Plane will not stay on runway during autonomous takeoff

Plane: Senior Telemaster (conventional gear - tail dragger) about 90 inch wingspan. 5000 6-cell battery power.
In autonomous takeoff mode, the plane veers off the runway to the left most times. It generally rotates 45 - 90 degrees from the initial direction before I abort.
In manual mode, the plane also tends to veer left (like most tail-draggers), but I can apply right rudder to make it track down the runway. But in autonomous mode, there is very little if any correction being applied. I can see the rudder and it barely moves at all as the plane is yawing to the left and rolling off the runway into the grass.
I have set the TKOFF_TDRAG_ELEV parameter such that there is up elevator during the initial takeoff roll and this is working.
The plane is using PixHawk hardware with GPS and magnetic compass. The plane flies great in manual mode and in FBWA mode. I point the plane right down the runway before engaging the “AUTO” mode. The throttle spools up over about 3 or 4 seconds, but about the time t reaches full throttle, it is already off-course by 45 degrees or more.

Are you using ground steering? If so, what happens if you reverse the rudder channel in mission planner?

Yes, I am certainly attempting to use ground steering. Good idea (to reverse direction). We have not tried to reverse the direction of rudder. Will try that.

Here’s the parameters we are using generally. This is from memory as I don’t have access to the software or plane right now.

TKOFF_TDRAG_SPD1 is set to 2 or 3 meters per second
TKOFF_THR_SLEW set to 30
GROUND_STEER_ALT set to 3 meters
STEER2SRV_TCONST set to 0.5

We have successfully completed a few AUTO take-offs but generally by the time the plane breaks ground it is 10 - 30 degrees from its initial direction. And on our last attempts we were unsuccessful about 10 times in a row. There was about a 20 degree crosswind of 5 knots from the left. And the plane is turning left (into the wind). Note however, that with this same crosswind, I was able to take off uneventfully in MANUAL mode with just some slight right rudder as needed to make the plane track down the runway. I think the PixHawk should be able to make the same corrections that I am making manually, right?

Can you please post your log so we can do some analysis?

Thanks, Grant.

[quote=“gmorph”]Can you please post your log so we can do some analysis?

Thanks, Grant.[/quote]

Yes, will do. The plane and computer are owned by a friend, so I don’t have possession of the logs right now. I’ll get them and post as soon as I can

UPDATE: we reconfigured some things on the plane itself: replaced main gear and tail gear. Added some right motor thrust. We were able to get one takeoff in AUTO mode. The plane lifted off just before it reached the edge of the runway – perhaps 10 degrees skewed to the left of the runway center-line. I don’t believe the PixHawk was making any rudder corrections at all (or perhaps very minor corrections). But the flight was very successful. The plane flew to about 10 way points and then circled our takeoff position until I switch to manual mode and landed. This was our only test flight today.

Here is our parameter list:

