Cockpit SX Tutorials: DLG setup

Mike Shellim,
updated 5 Dec 2006

updated 29 Sept 2011 (DLG launch offsets for left-handers)

1 - Setting up a DLG

This page describes some advanced programming techniques for DLG models such as the popular Longshot. The techniques on this page show how to:

The techniques can also be applied to non-DLG sailplanes with similar configurations.

1.1 - DLG with 'up' brakes

If the ailerons on your DLG go up under braking, then this is the easiest to program. Simply connect the servos to channels 1 and 5 and set up the mixers according to Table 1 below:

Table 1: 'ailerons up' type brakes, 5-channel Rx

Mixer Mixer Description Usage
AI-AI Aileron stick to aileron servos Differential
SP-AI Spoiler stick to aileron servos Surfaces go up as spoiler is applied
F-AI Flap slider to aileron servos Camber adjustment
SP-CO Spoiler compensation Elevator correction due to spoiler deployment
F-CO Flap compensation Elevator correction due to camber change
FIX   Launch offsets

Note that the ADS feature means that diff is automatically suppressed as brakes are deployed.

ADS (Auto Diff Suppression) is a feature of the SP-AI (Spoiler stick to ailerons) mixer. As spoiler is deployed, any aileron differential you may have programmed is automatically reduced. At full spoiler, the downgoing aileron has maximum travel.

This improves aileron response under braking on sailplanes where the surfaces go up with spoiler. However, if the control surfaces go down, then ADS may reduce aileron response.

1.2 - DLG with 'down' brakes using 7-channel Rx.

If the control surfaces go down under braking (e.g. Longshot), ideally we's like extra differential at full brake to maximise the upgoing aileron movement, but this is not possible on the Cockpit SX.

The best we can do is to disable ADS. We can do this by designating the wing servos as flaps instead of ailerons, i.e. to connect them to channels 6 & 7 (instead of 1 & 5). ADS is not active with these outputs. All the same mixing is available on the flaps as with ailerons, i.e. you can use the flaps for roll control, camber, snapflap etc..

Table 2 - 'ailerons down' brakes plus 7-channel Rx

Mixer Mixer Description Usage
AI-F Aileron stick to flap servos Differential
SP-F Spoiler stick to flap servos Surfaces go down as spoiler is applied
F-F Flap slider to flap servos Camber adjustment
SP-CO Spoiler compensation Elevator correction due to spoiler deployment
F-CO Flap compensation Elevator correction due to camber change
FIX   Launch offsets

This method requires a 7 channel receiver, so in the next section will see how to get round this.

1.3 - 'down' brakes using 5-channel Rx

This setup shows how to disable ADS for 'down-brake' models, when a seven channel receiver is not available. For this setup, we revert to using a 5-channel receiver, with the servos connected to channels 1 and 5.

Since ADS is linked to the SP-AI mixer, the solution is bypass the SP-AI mixer altogether, and to employ a couple of free mixers instead.

Table 3: 'ailerons down' brakes and 5-channel Rx

Mixer Mixer Description Usage
AI-AI Aileron stick to aileron servos Differential
SP-AI Spoiler stick to aileron servos [disable - set mixer value to zero]
MIX-1 Free Mix Spoiler stick to channel 1
MIX-2 Free Mix Spoiler stick to channel 5
F-AI Flap slider to aileron servos Camber adjustment
SP-CO Spoiler compensation Elevator correction due to spoiler deployment
F-CO Flap compensation Elevator correction due to camber change
FIX   Launch offsets

1.4 - 'Down' brakes + spoiler-enable switch + Combi

Some flyers like to disable the spoiler in order to prevent accidental deployment. Fortunately, the solution in 1.3 above lends itself well to the addition of a 'spoiler enable' switch.

It's easy - just assign the free mixers MIX-1 and MIX-2 in Table 3 to a switch. If you use the Combi switch, then Combi will be enabled at the same time as the spoiler, which will further improve roll response on the landing approach.

There's still a small problem, however. The spoiler compensation mixer (SP-CO) continues to respond to the spoiler stick even if the spoiler is disabled. The solution is to replace the SP-CO mixer with the third free mixer, and slave that off the Combi switch too. This will ensure that both the spoiler function, and spoiler compensation, are enabled via from the Combi switch.

Here's the finished configuration:

Table 4 - 5 channel Rx and 'ailerons down' brakes (switchable) + Combi

Mixer Mixer Description Usage
Combi Aileron stick to rudder servo Combi (coupled aileron and rudder)
AI-AI Aileron stick to aileron servos Differential
SP-AI Spoiler stick to aileron servos [disable - set mixer value to zero]
F-AI Flap slider to aileron servos Camber
SP-CO Spoiler compensation [Disable - set mixer value to zero]
F-CO Flap compensation Elevator correction due to camber change
MIX-1 Free Mix Spoiler stick to channel 1 (aileron) - activate via Combi switch
MIX-2 Free Mix Spoiler stick to channel 5 (aileron) - activate via Combi switch
MIX-3 Free Mix Spoiler stick to channel 2 (elevator) - activate via Combi switch
FIX   Launch offsets

2 - Maximising servo movement

DLG's place considerable demands on the tiny servos employed to drive the wing servos. It's therefore important to maximise the amount of movement at the servo arm, in order to maximise torque and reduce slop. This is easy to do using if the control surfaces move the same amount either side of neutral.

Asymmetric movements however, e.g. on flapperons, present problems for most radios. Fortunately the Cockpit SX has a servo neutral offset facility. This is well described in the manual, and I won't go into it further here except to say that it's well worth understanding how this advanced feature works in order to maximise servo movement.

3. - Configuring for left-handed operation

Left-handed launchers normally will want the launch presets to be activated from the right hand button, however the RH button is assigned as a throttle kill switch and there's no way to reassign it. However we can get over this with a little mixer trickery. Note the solution presented here only works on a conventional layout i.e. with separate elevator and rudder. It also takes up two mixers.

First, ensure that you're in a stick mode with the throttle on the RH lever e.g. mode 6. Also ensure that you have two free mixers available.

Here's the procedure for configuring the RH switch for rudder offset:

  1. Make sure that 'Throttle Check' in the Setup->Model menu is zero (off).
  2. Set up MIX1 =Throttle -> S3. The mixer must be 'always on', i.e. the mixer switch should be blank.
  3. Make sure the mix value in MIX1 is zero (we'll alter it later in step 5).
  4. Move the throttle lever to the fully forward position (and keep it there)
  5. Now go into the Servo Centre menu for servo 3 (rudder), and adjust for desired launch offset.
  6. Adjust the MIX 1 value so as to bring the rudder back to the centre.

Operating the RH switch will activate the rudder preset Releasing the switch returns the rudder to centre.

Repeat for the elevator, by setting up a MIX2 Throttle->S2.

(My thanks to Andy Brett for raising this issue and suggesting a solution- MS).

4 - Schulze 535 Receiver Tip

Here's a tip if using the popular Schulze 535 (not 435) with the Cockpit SX. The Rx can be programmed to re-map input #5 to output #4 . This does not involve any soldering, see the rx manual. It makes the receiver much easier to wire up when used with two aileron servos on 1 and 5. However a Y-lead will still be required to connect the battery.