THE NEW JRXP8103 COMPUTER RADIO
(both early and digital trim versions)
By: Sherman L. Knight
Kirkland, Washington
The evolution of JR’s computerized radios continues with the introduction of the new XP8103. This new radio adds some exciting features. The most important is multi-point programmable mixing which completely eliminates that annoying bump the model takes when you first pull the flap stick down. Landing approaches are very smoooooth. This feature alone is well worth the cost of a new radio.
The JR X388S and the JR X347 has been discontinued. The 347 has been replaced by the JR783. The JR X388S has been replaced by the new JR XP8103. In case you are wondering, the new JR783 is virtually an identical radio to the JR388. If you take the two manuals and compare them page for page, they are exactly the same except for channel number eight (Aux3) is no longer available on the JR783.
If you owned either the JR347 or the 388, you will find that there is very little learning curve with this new radio. The switches and knobs are in the same place as they were on the 388 or on the 347. The programming language is also the same.
There are a few new mixes in the radio such as multi-point programmable mixing. (It makes landing approaches so smoooooth.) There are several new screens which have revised, simplified, and made the programming easier than it was before.
There are now two versions of the XP8103. Regular and digital trims. A few functions are different. When ever you see [DT] in the text, this represents a digital trim only issue.
The XP8103 also sports a new and much larger screen. The new screen is nearly twice the size of that found on the 347 or the 388. The screen is pixilated, allowing the computer to place four times the amount of information on the screen at one time, as the 388 or 347. The larger screen also contains an X\Y axis to be displayed on the screen so you can see a visual representation of dual rates, exponential rates, and the multi-point programmable mixing.
The new XP8103 supports a case similar to the 347 and the 388. The new radio still fits my small hands just perfect. Some of the additional changes to the case include:
1. Eight buttons across the face instead of six.
2. The on/off switch has been recessed into the face making accidentally turning off the
transmitter much more difficult.
3. The charged jack receptacle has been placed on the side of the transmitter housing
rather than the back. You can now lay the transmitter down on its back during charging and not have to worry about it falling over.
The XP8103’s transmitter modules are interchangeable with all other JR radio modules.
The new radio is only sold in two versions. One for aircraft and a second one for helicopters. The aircraft version is sold in either an FM or PCM version. Both versions come with four NES517 servos, the ball bearing version of the 507. [DT] Digital trim is available in a sailplane version that comes with two NES-341 servos
Other improvements to the programming features include a much easier to use trim offset memory. Trim offset memory allows you to fly the airplane while making all the necessary trim adjustments. Upon landing, with the push of a button, the trim positions are memorized, and each individual trim knob can be reset to center. In the new XP8103, the instructions on how to go about the process are actually written right on the screen and much easier to use than before.
[DT] JR did remove the trim offset from the digital trim model. You no longer have to save your trim settings before you switch to a different model in the radio. As you switch from model to model with the digital trim version, the radio remembers the last location of each models trim settings. If you fly two classes in your local competitions, you no longer swear at yourself for forgetting to save your last trim locations. No more sub par launches when you forget to reset the trim lever to neutral before launching a different model. [DT] The new 8103 with digital trims make some refinements to the earlier programming and adds the digital trim levers. The old style trim levers are no more. The trims for rudder, elevator, and aileron have been replaced with a trim lever that moves one click each way, beeps and then the spring loaded lever automatically returns to center. The large display of the 8103 now contains a sliding bar graph for each trim lever. [DT] To change the trims, you simply bump the trim lever. Each time you bump the trim lever there is a corresponding change in the position of the control surface on the aircraft. A black dot moves along the graphic bar on the display screen and the radio makes a beep each time you bump the lever. If you bump the lever and hold it down, the trim will make rapid advancement in the direction the lever is held down. As the trim is changed to the top or to the right, the beeps become come higher in pitch. As the trim is changed to the left or bottom, the beeps become lower in pitch. As the trim passes through the center position, a louder and easily recognizable beep occurs. [DT] On the surface, digital trims do not sound like much of an improvement. Boy, was I surprised. The resolution of the digital trims is adjustable. In its default mode, one click of the digital trim is approximately 20% less trim than the old style radio. The default can be changed so that 5 or 6 clicks of the digital trim is required to equal one click in the old style radio. With the digital trims finer resolution, the elevator “sweet spot” was much easier to find. Even if you change the defaults to the finer resolution, the total amount of servo trim adjustment remains unchanged. Whether the resolution is fine or course, the total amount of trim adjustment remains the same (approximately 15 degrees each way from center). [DT] Over the last six or seven years, there has been a significant amount of discussion concerning elevator “dead band”. “Dead band” may appear in several forms or any combination of forms. The most common is lack of pitch change with small stick changes near center. Another is an plane that cannot hunt. In other words, upon moving to level flight, the aircraft feels like its mushing along (nose high). The next time the aircraft moves to level flight, it feels like it will not slow down (nose down). It seems to occur most often on aircraft with full flying stabs. [DT] There are many items that can contribute to “dead band”. The ones most often discussed are sloppy linkages, air foil cross section and worn out servo pots. Add a new “dead band” contributor to the discussion. Lack of trim resolution in the radio.The trainer function instructions are now written right into the radio screen. The trainer function allows you to select the servos in the airplane that the trainee has control of. In other words, you can selectively allow them to learn elevator first, then add rudder second, etc.