#NOTE: LandTest
ACRO_LOCKING,0
ACRO_PITCH_RATE,180
ACRO_ROLL_RATE,180
AFS_AMSL_ERR_GPS,-1
AFS_AMSL_LIMIT,0
AFS_ENABLE,0
AFS_HB_PIN,-1
AFS_MAN_PIN,-1
AFS_MAX_COM_LOSS,0
AFS_MAX_GPS_LOSS,0
AFS_QNH_PRESSURE,0
AFS_RC_FAIL_MS,0
AFS_TERM_ACTION,0
AFS_TERM_PIN,-1
AFS_TERMINATE,0
AFS_WP_COMMS,0
AFS_WP_GPS_LOSS,0
AHRS_COMP_BETA,0.1
AHRS_EKF_USE,0
AHRS_GPS_GAIN,1
AHRS_GPS_MINSATS,6
AHRS_GPS_USE,1
AHRS_ORIENTATION,0
AHRS_RP_P,0.2
AHRS_TRIM_X,0.0184454
AHRS_TRIM_Y,-0.06842938
AHRS_TRIM_Z,0
AHRS_WIND_MAX,0
AHRS_YAW_P,0.2
ALT_CTRL_ALG,0
ALT_HOLD_FBWCM,0
ALT_HOLD_RTL,10000
ALT_MIX,1
ALT_OFFSET,0
ARMING_CHECK,1
ARMING_DIS_RUD,0
ARMING_REQUIRE,0
ARSPD_AUTOCAL,0
ARSPD_ENABLE,1
ARSPD_FBW_MAX,22
ARSPD_FBW_MIN,9
ARSPD_OFFSET,72.78117
ARSPD_PIN,65
ARSPD_RATIO,2.088523
ARSPD_SKIP_CAL,0
ARSPD_TUBE_ORDER,2
ARSPD_USE,1
AUTO_FBW_STEER,0
AUTOTUNE_LEVEL,6
BATT_AMP_OFFSET,0
BATT_AMP_PERVOLT,39.877
BATT_CAPACITY,8000
BATT_CURR_PIN,3
BATT_MONITOR,4
BATT_VOLT_MULT,12.02
BATT_VOLT_PIN,2
BATT2_AMP_OFFSET,0
BATT2_AMP_PERVOL,17
BATT2_CAPACITY,3300
BATT2_CURR_PIN,3
BATT2_MONITOR,0
BATT2_VOLT_MULT,10.1
BATT2_VOLT_PIN,2
BRD_PWM_COUNT,4
BRD_SAFETYENABLE,1
BRD_SER1_RTSCTS,2
BRD_SER2_RTSCTS,2
CAM_DURATION,10
CAM_SERVO_OFF,1100
CAM_SERVO_ON,1300
CAM_TRIGG_DIST,0
CAM_TRIGG_TYPE,0
COMPASS_AUTODEC,1
COMPASS_DEC,-0.007763691
COMPASS_DEV_ID,73225
COMPASS_DEV_ID2,131594
COMPASS_DEV_ID3,0
COMPASS_EXTERN2,0
COMPASS_EXTERN3,0
COMPASS_EXTERNAL,1
COMPASS_LEARN,0
COMPASS_MOT_X,0
COMPASS_MOT_Y,0
COMPASS_MOT_Z,0
COMPASS_MOT2_X,0
COMPASS_MOT2_Y,0
COMPASS_MOT2_Z,0
COMPASS_MOT3_X,0
COMPASS_MOT3_Y,0
COMPASS_MOT3_Z,0
COMPASS_MOTCT,0
COMPASS_OFS_X,-169
COMPASS_OFS_Y,-47
COMPASS_OFS_Z,-142
COMPASS_OFS2_X,421
COMPASS_OFS2_Y,-302
COMPASS_OFS2_Z,-251
COMPASS_OFS3_X,0
COMPASS_OFS3_Y,0
COMPASS_OFS3_Z,0
COMPASS_ORIENT,0
COMPASS_ORIENT2,0
COMPASS_ORIENT3,0
COMPASS_PRIMARY,0
COMPASS_USE,1
COMPASS_USE2,1
COMPASS_USE3,1
EKF_ABIAS_PNOISE,0.0002
EKF_ACC_PNOISE,0.5
EKF_ALT_NOISE,0.5
EKF_EAS_GATE,10
EKF_EAS_NOISE,1.4
EKF_FALLBACK,1
EKF_FLOW_DELAY,25
EKF_FLOW_GATE,3
EKF_FLOW_NOISE,0.3
EKF_GBIAS_PNOISE,1E-06
