Fig. 12 · Tricopter · Betaflight 2026.6.2

Tricopter

Fly it

Parts: …
Battery: unplugged
Fault: none

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Pick the battery, motors and props. Every number below is recalculated from this craft's own model.

Battery

Motors

Props

Calculated for this build

All-up weight: 655 g
Thrust : weight: 5.1 : 1
Hover throttle: 44%
Max current: 113 A
Hover time: 16.2 min
Hard-flying time: 6.8 min

Checks

A good all-round tri: 5.1:1 thrust to weight. If the ESC check below speaks up, one motor's full-throttle current is over its ESC's rating: a gentler prop or bigger ESCs fix it.

No problems found with this combination.

Cost

Category	Parts	Cost
Electrical	8	$242
Mechanical	5	$78
Total (approx.)	13	$320

A working emulation of the Betaflight command line for this craft: real setting names, real limits and real error messages.

Entering CLI Mode, type 'exit' to return, or 'help'

Up and down recall earlier commands.

Configuration snippets

First setup after the build

Betaflight still flies tricopters, but servo support is a build option that is off in the default cloud build: tick Servos when you flash, or the TRI mixer has no yaw at all. Then the TRI mixer, the board's arrow forward, DShot600 with telemetry for the RPM filter, and the two serial ports: ELRS on UART2 and SmartAudio on UART1.

# Betaflight 2026.6.2, flashed with the "Servos" build option ticked (USE_SERVOS; off by default)
# 30.5 mm F405 with its own power board: ELRS on UART2, SmartAudio VTX on UART1
mixer TRI                          # M1 tail, M2 front right, M3 front left, servo 5 on SERVO 1
set align_board_yaw = 0            # arrow to the nose; 180 if it points back
set motor_pwm_protocol = DSHOT600
set dshot_bidir = ON               # rpm telemetry for the RPM filter
set motor_poles = 14               # 14 magnets in a 2306 bell
serial UART2 64 115200 57600 0 115200    # 64 = serial RX (ELRS)
set serialrx_provider = CRSF
serial UART1 2048 115200 57600 0 115200  # 2048 = SmartAudio (VTX)
save

The tail servo after the build

333 Hz suits a digital servo; an analog one stays at 50 Hz or it burns. With tri_unarmed_servo on, the tail follows the yaw stick while disarmed, so you can test it with the props off. Centre and travel are set with the servo command or in the Servos tab. Then check the direction with the tail servo test: yaw right must tilt the tail thrust left. If it tilts it right, type smix reverse 5 2 r and save, or turn the servo round.

# The tail servo: TRI mixes stabilised yaw into servo 5, on SERVO 1 (the S9 pad on a SpeedyBee F405 V4)
set servo_pwm_rate = 333           # a digital servo; leave 50 Hz for an analog one
set tri_unarmed_servo = ON         # the tail follows the yaw stick while disarmed, for the bench check
# Centre, then travel (or the Servos tab): servo <n> <min> <max> <middle> <rate> <forward>
servo 5 1000 2000 1520 100 -1      # middle 1520 us levels this tail plate; -1 = no channel forwarding
servo 5 1100 1950 1520 100 -1      # endpoints that stop short of the hinge binding, about 40 deg each way
# Yaw right must tilt the tail thrust LEFT. Only if it tilts it right, reverse servo 5 for input 2,
# stabilised yaw (or turn the servo round):
#   smix reverse 5 2 r
save

Failsafe: drop after the build

If the radio link is lost for 1.5 s, stop the motors. Without GPS a tri has no way home, and dropping into the park beats flying away.

# Lost link: hold for 1.5 s (stage 1), then stop the motors (stage 2)
set failsafe_delay = 15            # tenths of a second
set failsafe_procedure = DROP
save

Altitude hold for Altitude hold

ALTHOLD (mode id 3) on AUX3, on top of ANGLE on AUX2. With the throttle stick in the middle 15 % the tri holds its height on the barometer; push it up or down to climb or sink. The easiest way to learn how the tail feels.

# Altitude hold (needs the barometer): ANGLE on AUX2, ALTHOLD on AUX3 high
aux 1 1 1 1300 2100 0 0      # ANGLE on AUX2 mid + high
aux 2 3 2 1700 2100 0 0      # ALTHOLD on AUX3 high
set alt_hold_deadband = 15   # % of throttle stick round the centre that holds height (0-70, default 20)
save

Angle mode for Angle

Self-levelling with the tilt capped at 60°: let go of the right stick and it levels. You fly the height on the throttle.