One feature that you are not going to discover unless you read the entire manual is that the contrast of the display screen is adjustable. Not only is it a nice feature but, it is necessary. The contrast setting for viewing the screen in your shop, late at night, is significantly different than the best viewable screen in full daylight. For those of you who didn’t bother to read the entire manual, the screen contrast adjustments can be found on page 19.
The XP8103 allows you to transfer all the trim settings directly into another XP8103 through a trainer cord. [DT] You may not transfer trim settings from an original XP8103 and a digital one. Several mix values changed in the radio making them incompatable for transfer through the trainer cord.
Some of you may be confused by the lack of a “OFF” setting for much of the programming. Most all computer radios do not contain a setting called “OFF”. Why? Because every function is “ON” all the time. As long as the mix value is set to -0-, nothing will happen. In other words, “OFF” and “-0-” are the same thing.
Programming the XP8103 for a full function six servo sailplane.
Flexibility is a wonderful thing. However, programming the JR is complicated by the fact that the radio’s flexibility may provide more than one way in which to accomplish the same result. Although more than one means may be available, it is important to select and use only one method to accomplish your objective. Otherwise, programming functions may be in conflict and actually cancel themselves out. This article is only one of the many methods to accomplish the objectives below. If you disagree with my methods, or have found one that is better, please let me know what they are for use in a future article.
This article also assumes that you own an XP8103, have the manual handy and are familiar with the eight programming buttons across the face of the radio. The page numbers referenced in the article are the page numbers found in the manual.
The transmitter has two separate programming modes. These are the system setup mode and the function mode. The system setup mode comes at the beginning of the instruction manual (Page 104) and must be completed before you perform any of the function modes. (Page 113) If you program the function settings first, and then revise the system setup settings second, it may result in wiping out your programming and returning to the system defaults.
There are also some revisions to the manual you may want to make before getting started. The first one, is to photocopy page 105 and 106, re-label them 4.1 function mode and insert them in you manual at page 113. The second is to re-label the servo to receiver connection diagrams found on page 100, 102, 114 and 115 to the following:
Channel # TX Function Airplane Function
1 Spoi Empty
2 Ail 1 Right Aileron
3 Elev Elevator
4 Rudd Rudder
5 Ail 2 Left Aileron
6 Flap Left Flap
7 Aux 2 Right Flap
8 Aux 3 Empty
The battery may be plugged into any empty slot on the receiver.
System Setup Mode.
You enter the system setup mode by pressing and holding down the UP and DN buttons on the face of the transmitter while turning the transmitter on. You will then be confronted with the screen entitled [System M]. You won’t find this display in the manual anywhere.
On the left hand side of the display you will see a triangle pointed at Model SEL. This triangle (and later an arrow) will be referred to throughout the article as the cursor. The cursor can be moved around the screen by pressing the UP or DN buttons. After you have selected the area you wish to enter, press the up and down buttons simultaneously.
Start the programming by placing the cursor before Model SEL. Press the UP and DN buttons simultaneously. Press the (+) or (-) buttons and select a model number (1 thru10) that is empty.
Press the UP button to assign a [MDL Name]. (page 107)
Press the UP button again. Touch the (+) or (-) buttons to move the cursor to glider. (page 108). Press the UP button two more times to select the [MODULAT.] of your receiver. (page 109) Every XP8103 sold will transmit in FM,S-PCM or Z-PCM. If you ordered the FM version, you may have received an FM receiver but your transmitter will still broadcast in all three formats.
Touch the UP button two more times to select the [Wing Type] of your aircraft. Touch the CH key to move the cursor from V-tail to dual-flap. Touch the (+) or (-) button to change dual flap from inactive (INH) to active (ACT). Perform the same function if you have a V-tail.
Touch the UP button again to select the method of flap input.[INPUT SEL] Touch the (+) or (-) button until input reads FLP.SW+P6.
Touch the UP and DN buttons simultaneously to return to the general information display.
Function Mode.
After turning the radio on you will see the general information display. To enter the function mode simply touch the UP and DN buttons simultaneously.
Before you begin, make sure the servos in the wings are inserted so that the arm side of the servo faces the wing tip and closest to the trailing edge of the wing. I further recommend, that during normal flight mode, you set up your radio so that all of the switches are in the same direction. I prefer starting at the top back of the radio and pulling my hand forward and down and move all the switches in that direction. That way, during normal flight mode, the switches all match the direction of the aileron/rudder mix switch when it is in the “on” position. This further simplifies flying and allows you to quickly check your radio without looking down at it by simply passing your hands over all the switches. If you have a V-tail, perform the V-tail mixing at the end of this article first.