EKF_GLITCH_ACCEL,150
EKF_GLITCH_RAD,20
EKF_GND_GRADIENT,2
EKF_GPS_TYPE,0
EKF_GYRO_PNOISE,0.015
EKF_HGT_GATE,20
EKF_MAG_CAL,0
EKF_MAG_GATE,3
EKF_MAG_NOISE,0.05
EKF_MAGB_PNOISE,0.0003
EKF_MAGE_PNOISE,0.0003
EKF_MAX_FLOW,2.5
EKF_POS_DELAY,220
EKF_POS_GATE,30
EKF_POSNE_NOISE,0.5
EKF_RNG_GATE,5
EKF_VEL_DELAY,220
EKF_VEL_GATE,6
EKF_VELD_NOISE,0.5
EKF_VELNE_NOISE,0.3
EKF_WIND_PNOISE,0.1
EKF_WIND_PSCALE,0.5
ELEVON_CH1_REV,0
ELEVON_CH2_REV,0
ELEVON_MIXING,0
ELEVON_OUTPUT,0
ELEVON_REVERSE,0
FBWA_TDRAG_CHAN,0
FBWB_CLIMB_RATE,2
FBWB_ELEV_REV,0
FENCE_ACTION,0
FENCE_AUTOENABLE,0
FENCE_CHANNEL,0
FENCE_MAXALT,160
FENCE_MINALT,60
FENCE_RET_RALLY,0
FENCE_RETALT,0
FENCE_TOTAL,0
FLAP_1_PERCNT,0
FLAP_1_SPEED,0
FLAP_2_PERCNT,0
FLAP_2_SPEED,0
FLAP_IN_CHANNEL,0
FLAP_SLEWRATE,75
FLAPERON_OUTPUT,0
FLOW_ENABLE,0
FLOW_FXSCALER,0
FLOW_FYSCALER,0
FLTMODE_CH,8
FLTMODE1,2
FLTMODE2,0
FLTMODE3,0
FLTMODE4,0
FLTMODE5,10
FLTMODE6,0
FORMAT_VERSION,13
FS_BATT_MAH,0
FS_BATT_VOLTAGE,0
FS_GCS_ENABL,0
FS_LONG_ACTN,0
FS_LONG_TIMEOUT,20
FS_SHORT_ACTN,0
FS_SHORT_TIMEOUT,1.5
GLIDE_SLOPE_MIN,15
GND_ABS_PRESS,100841.8
GND_ALT_OFFSET,0
GND_TEMP,40.87147
GPS_AUTO_SWITCH,1
GPS_MIN_DGPS,100
GPS_MIN_ELEV,-10
GPS_NAVFILTER,8
GPS_SBAS_MODE,2
GPS_TYPE,1
GPS_TYPE2,0
GROUND_STEER_ALT,1
GROUND_STEER_DPS,90
INS_ACC2OFFS_X,1.177495
INS_ACC2OFFS_Y,1.313911
INS_ACC2OFFS_Z,1.500832
INS_ACC2SCAL_X,1.017729
INS_ACC2SCAL_Y,1.033466
INS_ACC2SCAL_Z,1.011063
INS_ACC3OFFS_X,0
INS_ACC3OFFS_Y,0
INS_ACC3OFFS_Z,0
INS_ACC3SCAL_X,0
INS_ACC3SCAL_Y,0
INS_ACC3SCAL_Z,0
INS_ACCOFFS_X,-0.2077458
INS_ACCOFFS_Y,-0.4260187
INS_ACCOFFS_Z,-0.3275968
INS_ACCSCAL_X,0.993928
INS_ACCSCAL_Y,0.9998984
INS_ACCSCAL_Z,0.9967155
INS_GYR2OFFS_X,0.00936735
INS_GYR2OFFS_Y,0.0005786924
INS_GYR2OFFS_Z,0.002697701
INS_GYR3OFFS_X,0
INS_GYR3OFFS_Y,0
INS_GYR3OFFS_Z,0
INS_GYROFFS_X,0.01548751
INS_GYROFFS_Y,0.03499942
INS_GYROFFS_Z,-0.06441472
INS_MPU6K_FILTER,0
INS_PRODUCT_ID,5
INVERTEDFLT_CH,0
KFF_RDDRMIX,0.5
KFF_THR2PTCH,0
LAND_FLAP_PERCNT,0
LAND_FLARE_ALT,2
LAND_FLARE_SEC,1.5
LAND_PITCH_CD,300
LEVEL_ROLL_LIMIT,5
LIM_PITCH_MAX,2000
LIM_PITCH_MIN,-2500