# Angle mode: self-levelling, tilt capped; you hold the height on the throttle
aux 1 1 1 1300 2100 0 0      # ANGLE on AUX2 mid + high
set angle_limit = 60         # max tilt, degrees (10-80, default 60)
set angle_p_gain = 50        # how hard it levels (0-200, default 50)
save

Acro rates for Acro

With ANGLE and ALTHOLD both off the sticks set rotation rates: 540°/s roll and pitch at full stick, and 400°/s yaw, because the servo has to swing the tail. More P and I on yaw than a quad's defaults help the tail hold its heading when the tail motor's torque changes with the throttle.

# Acro (ANGLE and ALTHOLD off): rates for the tri, yaw slower than a quad because a servo swings it
set rates_type = ACTUAL
set roll_rc_rate = 7         # centre: 70 deg/s per full stick
set roll_srate = 54          # full stick: 540 deg/s
set pitch_rc_rate = 7
set pitch_srate = 54
set yaw_rc_rate = 7
set yaw_srate = 40           # yaw: 400 deg/s
set p_yaw = 60               # firmer yaw hold for the tail (default 45)
set i_yaw = 90               # and less drift when the tail motor sags (default 80)
save

Race laps for Race (angle)

Angle mode for the gates and the race timer on the OSD: osd_tim1 = 18 counts from the last arm in hundredths, and 2103 puts it near the top right of the screen in OSD profile 1.

# Gate laps in angle mode with the race timer on the OSD
aux 1 1 1 1300 2100 0 0      # ANGLE on AUX2 mid + high, ALTHOLD off
set osd_tim1 = 18            # source 2 (last armed) + precision 1 (hundredths) << 4
set osd_tim_1_pos = 2103     # 2048 (OSD profile 1) + column 23 + row 1 x 32
save

Park run for Park run (altitude hold)

The park run in altitude hold, with the same timer as the race. The stick climbs and sinks and holds the height when centred, so your attention can go on the yaw round the posts.

# The park run in altitude hold: the stick climbs and sinks, centred it holds
aux 1 1 1 1300 2100 0 0      # ANGLE on AUX2 mid + high
aux 2 3 2 1700 2100 0 0      # ALTHOLD on AUX3 high
set osd_tim1 = 18            # the same timer as the race
set osd_tim_1_pos = 2103
save

Meet the tricopter

A tricopter has three motors in a Y: two out front and one on a tail boom. Three props can't cancel each other's torque the way four can, so the tail motor sits on a hinge and a servo tilts it a few degrees left or right. That sideways push swings the tail round and turns the nose: yaw by thrust vectoring, which makes a tri lean into its turns like a small plane. This one is a 5-inch build on 4S: three 2306 motors on single ESCs, an F405 flight controller with its own power board, a metal-gear tail servo and analog FPV, about 655 g with a 2200 mAh pack and 5:1 thrust to weight. The servo is the part that makes a tri a tri, and the part that breaks: test it before the props go on. Pick the parts here and watch the numbers, build it, run the safety tests, then fly the town park.

Practice task

Hover in altitude hold first and watch the tail: it holds a few degrees of tilt even when you don't touch the yaw stick, cancelling the tail prop's torque. Then weave the lamp posts in the town park and circle the fountain; tight yaw is where a tri feels different from a quad. Race the park laps in angle mode once that is easy, and try acro last. On a real build: a smoke stopper on the first plug, the servo test with the props off (yaw right must tilt the tail thrust left), the motor direction check and the failsafe with the radio off. Make the first hover low and trim the servo centre if the tri creeps round. Land at about 3.5 V per cell.

Build a Y frame with a tilting tail, test the servo, then fly the town park

Category

Parts

Cost

Electrical

$242

Mechanical

$78

Total (approx.)