Inhibit Pots 5, 6, & 7
Touch the UP or DN buttons until [D/FLAP T.] appears in the upper left hand part of the screen. (Page 122) Press the CH button until the cursor appears before POT.5, press the (+) or (-) buttons until it indicates that it has been inhibited (INH). Do the same for POT.6 and POT.7. You don’t need these functions. Leaving them active will just allow mistakes to be made during flight.
Servo Reversing.
Touch the up or down button until [REV.SW] appears in the upper left hand part of the screen. (page 114) Slowly operate the rudder (left hand stick), the elevator and ailerons (right hand stick). Make sure that all of the control surfaces move in the correct direction. To reverse the servo, touch the CH button until the cursor moves to the appropriate servo. Touch the (+) or (-) button to reverse its direction.
Aileron Differential.
Touch the UP or DN button until [DIFFEREN.] appears in the upper left hand portion of the screen.(page117) Push the aileron stick all the way to the left or right (do it slowly and if the control surfaces encounter binding, don’t move the stick any further). Press the (+) key while watching the down aileron. If the down aileron starts moving up, you can move onto the next step. However, if the up aileron moves down perform the following. At the receiver, pull the plugs for the aileron servos (channel 2 and 5), reverse the plugs and then check the aileron stick for aileron movement. If the ailerons are backwards simply return to the servo reversing switch function and reverse the servo throw on servos 2 and 5. Check Differential again, if the down aileron moves up then the settings are correct. (At this stage of programming, you should have control over the ailerons, elevator and rudder.)
There is a three position switch just above the throttle stick Move the switch to the down position. If the flaps move up reverse the servo leads at the receiver, just like the ailerons.
Sub Trim.
Sub trim allows you to electronically center all of your control surfaces. Now that the servo direction is correct, and the aileron servos are properly plugged in, it is time to align all of the control surfaces.
All of the control surfaces must be aligned mechanically first. Adjust the linkages and servo arms for the elevator and the rudder so that they are as close to neutral as possible. Remove the servo arms from the aileron servos and rotate the arm forward (toward the leading edge) similar to the diagram found on page 134. Do not connect the flap servo arm at this time. It’s important to perform this function with the transmitter and receiver turned on.
Touch the UP or DN button until [Sub Trim] appears in the upper left hand portion of the screen. (Page 114) All of your sub trim values should read 0%.
Do not make adjustments or try to align the flaps at this time. Flaps will be covered later. Touch the CH button until the cursor stops beside the control surface you wish to adjust. Touch the (+) or (-) keys until the control surface is exactly centered. (ailerons, elevator and rudder)
End Point Adjustments.
We have reached one of those situations where there is more than one means to accomplish the end result. That end result is changing the amount of servo throw which in turn effects the amount of the control surface movement. The manual advocates the use of travel adjustments [TRVL ADJ.] (page 115) as a means of adjusting servo throws. However, this means you must make at least two adjustments for each servo. If you are using flaperons (flaps that follow your ailerons) to change the differential you may have to change as many as eight end-point adjustments. In the alternative, you can adjust the amount of aileron throw by using the dual rate function. (If ailerons are mixed to flaps, this duel rate function will adjust the amount of throw on all four wing servos at the same time.) Further, you can also adjust the differential between up and down aileron or flaperon for all four servos by a single adjustment.
Most models today come with instructions and recommended control throws of the ailerons, elevator and rudder. Instead of using the travel adjustment function, use a combination of dual rate and differential mixing to simplify the process. More importantly it makes field adjustments easier.
Dual Rates.
Duel Rate functions are available for elevator, rudder and ailerons. Touch the UP or DN button until [D/R & EXP] appears in the upper left hand corner of the screen. (Page 113)
Let’s start with the elevator. Touch the CH button until ELEV appears. Touch the select button until the cursor is before D\R. Move the elevator stick slowly, until it stops and hold it in that position. If the actual elevator throw is greater than that recommended in the plans, touch the (-) button while holding the elevator stick against the stop. The amount of elevator deflection will slowly decrease. Stop when the amount of elevator throw is correct.
Now move the elevator stick in the other direction. As you can see, the dual rate function should have effected both the up and down elevator. (However, if your mechanical linkages are not symmetrical you still have more deflection in one direction than the other.)
Touch the CH button again until AILE appears on the screen. Again, move the aileron stick all the way to the stop. Measure the amount of up aileron and compare it to the amount recommended in the plans and specifications. Too much or too little aileron deflection, adjusts the dual rate function appropriately until you get the right amount. At this stage, only concern yourself with the amount of up deflection of the ailerons. Be careful, watch the down aileron carefully, if binding develops, stop moving the stick. Continue to reduce the dual rate until there is no binding at full stick movement or until you reach the recommended throws in the models instructions.