LIM_ROLL_CD,4500
LOG_BITMASK,65535
MAG_ENABLE,1
MIN_GNDSPD_CM,0
MIS_RESTART,0
MIS_TOTAL,7
MIXING_GAIN,0.5
MNT_ANGMAX_PAN,4500
MNT_ANGMAX_ROL,4500
MNT_ANGMAX_TIL,4500
MNT_ANGMIN_PAN,-4500
MNT_ANGMIN_ROL,-4500
MNT_ANGMIN_TIL,-4500
MNT_CONTROL_X,0
MNT_CONTROL_Y,0
MNT_CONTROL_Z,0
MNT_JSTICK_SPD,0
MNT_LEAD_PTCH,0
MNT_LEAD_RLL,0
MNT_MODE,0
MNT_NEUTRAL_X,0
MNT_NEUTRAL_Y,0
MNT_NEUTRAL_Z,0
MNT_RC_IN_PAN,0
MNT_RC_IN_ROLL,0
MNT_RC_IN_TILT,0
MNT_RETRACT_X,0
MNT_RETRACT_Y,0
MNT_RETRACT_Z,0
MNT_STAB_PAN,0
MNT_STAB_ROLL,0
MNT_STAB_TILT,0
NAV_CONTROLLER,1
NAVL1_DAMPING,0.75
NAVL1_PERIOD,20
OVERRIDE_CHAN,0
PTCH2SRV_D,0.1168775
PTCH2SRV_I,0.09229187
PTCH2SRV_IMAX,2000
PTCH2SRV_P,1.558367
PTCH2SRV_RLL,1
PTCH2SRV_RMAX_DN,75
PTCH2SRV_RMAX_UP,75
PTCH2SRV_TCONST,0.45
RALLY_LIMIT_KM,5
RALLY_TOTAL,0
RC1_DZ,30
RC1_MAX,1980
RC1_MIN,1154
RC1_REV,1
RC1_TRIM,1602
RC10_DZ,0
RC10_FUNCTION,0
RC10_MAX,1900
RC10_MIN,1100
RC10_REV,1
RC10_TRIM,1500
RC11_DZ,0
RC11_FUNCTION,0
RC11_MAX,1900
RC11_MIN,1100
RC11_REV,1
RC11_TRIM,1500
RC12_DZ,0
RC12_FUNCTION,0
RC12_MAX,1900
RC12_MIN,1100
RC12_REV,1
RC12_TRIM,1500
RC13_DZ,0
RC13_FUNCTION,0
RC13_MAX,1900
RC13_MIN,1100
RC13_REV,1
RC13_TRIM,1500
RC14_DZ,0
RC14_FUNCTION,0
RC14_MAX,1900
RC14_MIN,1100
RC14_REV,1
RC14_TRIM,1500
RC2_DZ,30
RC2_MAX,2026
RC2_MIN,1200
RC2_REV,1
RC2_TRIM,1616
RC3_DZ,30
RC3_MAX,1933
RC3_MIN,1106
RC3_REV,1
RC3_TRIM,1106
RC4_DZ,30
RC4_MAX,2015
RC4_MIN,1190
RC4_REV,1
RC4_TRIM,1602
RC5_DZ,0
RC5_FUNCTION,0
RC5_MAX,1555
RC5_MIN,1554
RC5_REV,1
RC5_TRIM,1555
RC6_DZ,0
RC6_FUNCTION,0
RC6_MAX,1500
RC6_MIN,1499
RC6_REV,1
RC6_TRIM,1499
RC7_DZ,0
RC7_FUNCTION,0
RC7_MAX,1500
RC7_MIN,1499
RC7_REV,1
RC7_TRIM,1499
RC8_DZ,0
RC8_FUNCTION,0
RC8_MAX,2074
RC8_MIN,965
RC8_REV,1
RC8_TRIM,1521
RC9_DZ,0
RC9_FUNCTION,0
RC9_MAX,1900
RC9_MIN,1100
RC9_REV,1
RC9_TRIM,1500
RCMAP_PITCH,2
RCMAP_ROLL,1
RCMAP_THROTTLE,3
RCMAP_YAW,4
RELAY_DEFAULT,0
RELAY_PIN,54
RELAY_PIN2,55
RELAY_PIN3,-1
RELAY_PIN4,-1
RLL2SRV_D,0.1124097
RLL2SRV_I,0.1309075
RLL2SRV_IMAX,2000
RLL2SRV_P,1.498796
RLL2SRV_RMAX,75
RLL2SRV_TCONST,0.45
RNGFND_FUNCTION,0
RNGFND_LANDING,1
