Understanding the JR Propo X-388S Radio – Part 3

By Richard A. Eckel

©Copyright 1994 All Rights Reserved

Now that you have suffered through the verbage about all of the radio functions its time to put your knowledge to practical use. One of the best parts of the sailplane portion of the JR manual is the last section. It is there that the writer gives a sequence of steps to set up the radio for a sailplane. I suspect that many users of the JR388 have gotten their radios to work using that last section but find themselves facing obstacles when they try to vary from those specific instructions. Hopefully the previous two parts of this series have shed a lot of light on how to successfully vary the programming in the radio. To pull it all together and add some fun to this otherwise dreary mess I will now propose a procedure to follow when setting up a new plane or resetting an existing plane.

Sailplane Setup
Setting up the radio starts before the servos are mounted in their final positions and begins by resetting the model memory that you are going to use.

The following procedure will get a plane set up and ready for additional mixes to be added. I can tell you from experience that if you fail to get the basic setup right mixing can be a nightmare.

Servo Setup
Clear the model memory using the RSET function and set all ratched trims to their centered position.
Set DUAF to ACT and FLAPS to SW+T (if setting up a full house plane with a 7 channel receiver) and then switch to the transmit or Function Setup mode.
The servos should now be in their natural zero positions.
Check and adjust the throw direction of each servo. Use the Flaps switch to check the throw direction of the flap servos but don’t worry about the amount of throw yet. (If you have the flap servos travel backwards you won’t be able to use the Flaps Switch and the SP offset and mixes will be backwards). Reverse as required.
Adjust (by moving the arm on the shaft splines) the arms on the wing servos so that arms stick vertically out of the wings. (Servos can now be rigidly mounted in the wing.)
Adjust linkages to neutralize the rudder and elevator
Adjust flap and aileron linkages for 10 deg. of down flaps and 10 deg of up in both ailerons with the servos in their neutral position (both ailerons are up at this point).
Adjust subtrim of Flap to neutralize the left flap (the right flap will move also). Adjust subtrim of AUX2 to neutralize the right flap (the left flap will not move). Flap servo arms should now be offset aft about 10 to 15 degrees.
Adjust the subtrim of AIL1 to neutralize the left aileron. Adjust the subtrim of AUX1 to neutralize the right aileron. Aileron servo arms should now be offset about 10 to 15 degrees forward.
Use travel adjust to adjust the travel of the elevator, rudder, flaps and each aileron. Set the ailerons for 1/2 to 3/4″ of up travel and 1/4″ of down travel. Don’t go for an extreme setup on the first try, just set up moderate throws on flaps and ailerons.
The plane should now be flyable using the basic controls. The following two procedures will add full wing trailing edge control for launching and speed flight as well as flaps or full crow for landing.

Flaps Switch Setup (With FLAPS set to SW+T)
Since we selected SW+T for our FLAPS settings in the Model Setup Functions we can now use the three position Flaps switch for programming two flap preset positions for selection with the switch. If we had not selected SW+T the Flaps switch could only be used to control some of the Free Mixes.

Remember that when you set FLAPS to SW+T the travel adjustment (T.Adj) for Flaps became the offset settings for the Flaps Switch. Put the Flaps Switch in the up (F+U) position and use the Flaps T.ADJ. to set perhaps 1/8″ reflex into the flaps. Put the Flaps Switch in the down (F+D) position and use the Flaps T.ADJ to set in about 1/4″ of down flaps for launching. Move the switch to its mid position and the flaps should center.

The Flaps switch is now set for launching and speed flying. You will probably want to fly the plane and experiment with different amounts of reflex and flaps. Some fliers also use the AL-F mix to add the ailerons for full trailing edge movement.

Crow Switch and Throttle Stick Setup
The Crow switch is generally used as a landing setup selection switch. JR has provided the SP mix for easily setting up all the mixes usually included in the landing function.

The SP mix is used to set up the Flaps, Ailerons and Elevator to move with the Throttle Stick.