Finally, perform the same function for rudder throw by fully deflecting the rudder stick (left stick) and adjusting the rudder dual rate appropriately.
These instructions will only get you in the general area for the particular type, style and trim of your airplane. Use the dual rate function to modify the pitch or roll sensitivity of the aircraft to satisfy your personal taste. I highly recommend, that once you have determined the optimum setting, that you program both switch positions for dual rate and exponential to be exactly the same. This alleviates you from accidentally bumping a switch in flight and suddenly having an aircraft with different flying characteristics.
Aileron Differential.
Touch the UP or DN button until [DIFFEREN] appears in the upper left hand portion of the screen. (Page 117) Hold the aileron stick against the stop. Touch the (+) or (-) buttons to adjust the differential between the left and right aileron. The low aileron will move up. Move the aileron stick to the opposite stop and notice that the differential setting works for both ailerons.
Travel Adjustment.
Now that you have the four basic control surfaces (both ailerons, the elevator and the rudder) adjusted to appropriate amount of control throw, it is now time for the final adjustments. (The final adjustment of these control surfaces should be done at home on your work bench and not in the field.) The goal is to obtain travel adjustment as close to 100% as possible for the four servos.
Unless you are an expert builder or awful darn lucky the control surfaces will not move equally. One aileron will move up further than the other one or the rudder will move further to the left than it does to the right. The fine tuning of these control throws is now done using travel adjustment.
Touch the UP or DN button until [TRVL ADJ.] appears in the upper left hand side of the screen. (Page 115) Your new XP8103 screen contains all of the travel adjustments for four servos at one time. Touch the select button to change the screen to the other four servos.
Touch the CH button until the cursor moves to AIL 1. Move the aileron stick from left to right and notice that the cursor shifts from left to right.
Move the aileron stick all the way to one side. Measure the deflection of each control surface. Move the aileron stick in the other direction and measure the opposite control throws. Compare the two ailerons to see if they deflect the same amount. (If they are off they should only be by a very small amount). Use the travel adjustment to fine tune them until they are the same.
The same travel adjustments should be made to make sure that the rudder deflects the same both left and right.
The elevator is the one place where I typically install more throw in one direction than the other. Additional down elevator is useful at the top of the zoom, right before the aircraft loses air speed and the control surface becomes unusable. Sometimes that push over needs to be fairly abrupt and additional down elevator is helpful.
Aileron to Rudder Mixing.
Most pilots like to set up their model, so that when ailerons move, the computer automatically mixes in a predetermined amount of rudder. Touch the UP or DN button until [AILE RUDD MIX] appears in the upper left hand part of the screen.(page 120) Touch the CH button again until the cursor moves to SW: Press the (+) or (-) buttons until the word MIX appears on the screen. The rudder mix can now be turned on and off by the switch in the back, right hand corner of the radio. If you flip the switch back and forth, you will see the words SW OFF appear and disappear on the screen.
Touch the CH button until the cursor is beside the word Rate: Push the aileron stick all the way to the left and press the (+) or (-) buttons until the rudder moves in the appropriate direction. Insert the amount of rudder mix recommended in the instructions for your model.
You now have control sufficient for the flying of the aircraft. You just don’t have any landing control devises yet.
Flaps and Landing Mode.
Now that the basic control surfaces of the aircraft have been completed, the remainder of this section will focus on various flight modes which involve the use of flaps. These will include landing, launch presets, trailing edge reflex, and full span and camber charging.
Push the UP or DN button until [Sub Trim] appears in the upper left hand portion of the screen. (Page 114) Press the SELECT button until you are on the screen that includes FLAP. Press the CH button until the cursor stops before FLAP. Touch the (+) or (-) button and adjust the servo arm in the direction that raises the flaps. You will need to disconnect the flap servo arms from the servo as they will obviously have to be readjusted. A suggested starting value for the flap setting is UP-100. [DT] UP-200. When complete, touch the CH button, and perform the same function for AUX2. Failure to perform this function will reduce flap movement in landing mode to less than 45°. Re-install the servo arm as shown on page 134 of the manual. Adjust the control linkage to the flaps so that the flap is in neutral on normal flight position.
Touch the UP or DN buttons until [Butterfly] appears in the upper left hand portion of the screen. (Page 121) Touch the CH button until the cursor stops before SPOI OFFSET. Push the throttle stick all the way to the top and press the Clear button. A value should appear to the left of SPOI OFFSET between 160 and 180.
The switch on the upper left front corner of the radio is for switching between flight mode and landing mode or between various types of landing set ups. The manual refers to this switch as the butterfly switch. (Page 121) Again, I like to set up my radio so that all the switches, during normal flight mode, are either in the forward or down position. To set up the flaps for landing and before performing the next step push this switch towards the back of the radio. The switch must be in this position for the landing flaps to work.