RNGFND_MAX_CM,4000
RNGFND_MIN_CM,30
RNGFND_OFFSET,0
RNGFND_PIN,-1
RNGFND_RMETRIC,1
RNGFND_SCALING,0.9494
RNGFND_SETTLE,0
RNGFND_STOP_PIN,55
RNGFND_TYPE,5
RNGFND2_FUNCTION,0
RNGFND2_MAX_CM,4000
RNGFND2_MIN_CM,20
RNGFND2_OFFSET,0
RNGFND2_PIN,-1
RNGFND2_RMETRIC,1
RNGFND2_SCALING,3
RNGFND2_SETTLE,0
RNGFND2_STOP_PIN,-1
RNGFND2_TYPE,0
RSSI_PIN,-1
RSSI_RANGE,5
RST_MISSION_CH,0
RST_SWITCH_CH,0
RTL_AUTOLAND,0
SCALING_SPEED,15
SCHED_DEBUG,0
SERIAL0_BAUD,115
SERIAL1_BAUD,57
SERIAL2_BAUD,57
SERIAL2_PROTOCOL,1
SKIP_GYRO_CAL,0
SR0_EXT_STAT,2
SR0_EXTRA1,10
SR0_EXTRA2,10
SR0_EXTRA3,2
SR0_PARAMS,10
SR0_POSITION,3
SR0_RAW_CTRL,2
SR0_RAW_SENS,2
SR0_RC_CHAN,2
SR1_EXT_STAT,2
SR1_EXTRA1,10
SR1_EXTRA2,10
SR1_EXTRA3,2
SR1_PARAMS,10
SR1_POSITION,3
SR1_RAW_CTRL,2
SR1_RAW_SENS,2
SR1_RC_CHAN,2
SR2_EXT_STAT,2
SR2_EXTRA1,5
SR2_EXTRA2,2
SR2_EXTRA3,1
SR2_PARAMS,10
SR2_POSITION,2
SR2_RAW_CTRL,1
SR2_RAW_SENS,2
SR2_RC_CHAN,5
STAB_PITCH_DOWN,2
STALL_PREVENTION,1
STEER2SRV_D,0.02
STEER2SRV_I,0.1
STEER2SRV_IMAX,1500
STEER2SRV_MINSPD,1
STEER2SRV_P,5.5626
STEER2SRV_TCONST,0.5
STICK_MIXING,1
SYS_NUM_RESETS,160
SYSID_MYGCS,255
SYSID_SW_TYPE,0
SYSID_THISMAV,1
TECS_CLMB_MAX,5
TECS_HGT_OMEGA,3
TECS_INTEG_GAIN,0.1
TECS_LAND_ARSPD,33
TECS_LAND_DAMP,0.5
TECS_LAND_SINK,0.25
TECS_LAND_SPDWGT,0.2
TECS_LAND_TCONST,2
TECS_LAND_THR,-1
TECS_PITCH_MAX,20
TECS_PITCH_MIN,0
TECS_PTCH_DAMP,0
TECS_RLL2THR,10
TECS_SINK_MAX,5
TECS_SINK_MIN,2
TECS_SPD_OMEGA,2
TECS_SPDWEIGHT,1
TECS_THR_DAMP,0.5
TECS_TIME_CONST,5
TECS_VERT_ACC,7
TELEM_DELAY,0
TERRAIN_ENABLE,1
TERRAIN_FOLLOW,0
TERRAIN_LOOKAHD,2000
TERRAIN_SPACING,100
THR_FAILSAFE,1
THR_FS_VALUE,950
THR_MAX,75
THR_MIN,0
THR_PASS_STAB,0
THR_SLEWRATE,100
THR_SUPP_MAN,0
THROTTLE_NUDGE,1
TKOFF_FLAP_PCNT,0
TKOFF_ROTATE_SPD,10
TKOFF_TDRAG_ELEV,50
TKOFF_TDRAG_SPD1,5
TKOFF_THR_DELAY,2
TKOFF_THR_MAX,0
TKOFF_THR_MINACC,0
TKOFF_THR_MINSPD,0
TKOFF_THR_SLEW,30
TRIM_ARSPD_CM,1200
TRIM_AUTO,0
TRIM_PITCH_CD,0
TRIM_THROTTLE,60
VTAIL_OUTPUT,0
WP_LOITER_RAD,60
WP_MAX_RADIUS,0
WP_RADIUS,10
YAW2SRV_DAMP,0
YAW2SRV_IMAX,1500
YAW2SRV_INT,0
YAW2SRV_RLL,1
YAW2SRV_SLIP,0