Set the Crow Switch to the 1 position (BTF1) and step thru the menu to the mixSP function.
Set the throttle stick offset by placing the throttle stick where you want neutral to be (full down is recommended) and pressing CLR while in SP offset.
Move the throttle stick to full up position.
If you want to crow the ailerons change to the Aileron% subfunction and use the + or – key to move the ailerons to about 1/4″ up.
Change to the Flap% subfunction and use the + or – keys to set in about 45 degrees of flaps
Wait until you fly the airplane to set any elevator mix or set additional flap or aileron throw. Try the flap function at high altitude and see if the plane dives (unlikely) or pulls up (likely). Add the appropriate elevator mix to compensate for the change in pitch. (You can select the mixSP function and the elevator% mix before you launch and adjust while you fly if you wish.)
With the Crow switch in the 1 position (BTF1) the throttle stick will activate the flaps and ailerons. With the Crow switch in the 0 position (BTF0) the throttle stick will be deactivated. If you want flaps available all the time simply program both positions with the same settings.

Rudder on Right Stick Setup
Many fliers like to mix the rudder to the right stick with ailerons in order to have coordinated turns using only the right stick. This can be done using mixD of the Free Mixes. The radio is preprogrammed for mixing the proper channels. Simply select an activation switch or use ON for full time mixing, and set the % of rudder to mix to the right stick. Be aware that the left stick will still also control the rudder and any left stick movement used for rudder will be additive to the right stick movement.

Additional Mixes
You now have the basic mixes to fly a full function sailplane set up. Additional mixing, either preprogrammed mixes or free mixes can be added according to your preferences. I recommend flying with the basic setups for a while and getting everything tweaked in before you add additional mixing. Remember that if you are getting seemingly unpredictable results on a mix or function it is always wise to reset the entire model setup and start from scratch. I haven’t counted the number of times that resetting has cleared up my problems.

Programming Tips
I have picked up a couple programming tips from other fliers and developed one myself. I will pass two of them along to you. They are excellent tips on their own, but they also illustrate how the radio becomes more than just the built in functions with a little imagination and programming.

Example Programming
Snap Flaps

I got this tip from Dennis Phalen while corrosponding via Model+Net:

“The 388 doesn’t have snap flaps, but the programmables make it easy. I leave them on all the time, if you try it this way, you will too.Use the 3>5 and 3>6 mixes to get ALL surfaces into it. Set the travel for them so you have an even camber change across the TE. Now OFFSET by pulling the elev stick back about 3/4 of travel, get all surfaces to kick in at the same time, 1/8 to 1/4 inch will work for travel. This is an easy mix on the Vision, just as nice on the JR. Now you have camber added only when you use a LOT of elevator, most of the time you’ll never see it added. Most pilots don’t like snap flaps as they sensitize the elevator when they start acting from the moment the stick is moved, also BAD when you have it set up to push reflex on down stick.”

To implement this trick use the A and B mixes if you will leave it on full time. If you want to switch it on and off you will have to use two mixes that can be activated with the same switch such as B and C mixes.

Proportional Throttle for Full Function Electric Sailplane
I developed this mix for flying my full function electric sailplane. I wanted full trailing edge control (flaps and ailerons) as well as proportional throttle. Simply plugging the speed control into channel 1 made the motor active with any movement of the throttle stick. Plugging the speed control into channel 8 made the motor come full on any time the Crow switch was turned on. Neither of these gave me the flexibility I wanted.

So I program mix B for channel 8 as master and channel 8 as slave with the Crow switch activating it. I set the offset with the Crow switch on. Then I set the Crow switch off and adjust the % until the motor is turned off. This effectively defeats the coupling of channel 8 with the Crow switch.

Next I program mix C for channel 1 as master and channel 8 as slave with the Crow switch off. I set the throttle stick position and offset and then adjust the % until the motor goes full speed with maximum throttle and stops at minimum throttle. When I fly I launch with the Crow switch off and have full proportional motor control. When I reach altitude I flip the Crow switch on so that I have flaps for landing.

The JR Propo X-388s radio is a very flexible transmitter for sailplanes. It has been preprogrammed to a large extent to make the basic sailplane functions easy to set up. The eight free mixes provide for an amazing amount of added flexibility.

Having the X-388s radio is almost like having a bunch of new airplanes. Making adjustments to the flying characteristics is fast and easy. The variety of mixes makes every day at the field an day of new experiments. Its almost as if I have taken up a new hobby! Hope you all have the same experience.

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