Touch the CH button again until the cursor stops before SPOI FLAP. Pull the flap stick (formerly the throttle stick) all the way to the bottom. Press the (+) or (-) button until the flaps move in the proper direction and in the desired amount. You should be able to obtain 90° flaps quite easily. If you can’t obtain 90 degrees of flap there is probably a mechanical linkage problem. Try shortening the flap control horn or lengthen the servo arm.
Touch the CH button again until the cursor stops before SPOI AILE. If you want to add a little crow to your landing routine, again, pull the flap stick all the way to the bottom, and touch the (+) or (-) buttons until both ailerons move in the appropriate direction and the desired amount.
Finally, touch the CH button one more time before the cursor stops before SPOI ELEV. Again, with the flap stick all the way at the bottom, touch the (+) or (-) buttons until the elevator provides the appropriate amount of down elevator to compensate for the pitch up moment created when the flaps are lowered. Every airplane is different and the amount that you ultimately use will depend on your aircraft and your flying style. A recommended starting point is approximately 35%. Remember, the proper compensation is down elevator with full flaps. You must fly and experiment with the mix percentage, 35% is only a starting point.
The XP8103 also provides for a specialized mix function which will completely eliminate that annoying bump that the airplane makes when you first pull the flaps down. That specialized mixing function is discussed later under Multi-Pint Programmable Mixing.
Launch Flap Preset.
Launch flap preset is available on a long three position switch immediately above the flap stick. Move that switch to the low position. Undoubtedly, you will have more launch flap than you desire. Touch the UP or DN buttons until [TRVL ADJ.] appears in the upper left hand portion of the screen. (Page 115) Touch the Select button to move to the second of the two screens that contain both FLAP and AUX2. Touch the CH button until the cursor moves before Flap. Move the launch switch to the low position, and the cursor should automatically appear beside the letter D. Touch the (+) or (-) button until the flaps move to the desired location for launch. Flipping the launch switch back to the center position should instantly return the flap to the neutral position.
Trailing Edge Reflex.
First, turn the receiver off. The factory default setting for reflex will push the flaps up to approximately a 40° angle. You probably don’t have that much throw available and you may wind up breaking a servo free or tearing up some gears.
Move the three position flap switch to the high position. The cursor should move from beside the letter D to the letter U on the screen. Touch the (-) button and reduce the setting to approximately 5%. Now go ahead and turn the receiver back on. Your flaps should immediately jump upward, but a very small amount. Adjust the setting to the desired amount of reflex.
Reflex doesn’t work very well unless your ailerons match your flaps. But that is easy to accomplish. Touch the UP or DN button until [FLAP AILE MIX] appears in the upper left hand portion of the screen. (P. 121) With the reflex switch in the high position, touch the (+) or (-) buttons until the ailerons match the flaps. At first, nothing will appear to happen. The percentage mix will probably exceed 100%.
Touch the CH button until the cursor moves to SW:. Touch the (+) or (-) buttons until the display reads F-U&D. This turns the flap to aileron mix on whenever this switch is in the up or down position. You will now find that by flipping the switch to the low position, the ailerons also droop with launch flaps. You may want to readjust your launch flaps accordingly.
Full Span Camber Adjustment.
The purpose of this function is to allow you to vary the camber or position of the trailing edge on your wings’ airfoil while flying. This is one of those settings that you must experiment with over time to determine whether or not you wish to add it to your bag of tricks.
First, make sure the butterfly switch on the front upper left hand corner is in the forward position. (Normal flight mode) (P. 121) Touch the UP or DN buttons until [Butterfly] appears in the upper left hand portion of the screen. Touch the CH button until the cursor appears before SPOI FLAP. Now pull the flap stick all the way to the bottom. Nothing should happen. Now press the (+) or (-) buttons until the flap droops the amount indicated in your models’ instructions. (Recommended camber adjustments may vary from 1/16th to 3/8th of an inch.)
Touch the CH button again until the cursor appears before SPOI AILE. Again, pull the flap stick all the way to the bottom and touch the (+) or (-) buttons until the ailerons match the droop of the flaps.
The butterfly switch allows you to switch back and forth from normal flight mode (camber adjustment with switch in the forward position) to landing mode (90° flaps with the switch in the back position).
Multi-Point Programmable Mixing.
(or how to get rid of that annoying bump as you begin to pull the flaps down)
Traditionally, mixing functions in computer radios only allow a linear mix between the master and the slave channels. As an example, when the aileron to rudder mix is activated, and you push the aileron stick all the way to the stop, it mixes in a pre-programmed amount of rudder deflection. With multi-point programmable mixing, the XP8103 radio allows you to insert up to five different mix points anywhere on the curve. In other words, as you slowly push the aileron stick all the way to the stop, you could literally make the rudder waggle back and forth.