[quote=“gmorph”]Can you please post your log so we can do some analysis?

Thanks, Grant.[/quote]

I have attached one of the larger log files. Thanks

We achieved several autonomous take-offs today. We extended the time to ramp the throttle to 8 seconds. So the plane does not accelerate so quickly. And we lengthened the time the tail wheel is held to the ground. It appears that as long as the tail wheel is in contact with the runway, the steering is OK. But when the elevator is neutralized and the tail-wheel leaves the runway, then the plane tends to veer off and the rudder - controlled by the PixHawk - is not moved aggressively enough to compensate.

Also, I learned today that we are not running version 3.3. We are running “one version back” according to the plane owner.

Another update: We added more right thrust and were able to make two almost perfect take-offs in very calm conditions. I really don’t think the controller is correcting much if any with the rudder / tailwheel during the take-off run. However, the plane is tuned up enough that it does not matter so much.

Autonomous landing, however, is another story. I may open another thread about this topic when i have more data.

Hi. A couple of your parameters seem incorrect. From your log:
Your TKOFF_THR_MAX is set to 20 which seems very very low. Your limiting your takeoff to a maximum of 20% throttle. Will your plane even fly at 20% throttle?
TKOFF_TDRAG_SPD1 is set to 30 (the maximum). This parameter sets the airspeed at which to stop holding the tail down and transition to rudder control of steering on the ground. So you want your plane to be doing 30m/s with the tail on the ground?
TKOFF_ROTATE_SPD is 10. So this says at 10m/s we are ok to take off. This should be set just above your stall speed. Is that 10m/s?

If you do change the above parameters love to hear back that its working. A video would be great!

Thanks, Grant

[quote=“gmorph”]Hi. A couple of your parameters seem incorrect. From your log:
Your TKOFF_THR_MAX is set to 20 which seems very very low. Your limiting your takeoff to a maximum of 20% throttle. Will your plane even fly at 20% throttle?
TKOFF_TDRAG_SPD1 is set to 30 (the maximum). This parameter sets the airspeed at which to stop holding the tail down and transition to rudder control of steering on the ground. So you want your plane to be doing 30m/s with the tail on the ground?
TKOFF_ROTATE_SPD is 10. So this says at 10m/s we are ok to take off. This should be set just above your stall speed. Is that 10m/s?

If you do change the above parameters love to hear back that its working. A video would be great!

Thanks, Grant[/quote]

Did you get the parameters from my post where I pasted them in text form? Or did you get them from the log file? In my post, I see this:
TKOFF_THR_MAX,0
TKOFF_ROTATE_SPD,10
TKOFF_TDRAG_SPD1,5

I must have sent you either the wrong parameters or the wrong log files or both. I will be more rigorous next time. We did so many tests and tried so many different combinations that I’m not sure exactly what I sent you.

I know from observing the plane that the throttle rams up from zero to approximately 80% or 100% over 8 seconds time. We initially had this set to 30% (TKOFF_THR_SLEW,30) throttle per second, but changed it to 20% throttle per second to ramp more slowly. This seemed to help with the steering.

Our plane stalls at 7 M/s and cruises nicely at 10 m/s

The plane is out of town for the next week, so no testing opportunity this week.