$320

# Betaflight 2026.6.2, flashed with the "Servos" build option ticked (USE_SERVOS; off by default) # 30.5 mm F405 with its own power board: ELRS on UART2, SmartAudio VTX on UART1 mixer TRI # M1 tail, M2 front right, M3 front left, servo 5 on SERVO 1 set align_board_yaw = 0 # arrow to the nose; 180 if it points back set motor_pwm_protocol = DSHOT600 set dshot_bidir = ON # rpm telemetry for the RPM filter set motor_poles = 14 # 14 magnets in a 2306 bell serial UART2 64 115200 57600 0 115200 # 64 = serial RX (ELRS) set serialrx_provider = CRSF serial UART1 2048 115200 57600 0 115200 # 2048 = SmartAudio (VTX) save

# The tail servo: TRI mixes stabilised yaw into servo 5, on SERVO 1 (the S9 pad on a SpeedyBee F405 V4) set servo_pwm_rate = 333 # a digital servo; leave 50 Hz for an analog one set tri_unarmed_servo = ON # the tail follows the yaw stick while disarmed, for the bench check # Centre, then travel (or the Servos tab): servo <n> <min> <max> <middle> <rate> <forward> servo 5 1000 2000 1520 100 -1 # middle 1520 us levels this tail plate; -1 = no channel forwarding servo 5 1100 1950 1520 100 -1 # endpoints that stop short of the hinge binding, about 40 deg each way # Yaw right must tilt the tail thrust LEFT. Only if it tilts it right, reverse servo 5 for input 2, # stabilised yaw (or turn the servo round): # smix reverse 5 2 r save

# Altitude hold (needs the barometer): ANGLE on AUX2, ALTHOLD on AUX3 high aux 1 1 1 1300 2100 0 0 # ANGLE on AUX2 mid + high aux 2 3 2 1700 2100 0 0 # ALTHOLD on AUX3 high set alt_hold_deadband = 15 # % of throttle stick round the centre that holds height (0-70, default 20) save

# Angle mode: self-levelling, tilt capped; you hold the height on the throttle aux 1 1 1 1300 2100 0 0 # ANGLE on AUX2 mid + high set angle_limit = 60 # max tilt, degrees (10-80, default 60) set angle_p_gain = 50 # how hard it levels (0-200, default 50) save

# Acro (ANGLE and ALTHOLD off): rates for the tri, yaw slower than a quad because a servo swings it set rates_type = ACTUAL set roll_rc_rate = 7 # centre: 70 deg/s per full stick set roll_srate = 54 # full stick: 540 deg/s set pitch_rc_rate = 7 set pitch_srate = 54 set yaw_rc_rate = 7 set yaw_srate = 40 # yaw: 400 deg/s set p_yaw = 60 # firmer yaw hold for the tail (default 45) set i_yaw = 90 # and less drift when the tail motor sags (default 80) save

# Gate laps in angle mode with the race timer on the OSD aux 1 1 1 1300 2100 0 0 # ANGLE on AUX2 mid + high, ALTHOLD off set osd_tim1 = 18 # source 2 (last armed) + precision 1 (hundredths) << 4 set osd_tim_1_pos = 2103 # 2048 (OSD profile 1) + column 23 + row 1 x 32 save

# The park run in altitude hold: the stick climbs and sinks, centred it holds aux 1 1 1 1300 2100 0 0 # ANGLE on AUX2 mid + high aux 2 3 2 1700 2100 0 0 # ALTHOLD on AUX3 high set osd_tim1 = 18 # the same timer as the race set osd_tim_1_pos = 2103 save

Meet the tricopter

Practice task

Build a Y frame with a tilting tail, test the servo, then fly the town park

Tricopter

Design it

Calculated for this build

Checks

Cost

Build it

Try a real mistake

Selected part

Parts in the box

Wiring

Safety tests

Smoke stopper test

Motor direction check (props off)

Accelerometer calibration

Tail servo test (props off)

Failsafe test (props off, radio off)

Betaflight CLI console

Configuration snippets

First setup after the build

The tail servo after the build

Failsafe: drop after the build

Altitude hold for Altitude hold

Angle mode for Angle

Acro rates for Acro

Race laps for Race (angle)

Park run for Park run (altitude hold)

Check yourself · Fit the tail servo

Check yourself · Solder the XT60 and the capacitor

Check yourself

Meet the tricopter

Practice task

Tricopter

Design it

Calculated for this build

Checks

Cost

Build it

Try a real mistake

Selected part

Parts in the box

Wiring

Safety tests

Smoke stopper test

Motor direction check (props off)

Accelerometer calibration

Tail servo test (props off)

Failsafe test (props off, radio off)

Betaflight CLI console

Configuration snippets

First setup after the build

The tail servo after the build

Failsafe: drop after the build

Altitude hold for Altitude hold

Angle mode for Angle

Acro rates for Acro

Race laps for Race (angle)

Park run for Park run (altitude hold)

Check yourself · Fit the tail servo

Check yourself · Solder the XT60 and the capacitor

Check yourself

Meet the tricopter

Practice task