In the case of model sailplanes, this allows you to mix a larger percentage of elevator compensation during the initial part of flap movement and less elevator compensation as flaps approach 90°. This completely eliminates that bump your airplane takes on approach as you pull the flap stick down.
The XP8103 radio provides six extra programming functions that allow you to assign any slave to any master channel. The first two of these additional mix functions allow the multi-point programmable mixing. The remaining four provide the ability to do things like add additional aileron/rudder mix during launch, and automatically eliminate the aileron/rudder mix in reflex mode.
To eliminate that annoying bump on approach when you pull down the flap stick, there is a very deliberate sequence of steps that you should follow. First, program the radio as indicated above for flap and elevator compensation on approach. Launch the airplane and adjust the elevator compensation until you achieve the proper glide path at full flap. Ignore the bump for now. Some individuals want the airplane, at full flap to continue on the same flight path before the flaps were lowered. Other individuals like the airplane to take a decidedly strong downward pitch when the flaps are lowered. This insures that you don’t lose flying speed and stall your airplane. However, there is no situation where after pulling the flaps all the way down, the plane should pitch upward. This situation is unacceptable and should be avoided.
Before you begin the multi-point programmable mixing, make sure that the amount of elevator compensation is satisfactory at full flap.
It is important to mark the amount of elevator compensation, on the elevator, with full flap.
Touch the UP or DN button until [Butterfly] appears in the upper left hand corner of the screen. (P. 121)
Touch the Select button again until the cursor appears next to SW:. Touch the (+) or (-) button until BTFY1 appears on the screen. This means that when the butterfly switch is in position one, this mix is active. Position one is towards the rear of the radio. (landing mode)
Touch the CH button until the cursor appears before SPOI ELEV. Make sure that the butterfly/crow switch (front upper left hand corner) is in the rear position. (This should be your landing mode.) Turning the switch back and forth moves the cursor from position 0 to position 1. With the butterfly/crow switch in the landing mode position, touch the (+) or (-) buttons until the percentage of mix is 0%. You just eliminated the linear elevator compensation, but you performed the important step of determining the proper amount of compensation at full flap.
To program compensation back in but in a non linear fashion touch the UP or DN button again until [PROG. Mix2] appears in the upper left hand portion of the screen. (P. 125) Touch the Select button and notice how the cursor moves between the three selected portions on the screen. Stop the cursor when it is in the top position. Now touch the CH button and notice how an underline switches back and forth between the master and the slave channel. With the underline under the master channel (the one on the left) touch the (+) or (-) button until SPOI appears. Touch the CH button until the underline moves to the slave channel. Touch the (+) or (-) button until ELEV appears. You have now told the radio, that when the flap stick is pulled down, it should make adjustments to the elevator.
Touch the Select button until the cursor moves to the middle area. Touch the CH button until the display at the cursor reads POINT-H. Touch the (+) or (-) buttons until the value below the H becomes 0.
Touch the CH button again until the display next to the cursor reads POINT-L. Pull the flap stick all the way to the bottom. Touch the (+) or (-) buttons until the elevator moves in the appropriate direction. Using the mark on the fin, continue to touch the (+) or (-) buttons until you have achieved the same amount of down elevator compensation that you achieved earlier using butterfly mixing.
Again, touch the CH button until POINT-1 appears next to the cursor. Touch the Clear button. This should inhibit programmable point-1 and the letters INH should appear.
Touch the CH button again until POINT-2 appears beside the cursor. Set this adjustment to exactly half way between the points you have previously adjusted for L and H.
Touch the CH button again until POINT-3 appears beside the cursor. Touch Clear to inhibit.
After all of that work, you have now accomplished exactly what the elevator compensation section in the butterfly mixing was able to perform with a single button. Now, let the magic begin.
Launch your aircraft and verify, at least three or four mistakes high, that the elevator compensation is correct at full flap. If it is not, land and adjust Point-L until you have achieved the proper amount of elevator compensation with full flaps.
Once adjusted, touch the UP or DN button until [PROG. Mix2] appears in the upper left hand portion of the screen. Touch the Select button until cursor appears in the middle of the three programmable functions. Touch the CH button until POINT-3 appears on the screen. Touch the (+) or (-) buttons until a slight bump appears in the graphic display. As an example, if Point-3 was a +12, try increasing it to +16. Touch the CH button again until the display reads POINT-2. Add additional mix at this point until a straight line appears between POINT-L and POINT-3.
Launch the aircraft again. Three or four mistakes high pull the flap sticks down to determine whether or not the bump has disappeared. It takes a while to get this right. You are not going to get it on your first try. You may have to increase or decrease the mixing at POINT-3 until it is perfect. You may also need to adjust POINT-2. Variations in the size of flaps and effectiveness of different elevators will require experimentation. Two meter aircraft respond well to a single but strong bump on the curve at POINT-3. Unlimited aircraft respond to a more gentle curve by adding additional compensation at POINT-2. When its perfect, its sweet. It is worth the price of admission.