I am just guessing but would KFF_RDDRMIX be part of the solution? As it’s veering off course on the ground can you see it applying ailerons? Does your plane have ailerons? Maybe the controller is not set up %100 right yet for a tail dragger??

KFF_RUDDERMIX is set to 0.5. Yes it has ailerons. I am getting some rudder deflection when the plane is rolled left or right (roll left causes right aileron and right rudder). Maybe increasing this mix will help. Since improving the physical characteristics of the plane (right thrust), we have made several autonomous take-offs.

We did this test: restrain the plane by the tail. Flip the mode switch to “AUTO” (the motor ramps up to full throttle over the next few seconds). yaw the plane left and right by 20 degrees or more. The rudder does not move. I would expect the rudder to make corrections to yaw in this case.

When the plane is on its takeoff roll and both wheels are on the ground, it is not going to change in the roll axis, but it does change in the yaw axis. It seems to me the control algorithms for the rudder are driven mainly from the roll gyro and not enough from the yaw gyro.

This issue is now mostly resolved. I have made 4 successful takeoffs where the plane tracked pretty true down the runway. I think the setting that made the most impact was changing GROUND_STEER_ALT from 1 to 3.

Also, for unrelated reasons, I am using a different but similar airframe (Sig Kadet 80 inch span versus the Senior Telemaster I was using)

I can definitely see rudder correction being applied as the plane takes off. I was not seeing that a couple weeks ago when I first started experimenting with auto-take off.

To: @dmcquinn , @gmorph

Now I am currently trying to adjust PID for ground Steering for my plane, as I want to do Runway TakeOff.
But whenever I switch to “FBWA” or “Auto” mode for Runway TakeOff, the arduplane controller will always ask my plane to make a “U-turn” first, then only it started to run straight.
Why is this happening? Did your plane also have same situation?

Besides, after this “U-turn”, my plane always run with zig-zagging along the straight line.
Why is this happening? I am really being troubled by these issues for a week of trying.

Tell me more about your plane. Is it tricycle gear or tail dragger? When you take off manually, does it seem to track pretty straight or do you have to really fight it to keep it on the runway? If it has a nosewheel, how many degrees does it move each way? When you push the plane down the runway (engine off) , does it roll straight?

Basically, you will have a lot better luck with auto-takeoff if the plane is mechanically set up pretty good to begin with.

To: @dmcquinn

Plane Model: Skyfun
Landing Gear: Tricycle Gear

Yes, it can run pretty straight when takeoff manually.

I did post a new thread to ask for help. There I write the details. But I can write it again here.
Topic: Ground-Steering started with “U-Turn” ???

I just don’t know why whenever I tried to use FBWA or Auto, it will first make a “U-Turn” first, then only it going straight, actually not tracking straight, a bit run like zig-zagging. Even manual - RUN is better than the controller, but that’s not what i want. This happen everytime I try. I still fighting to make it track the runway straight, so I can rely on the Auto-TakeOFF. But I found quite hard tune the STEER2SRV - PID.

Note: “U-Turn” means the final TakeOff direction is opposite to the original direction I want it to (The direction I put it on the ground).

OK, thanks. I’m not sure what is going on. How much does your nose wheel move each way ((in degrees)? I like about 10-20 degrees each way. If you are getting 45 degrees each way this is probably too much and the Pixhawk is maybe over-controlling. The zip-zagging is also indicative of too high of a gain on the steering controller (the “PID” settings of the ground steering).

I can’t explain the U-turn at all. I know from experience that the first way-point in the auto flight plan has little or no effect on the take-off run in auto mode. (early on I thought that making the first way point straight off the end of the runway would cause it to track straight on the ground but this is not the case). During auto-takeoff, the controller attempts to keep the nose pointed the same direction while it accelerates down the runway.

Have you checked that the rudder goes the right way when in auto mode? Hold onto the airplane. flip the transmitter switch into “auto”. The prop should start to spin. Now quickly rotate the plane (yaw) to the right. The rudder should deflect to the left.