separate aileron servos for each wing the amount of differential movement can be programmed. It also then becomes possible to operate the ailerons together via the flap control (flapperons).
The 'acro' mode also has two unique functions. One is an automatic rudder dual rate which can change the rudder rate at a preset point on the throttle stick. The other is a low receiver battery warning which closes the throttle when the battery voltage reaches a predetermined point. Closing and then opening the throttle will restore normal operation.
There are 4 pitch curves (N, 1, 2 and Hold) and 3 throttle curves (N, 1, and 2). Pitch and throttle curves can have high, low and three intermediate positions (5 in all) set for each range. The high throttle setting is set on the 'N' range and remains the same for all. There is no adjustment for the inverted pitch curve, so the model will require careful adjustment, but there is a facility to set a point where the pitch servo position will not change when the switch is operated. This effectively means that the inverted pitch can be offset from the normal pitch range. No adjustment is available for the inverted throttle curve and you have to choose one of the existing curves. When the hold switch is operated, the throttle goes to a preset point.
In addition to the above, there are a number of manual trim adjustments. The throttle can be varied around the mid-point by means of the 'hovering throttle' knob. The throttle trim lever only works on the lower half of the throttle movement. Both of these controls are only effective when the pitch curve switch is in the 'N' position.
The pitch can be varied around the mid-point by means of the 'hovering pitch' knob. This is only effective when the pitch curve switch is in the 'N' position. There is also a 'pitch trim' knob which moves the entire pitch range up and down on all ranges. While still common on Japanese equipment, the provision of this particular control continues to baffle this writer. If it is in the wrong position, all of your careful setting-up is wasted!
An ATS system is incorporated which allows the tail rotor trim to be changed when the throttle is opened or closed. This is effected via adjustments for 'up' or 'down' mix. The system can be set for clockwise or anticlockwise rotors. Two settings are available; one with the pitch curve switch in the ³N³ position and one when it is in the '1' or '2' position.
For those models which feature moving swashplate systems and require electronic mixing, two mixers are included which cater for 2 or 3 servo systems.
This has elevator/flap, flap/elevator flap/aileron and differential aileron mixing which is generally similar to the 'acro' mode. An extra feature is the ability to use four servos for ailerons and flaps and move all four in varying degrees for aileron or flap control. In this configuration, the 'auxiliary 2' knob now becomes a roll trimmer for the flaps.
The throttle stick now operates the spoilers, if fitted, and it is possible to mix this signal into the above mixer and operate spoilers, elevators, flapperons and flaps together. There is also a 'V' tail mixer!
It may not quite be all things to all men, but it certainly has a pretty good shot at it! No doubt the dedicated contest flyer will find something missing (he would anyway), but then it is not really intended for him. For the average flyer who wants to try his hand at more than one type of model, it is just about ideal.
The inclusion of a training facility, which was almost going out of fashion, should make it very useful to a lot of new modellers - and that alone should make it worth the price.
For those readers who would have liked more information on one or more aspect of the equipment, my apologies. It just was not possible within the limits of one article.