Increasing Aileron to Rudder Mix During Launch.
I trim my models to fly with very little aileron/rudder mixing. However, this means at launch that I have little if any rudder to recover from a bad throw. (aileron by it self is virtually worthless in this situation) Its easy to increase the aileron/rudder mix during launch with the launch flap switch.
Touch the UP or DN button until you see [PROG. Mix4] in the upper left hand portion of the screen. Touch the Select button until the cursor moves to the upper of the three lines. Touch the CH button until the underline appears under the master channel. Touch the (+) or (-) buttons until AILE appears. Touch the CH button to move the underline to the slave channel. Touch the (+) or (-) buttons until RUDD appears.
Touch the Select button twice until the cursor is before SW:. Touch the (+) or (-) buttons until FLP-D appears.
Touch the Select button again until the cursor appears next to RATE:. Pull the launch switch to the low position. (the three position switch just above the throttle stick) An arrow will appear before the two values. If you move the aileron stick left and right, the arrow will move from one value to the next. Move the aileron stick to the left and hold it there. If your aileron to rudder mix is turned on, (long switch on the right top rear) the rudder will move according to that mix. Touch the (+) or (-) button to increase the amount of rudder mix. Stop when you think it has moved enough. Make sure that you now push the aileron stick all the way to the stop on the opposite side and again touch the (+) or (-) button until you have added an equal amount of mix in the opposite direction.
The additional rudder mix is easily verified. Hold the aileron stick all the way to the stop. Move the launch flap switch from the down to the middle position. The rudder should move back and forth as the switch is moved.
Reduced Aileron to Rudder Mix During Reflex. (Trailing edge up for speed)
The reduction of aileron to rudder mix when in reflex is virtually an identical exercise as that indicated for increasing the rudder mix during launch flap. First move the three position switch to the high (up) position. Touch the UP or DN button until you see [PROG.Mix5] in the upper left hand portion of the screen. (P. 125) Set SW: to FLP-U. Set the master to aileron and the slave to rudder. Now, move the aileron stick to the stop while pushing the (+) or (-) buttons to decrease the rudder throw. Make sure that you perform this exercise for both left and right rudder.
Elevator to Flap Mix.
The most efficient way to turn is by using the wing, not the elevator. After an airplane has rolled, it is much more efficient to lift the airplane with the wing in the direction you wish to travel rather than forcing the airplane into the turn with the elevator. This is accomplished by mixing full span camber with up elevator.
Touch the UP or DN button until [ELEV FLAP Mix] appears in the upper left hand portion of the screen. Touch the CH button until the cursor moves next to SW:. Touch the (+) or (-) button until FLP-U appears. This, allows you to turn this function on and off by moving the launch/reflex switch into the high position. Unfortunately, you can only place elevator to flap mixing or reflex on this switch but you really can’t place them both here. If you desire to have this mix on all the time, touch the (+) or (-) button until ON appears.
Move the launch flap/reflex switch into the high position. Touch the CH button until the cursor appears before RATE:. Notice that by moving the elevator stick up and down, the arrow moves from up to down. Move the elevator stick until the arrow appears beside U. Pull the elevator stick all the way to bottom then touch the (+) or (-) buttons until you have mixed the appropriate amount of flap. Model manufacturers have indicated that any where between 1/8th and 3/8th inch is appropriate. You need to do your own experimenting to determine whether or not this is a mix that you want to use.
If you haven’t already done it earlier, you also want the ailerons to match the flaps. Touch the UP or DN button until [FLAP AILE Mix] appears in the upper left hand portion of the screen. Press the CH button until the cursor appears beside SW:. Touch the (+) or (-) button until F-U&D appears. Touch the CH button until the cursor is beside RATE:. Touch the (+) or (-) buttons, until the ailerons match the flaps as you move the elevator stick. The value of the mix should be around 100%.
V-tail Mixing.
Return to the System Setup Mode by turning the radio off, touching both the UP and DN buttons simultaneously, while turning the radio back on. Touch the UP or DN button until the cursor appears beside WING TYPE.(P. 112) Touch the UP and DN buttons simultaneously. Press the CH button until the cursor appears beside V-tail. Touch the (+) or (-) buttons until it reads ACT.
Touch both the UP and DN buttons again, which returns you to the general information screen. Touch both the UP and DN buttons simultaneously again to enter the function mode.
The two tail servos are connected to the receiver as follows: elevator servo to left ruddervator and the rudder servo to the right ruddervator. (Check to make sure that each servo is operating in the correct direction.) At this stage, the rudder stick (left) on your transmitter should move both ruddervators as rudders. The elevator stick (right) on your transmitter should move both rudder ruddervators as elevators. Make sure both control surfaces are moving in the proper direction in relationship to the transmitter sticks. If they are not, push the UP or DN buttons until you enter the screen identified by [REV.SW] in the upper left hand portion of the screen. (P.114) Reverse whatever servos are necessary to make sure that they move in the proper direction.
