V-tail configuration in Pitlab&Zbig FPV system.
Note: This manual describes only V-tail configuration, for Aileron configuration please refer to Classic T-tail configuration manual.
First of all your transmitter must be properly configured as for normal (manual) flight without autopilot, with all mixers (V-tail) and reverses properly set. Only when transmitter is properly configured, FPV system may be properly set.
Receiver connection
There are 3 ways of connecting receiver channels to autopilot, depending on your device abilities: Parallel connection where all channels are connected by separate wires to Autopilot’s inputs, and serial CPPM/SBus when only one signal wire is needed to transmit all channels. Almost all LRS (long range systems) has serial mode, which is more convenient than parallel one.
Which channels numbers are used for control V-tail depends on your RC system, and may vary from one system to another (for some systems like Taranis you may choose any channels you like).
Parallel connections
You need to know which two channels from your receiver are used for V-tail. You must connect these receiver’s outputs into Autopilot’s inputs called “Elevator” (input pin #2) and “Rudder” (input pin #3).
Note: the most common mistake is to connect all receiver pins in this same order into autopilot (pin #1 from receiver into pin #1 of autopilot, pin #2 from receiver into pin #2 of autopilot and so on). This may be wrong, and with such connection you can’t be able to properly configure Autopilot’s mixers.
TODO picture with V-tail connections
Next connect receiver’s throttle channel to 4-th Autopilot inputs (throttle), and three-state channels output for mode and menu navigation (inputs #6 and #7 respectively).
It is enough to connect only one channel with full 3 wires (signal, +5V and ground) between autopilot and receiver and rest of the channels may be connected only by signal wire, because +5V and ground pins are common (and internally tied together) for all channels.
Connect your Autopilot board into PC using mini USB cable, run FPV_manager and go into Autopilot->Radio PPM page.
Select option (*) Parallel PPM inputs, and click [Save]
Todo: picture of FPV_manager
Now set Autopilot’s mode to OFF when you move rudder/elevator stick, green bars 2 and 3 (elevation and rudder) will respond to these movements.
Todo: Ap mode OFF and ailerons bars.
Serial connections
Many receivers (especially long range UHF systems) has got serial CPPM or SBUS output, but in many cases such output needs to be properly configured or enabled. Refer to user manual of your RC system, and configure receiver before making connections to Autopilot.
With serial connection (CPPM or SBUS) connect your receiver serial output (refer for its manual for more info) into Autopilot input #1 by single 3-wire connection.
TODO: picture with serial CPPM/SBUS connection
Note: when using serial CPPM signal, you may choose autopilot input #6 instead of input #1.
To activate and configure serial connection you need to connect your Autopilot board to the PC using mini USB cable, run FPV_manager and go into Autopilot->Radio PPM page.
Select option according to your receiver type and preferences:
(*) Serial CPPM input at #1
(*) Serial CPPM input at #6
(*) Serial SBUS input at #1
And click [Save] to store settings into autopilot.
TODO: picture of FPV_manager with serial options
You must select proper RC channel numbers from receiver (maps these channels) for Autopilot’s functions “elevator” and “rudder”. Next choose valid receiver’s channel numbers for Mode and Menu navigation. After selecting valid channels press [Save] button to store settings into Autopilot.
TODO: manager with channels mapping
Now set Autopilot’s mode to OFF, and when you move rudder/elevator stick, green bars 2 and 3 (named elevator and rudder) will respond to these movements.
Todo: Ap mode OFF and bars.
Note: the most common mistake is to left all receiver channels mapping unchanged (CH1 for Elevator, CH2 for elevator, CH for rudder and so on). This may be wrong, and with such mapping you can’t be able to properly configure Autopilot’s mixers.
Servos/UBEC/ESC connections
Typical (PPM) servos
Servos for elevons must be connected to Autopilot’s output #2 and #3 (Elevator and Rudder), regardless of RC input mode (parallel, serial) or channel assignment in serial modes.
Todo: picture with servo connection, throttle and ubec
SBUS servos
If you use Futaba or compatible SBUS servos, connect them (with proper HUBs) to Autopilot’s output #6. Assign SBUS channels for servos identical as for manual flight without Autopilot (regardless how you assign channels for Autopilot’s functions in FPV_manager).