Control Throw Adjustments.
Review the instructions from your kit to determine the amount of control throw necessary for your model.
Adjust the amount of throw by using the dual rate functions. (Page 113). Press the UP or DN button until [D/R & EXP] appears in the upper left hand portion of the screen. Touch the CH button until ELEV appears in the upper portion of the screen. Touch the Select button until the cursor appears beside D/R.
Move the elevator stick all the way to the stop. Adjust for the proper amount of throw by touching the (+) or (-) buttons to match the elevator throw recommended in the model instructions. Both ruddervators should move in the same direction.
Perform the same function for the rudder. (At this stage, use the rudder stick, the one on the left side of the model.) Both ruddervators should move in the same direction.
Adjust the amount of rudder to be mixed into the aileron stick (the right stick) by using aileron rudder mix described above.
These instructions will only get you in the general area for the particular type, style and trim of your airplane. Use the dual rate function to modify the pitch or roll sensitivity of the aircraft to satisfy your personal taste. I highly recommend, that once you have determined the optimum setting, that you program both switch positions for dual rate and exponential to be exactly the same. This alleviates you from accidentally bumping a switch in flight and suddenly having an aircraft with different flying characteristics.
Use the end point adjustments [TRVL ADJ.] to give both sides of the ruddervator the same amount of travel.
Placing both the rudder and elevator controls in the right transmitter stick.
Touch the (UP) or (DN) buttons until [AILE RUDD Mix] appears in the upper left hand portion of the screen. (P. 120) Touch the CH button until the cursor appears alongside SW:. Touch the (+) or (-) buttons until Mix appears. This allows you to turn the rudder mixing on or off with the switch at the rear right hand corner of the radio.
If you are flying a polyhyhedral airplane with no control surfaces on the wing, continue to press the (+) or (-) buttons until ON appears on the screen. Now, no matter what buttons you push or switch as you flip during flight, your rudder and elevator controls will always be on the right hand stick.
Touch the CH button until the cursor appears beside Rate:. Move the aileron stick all the way to the left or the right. Touch the (+) or (-) buttons until the appropriate amount of rudder mix is encountered.
V-tail Differential.
To enhance the turning performance of your aircraft, you can now change the difference between the UP and DN deflection of the control servos on either side of the V-tail. This is performed by changing the end point adjustments for these two servos.
Up to this point, when adjusting elevator or rudder throws, both left and right ruddervators act in unison. End point adjustments now adjust the left and right ruddervators separately. For example with a rudder turn only, the nose of your aircraft may pitch up. Now, by modifying the end point to increase the amount of down throw of each ruddervator, up pitch can be eliminated. Different from the control throw adjustments above, adjusting end points requires that you adjust the throw of both the left (elevator servo) and right (rudder servo) ruddervators separately, but in equal amounts.
Touch the UP or DN button until [TRVL ADJ.] appears in the upper left hand portion of the screen. (Page 115). Touch the Select button until you obtain the screen that contains end point adjustments for elevator and rudder. Touch the CH button until the cursor appears alongside of elevator or rudder. (Rudder = Right Ruddervator, Elevator = Left Ruddervator). Then, push the aileron stick all the way to the left or right and touch the (+) or (-) buttons until the control surface you wish to adjust moves the proper distance and direction.
The need for V-tail differential is a byproduct of not understanding the exact ducalage between the V-tail and the wing. Ducalage is the difference in angle between the tail control surfaces and the wings. Even if the ducalage perfect, changes in the CG, area and aspect ratio of the v-tail and the angle between the v-tails may result in a aircraft that requires differential in the tail. Rudder deflection will not only cause the aircraft to roll, it may also cause the aircraft to pitch up or down. This same effect may occur if your rudder or servo control horns are not perfectly placed over the center hinge line (creating a built in mechanical differential.)
To determine if your aircraft can benefit from differential, launch the aircraft and in slow level flight, level with the ground, move the left control stick (rudder only) on the transmitter. If the aircraft begins to yaw or roll, or if it pitches up or down, you may wish to experiment with modifying the end point adjustments to compensate for that pitching motion. If the airplane pitches up with rudder only input, then you need to change the end point adjustments on both sides of the ruddervator to increase the amount of down movement of the control surface. (In the alternative, try less up movement.) The opposite is true if the aircraft pitches down.
If you are flying a polyhedral airplane, you are done. For a full six servo set up, you need to perform the same type of flight testing to insure that the V-tail is not inducing a pitching movement in the airplane with rudder only control. Other than that, all the remaining functions of the radio are still available, including elevator compensation for flaps, elevator to flap mixing, and all of the butterfly mixes.
If you have any questions, please don’t be afraid to call
Sherman Knight
425-576-4028 Pacific std time
e-mail DUWorm@aol.com