TODO: SBUS servo connections
Note: You may use SBUS and PPM servos together in one airplane.
Speed controller and power supply
Connect your speed controller (ESC) to Autopilot’s output #4 (throttle), regardless of RC input mode (parallel, serial) or channel assignment in serial modes.
Disconnect red wire (+5V) of ESC plug, and connect external high current, switching UBEC to any spare Autopilot’s output or input (all GND and +5V pins are internally tied together).
Note: Use of internal linear voltage regulator (BEC) build-in into ESC may lead to crash or other malfunction of your airplane. In STAB and AUTO mode Autopilot uses servos extensively to keep airplane in desired position, and this requires much more current than in manual flight. Internal regulator will easily overheat and its output voltage may drops below safe minimum during flight.
Configuration of mixers and reverses
Easy Setup
Since OSD firmware 2.40 there is a way of easy setup all necessary mixers and reverses using transmitter sticks and 3-button keyboard connected to OSD board. It simplified all setup process and reduces risk of improper setup. Easy setup should be invoked after proper configuration of connection type an RC channel assignment.
Just execute OSD menu Autopilot->Mixers->Easy Setup and follow 4 steps from wizard to complete configuration.
Note: to avoid weird servo movements during setup select OFF mode for autopilot. This is not necessary for proper configuration, but until proper settings is discovered and stored you may be confused by unexpected servos behaviour.
On each steps you need to move transmitter sticks to certain position (at maximum extend), and while keeping it press [Enter] key on 3-button keyboard connected to OSD.
At the end of EasySetup OSD will show resume with your airplane configuration (mixers and reverses).
To verify setup turn on STAB mode of Autopilot and keeping sticks in neutral position rotate your airplane right nose down. V-tail should move up reacting “against” such rotation.
Manual setup
Manual setup is for advanced users, or for those who want to change only one, particular settings, or just verify settings already made by EasySetup.
Servo alignment
To move steering surface e.g. down servo may rotate clockwise or counterclockwise, depending on servo type, mechanical way of mounting servo, arm, and pushrod. This apply independently for both V-tail surfaces, and thus moving both surfaces up and may require rotating both servos in this same direction (we call it “servos aligned”) or in counter directions (we call it “servos opposite”). Autopilot must know how your servos are aligned, to make proper movements when in stabilisation or autonomous flight.
Todo: servo opposite / aligned picture with servo rotation aligned
The simplest way to manually set servo alignment is:
- from OSD menu Autopilot->mixers select V-tail (aligned),
- turn on STAB mode and move airplane nose down.
- if both surfaces moves in this same directions (up or down but both in this same direction), your settings is correct
- If surfaces moves in different direction (one up and another down), you need to change settings to V-tail (opposite)
Todo: picture with proper servos alignment
Reverses
When servo alignment is properly set, next step is to set proper reverse for elevator and rudder. Next steps will be performed with STAB mode.
Once more rotate your airplane nose down. If both surfaces moves up, Elevator reverse is already set properly. If surfaces moves down, change Elevator reverse menu settings opposite way
TODO: Rudder reverse
Store trims
After manual settings of mixers and reverses set your transmitter sticks in neutral positions (and with throttle to minimum) and execute command from OSD menu Autopilot->Store trims.
Note: In STAB mode when airplane is level V-tail may react strongly (stronger than in OFF mode) to stick movements. It is natural behaviour of stabilisation mode, and depends on stabilization force. In AUTO mode, when airplane is on the ground V-tail may move to its maximum positions and this is normal behaviour.
Now your airplane has radio channels, mixers and reverses properly configured for V-tail.
Next step is to set stabilisation forces according to your needs and airplane characteristics, and then setup autonomous flight parameters. Good starting point is to set parameters in the middle of available min/max range.
Note: All Autopilot settings are not transferable from one airplane to another, even this same type of airplane. Servos may vary in rotation directions, angle of movements or arm length, which may result in different settings for these airplanes.
We wish you many safe and satisfying flights with our FPV system
Pitlab Team.